HBT-EP Archives 2002 - present
Wednesday December 18 03 58 36492-36513 External Field
During the run I was working with 'high beta' shots that I usually use in my 3/1 experiments. I was trying to develope a model discharge that would be stable to low frequency 3/1 oscilations with the aluminum shells fully inserted and unstable when they're retracted. Due to certain problems with the CAMAC racks and Crunch cabinet I didn't get much run time. Never the less I got several good shots. The data is being analyzed. Regards, Mikhail

Wednesday December 18 05 32 36514-36542 FB setup shots
Developed a "long lived" saturated RWM target mode that lasts about 2 to (sometimes even) 3 ms near the end of the shot. These plasmas were made with the Al shells inserted to suppress higher m/n=4/1 and 3/1 RWMs and 2/1 tearing type modes also. I was successful in bringing the q=2 surface external with a Ip ramp style shot. These shots have an Ip ramp of 2 MA/sec during the first half of the shot and then Ip rolls over somewhat at ~15kA during the last half of the shot when the kink is excited. The kink is of m/n=2/1 helicity instead of our more typical 3/1 variety. The q=2 surface goes out into the vacuum at ~ 4.5ms. The shots typically disrupted at about 8 to 9ms (see shot#35642 as an example). Feedback next.

Thursday December 19 05 38 36543 ICRH
Disappointingly, the large oscillations on the loop voltage now appear not to be related to the plasma after all. Today, in contrast to last week, the oscillation was there even in the absence of plasma. Last week we had one shot, 36486, without plasma, and the loop voltage oscillation was absent. However, today, we took several non-plasma shots, with and without banks firing, 36562, 36564, 36565, where the loop voltage clearly oscillated during the RF. On the bright side, the RF B probe is now absolutely calibrated. The RF B field at the probe is about 1 Gauss, within expectations for vacuum. No clear coupling was seen today, ie. vacuum B fields were basically the same as those when the plasma was around. The calibration factors have all been worked into the MDSPlus tree, so the f_bprobe tag now directly reflects the RF B-field in Gauss. Cory developed some good discharges that would hang around 92-91 cm for a couple of milliseconds. Nonetheless, Q was only observed to dip during inboard disruptions. We did not make significant progress on the triple probe, for lack of time, mostly.

Thursday December 19 05 43 -36603 ICRH Addendum
Two things to add to the report: We just discovered that by mistake, we ran today with the 10% helium mixture instead of the 20% hydrogen. So no chance of heating today. The other thing: I forgot to put in the last shot number of the day. It was 36603.

Friday December 20 04 20 none
Steve Paul was in today and reinstalled a new fiber optic bundle and optics to carry light from the machine to the screen room, as a consequence of that and some work on TS triggering we did not run today. Steve expects a factor of roughly 4 increase in collected light. He also stated he has made progress on fixing the systematic errors in the measurement through calibration improvements. Since the machine will not be running next week we took the opportunity to pump on and bake the Mach and Biased probe bellows and opened them up to the chamber. They should be ready for experiments when we run again. The bake is on.

2003

Friday January 10 04 25 Rivera null none
The lower 12 turn coil has been installed. The OH has been dismantled to facilitate installing the lower 21 turn coil.

Wednesday January 22 05 26 Maurer 36606-36619 shake-down
Finished getting the machine back in order(insulation, TF cooling oil, etc...) today after installation of majority of VF feeback coils during the past two weeks. Took initial OH and VF vacuum shots going in increments up to typical maximun runtime voltages ( e.g. VFEL=200V, OHEL=250V). Observed no problems with new coilsets. Ready for TF and plasma shots tomarrow. Since we are a day behind in getting the machine back together we are planning on moving the run schedule back a day. I will continue tomarrow and check out the TF and get first plasmas and Mikhail will then run on Friday.

Thursday January 23 06 10 Maurer 36620-36656 Clean-up
First plasmas were taken today since prior to Xmas and the new VF coil installation. Plasmas started out short (~2-3ms lifetime) but rather quickly started to last out to ~6ms after about ten shots. Tomarrow we should be able to get some real data. New mounts for the fan array sxr amplifier box were measured out and are being machined. They are needed because of the top middle new VF feedback coil location. The array will hopefully be up and running early next week after the table is installed and an extension is added to the copper bellows(Jim&John). Work on the TS triggering system and the new and repaired u-port adapters also piggy-backed on the run today(Alex&Royce).

Monday January 27 05 26 Mikhail Shilov 36657-36722 External Field
During Fri, Jan 24 and morning of Mon, Jan 27 runs I developed a reproducible discharge type which doesn't have low frequency external kink oscillations in the first phase of the discharge with the aluminum shells all the way in and q*

Monday January 27 05 28 Mikhail Shilov 36657-36722 External Field
During Fri, Jan 24 and morning of Mon, Jan 27 runs I developed a reproducible discharge type which doesn't have low frequency external kink oscillations in the first phase of the discharge with the aluminum shells all the way in and q* less ~ 3. In the afternoon of Mon, Jan 27 I applied external 3/1 corotating, static, static with 180 degree phase flip field to those kind of plasmas. The data is yet to be analyzed. Here is some good natural shots: 36664, 36668, 36671, 36688, 36691, 36703, 36720. -Mikhail

Thursday January 30 06 47 Maurer/Paul 36786-36833 Rotation&TS
Ran some calibrations of the new collection optics to start the day. Working out kinks with new collections optcs (for increased light collection). Ran in 10% and 100% He discharges. Small light levels seen on 100% He discharge cases. Currently not understood why light level is so low. Checking various possibilities. TS triggering progress made. Scope and laser triggered off of jorway pulse stopped pretriggering of scope. Need to AC couple the scope inputs to be able to bump the volts per division to measure TS scattered light.(Alex)

Wednesday February 5 05 31 Cates 36835-36943 Smart Shell RWM Feedback
On Tuesday, several hours were spent testing feedback preamps, and repairing small problems in the system. In the afternoon (shots 36855-65), some target current driven plasmas with 3/1 rwm induced disruptions were tested with and without feedback. Wednesday these current ramp shots were used to do a disruption study with feedback gains changed between full gain, half gain and quarter gain, in order to supplement previous gain studies with only full gain and 0.1 gain. I was also able to test the feedback shots (shots 36878-36891, 36939-43) with these gains against a smaller current ramp which is unstable for a longer period of time, hopefully allowing better observation of mode amplitude growth. As a side note, I have found Mikhail's improved solid_tok code (which now runs every shot automatically) to be a very helpful tool for run time analysis and correlating predicted mode stability with diagnostic signals.

Thursday February 6 05 24 Pedersen 36944-36985 ICRH/triple probe
We exercised the ICRF today and tested the triple probes with some new circuitry. We also took more data with the rf magnetic pickup probe, which was calibrated a while ago. ICRF worked as usual (hardware working fine, but no plasma heating) after a filter replacement. New triple probe circuitry allowed us to take useful data. The ion saturation currents were lower than expected and we changed some resistors to increase the signal levels. We took several good sets of data on the scope; they were stored on floppy and are being analyzed. We can extract a plasma density out of these measurements, and we expect it to be low - how low remains to be seen. Floating potentials were on the order of -40 volts (so Te=10 eV). A higher noise level was observed during the ICRF pulse, but it seems that the signals can still be extracted. RF pickup probe: We noticed small bumps (increases) in the signals when plasmas were inboard limited, but only for those plasmas which were still healthy (the current was still rising and the plasma had not disrupted). Examples: 36978, 83, 84 A typical increase was from 1.1 Gauss to 1.3 Gauss, noticeable but not dramatic.

Thursday February 6 09 33 Maurer 36896-37035 Rotation
... the second shift
Ran plasmas for equilibrium reconstructions for Youhong. Got well centered discharges with essentially constant edge q and major radius over a ~2msec(from about 2 to 4ms during the shot) period with limited MHD that should be good for the VALEN eddy current calculations and Tokamac runs. S. Paul came in for a late night run. We fixed the previous run's problems with signal level and then ran a series of discharges where we systematically varied the puff time to investigate changes in measured intensity levels and effects on the observed rotation rates. More analysis needed, but there were incouraging correlations between mini and major disruptions and the ion velocity being driven to zero. The ions are inferred to rotate in the direction of Ip. Also, TS triggering work was carried out during the ICRH run. There are still some noise issues to sort out with the AC coupled scope inputs. No recognizable scattered light was observed when we did take shots with the plasma. (Alex)

Tuesday February 11 06 08 Pedersen/Maurer etc 37036-45 VF Feedback
The feedback coils are all connected and polarities have been checked. The total series resistance is 32 mOhm, as expected. We pulsed the OH and the VF and looked at the induced voltages in the feedback system. These voltages peak at 2-4 kV. The VF start and the OH breakdown spike each contribute at that level but with opposite polarities. The OH spike induced voltages are roughly in line with expectations, but the VF start was not expected to induce as much voltage as it does. In other words, the coupling between the old VF and the feedback coils must be larger than expected. We consider the voltage level safe for the LANL power supply, which is a 10 kV power supply that will be connected to the FB system through a large transformer.

Thursday February 13 06 16 Maurer/Pedersen none Plasma position feedback
Good news and ...more good news: First, the previously reported induced voltages in the FB systems are off by a factor of 10. The scope probe used was actually a 1:100 divider rather than a 1:1000 divider. Hence the induced voltages were actually on the order of 200 V, which is much more in line with expectations. Nicolai calculated coupling coefficients as follows: Feedback coils - OH coils: c=0.0065 (design value 0.0025) Feedback coils - VF coils: c=0.027 (design value 0.018) No gross discrepancy, in other words. Second, we pulsed the Feedback system with the one LANL power supply. It worked very well with current rise from zero to about 200 A in about 100 microseconds. Data was recorded with the scope for a more precise analysis. The cos theta coil pickup will be recorded on a later run day.

Wednesday February 19 09 07 Nick none
The run-summary page is working again. Upgrading to 10.2.4, rewrote the httpd file without PHP support which is necessary for this script to work.

Wednesday February 19 05 17 Maurer fixing sxrs...
Yesterday and today were spent re-installing the sxr fan array which has been off the machine since the top middle VF feedback coil was installed about two weeks ago. The amplifier box, new table and extended bellows are now setup. The cabling was run differently to help minimize icrh pickup (hopefully) in the future. Initially there were 7 "bad" channels. All appear to be working except for channels 14 and 16 which are open circuit at the vacuum feedthrough. These two channels have been bad for some time. It is not known whether this is due to a bad vacuum side connection or if the diodes are bad (usually diodes fail short when the junction fails). The other channels (1,2,10, 13,15) had either faulty amplifiers or cabling problems that have been fixed except for a small oscillation on 13 and 15. We should be able to get an emissivity centroid out of the array as a check on open loop jog experiments with the new VF feedback coil.

Friday February 21 11 00 Pedersen/Maurer 371??-37206 Radial feedback/triple probe
We did several open loop tests using the LANL into the power supply and operated the triple probe as an ion saturation probe. Open loop tests The open loop test shots were 37190-37206. We found a significant pickup on the cos theta coil when pulsing the FB system. There is a simple proportional pickup but there also seems to be a smaller pick up that looks like it decays exponentially. Not sure about what to do about that one. We have enough data to nail down the calibration factor for the simple linear coupling, and can then proceed to get a believable major radius signal. The LANL worked very well, giving up to 300 A, but the signal generator used to drive the LANL waveforms gave us some problems. It is too early to conclude anything about the efficacy of the new feedback system, since the major radius measurement is contaminated by pickup. The sxr fan array may provide useful independent measurement of the radial position. We can report a preliminary analysis at the Monday meeting.
The triple probe was operated in ion saturation with a 300 V battery to ground, with a 24 Ohm resistor used to measure the ion saturation current. Signals were much better than when operated as a triple probe and the densities are higher too. I suspect that one of the probe leads/connections or the triple probe box is flaky, and I would discard the data taken last week on that basis. One probe tip seemed flaky at first but then started working, the other two were fine. Densities for outboard limited shots start out in the low 10^11 cm^-3 range and gradually increase to about 5*10^11 after about 5 ms. These numbers assume a constant 10 eV electron temperature and that other calibration constants are also accurate. They are a factor of 5 larger than the inboard limited plasma densities reported with the triple probe circuit. Signals are bursty but follow the overall evolution of the plasma well. We need to do inboard limited discharges next. At present, a single probe tip is being digitized in the north rack and a calibrated density (assuming Te=10 eV) is in the tree with the tag ne_inboard

Tuesday February 25 05 21 Maurer MC feedback
Reconfigured crunch amp box and input sensors today for mode control feedback using new gap coils. Checking polarity of signals and magnitude of feedback gains. Initial plasma shots with feedback taken. More of the same tomorrow.

Thursday February 27 05 45 Maurer/Pedersen 37265-37266 VF feedback
Todays run objective was to continue VF open loop jog experiments with the new VF feedback coil. Unfortunantly we did not get very far. The LANL charging supply failed at the start of the run day. The day was spent toubleshooting the supply(Nick has ordered the required parts to fix it). To be able to run we have currently swapped in the charging supply for the other LANL amplifier. Its installation is nearly complete (one dump relay is not working). It should be up and ready tomorrow morning. A calibration error was discovered in analyzing triple probe data. The calculated density form isat measurements is now approximately ~2e18 per cc on the inboard high field side edge plasma. This value is much more in line with other previous outboard Langmuir probe measurements. Also, mode control feedback data was taken yesterday. Analysis is underway. The new u-port adapter checked out OK and is currently installed in the icrh rack. Reminder: Tomorrow we going up to Argon to re-align Thomson scattering.

Friday February 28 05 16 Maurer/Klein
HBT-EP was up to ~200 Torr of Argon today in order to align Thomson scattering. We are currently pumped down using one cryo to 2e-6 Torr with the base pressure comprised of Argon and H2O. The bake has been turned on.

Friday February 28 05 20 Maurer/Klein
HBT-EP was up to ~200 Torr of Argon today in order to align Thomson scattering. We are currently pumped down using one cryo to 2e-6 Torr with the base pressure comprised of Argon and H2O. The bake has been turned on. Both cryos were regen'ed during the up to Argon. The TS align had some problems. The stray light level appears to be enhanced over the previous alignment in November. We can discuss this further at the Monday meeting. The LANL supply is back up and running. All the dump-interlocks are now working on the charging supply.

Monday March 3 05 56 Liu 37267-37300 clean up
1. shots 37271-37275 are vacuum shots. When all Krytrons were on and took OH only shot, there was current pickup (about 100-200A) in VF Rogowski coil. However, when VF Krytrons were off, there was no pickup in VF Rogowski coil. This is consistend with prof. Muael's prediction. 2. shots 37276-37300 are clean up shots. plasma lasts 6ms.

Wednesday March 5 06 46 Maurer/Paul 37308-37355 rotation
Doppler rotation data taken using the Thomson scattering viewport to measure the perpendicular plasma He emission. The measured wavelength shift is constant to within 2/100ths of an Angstrom (equivalent to +/- 1km/sec rotation). This constant value will be used to set the baseline of the measurement. There is a baseline shift due to temperature drift that is in the process of being calibrated out now that other systematic errors have been removed. Analysis underway. In taking off the TS collection optics to mount the rotation optics for todays run, a burn spot on the Nikon collection lens was noticed. This might be effecting the position alignment and calibration. Please stop in tomorrow Alex so we can talk. Lastly, we had problems initializing the crates at the end of the day. An unknown RMA error in the action monitor was a sympton. We were unable to correct the problem. cua900 will be rebooted tonight and we will try again tomorrow. This could delay the start of the VF feedback run Thurs.

Thursday March 6 05 27 Maurer/Pedersen 37363-373425 Radial Feedback open loop
Today we did the open loop tests of the radial position control system. It was a very successful day. With the aluminum shells at 8 cm, the plasma moved 2.5 cm in 1.5 msec when we applied a 4 msec square pulse of 250-300 A to the FB coil system. Positive current made the plasmas move inward, negative currents made the plasma move outward. Inward moving plasmas would disrupt early. With the shells at 4 cm, the plasmas were observed to move approximately the same amount but it took about twice as long to get there. The response looks approximately like an exponential decay, consistent with a resistive decay. The outward movements were confirmed by the soft x-ray centroid, which also moved outward. The inward moving plasmas did not have a clear signature on the soft x-ray centroid, presumably because we have several bad channels on the inboard side. Some problems with the LANL control prevented us from doing more fancy waveforms, and will need to be fixed before closed loop feedback can be attempted.

Wednesday March 12 07 07 Paul/Maurer/Cates 37429-37497 Rotation Diagnostic Comissioning
Run was devoted to gaining confidence in the toroidal rotation measurements. Known from earlier runs that the screenroom temperature slightly affects the diagnostic, even though the diagnostic housing is temperature controlled to within 0.2 degrees C. 37429-37445 optimize shots for duration and minimum MHD
37446-37452 track down noise appearing as isolated spikes in rotation diagostic
37453-37464 align detector to look perpendicular to plasma flow; take reproducible shots and record dependence on screenroom temperature
37465-37497 switched to normal toroidal view to look at rotation:
conclusion: 1. once the helium in the plasma is ionized (after 2 msec), the measured value of toroidal velocity is within ±1 km/sec of zero.
2. plasma seen to spin up steadily in the toroidal direction up to 6 km/sec in counter-clockwise (looking from above). Plasma velocity abruptly drops to zero (in < .5 msec) about 1 msec before the end of the shot. Plasma always disrupts subsequent to the locking of the plasma rotation. Sometimes the rotation will drop to near zero, but the plasma recovers and spins up again, only to lock a second time and disrupt fatally.
3. For most shots, plasma rotation increases over the lifetime of the shot, never reaching a steady value, when the locking and disruption occurs. On a few, the rotation appears to saturate. On such shots the SXR signal also saturates and rolls over. On the more common shots, SXR increases steadily and drops suddenly just prior to the disruption.
4. I am fairly confident in the results from the rotation diagnostic once the helium is ionized. The next step is to use various techniques, beginning with the bias probe to alter the plasma rotation and see the effect.

Thursday March 13 04 39 Maurer 37498-37514 Feedback & Setup
Today we ran plasmas in preparation for mode control feedback and started to set up the bias probe and mach probe for future experiments. The capacitor bank for the bais probe was run through a dummy load at the end of the day. It appears to be fine. I had a few problems with the pwr supply and a flakey trigger before it worked. We will re-route cabling tomorrow. We should have both probes in the edge plasma tomorrow(that was the goal for today). As a side note, the LANL unit was tested again on Tuesday with its repaired charging supply. The output is railed at 250A(as it was in last weeks expt) when no input is applied! For the initial VF feedback tests of Feb and early March we ran the unit about once a week for a 6-8 hour period. This output is possibly caused by an offset drift somewhere after the input stage that needs to be tweaked or a bad driver tube on the hot deck. We're flying somewhat blind without schematics for the amplifiers so it may take some time to figure out the actual cause. The output tubes appear to be OK in the sense that they turn on and draw the same filament current. Our attempts at actual position feedback will be stalled until this is fixed.

Tuesday March 25 05 21 Maurer 37588-37627 MC Feedback
Todays run goal was suppression of disruptions induced by 3/1 RWMs using the new mode control coil set in order to compare performance of the new system with smart shell feedback. I had great difficulty getting good RWMs to suppress in making the plasmas. The 3/1 external mode observed today was a short bursty fluctuation (almost delta function like) giving a fast kink that only caused minor disruptions. I am using similar bank settings, etc. that we have used in the past to make good RWMs for the smart shell experiments. Varying the Ip ramp rate and initial q after plasma startup did not have a significant effect. Shilov has agreed to run Friday instead of tomorrow, so I will continue with these experiments on Wednesday!

Thursday March 27 05 15 Pedersen 37640-683 ICRH
We ran the ICRH today. Not much progress to report. Most of the day was spent developing discharges that move inboard without disrupting but the run was cut short because of a water leak that is being fixed now. The ICRF was fired on a small number of shots and appeared to behave as usual.

Thursday April 24 05 42 Maurer 37940-37960 biased probe
Ran plasmas in D2 today. Checked out new triple probe circuitry. The new box is working fine (first actual triple probe operation!). Measured Te~12ev in the high field side edge and densities (a few 10^12 per cc) were similar to those that were measured when the probe was measuring just isat previously. Some minor wiring needs to be done and then we should be able to install the box in the north rack and have it as a day to day diagnostic in the tree (Pedersen). Ran biased probe shots later in the day. Had some problems with the floating potential measurement that need to be fixed. So the run was not too productive. More tomorrow. Ended the day by installing and testing the differential amps in the north rack for real time Ro in the control room for position control. One of the four chs checked out ok, but the other three had clipped square wave outputs with a sine wave input. Not sure why. I will pull the box out and we'll have to test it on the bench to see why. It was working previously. An aside on run summaries... As a group we have been somewhat forgetful as of late in writing up run summaries(myself included). To help in jogging our memories to do so Thomas and I thought it would be useful to remind run operators that writing the summaries is not optional. It is mandatory (similar to the checkout list that must be filled out prior to running hbtep). In the future please submit forgotten run reports the next day or asap. Thanks.

Friday April 25 05 43 Maurer 37961-37967 setup for VF feedback Progress was made on getting real time Ro in the control room today. (I thought this would take the morning, but it consumed the whole day) Pulled the differential amps for real time Ro in the control room out of the north rack this morning and bench tested them. The dip swtiches for the gain stage must have not been been switching properly. I had set them for unity gain yesterday and I must not have pushed down hard enough to engage the switch on the three that were not working. The clipping observed yesterday was due to them still being set for high gain (G=1000). They work fine now. I changed the input integrator on the board to have an RC time of a hundred microseconds so the west rack signals are not so highly attenuated but still low pass filtered for noise. Signals from the north rack and then west rack to the control room checked out ok through the whole isolation system. The differential amp gain was adjusted so that the "system" gain was ~1 at 1kHz. Plasmas were then made with the actual Ip and cos1theta signals form the west rack going over to the north rack and then via the iso-network to the control room. Good news: the data base signals for Ip and Ro look uneffected (recall that the everything looked like a flux loop when previously connected). Not so good news: the observed signals in the control room have features of being correct during the bias and startup phases of plasma operation, but then saturate and are pinned at 4.5V throughout the rest of the discharge. Perhaps there is an extra gain I measured incorrectly.

Tuesday April 29 05 08 Rivera/Maurer none
LANL fix Today we made some progress with fixing the LANLs. The LANL hotdecks were taken apart and tested. It looks like one side of the push-pull output now works. Some history: Previously, problems were fixed in the output stage of the low voltage feedback inputs(input trigger and feedback signal electronics). This had minor effects on the railed LANL output. A bad power supply was then found in one of the hot deck drivers and replaced. After which we were then unable to generate any output at all. Today the trigger and feedback signals were measured at the input to the hot deck and checked out OK. A mosfet that drives the hot deck driver tube on the A-side did not have the same feedback signal superimposed on it as on the B-side (A and B are the push-pull sides). This might still be a culprit in the way it was not working before. We can not say exactly because more than one thing has been fixed prior to being able to measure the output LANL current. We then carefully re-assembled the hot decks and powered the system up. The output is now a half wave rectified version of the input sine wave (with no large offset!). It looks like one side of the push pull configuration is now working. The lack of output after the first hot deck fix was probably due to bad/missed connections or the driver tubes weren't seated properly when it was re-assembled (we think).

Wednesday April 30 04 55 Maurer 37968-37977 biased probe
Ran plasmas in 10% Helium for biased probe rotation studies. Fixed the floating potential measurement box and reinstalled it for the days run. Still could not get a good Vf measurement. The digitizer signal looked essentially like a flux loop. I thought this was due to pickup from my extra long cable runs to the south and then north racks since we've moved the probe 180 degrees around the machine to the microwave interferometer section. Previously when the probe was at the old mach probe stand by the south rack I had no such difficulties with the measurement. After inserting the probe more deeply into the plasma to see some type of plasma potential fluctuation signiture on top of the flux loop pickup on the signal it still looked like a flux loop alone. I then checked continuity to the probe tip mechanically in two different ways. It appears that the feedthrough connections to the probe tip have opened up since it was installed. I believe I'll have to pull it behind the gate valve and check the internal connections out at atmospheric pressure. Too bad. This is now probably a good time to switch the positions of the internal magnetic probe and biased probe stands since I am bringing the bias probe head up to air ( so the new internal magnetic probe is at a chamber section with stainless shells instead of aluminium). We can start this in the background while people run Thurs and Fri.

Thursday May 1 05 05 Cates 37978-38020 RWM Smart Shell Feedback
The Smart Shell Feedback configuration was setup and tested for a RWM run using non disrupting RWM unstable plasmas. shots 37992-38007 were discharges with moderate current ramps which had sizable RWM modes and then large tearing modes later in the shot. Feedback with full gain and coverage was applied to these shots in an attempt to see changes in mode growth rate and rotation frequency. The rest of the shots were an attempt to get a plasma with a mild current ramp which was unstable for a longer period of time, but the plasma was moving around a lot in major radius so I was unable to get a better target plasma to apply feedback to.
ROTATION DIAGNOSTIC
I used the 10% He gas mix and Steve Paul's rotation diagnostic was online - there may have been some offset problems due to the screenroom being warm at the start of the run (shots 37981-37985). For a few shots (eg 38007,38015) the trend of the rotation signal was slowing down with time - the opposite of the normal temporal evolution - this may be due to a changing major radius, but is worth checking out because it is the first time we have seen this trend.
MAJOR RADIUS FEEDBACK
Dave was able to get real time signals of the plasma current and Cos Theta rogowski coils to the control room for use with the dsp.

Thursday May 8 10 43 Cates 38045-38064 RWM Traget Plasma Development
In the morning the Ebara cryo pump adsorber was replaced and the pump was regenerated. The pump temperature was cycling from 8K to ~40K before the change - this symptom was resolved with the new adsorber. Afternoon run was an attempt to create fast startup (high beta) discharges with unstable RWM. I had trouble getting a fast startup and could not drive the initial plasma current above 8 kA. Something seems to have changed in the breakdown. I was running in 100% D2 - last week I attributed this breakdown effect to the introduction of Helium, but maybe something else is going on. Thomas tested the recently modified triple probe box, but did not get good diagnostic signals. The connection of the Cos theta coil to the north rack and control room for use by the dsp for real time radius measurements had to be disconnected because it interfered with the normal digitized signal by introducing a large pickup.

Friday May 9 11 24 Shilov 38067-39106 External Field
I continued with 3/1 external field experiments with current ramps. Running in 100% D2, I experienced the same problem of low initial current as reported by C.Cates in the previous run summary. Raising puff time to 1.7 ms seemed to fix the problem. Something may be wrong with the puff system. I'll check it tomorrow. Data from static and rotating external field application on current ramps was gathered in the afternoon. Still needs to be analyzed.

Tuesday May 13 01 49 Rivera none LANL fix
The LANL amplifier is working again. The output looks the same as it did when first turned on ~2 months ago. However, it should be recalled that at that time there had been an offset in the feedback signal due to a failing tube in the ouput stage. A problem that was not addressed with this fix.

Thursday May 15 01 27 Shilov 38107-38158 External Field
(note: Shilov is referring to krytrons when he mentions ignitrons -Nick)
As I expected, the recent problems with plasma start up was due to a half-dead battery in the puff unit. After replacing the battery I was able to reduce the puff time 2 times compared to what I had to set it in the previous run. The reproducibility also improved. Some good data with rotating external field was collected. Later in the day I started having problems with VF CB bias ignitrons (both) firing spontaneously. Nick suggested it was due to ignitrons' age and cut the 'keep alive' wires from the ignitrons. It seemed to fix the problem with the spontaneous firing but produced another problem which was that the bank wouldn't fire ~20% of the shots. That was pretty annoying. The end.

Thursday May 15 04 29 Maurer none fixing cryo
Cates' run was postponed today so we could pump and purge the ebara cryo He supply to see if that stops the temperature cycling that started Monday afternoon (Shilov ran with only the cti cryo Wed). The adsorber that we replaced last Wednesday appears to have only temporarily solved the problem we were having. If this does not fix the problem the seals are mostly likely bad in the expander head and will either have to be replaced or a rebuilt pump head purchased.

Monday May 19 04 36 stillits 38163-38174 Ip signals
Ip raw signals from North rack were tested in DSP. Unfortunately, the output signal from the DSP did not give the correct profile for the plasma current because the raw data received from North rack was influenced by noise (similar to a flux loop). We have to check it out tomorrow (Tuesday).

Thursday May 22 10 35 Maurer none cryo repair
Wednesday was spent taking off the ebara cryo to be sent out and rebuilt. It was FedEx'ed by the end of the day. The gate valve on that pump stand has a through leak at atmospheric pressure. This brought the base pressure in the chamber up to a few times 1e-7Torr while we were taking the cryo off. We blanked off the 10" gate valve and pulled a rough vacuum behind it to stop the through leak. The base pressure in the chamber is now back down to what it was prior to taking the cryo off at 1e-8Torr.

Tuesday June 3 04 43 Pedersen/Stillits/Rivera none LANL/Radial feedback
Today's objective was to control the LANL power supply (driving the feedback coils) directly from the DSP in open loop configuration. We were partly successful: We were able to control the LANL with the DSP but the signals were noisy and distorted to the extent that this problem will need to be fixed. We narrowed the problem down to the optical isolation output having trouble driving the input on the LANL when the LANL is gated on. We are investigating why. Otherwise, the LANL was working well (except tripping too often), there were minimal current offsets, when driven directly by a signal generator. Also, the optical isolation network seems to be fully functional except for its inability to drive the LANL input. Signals looked clean when input into a scope at both 1MOhm and 50 Ohm.

Monday June 9 02 54 meeting time
The weekly HBTEP status meeting shall forthwith be held at 9:30am Monday mornings in the control room.

Thursday June 12 10 24 Muarer none intalling cryo
The rebuilt cryo arrived yesterday and was re-installed in the afternoon. It was cooled down late yesterday and was valved open to the chamber this morning. Base pressure is back down to 6.6 e-9Torr with the rebuilt cryo head a 8K. Shilov is making plasmas today.

Friday June 13 10 45 Shilov 38276-38314
Clean up shots. Plasmas OK

Monday June 16 05 19 Pedersen/Stillits/Rivera none LANL/Radial control
We used the afternoon to check out the LANL some more. A reference signal was reconnected following a conversation between Dave Nadle and Nick Rivera. This did not substantially improve the signals, which were rather noisy. We then tried to use a 1.5 V battery to generate an input signal to the LANL certifiably free of ground loops. The LANL basically ignored this signal and put out a current of -5 Amps regardless of the polarity of the battery, and whether it was hooked up at all, and even when it was connected in parallel with a large capacitor. I now suspect that the input on the LANL is malfunctioning. On the bright side, 5 A of offset is 40 times better than it used to be. An arc inside the LANL stopped the run and will be checked out tomorrow.

Wednesday June 18 10 30 Shilov 38315-38384 RWM, External Field
I spent the morning developing reproducible target discharge with q* approaching 3 slowly from below. It was successfully achieved after a while. Later in the day I applied static and phase flip external fields to the plasmas. The results look promising. The data is yet to be analyzed.

Monday June 23 03 04 Cates 38423-38454 RWM - IP Ramp
Friday 6/20 - Discharge development in an attempt to get a plasma with a RWM which grows slow enough to observe growth rates without disrupting the plasma. By the end of the run, I was able to get plasmas which would work well for a systematic feedback study. These shots (38444-38454) had large 3/1 modes which grew and saturated in .25-.75 ms with frequencies of 4-7 kHz - excellent targets for our smart shell feedback system.

Tuesday June 24 05 29 Cates 38455-38490 RWM Smart Shell Feedback
I continued making the mild current ramp discharges which looked promising from last week. After finding a fairly reproducible shot, I applied full gain smart shell feedback to the plasmas. The feedback clearly alters the rotation frequency of the mode, and sometimes reduces the amplitude. I will need to check the mode structure and growth rates more carefully. I am looking at the RWM in the first 4 ms of the shot - but these plasmas do last to 8-9 ms with significant sxr sawteeth and saturated tearing modes in the second half of the shot.

Tuesday June 24 09 03 Shilov 38385-38422 External Field
I continued with 3/1 external field experiments on the target discharge developed previous day ( ex. Shot #38371 ). The naturally growing RWM was observed with a short unstable time window between ~2.3 – 3 ms. The plasmas lasted for ~ 3-4 ms. I applied static external field with phase flips at 2.5ms and 3 ms. After analyzing the data, it looked like the RWM mode is unstable around q ~ 2.8 and stable above that value which could be related to the error of the edge q measurement. Unfortunately the data collected wasn’t sufficient to make any conclusion on the difference between plasma field phase rearrangement time at 2.5 and 3 ms. I will continue with the experiment this week.

Thursday June 26 11 51 Shilov 38492-38542 External field
Continued with 3/1 external field experiments with the previously developed discharge. Took a lot of phase flip shots with different flip times. The data is being analyzed.

Friday June 27 02 01 Alex Klein n.a. T.S. calibration
HBT-EP was filled to 170 Torr nitrogen. The non-laser wavelength channels showed a signal when laser was fired through the chamber, due to Raman scattering. I checked to note absence of breakdown in laser beam at this pressure. Collection optics were carefully aligned to maximize signal, then I proceeded to pump down and to collect sets of 5 data sets (for averaging) on scope at several pressures. The signals appear to depend linearly on fill pressure (good). Complete dissappearance of signals at pressures below 1 Torr show absence of stray light leakage into non-laser wavelength channels. Ease and accuracy of interpreting T.C. gauge for nitrogen is a plus. Ease of aligning collection optics in the absence of stray light is a great plus.
A minus: Chamber appears to be water logged; it remains to be seen how dirty of an ordeal a nitrogen calibration is. Will analyze todays data and write short report on Thomson Scattering system.

Monday June 30 05 04 cates/stillits 38542-38559 cleanup & ip-signal testing
Cleanup runs were performed. Ip-signals from north rack: signals are looking much better (having almost the right profile), but the signals are too constant - looks almost like a step-function (which gives a linearly increasing plasma current). We have to check that tomorrow.

Tuesday July 1 05 56 Cates 38560-38619 Clean Up
Clean Up shots taken to recover from up to nitrogen for Raman scattering calibration. Current Ramp discharges are fairly consistent, although the loop voltage is still around 10 V for a standard 10kA plasma (compared to around 5 V last week). Royce has been testing the triple probe: We tested the triple probe's electronics circuitry box today using the oscilloscope. Channel V1 and V3 performed as expected. V2 which will indicate the temperature is still saturating the scope so we are reducing the floating potential from 1/5 Vo to about 1/10 or 1/20 to get a complete measurement; Overall a successful test. Remi has noticed a large magnetic pickup on the soft xray tomography channels which is present even when diodes are disconnected and amplifiers are off - he is testing the system to see if he can improve the pickup.

Thursday July 3 01 48 Cates 38620-38656 CLean Up
On Wed. I tried to reproduce earlier RWM discharges, but the machine was not quite clean enough to get reproducible results. As a reference the Loop voltage for 10kA current ramp shots was down to 7-8 V. So half way through the day I switched to taking high current, outboard limited plasmas which lasted as long as possible in an attempt to scrape the limiters clean. These shots improved through the day. Several diagnostics were tested during the day: Yuhong discovered that the flux loops have been disconnected for the month of June (shots 38257-38647). Remi was able to improve the magnetic pickup on the soft xray tomography channels by finding and removing a ground loop in the copper box. The triple probe electronics box was tested by Royce and signals were very noisy.

Tuesday July 8 05 18 Cates 38691-38723 RWM Current Ramps
This morning I took about 15 shots with high current and edge q near 2 in order to help clean up the outboard limiters. These shots were also good for testing the SXT channels. In the afternoon I switched back to mild current ramps in order to produce observable RWM growth rates. I was able to get good target plasmas with Ip and minor radius increasing monotonically and q edge slowly dropping below 3 to induce a 3/1 RWM at around 2-3 ms. See shot 38719 as an example. Unfortunately about the same time that I was able to get reproducible plasmas - the South Rack digitizer signals became flaky and I had serial highway errors almost every shot when storing the South rack data (the feedback sensor coil data). The south rack is being cooled properly and I am not sure what is causing the serial highway errors. Royce, Remi and Nicolai were working on the triple probe, sxt and vf feedback diagnostics respectively throughout the day - no big news for any of those systems.

Thursday July 10 09 58 Shilov 38724 - 38777 Ext. Field I started developing a good discharge for RWM external field experiment in the morning. In the afternoon I started getting reproducible plasmas suitable for the experiment. Around that time the same serial highway error appeared and persisted as it did the day before. After a while it was in every shot. So no signals from the south rack could be digitized. I completed the run.

Friday July 11 05 01 Cates 38823-28870 RWM Smart Shell Feedback
First I examined some shots Mikhail has worked on with edge q going from 2.6 to above 3. After checking to make sure the feedback system was in good shape (one board needed a minor repair - signal 5BS1 was bad) I took full gain feedback shots on these discharges. The best shots are 38848-38859. I then switched back to the more standard current ramp shots I have worked with in the last couple weeks in order to complete a gain scan with feedback. Unfortunately the South rack serial highway problems began around 3:15. I did a few tests trying to eliminate this problem and found out that the problem does not go away after an hour with the south rack crate off, that it is not the crate controller or u-port adapter. It must be a problem with the camac crate itself, it did not occur until the crate had been on for about 6 hours, and did not go away in an hour. The plasmas were well behaved with loop voltages around 5V and the feedback system is working well, so it was a disappointment to quit early due to camac problems.

Tuesday July 15 06 08 Cates 38897-38960 RWM Smart Shell Feedback
I completed a gain scan with relative gain values of 1, .5 and .25 on current ramp plasmas with non-disruptive RWM's.
example shots:
38901 fb off
38902 fb on full gain
38934 fb 0.5 gain
38950 fb 0.25 gain
The plasmas were fairly reproducible and the feedback was working well. -Alex took Thomson scattering data - the laser fired flawlessly - the signal strengths were a little weak - which could be explained by lower density and temperature of plasma during current ramps. -Royce continued testing the triple probe circuitry and Remi tested soft x-ray tomography amplifiers. -Nicolai and Dave tested some buffer amps for getting coil current signals to the control room for use in the radial position feedback system.

Wednesday July 16 12 30 Alex Klein
Hello all: The following is a draft of the Thomson Scattering poster abstract to be submitted to APS. Any comments, suggestions, words of approval, etc. would be greatly appreciated. Thanks very much, Alex "Thomson Scattering on the HBT-EP Tokamak" A. Klein, D.A. Mauer, M.E. Mauel, G.A. Navratil, C. Cates, M. Shilov,??? Thomson Scattering can provide accurate, non-intrusive measurements of the electron density and temperature in a plasma at a spatially and temporally localized point. Thus, this diagnostic represents one of the most attractive methods for measuring essential plasma parameters. We have revived the existing Thomson Scattering system on HBT-EP and improved the resolution and calibration of the instrument. The system is based on a design in use at DIII-D (Carlstrom, et al, Rev. Sci. Instr. 61, 2858, 1990), and uses a 800 mJ pulsed Nd-YAG laser and a five channel interference filter polychromater. Absolute system calibration is achieved using Raman scattering in nitrogen (Yamada, et al, Rev. Sci. Instr. 74, 1675, 2003), because stray light levels have become excessively high and the Raman technique is more accurate than calibrartion based on Raleigh scattering alone. The scattering system is triggered at key times during the 10 msec tokamak discharge; the obtained measurements are compared with conductivity temperature data for several plasma configurations.

Wednesday July 16 06 15 Cates 38961-39009 RWM Smart Shell Feedback
In the morning I took some more feedback data with reduced feedback gain to complete yesterday's gain scan. In the afternoon I ran the feedback at full gain with only the 10 midplane coils activated. I was able to get several good shots with feedback. examples:
38987 fb on
38986 fb off
Unfortunately I lost about two hours due to yet another camac thermal problem - a crate in the west rack has a bad fan on its power supply, and the power supply would shut off every few minutes due to overheating. The crate was stable the rest of the afternoon after adding an external fan to the power supply case. Nicolai and Dave successfully tested a buffer amp to fan out the vfc and ohc signals to the control room for radial position feedback.

Sunday July 20 11 00 Shilov 39010-39133 Ext. Field
I continued with 3/1 external field experiments on "high beta" plasmas. Collected some good phase flip data on Thursday. On Friday I was struggling to get the same reproducible discharge but the plasma s were really disruptive and I couldn't sustained then for more than 4 ms. After a while I realized that the TF bank setting was changed from 6.1 to 5.7 kV some time from Thursday evening to Friday morning without indicating that in the data base. After raising it to regular value the plasmas got much better but unfortunately the south rack camac error appeared at the same time. So I had to finish the run.

Tuesday July 22 04 58 Alex Klein 39137-39195 T.S. parameter space
Rather than run Thomson scattering shots yesterday afternoon, the entire day today was used for that purpose. Yesterday, the biased probe and the internal magnetic probe were installed instead. Todays runs: D. Maurer spent a good bit of time trying to create low temp. high n plasmas, to see the T.S. signals clearly with those kinds of plasmas (Ch. 2,3,4 should vary greatly in the 1-10 eV range). A few shots appear to show low temps according to T.S. data. Fill pressure does correlate with higher n according to T.S. data. Ch. 4 gives generally very hefty signal (up to 250 mV) and correlates well with density for a range of temperatures. The afternoon was devoted to try to achieve max temp and moderate densities, to try to see a signal on channel 5, which is supposed to be sensitive to higher temperature plasmas. Unfortunately, could not see any signal in Ch. 5. Will analyze all data from today more thoroughly later.

Tuesday July 29 05 38 Maurer 39299-39333 cleanup
Cleanup shots only were taken today. As mentioned at the Monday meeting the base pressure was an order of mangitude too high after the weekend bake out and had a N2/O2 ratio characteristic of air. A blown circuit braker and bad pump on a manifold that has a high pressure leak caused the problem. The pump was replaced yesterday and the pressure came down to 1e-8Torr. The manifold that it was connected to contains the limiter piece that we had difficultly sealing after our last up-to-air. This is most likely the location of the leak although we did not leak check separate sections of the manifold to prove it. The first twenty shots taken today were cold with no sxrs and Vloop around 10V. By the end of the day I was seeing some sxrs and the loop voltage was coming back down to 7V. We probably need another morning of cleanup before we get good discharges.

Thursday July 31 04 40 stillits/shilov 39334-39362 testing of signal
The raw and semi-integrated cos1T-signals were finetuned. The signals match the signals on the HBTEP-Tree. PS. CTX has asked us to shot down their camac crate every evening.

Wednesday August 6 12 15 Shilov/S.Pauel 39377-39422 Rot. Diag/RWM The objective of the experiments was to reproduce RWM shots I use in my external field experiments running with 10%He 90%D2 so the Princeton rotation diagnostic can be used to measure ion rotation. As I pointed out before the plasmas were more disruptive compared to those with 100% D2 and it was hard to maintain q* between 2 and 3. In several discharges which parameters were close to those of target plasmas rotation diagnostic showed pretty constant ion rotation rate of 2-4 km/s. Also speculation can be made that the ion rotation is slowed down by the plasma magnetic field fluctuations. Good shot to look at are:
39413
39422
39409
Also, as S. Pauel noted, the ion rotation measurement could be affected by the plasma moving inwards, which was necessary to maintain the desired q* profile. Since the view line of the rotation diagnostic is fixed, the He rotation was measured at different plasma minor radial. On Friday 08/06 I tried reducing the He concentration from 10% to 5% by mixing gases from two bottles in the puff line. After the first attempt of mixing 100%D2 with 10%He and 90%D2. The rotation diagnostic radiation levels stayed the same. After the second attempt the levels went below the level required for rotation measurement. I assumed this technique of mixing wasn’t working properly.

Wednesday August 6 04 00 Maurer/James/Klein 39432-39442 Probes/TS
Fixed offsets on the triple probe today. Fixed cabling and setup Mach probe. Should be able to piggy back and get Mach ignals in the tree tomorrow. Bad news: TS laser alignment was bumped. The laser was realigned through the aperatures on the optical table. Thomson signal was seen with plasma shots. Data analysis underway to see how much realigned signal magnitude differs from last weeks shots.

Thursday August 7 04 02 Maurer/James/Klein none setup
No plasmas made today. Setup the capacitor bank, trigger and cabling for the bias probe. Finished setting up the Mach probe. In the process of installing the internal magnetic probe. Should have new data from all three tomorrow.

Friday August 8 05 28 Mauer/Liu/James 39447-39472 Diagnostic D. Mauer tested the Bias Probe and data was taken. R. James positioned the Mach probe in the plasma (shot 39469), but the signals were weak. We will investigate more next week to improve the signl strength. Y. Liu hooked up the Hall internal magnetic probe system. The whole system is now operational! But there are some things that need to be checked -- channel two is noisy compared to channels one and three; channel four has some problems with the amplifier.

Monday August 11 04 13 stillits/cates 39475-39483 vfc/R - signals
The VFC-signal was fine tuned. Output-signals for major radius, R, was obtained. The maximum difference in major radius from the MDS-scope and the output-signal on the scope is 3-4 mm.

Monday August 11 06 24 James/Cates 39484-39486 Triple Probe
Just a few shots taken. C. Cates gave an instructional session on how to affect changes to the plasma by adjusting various parameters. Unfortunately, we ran out of time. These 3 shots are an initial attempt to produce cold/inboard limited plasmas, ideal for testing the triple probe. We will continue to produce these cold plasmas plus hot, sparse, and dense plasmas for more testing in subsequent runs.

Friday August 15 11 52 Cates --- Power Outage
Due to the power outage yesterday the vacuum chamber went up to a maximum pressure of 2.2 mTorr. It quickly pumped down to 8e-8 Torr with the turbo pump, and is mostly water. Both cryo pumps have been regenerated and are now cooling. The ignitron cooling lines burst this morning when power was restored and flooded the basement. The water is mopped up and should be ok by Monday. The servers (cua900, beta, sherwood) are back up and running normally.

Tuesday August 19 04 36 Maurer/Rivera none none
No plasmas today. TF cooling oil system problems. The pump on the TF cooling oil turned on briefly and then tripped its 20A circuit breaker while getting ready to run. In inspecting the unit the pump motor is drawing 33A(the breaker appears OK). The starting and running capacitors both checked out OK. The bearings on the unit also seem OK. The compressor part of the unit turns on OK. The motor/pump unit does sound like its running loud compared to previous operation. We are not sure if it is the pump itself or the motor that is causing problems at this point. We will remove the motor and pump unit tomorrow and test the motor to sort out what is going on.

Wednesday August 20 10 45 M. Shilov/ S. Paul 39382-39422, 39537-39550 Princeton Rotation
Ion rotation rate in the shots similar to ‘high beta’ 3/1 shots stayed ~ 3 km/s. Natural mode rotation in these shots with 10%He is somewhat less and stays ~ 3-4 kHz whereas the mode rotation in 100% D2 shots is ~ 5-6 kHz.Also S. Paul noted that due to the plasma major radius shift by ~ 1-1.5 cm the rotation measurement could be taken for different minor radia and could not represent the plasma rotation dynamics. Good shots to look at: 39409 & 39412 & 39422 Ion rotation rate starts building up ( upto 8 ms/ in the shots with higher current ramp at ~ 4 ms when significant increase in SXR signals is observed and sawtoothing starts.Ex. Shot: #39538

Wednesday August 20 01 25 Rivera none
The motor was taken out of the TF cooling unit this morning and tested. It is broken. A new motor has been ordered ($350) and sent next day from a distribuor from NJ. If it gets shipped today we will have it Thursday, otherwise it should arrive Friday for installation. We are unable to run until this problem is fixed.

Thursday August 21 04 20 Maurer 39554-39574 clean up
The new motor for the TF chiller was installed this morning. The TF oil pump is working fine now. Clean up shots taken in the afternoon. I had about 0.25V of SXRs on the central fan array channels by the end of the run. The machine cleaned up in about 15 shots. The basement AC is broken. This caused serial highway errors at the start of the run. As a temporary fix until the AC is working, opening the basement rack door and using a fan to cool the rack got rid of the CAMAC errors. Shilov is running tomorrow.

Wednesday August 27 02 14 Maurer 39593-39621 Biased probe
Biased probe experiments were run all day Tues and Wed morning. The probe is up and running. The problems that I had last time with a fraction of the bank voltage appearing on the probe prior to gating the scr appear to be caused by leakage current through the scr itself. I removed a capacitor on the probe side of the scr that was put in place to attenuate high frequency noise on the floating potential measurement. The voltage that now appears on the probe prior to gating only charges the capacitance of the probe shaft which is small and quickly discharges through the plasma during the breakdown phase. I can run this way now, but we'll spec out a new scr for future use. The shots taken were essentially probe clean-up discharges. With V_probe=175V the probe current was maximum of about 60A and changed significantly during the shot. The probe was inserted 2cm into the plasma edge. The plasmas would typically be pushed in by the VF when the probe was pulsed on, most likely due to impurites coming off of the probe itself. I think I will probably need another 1/2 day of cleanup shots.

Wednesday August 27 07 06 Liu 39622-39649 calibrate hall probe
All channels of internal magnetic probe are currently working well. Thanks Nick! VF only shots were taken to check all the channels. From those VF only shots, it's obvious that the vacuum chamber delays the soaking through of the vertical field a lot. A few TF only shots were taken to calibrate the hall sensors and more analysis will come out later on. Plasma shots show that the hall sensor signals are pretty quiet, which are within the bit error (~1Gauss). However, I couldn't see the magnetic field fluctuation, which is about 5 Gausses seeing from SMPs.

Thursday August 28 03 06 stillits/rivera xxxx Lanl
The lanl is working ! Excellent job, Nick ! We triggered the lanl with pulses (from the dsp) of different polarities and durations, and the lanl did what it was supposed to do.

Tuesday September 2 04 48 stillits 39664-39726 Testing Lanl ouput-signal
Lanl's output-signal is on the Tree (hbtep::top.camac.north:L8210_3:input_2). We pulsed (with a square wave) the lanl by the use of the dsp. We did not get perfect, but ok, output-signals. The spikes on the scope (in the control room), however, are gone ! The maximum difference between the output-signal on the mds-scope and the scope (in the control room) is 20-30 A.

Thursday September 4 04 34 Maurer/Liu/Stillts 39746-39768 Bias probe
Ran more bias probe dischages with the probe tip inserted 4cm into the plasma and biased at 150V into electron stauration. Still cleaning up the tip during the first 10 or so shots. Later in the day I saw the first evidence of driving MHD mode rotation to zero and then in the reverse direction. This phase did not last long, maybe 1/2 to 1msec before the modes would re-accelerate in the opposite (natural rotation) direction. There appear to be amplitude effects while this occurs that can be looked at to see what the correlation is between mode rotation and mode amplitude. Facilites workmen finally stopped by and looked at the AC in the bank room. They need a part to fix the unit and said they will be back on Monday to finish the repair. Nicolai worked on radial position control signals during the run and took more shots afterward. They seem to be OK after some problems yesterday with one of the buffer amps. Yuhong also did some Hall probe shots at the end of the day to see how running more than one detector off of a single battery effects noise levels.

Thursday September 4 04 42 stillits/maurer 39726-39743 Signals. From yesterday:
We had hoped to take some open-loop shots, but we experienced some problems with the cos1T-signal. However, this problem was solved today.

Friday September 5 02 17 Maurer none
No shots today. H20 shutdown in Mudd Bldg for plumbing work. Regen'ed Ebara cryo since the compressor was turned off.

Saturday September 6 02 16 Maurer/Liu 39786-39820 Biased probe
Continued biased probe experiments from Thursday. Fixed a pretriggering problem and then slowly increased the bias probe voltage over the course of the run to V_bprobe=250V. The probe appears to be relatively clean now. I was able to reverse mode rotation from the induced Er. In some cases this did appear to effect the external mode amplitude. Hall probe data taken also.

Monday September 8 05 19 stillits/maurer 39821-39860 testing of signals
The cos1T- and Ip- channels on the diff. ampl. have been fixed and are now working. We are getting slightly better values for the major radius; the max. deviation is 3 mm (compared to the mds-scope).

Tuesday September 9 06 25 pedersen/stillits 39861-39884 open- and closed-loop tests
Open-loop tests (39862-39868) were conducted with success. Moreover, closed-loop tests (39883-39884) were conducted. The desired position was R = 93 cm. The lanl was triggered after 1.4 ms, and the closed-loop algorithm gave the correct lanl-current. In both closed-loop runs the plasma moved in to R = 93 cm after 2ms before it moved out to R ~ 93.5 cm. So, fine-tuning of the feedback coefficients needs to be conducted to improve the feedback system.

Wednesday September 10 06 34 Maurer/Pedersen/Stillits 39885-39951 Biased probe/VFFB
Plasmas were ran today for closed loop VFFB tests and biased probe rotation experiments. The biased probe voltage was systematically scanned from 100V up to 400V in a series of current ramp discharges that caused the q=3 surface to go external at about 2ms. The induced rotation appears to stabilize the m=3 mode as it goes out into the vacuum. More data analysis needed though. Also, in monitoring the triple probe density signal there was a systematic density increase with increasing applied bias voltage from 100V to 250V on the probe. Unfortunantly the triple probe stopped working during the run, most likely due to a blown chip, so I was not able to see the increase up to the 400V level. The probe current appears to saturate somewhat once the voltage is up past 150V at 50 to 60A. Tomorrow I will run plasmas with 10% He and the Doppler rotation diagnostic. We made several closed-loop runs today (39891-39906) with different desired positions of the major radius (91, 92, and 93 cm). Some runs were more successfull than others. The biggest problem with the closed-loop runs seems to be the spikes in the dsp-calculation of the major radius, but we have fixed that by using an interpolation of the major radius. Moreover, we also experienced problems with triggering of the DSP; that also needs to be fixed. We will continue the closed-loop runs tomorrow.

Thursday September 11 05 37 Maurer 39952-39991 Biased probe RWM expts
Discharges were made today in 10% He 90% D2 to study the effects of biased probe driven ExB rotation on m=3 RWMs. I setup a control shot similar to Shilov's with an initial edge q of about 2.7 slowly moving inward in major radius. The edge q would go through the 3 surface at about 3ms. This gave me a burst of m=3 RWM that lasted from 2 to 3ms of typically 3G max amplitude and frequency around 2 to 5kHz. To try and keep the RWM stability evolution due to the evolving current profile the same on a shot to shot basis I kept the start up bank settings the same and varied the OHEL a little on a shot to shot basis to always keep the q=3 surface entering the plasma edge at 3ms. I gated the Bprobe on at different times during the wall mode burst with 100V or 200V on the tip. At the lower voltage I was able to torque the RWM frequency to zero and then down to -5 or sometimes -10kHz. The mode was still present at these rotation speeds. There were periods where the RWM amplitude appears modulated and correlated with frequency modulations as the mode rotation changed due to the probe. The most interesting effects were observed at 200V on the tip. Gating the probe on at 1.5ms just prior to the usual onset of the RWM at 2ms spins the plasma enough to essentially suppress the RWM. What MHD is there before the probe is turned on (start up modes/noise) appear to rotate up -20kHz or so. More data analysis needed. To see this effect look at shots 39986 or 39987. A control shot is 39971 to see the typical RWM burst with no probe voltage. Unfortunantly, the Bprobe had some arcing problems at 200V that I don't understand, so I don't have too many shots like these yet. There also was a systematic change at 200V on the rotation diagnostic (although somewhat small maybe?). I will continue the run tomorrow once I cure the arcing problem.

Monday September 15 04 16 Maurer 39998-4007
Attempted to fix the bias probe by conditioning the tip with 1.5KV at 5mA power supply. The probe tip to ground resistance was 85kOhms before conditioning. After high-potting, the resistance to ground was about 5MOhms measured using the 500V meter. Vacuum shots with the probe tip at 350V had the correct RC decay. Plasma shots with the probe tip inserted 4cm into the plasma with 200V on the tip are still arcing unfortunantly. I will take the probe out tommorrow morning. Good news: Triple probe electronics were re-installed and are up and running. Royce also finished bench tests of the differential amp for the Mach probe. We should be able to install it tomorrow. Nicolai re-intalled his differential amp and tested out his signals. Everything is OK.

Tuesday September 16 05 38 stillits/maurer 40008-40030 testing of signals
Biased probe removed this morning. Arcing damage was found from the copper conductor to the stainless steel housing back by the mounting conflate flange. There did not appear to be substantial arcing or tracking on the Alumina itself from the Moly electrode. The probe is already under repair. We are shooting to have it fixed and re-installed by Friday. The Hall probe saw its first kink mode fluctuations! The signals were tested and are now working. Moreover, the new interpolated major radius calculation is also working (max. deviation is 1-2 mm) and without any significiant spikes.

Wednesday September 17 05 38 stillits 40031-40066 Testing of algoritm
I spent most of the day eliminating bugs in the feedback program. They were found and eliminated, and we got very nice and smooth output signals for the major radius. However, the output signal for the plasma velocity is not smooth enough, but that will be fixed tomorrow.

Thursday September 18 06 50 stillits 40067-40090 Testing algoritm
The new feedback algoritm with the velocity term added is working. The major radius has a max. deviation of 2-3 mm, and the calculated plasma velocity is close to the velocity in the scope. Thus, we should be ready to make the first closed-loop run tomorrow morning.

Friday September 19 05 18 stillits 40091-40114 cloased-loop runs and testing
40091-40108: testing of feedback algorithm with derivative gain. closed-loop runs: 40109-40110, we tried to stabilize the plasma at R=93 cm. It was partly successfull. 40111-40114 (except 40112, the dsp was not triggered), the desired position was R=92 cm (40111 is awesome !). In these shots there are small deviations in the actual position, but they are only of a few milimeters. In future runs we will let the lanl be switched on for more than 3 msec because 3 msec is too short, as can be seen in some of the runs.

Monday September 22 06 45 stillits 40123-40146 cloased-loop runs and testing
Today, the lanl was turned on for 6ms (earlier it was 3 ms). Moreover, in all shots the desired major radius was R=93 cm. We were able to stabilize the plasma at ~ 93 cm for almost 7 ms (shot number 40134). So, the lanl is working for 6ms. We are experiencing problems shutting off the lanl when cos1T reaches a certain value. That needs to be fixed. Corey fixed the major radius so that the major radius, which influences q and beta, is automatically recalibrated.

Tuesday September 23 06 36 Liu/Stillits 40147-40202 Feedback + Hall probe
We ran the feedback for R=93 cm (40147-40154), R=92 cm (40155-40165), and R=94 cm (40166-40178). Moreover, the duration of how long the lanl is switched on was increased from 6ms to 9 ms (from shot 40169). Because of that we were able to repeatedly create plasma of 7-8ms duration. However, the shots for R=94 cm are little too volatile, but that can be adjusted by lowering VF (the lanl was not triggered in shot 40170 and 40173). (Stillits) Hall probe was checked for its low measurements on poloidal field. The reason is supposed to be the influence of the high toroidal field. I am trying to figure out if I can fix this problem. (Liu)

Wednesday September 24 05 21 stillits 40203-40229 feedback
Channel 2 (the Ip-signal) on the diff. ampl. was down today. So, shots 40203-40217 are useless. In shots 40218-40222 we tried to stabilize the plasma at R=94 cm, and in 40222 we created a hot plasma that lasted for ~ 8.5 ms. In the rest of the shots we tried R=91 cm, but it was not a huge success. We were able to stabilize the plasma at R=91 cm for max. 1.5 ms (40223 and 40226). But it can probably be improved by changing some of the parameters.

Tuesday September 30 04 51 stillits 40285-40287 testing signals
We tested the Ip-signal (ch. 2). We are getting a signal now, but the signal looks like a ground-loop signal.

Wednesday October 1 05 13 Mauer/James 40288 - 40305 ICRH/Bias Probe
ICRH fired successfully today! We are still waiting for another crate power supply from Princeton or to receive one being repaired to get comprehensive data, but we did see the ICRH fire via an oscilloscope. We also saw pickups on the mach probe from ICRH which fires at about .002 sec. It looks like one of the channels is OOC on the Mach probe again so I am going to trouble shoot it tomorrow [James]. The bias probe is up and running again(only tested at low voltage yet). I had some problems with triggering that are fixed now at the start of the run. The SCR does appear to be going bad that is used to switch the bank voltage on to the probe tip. I was getting about 10V leakage on the tip prior to pulsing it with only 50V total on the bank. Probe cleanup shots tomorrow.

Thursday October 2 05 22 Maurer biased probe
Took biased probe cleanup shots today. The run was cut short because of problems with the TF bank. An eyebolt nut came loose and caused the one side of the rope dump to short the bank while it was being charged (the bank was at about 5kV). This boiled the local dump water resistor and blew its top off. The cupper sulfate H20 blown out of the first dump resistor appears to have then allowed a conductive path from the neighboring dump resistor, which was at whatever residual voltage was left on the bank, and then shorted the rest of the TF charge to ground burning an arc path in the wood shelf that the dump resistors sit on. The H20 has been cleaned up. We still need to cut out the carbonized material on the wooden shelf before we run again. This should be finished tomorrow morning.

Friday October 3 06 07 Maurer/James/Klein 40319 - 40350 Bias probe/ICRH
Tf repair was completed this morning(Nick and Jim). The bank was brought up to full voltage before lunch and tested OK. Plasmas were made in the afternoon and more biased probe clean-up shots taken. The probe tip was biased to 200V by the end of the day. It appears to still be a little dirty. More clean-up tomorrow at higher voltage. The power supply for the ICRH crate was installed and is a permanent member of the serial highway! Took a few shots and worked out some triggering bugs. Now, the signals are in the tree and showing up on the scope but some of the inputs look switched (will diagnose this weekend). The Mach Probe is also installed and the digitizer for one of the channels is the problem and not the electronics; it will be switched to another open channel.[James]

Saturday October 4 01 45 Maurer 40352-40382 biased probe
Continued taking biased probe cleanup shots today. V_probe= 300V with I_probe=30 to 50A. Nothing exciting to report.

Tuesday October 7 05 34 Maurer/Stillits 40383-40422 Biased probe/VFFB
More bias probe clean-up shots and work on the VFFB signal problem today. First hints of a temperature increase on the triple probe were seen in some shots today. Not as dramatic as previously observed but an improvement from Saturdays run. Typical currents with 300V on the probe are about 50A. The probe appears to be clean enough to apply 100 to maybe 200V on the tip without disrupting the plasma. shots taken with 300Vs still cause the plasma to move in and disrupt, probably due to impurity influx. Hopefully the 200V case will be a useful ICRH target for tomorrows run. The feedback system is up and running. Nick solved the problem we have had with ch. 2 on the dsp.

Wednesday October 8 06 36 Mauer/James/Stillits 40423-40461 ICRH/Feedback
It took about half he day to with the scope and signal generator to put the ICRH system back together again. Once that was figured out, we took a few shots before Shilov’s Invited talk dry run. We were unable to perform the ”high density inboard limited” plasmas with the working ICRF because of time restraints, but we were able to get some good baseline ICRF data while tuning the feedback system. If there is time, tomorrow afternoon we will try again with the bias probe (to get high density plasmas). Subsequently, the feedback system has been fixed and all channels are operating normally. The feedback system (and most of the other diagnostics) was greatly affected by the ICRH discharge. Some sort of filter or shielding will have to be explored now that we are actively trying to couple the plasma.[James]

Monday October 13 05 22 James/Stillits 40557 - 40590 Testing (Triple Probe/Feedback)
Shots 40557-40579 Feedback shots to calibrate system with newly installed filters. ICRH Will fire tomorrow to test filters. [Stillits] Shots 405780-40590 Tested the triple probe and mach probe electronics and they are working at spec. on the bench. When installed in the rack, density signal (triple probe) is still erratic and the right channel (mach probe) is flat/no signal. Concentrating on the triple probe (for the ICRH run on wed. and thurs.), I tested the cabling from the probe to the electronics with the high voltage meter and they were good. Next I bypassed the t-probe electronics and used the m-probe’s power supply, rogowski coils, and electronics/o-scope to test the raw t-probe signals. After 10 shots, the probe appears to be working normally, but more testing tomorrow so we hope to lock in a solution. Alex was able to prep Thompson Scattering and get signals into the o-scope. It is ready to go for tomorrows Testing. Thanks to Yuhong for hanging around and babysitting the new plasma shooters! [James]

Tuesday October 14 05 35 Klein/Stillits 40610-40630 Thomson Scattering The plan was to create very hot plasmas which tend to be outboard limited, then use position control to (rapidly) push the plasma inwards into the field of view of the TS collection optics. In preparation yesterday, I (Klein) crudely aligned the laser. Should have done this more critically. Today: Very healthy signals on all channels, including #5, which is supposed to come in to play for hot plasmas, was very encouraging. These signals were present for warm plasmas at r = >94 cm, surprising. Then we made hotter plasmas and pushed them inboards, as planned. Timed TS to coincide with r= 92 cm position. Signals looked the same. Finally, TS was fired after plasmas had long died: signals looked the same. Conclusion: laser beam is poorly aligned, scraping some edge or surface, overwhelming stray light is creeping into each channel. Will re-align laser and try again...

Tuesday October 14 05 50 stillits/klein/james 40592-40649 testing of signal + TS + IRCH
The feedback system is up and running again with the new filters installed. The max. deviation is only a few millimeters. That is also the case when ICRH is turned on. The problem we had getting the lanl to give a zero current when the semi-integrated signal for cos1T is less than zero has been fixed. So, we should be able to run the ICRH with feedback tomorrow.

Wednesday October 15 05 27 stillits/james 40652-40667 feedback + ICRH
40652-40655: The signals were tested with IRCH on.
40657-40669: The feedback was turned on and the plasma was positioned at 92cm.
40660-40662: The feedback was turned on and the plasma was positioned at 91.5cm.
40663: The feedback was turned on and the plasma was positioned at 92 cm. The IRCH was turned on at 2ms.
40663: The feedback was turned on and the plasma was positioned at 91.5 cm. The IRCH was turned on at 2ms.
Rough day at the shop for the triple probe. I was unable to diagnose the problem with the density channel. After making some repairs to the electronics and installing protection, the output was not correct. I was also unable to get the third channel to trigger on the scope and ran out of time before I could try the others. I will try those early tomorrow and if I can’t get the probe to function as a triple probe, then I will run it as an Isat probe or use the mach probe electronics and use it as a double probe for ICRF testing with the Feedback system. [James]

Friday October 17 09 24 Pedersen/Stillits/James 40680-40733 ICRH
Today's objective was to do plasma-RF antenna coupling experiments using the radial feedback system to move the plasmas inboard in a controlled way, and the triple probe to confirm increased densities. Although we did not observe any clear signs of heating, we did see some antenna loading, so the run was successful overall. Transient loading of the ICRF antenna was clearly observed on a number of shots, including on the order of 10 shots where the loading was clearly observed before the plasma disrupted (eg. 40692). Towards the end of the run day, a decent target discharge for further studies was developed. Shots 40720 and 40723 are good examples of this discharge without ICRH. The radial feedback was preprogrammed to move the plasma from outboard limited to inboard limited for 1 msec, then back to being outboard limited. Ion saturation current from the inboard side triple probe (the box is still bad, hence no real density measurement) would increase by 30-80% during these jogs. On a number of shots we hit the plasma with ICRF during this phase. Most of these shots disrupted but a few survived (40728 and 29). These two plasmas were apparently not pushed far enough inboard to couple to the antenna. We will want to continue development of these discharges next week, hopefully with the Bdot probe and the triple probe box up and running.

Monday October 20 07 55 James 40734 - 40749 ICRH-RF Pickup Probe Ran ICRF this afternoon to prepare for tomorrows run. I first used the o-scope to insure that the probe and transmission lines were operational. They did in fact produce a signal, though it seemed a little askew. I then tested multiple digitizers until I was able to get a signal. Finally I was able to reproduce a signal in the tree that resembled the signal in the scope, but not the typical RF B probe in absences of plasma; see shot #40749 (atypical) and compare to #36547 (typical). Also notice that the loop voltages are very different in these two shots, but I am not sure it could cause such a drastic difference in the RF B probe signal. In the morning I will run with a plasma and the ICRF and diagnose the problem if indeed there is one.

Monday October 20 10 32 Nick None Since no runs were scheduled at this morning's meeting we, the technical staff, used the time to modify the ICRH cabinet. The ICRH should not be run until I have time to inspect the cabinet for run readiness!!!

Tuesday November 11 04 31 pedersen/stillits 40751-40758 ICRH + feedback
We did not make any plasmas today because of problems with some of the U-port adapters.

Wednesday November 12 05 38 pedersen/stillits 40760-40802 ICRH + feedback. We tried to create reproducible plasmas that behaved like preprogrammed in feedback:
1.8msec - 2.8msec: R = 93 cm
2.8msec - 3.8msec: R = 91.5 cm
3.8msec - disruption: R = 93 cm
At the end (shot#: 40795-40802), we were finally able to create reproducible plasmas that behaved as preprogrammed in feedback. The ICRH was turned on in shot# 40796, 40798, 40800, and 40802, but turned off in shot# 40795, 40797, 40799, 40801. However, we did not see any heating of the plasma that could be a consequence of ICRH. Next ime we will try to push the plasma farther inboard (to R ~ 90-91 cm).

Thursday November 13 05 23 pedersen/stillits 40803-40836 ICRH/radial feedback
We continued developing discharges for ICRH coupling using the radial position control system. The ICRH rack appears to give serial highway problems so it was bypassed. We (Corey+Dave) suspect the power supply is faulty. The rack was bypassed, so no antenna loading measurements today. On the positive side, the triple probe box works fine, and did so all day yesterday as well, except for some minor offsets on the temperature. Using the triple probe inboard density measurement, we developed discharges that have 3.5-5*10^18 m^-3 density for about 1 msec as the plasma is shoved inboard by the radial control system (used in both closed loop and open loop feedback today). This is a factor of 2 improvement over typical inboard densities (2*10^18), and is close to inboard densities seen during inward disruptions (5 to 8*10^18). The ICRH was pulsed during some of these discharges. No clear effects of heating but we are somewhat limited by several diagnostics being offline (ICRH diagnostics were out due to CAMAC problems and the soft x-rays appear not to be working). Further discharge development will be done when we have ICRH diagnostics available to confirm loading and coupling.

Friday November 14 04 10 stillits 40837-40877 ICRH + feedback
Shot# 40837-40867: We tried to creaty discharges (with 20% H2) with and without ICRH. We were able to obtain inboard edge densities around ~ 5e18 m^-3 (shot# 40863, ICRH turned on at 3.5 msec), and we presumably saw an increase in temperature in shot# 40855 (ICRH turned on at 3ms). Shot# 40868-40877 (Steve):
We tried with He 10% to create discharges that stayed at R = 92 cm for a considerable time. In the last shot we succeed in doing that.

Friday November 21 02 51 steve paul/stillits 40868-40922 rotation + feedback.

Friday December 5 07 37 Rivera/James/Mauer 40923 - 40937 ICRH
We tested the voltage dividers on the ICRF today via the oscilloscope and they performed as expected! Data from the run with voltage and current measurements is being analyzed. We are in the process of setting up the digitizer to make the dividers a permanent diagnostic measurement for the ICRH system. The CAMAC crate and power supply we ordered came in about mid-day and was immediately tested and installed. Preliminary tests show that it is operating normally. Shot # 40936 shows an ICRF only shot through the tree. The B-dot probe is not set up correctly, but the others are performing normally. Soon after this shot, we had some trouble with the dumps not responding to the reset controls in the control room. This problem fixed itself, but we are not sure of the cause or the fix. The air conditioners in the basement also froze causing the CAMAC racks to fail. We shut down in effort to let them cool off with external fans, but they were still over heated by the end of the day. Nick is working on the air conditioner repair, but until that is complete, we may have to revert back to shutting down during lunch and any other periods of extended down time between shots.

Friday December 5 12 24 STILLITS 40939-40941 testing software
Thanks to Mikhail, the software for the feedback system is now up and running. John (study group) put the feedback current cable in the ceiling, and it is working.

Monday December 8 06 27 Maurer/Stillits/James 40949-40967 A little bit of everything
CAMAC problems from last week caused by ICRH rack, possibly due to the fiber optic cable to the u-port adapter. Everything is working OK now. Worked on circiuitry for capacitive dividers for ICRH. (James) Shots taken to check out new control panel operation of radial position feedback setup writing text file to dsp, recompiling the program, and initializing the dsp fro an external trigger. So far so good! (Stillits) Turned up gains for new RWM feedback. Checking out sensor and control coil signals. Real feedback on current ramps tomorrow. (Maurer) S. Paul called and is planning on coming up Friday.

Tuesday December 9 05 15 Maurer/Stillits 40968-41007 testing feedback and software.
Checking, correcting and figuring out some errors in the RWM feedback wiring. Nothing important to discuss yet. (Maurer) The software for the radial position feedback control system is up and running. The feedback system was successfully tested with new software and the new feedback-current cable. So, the feedback system is now operational!!! (Stillits)

Thursday December 11 10 33 Maurer 41007-41021 RWM feedback
Yesterdays run was cut short due to the same intermittent bank problem we had last week. The cap bank dumps were not reseting properly from the panic panel. Nick and I went to work on it this morning but the dumps worked fine. Again, the problem "fixed" itself. So we will have to wait until it breaks again(and stays broken long enough that we can diagnosis whats going on). When problems are about to occur the bias bank dump fails first. If you are taking shots the signature of this to look for is the OH bias bank controller not reaching full charge while the rest of the banks do(red light never goes on). The next time the dump button is hit on the panic panel the dumps will not reset. If this happens let Nick and I know so we can fix try and diagnosis whats going on.

Thursday December 11 12 01
Today at 1pm, I'll show how to use the feedback system. Nicolai

Thursday December 11 03 59 james/pedersen/stillits 41025-41036 ICRH + feedback
We tried to create a discharge that behaved as a square-wave with respect to major radius. We succeeded in doing that when we got problems with the ICRH. The charging power supply in the basement is down.

Monday December 15 06 12 James 41069 - 41099 ICRF
It was slow running today. The CAMAC Serial Highway was down most of the morning and half the afternoon. Apparently there were some access violations that fixed themselves after Cory rebooted the system as the administrator. Some good news, the circuit breaker seems to be holding on between shots. Had trouble with the B-probe as well. The L_8210 did not seem to be working. I replaced it with another and tested it with an fxn generator. Then tested again with new digitizer and both rectified and un-rectified signals. Neither signal was seen via the digitizer or the scope (turns out that the new L_8210 is not 1 mega-ohm, and a new 1mega-ohm will have to be found and installed, but the scope was set for 1 mega-ohm and it did not see a signal). I tested the resistance of the lead wire form the probe coil in the machine to the ICRH crate and there was none. There may be a problem with the wire, connections or the probe itself. I did just get signals from this probe after APS, so the failure is even more peculiar and recent. I checked the connector, and it was tightly fixed so I will have to ‘probe’ deeper to find the solution. I was unable to test the capacitive dividers at high voltage, but further analysis of the low voltage tests performed earlier last week show the frequency to be ~4.505 MHz.

Tuesday December 16 07 01 D. Maurer/S. Paul 41100-41174 bias probe with radial control
We were looking for fluid rotation effects with the bias probe turned on. Typical example without probe is 41124, where the natural rotation is about 5 km/sec in the ion drift direction (toroidally clockwise, when viewed from above HBTEP). Edge MHD measured by the shell probe increases from 5.2 msec onward on that shot, and the mode growth is coincident with the braking of the plasma. The plasma rotation slows to near zero by 5.9 msec, at which time the plasma disrupts. For the most part, the probe seemed to make the plasma cold and difficult to control. Perhaps the reason is lack of conditioning as the probe was last used some time before the APS meeting. The best example of the bias probe's effect the rotation is 41145, where the ion flow was reversed, however that does not occur often. Shot 41142 had the bias probe turned on, yet the results were very similar to shot 41124, as described above. The best correlate with high rotation appears to be a strong SXR signal. A good example is 41109 and 41127, where the edge rotation jumps following each sawtooth crash.

2004

Friday January 9 03 42 Alex Klein n.a. TS calibration
Filled chamber with nitrogen and performed Raman type Thomson Scattering system calibration. Laser was stil aligned through the chamber, needed no adjustment, near perfect burn spot on inboard side. Laser energy still 800 mJ. Inspected optics, all clean and good. Collection lens was aligned carefully. Took 5 shots at each pressure (from 150 to 5 Torr), swapped Ch. 3 and Ch. 5 electronics to calibrate Ch. 5 and repeated. Data was saved in spreadsheet form for more precise analysis. Now will have to calculate gain coefficients for each channel. Water contamination appears to be minimal (RGA says 10^-7 Torr, mostly nitrogen, after 1 hour pump down).

Wednesday January 14 04 06 Maurer 41175-41205 Clean-up
Clean-up shots taken after up to N2 for TS realignment and calibration. Plasmas lasting 5 to 6 msec by the end of the day. SXRs visible after only 10 shots or so. Will continue tomorrow.

Tuesday January 20 06 31 T. Pedersen, R.James, N. Stillits 41242 - 41257 ICRF
We were able to run ICRF (with no B probe) today. We took about 15 shots with the Feedback system on. We did see some signs of loading (comparing shots 41249 vacuum shot to 41256), but were again stopped short by what seems to be more CAMAC problems. This time in the VF current, and it seems to be intermittent. We will look into it more tomorrow. We are planning to try again on next Tuesday. It seems like we are on the right track with the high density plasmas moved into the antenna with the feedback system approach.

Monday January 26 04 16 Maurer 41258-41279 feedback
Took several VF only shots to start the day and check out the VF bank current monitor problems from last week. The digitizer/circuitry behaved correctly the whole run day. I will keep an eye on it this week to see if the problem re-occurs.
The rest of the day was spent taking set-up shots for the weeks feedback runs. I am starting to see some nice m=3 fluctuations as the edge q drops below 3. These are in shots that start with an initially low plasma current, have a rapid Ip ramp and send the q=3 surface into the vacuum anywhere from 2 to 4ms depending upon the bank voltages. I had some difficulty keeping the plasma centered and this would lead to some shot-to-shot variability. I plan to run tomorrow with the radial position control from the start to help keep the major radius from moving out and forcing the edge q too low. Todays run is cut short because I have to go in for my allergy shots at 5pm. I will continue tomorrow.

Tuesday February 17 07 49 Maurer 41477-41506 MC feedback
Todays run goal was to continue the feedback experiments of a week ago using the new mode control coil set with poloidal field sensors. I had some difficulty during the whole run generating target RWMs to feedback on. Started to see small RWM fluctuations near the end of the day. Also had some difficulty breaking down late in the day. The D2 bottle is nearly empty (has been low for awhile) and I plan on changing it before tomorrows run. This might have lead to some of the problems getting a nice fluctuation to feedback on relative to last week where I was adjusted the puff time to change the RWM onset time with qstar. The feedback was turned on during a few shots to check the loop. Things seem to be OK. I will continue again tomorrow.

Wednesday February 18 05 28 Maurer 41507-41531 Feedback
Spent the day trying to setup plasmas for feedback. Still had problems with the breakdown off and on again. Changing the D2 bottle had small effect on the breakdown problems. As an aside the D2 manifold is showing its age. It has to be maxed out to just barely get the fill line pressure above 20 psig(where we usually run). This was one of the reasons I though the bottle was low and the high pressure side gauge might have been reading incorrectly. I now think think the high pressure gauge is OK. Also checked the puff fill pressure and it seemed reasonable at 2.4 e-5 for 1.5ms puff with the puff battery voltage at 223V (the input circuitry for the puffline says it needs 220V). Checked the egun and its working OK with 9A of filament current and 220V bias. Later in the day I replaced the puff line battery with a new one (246V) and the breakdown became more consistent. I was able to get the puff time back down to 1ms and still had it breakdown. It looks like the battery was marginal and giving rise to most of the problems breaking down. Not much progress in setting up target plasmas as a result. More tomorrow.

Thursday February 19 05 55 Maurer 41533-41557 Discharge development
Spent the day trying to develop an Ip ramp down case with nice m=3 RWM fluctuations for feedback. Had no breakdown problems today. Discharges exhibited lots of tearing activity with minor or major disruptions before the q=3 surface went external. Some signs of RWMs but nothing as nice as the target plasma fluctuations of last weeks runs. The change in puff valve pulser battery has changed the machine fill pressure for a given puff valve pulse time. I am adjusting for this to effect to try an reproduce the previous runs RWMs with essentially the same bank settings. It hasn't quite worked out yet. I will continue tommorrow.

Friday February 20 05 17 Maurer
No shots taken today. Planning on Saturday feedback run.

Saturday February 21 12 58 Maurer none none
Came in this morning to run and found the base pressure at 5.5e-5Torr and the Ebara cryo head at 268K. The CTI cryo was still pumping, but the head temp was at 15K(a little warm, should less than 10K). After valving off the Ebara the pressure came down to 3e-7Torr and was composed mostly of water on the RGA readout. I spun up the turbo and switched over to it so I could regen the CTI cryo. The base pressure went up slightly to 5.3e-7Torr. I am currently pumping on the CTI head. I have also pumped out the Ebara cryo head. I turned on the bake to help get rid of the water. The base pressure is now in the low 1e-6 range with the turbo only. I am not sure what happened to the Ebara cryo. After inspecting the compressor it appears to have blown one phase of its 220V, 3phase pwr. I found the cable plug had a blackened pwr pin on it. The circuit breaker appears not to have blown which I find confusing. Hopefully the compressor is not damaged. I will stay until the CTI head has been pumped on fully and turned back on to cool down. This takes 2 to 3 hours to reach final temperature. If someone who lives nearby wants to stop in at 5 or 6PM and switch over pumping to the CTI cryo once it is cold let me know. Otherwise I'll stop in Sunday and do it.

Sunday February 22 03 55 pedersen
I switched over from the turbo to the CTI cryo at ~3:30pm today (Sunday). Pressure was 2.7e-7 before the switchover and started dropping at a good rate when the gate valve was opened to the cryo. It is currently 9.7e-8 and continues to drop.

Monday February 23 03 53 Maurer None
Opened up the Hall probe array bellows to the vacuum chamber after the group meeting. The pressure went up to a few 1e-7 composed mostly of water. Kept the bake on until midafternoon. The base pressure is now in the low 1e-8 range. Nick is currently inspecting the compressor to make sure it has failed. We will try hooking it back up to pwr tomorrow when new plug ends arrive from McMaster. There was no obvious damage inside the compressor housing. Maybe it was just the plug ends that failed. We have a quotation for an advanced exchange with a 2 day turn-around time (they have a matching compressor in stock) from Genesis Vac Tech if it turns out the compressor is bad. The price is $3950. I did not get a chance to take any cleanup shots today. I plan on starting tomorrow morning. After about ten shots or so if the machine still looks dirty I will glow in He. Also, Yuhong is ready to piggy-back and test the four Hall probe channels that she has installed.

Tuesday February 24 04 19 Liu 41560-41573 test Hall array
There were just two shots were caught in today's run and the rest of the day we experienced serial highway failure. Mikhail tried to bypass CTX and ICRH, but it didn't work out. The Hall array was working except they were more noisy than the old array. More shots need to run to analyze the reason.

Wednesday February 25 06 01 Maurer/Liu 41578-41639 Clean-up shots
Took clean-up shots today. Started to see sxrs and tiny sawteeth by the end of the day. The Ebara compressor is OK. The cable end only was damaged in the weekend failure. This is very good news. It has been re-installed and was opened during the last 1/3 of todays run. This helped quite a bit in pumping out stuff knocked off the walls. I had to raise the puff because I had trouble initially breaking down with both cryos pumping. It was after this that I was able to get some sxr signals on the fan array. Yuhong ran piggy back and worked on her Hall sensor signals. The noise problem of the Hall sensors comes from the power of the amplifier. When I used a battery, one of which were used for Hall sensor current source, together with a car battery powered the amplifier, the annoying random noise was gone. Also, G=10/100 were tested for vacuum shots and both worked fine. I will monitor the Hall sensor's behavior when Dave runs tomorrow.

Thursday February 26 05 20 Maurer 41640-41682 Clean-up shots
Took more clean-up shots today. By the end of the day things were looking good enough that I was starting to develop a target plasma for feedback. Vloop was less than 10V at plasma start-up evolving down to 5 or 6V at discharge termination compared to greater than 12V yesterday during most of the run. I am switching to the shot type with a RWM generated by the initial qstar less than 3 and slowly evolving up to 3 (similar to shilov's case) that I used for RWM bias probe experiments this fall. This would typically give a burst of m=3 magnetic fluctuations between 2 to 3 ms. Yuhong also worked on her Hall probe sensor signals. There appears to be high frequency noise on the signals at discharge start-up and termination that might require filtering.

Friday February 27 05 16 Maurer 41683-41691
Only a few shots taken today. Tested out the Hall sensor array. The problems with noise are a result of layout and cabling problems. This is good news in that an input filter will not be needed. The actual layout of the 20 channel array will have to be done very carefully.

Monday March 1 04 12 Maurer 41692-41732 target plasma development
Spent the day trying to generate m/n=3/1 RWM fluctuations. Tried dialing in old shot number bank settings that Shilov used as a target shot. Plasmas generated this way were different from the database case, with typically higher loop voltage and different major radial and qstar evolution. The wall-limiter conditioning must still be not quite up to what we need to generate these plasmas. Spent the rest of the day trying to develop a case with the initial qstar at about 2.7 after discharge start-up evolving toward qstar of 3 by 2 to 3ms into the shot. This would traditionally have a RWM fluctuation from 2 to 2.5ms and a few Gauss amplitude in the past. Was somewhat successful at this but the plasmas did not have a good m=3 fluctuation to feedback on perhaps due to profile effects. I will continue tomorrow and turn the feedback on even if I don't have a mode just to check things out. I am out early today to go and get my allergy shots.

Tuesday March 2 07 15 Maurer 41733-41780 Setting up target
Took more shots today trying to develop target for RWM feedback experiments. I had one clear example of an m/n=3/1 RWM on shot 41744. This can be seen on the smps and ssi Br sensors just around 3ms. I took this shot after the machine sat for 1 hr, so the prior shots residual gas was well pumped away. I was unable to reproduce this plasma by lowering the puff (so far at least). Comments and suggestions welcome. Also, the Ebara cryo head has recently started to make pinging noises most likely due to the seals starting to go bad in the head. It was rebuilt last June so I hope it is under warranty.

Wednesday March 3 05 17 Maurer 41781-41792 target development
Working on target plasmas (still). Trying to adjust puff time and bank settings to generate RWM fluctuation burst as qstart approaches 3. More work to be done tomorrow. Both beta and sherwood had to be restarted this afternoon. I hope this did not disturb peoples work too much. Nick has contacted the company who rebuilt the Ebara cryo head this summer about warranty coverage. Hopefully we'll know by tomorrow or the end of the week what the situation is. As it stands now the head is holding its 8 K temperature. There has been to signs of temperature cycling yet.

Thursday March 4 05 31 Maurer 41781-41826 target development
More of the same. Another day of trying to get a good RWM for feedback studies. I am contemplating going back to the ramp down case. Comments.

Sunday March 7 10 47 Maurer 41728-41778 target development
Took more shots Saturday. After trying to develop target discharges, I switched to a high Ohmic input plasma to generate sxrs and cleanup the limiters and walls.

Tuesday March 9 07 13 Maurer 41881-41891 clean-up
Had a short clean-up run only today. I will try the RWM case tomorrow. In other news the Ebara cryo head has stopped squeaking for at least the last two days (maybe Sunday too). Maybe it will last longer than was first thought after all. I will keep a close watch on it. The FPGA arrived yesterday. Alex is sorting out some software driver issues with NI. The leaking pipe in the bank room is sceduled to be fixed tomorrow morning. The run will commence after that is finished.

Wednesday March 10 05 29 Maurer 41892-41942 Clean Up/Target development
Took 30 clean up shots to start the day. Then switched to target development shots. Started to see a choppy burst of MHD fluctuations as q_star was approaching and going though 3 from below. The fluctuations were of lower frequency than the background MHD nosie. Reproducibility was better than during the last weeks, but still not too robust. These are the first encouraging results in about two weeks! Here's looking forward to tomorrow.

Thursday March 11 12 40 stillits 41953-41960 Testing RPFB
The RPFB is up and running again. Moreover, we have modified the control panel application.

Thursday March 11 04 36 stillits none Modification of Control panel application.
- the control panel application has been modified to use triangles instead of square-wave as input for RPFB.

Monday March 15 06 12 stillits 41962-42017 feedback
Feedback on major radius (with the new application) is now working. Feedback on q* seems to be working, but some more finetuning needs to be done.

Friday March 19 10 11 Maurer 42018-42027
Yesterdays run was cut short by a problem with the TF charging resistor. There was some arcing from the top of the resistor to the water column. The top electrode had broken off from the charging supply lead during the run. A new electode is being manufactured and will be installed asap.

Monday March 22 05 26 stillits 42069-42124 q*-feedback
We tried to perform feedback on q*. The algorithm does the right things, but there are some minor problems with the gains, which need to be finetuned. We'll work on that tomorrow.

Tuesday March 23 04 35 stillits 42125-42154 q*-feedback
We were able to get the feedback on q* up and running today. There are, however, some "small" deviations between q* in the scope and q* we calculate. The max. deviations in q* are approximately 0.2-0.3 and in some cases 0.4. The reason for this is the small value of the minor radius a squared (a^2 ~ q*), which will change q* by 5-10% when the major radius in the scope deviates by, for example, 4 mm compared to the major radius we calculate. When we take into account these deviations, we can still get very nice feedback values on q*:
Shot #42137-42146: We tried to put the plasma at q*=3.5. After having chosen the suitable parameters (which only took a few shots), we were able to get some nice shots #42141 and #42142 (and also #42143).
Shot# 42147-42154: We tried to ramp up the plasma from q*=2.7 at 2.4 msec to q* = 3.1 at 4 msec. Again, it took only at few shots to tune the parameters. The nice shots are #42150, (#42151), and #42154.

Monday March 29 04 12 stillits No shots. Application.
The Control Panel Application has been modified. Control of q* (including q*-ramps) has been included.

Tuesday March 30 07 23 James No Shots Maintenance
At about 9:45 last night I found a large amount of water on the floor in the basement. It was centered on the bias probe electronics and when I looked to find the source I noticed that it was the leak that Jim has been trying to get maintenance to repair. Over the weekend I guess it had filled the drip pan. It was a lot of water and it spread over to the dump, I vacuumed it up with the wet-vac, but before we run today that space (from the wall behind the bias probe to the dump) should be checked again to be sure I didn’t miss anything before it is powered up.

Tuesday March 30 07 26 James No Shots Maintenance
At about 9:45 last night I found a large amount of water on the floor in the basement. It was centered on the bias probe electronics and when I looked to find the source I noticed that it was the leak that Jim has been trying to get maintenance to repair. Over the weekend I guess it had filled the drip pan. It was a lot of water and it spread over to the dump, I vacuumed it up with the wet-vac, but before we run today that space (from the wall behind the bias probe to the dump) should be checked again to be sure I didn’t miss anything before it is powered up.

Wednesday March 31 05 10 Maurer RWM development
News from Tuesday: the leaking pipe in the bank room was finally fixed by facilities. Todays run was cut short by a minor arc on the TF coil set. A nut on one of the coils for the lug connection to the current feedthru had come loose. When the last shot of the day was taken part of the lug was vaporized giving rise to a big flash when the arc occured. The TF current trace looks just like the previous shot, so the full bank current still flowed through the arc to the coils. Nick and Jim have cleaned up the contacts and re-made the lug connection. All other TF connections have been checked also. I will check the resistiance and inductance of the coil and compare it to others before running tomorrow.

Thursday April 1 03 52 Maurer 42176-42185 checking out TF
We had another TF lug arc at the same spot as yesterday. Started the run today by bringing the TF up a kV at a time until we reached 6.1 kV to check out the new lug end. Everything appeared to be fine. Took one plasma shot with full TF, VF and OH banks. On the second plasma shot the lug arced at the TF current feed just like yesterday, blowing off the end of the lug. Apparently, the threads were damaged enough that the nut loosened up again an caused an another arc. We are discussing various possiblities about how to proceed. Input and any comments are welcome. New lugs have to be ordered and should be in tomorrow.

Monday April 5 05 05 Maurer 42185-42205 TF check-out
Checked out the new TF coil lug attachment today that was arcing last week. So far so good. I brought the TF up in kV steps initially checking the lug nuts between every shot. After reaching 6kV with the TF only I took about 5 shots with full banks making plasmas while still checking the lug nuts every shot. They were nice and tight every time. After that the remainder of the plasma shots were taken checking the lug nuts every 2 shots then 3 shots. They were OK the whole afternoon. I will continue to check them tomorrow gradually increasing the number of shots between inspections. Tomorrow I will be attempting to generate RWMs approaching qstar=3 from below using the Ro-qstar equilibrium feedback to help reproducibility.

Wednesday April 14 10 43 D. Maurer, Alex K. 42248-42270 FPGA tests
Yesterdays run summary... Inserted FPGA processor into one poloidal set of sensors/control coils (bottom shell, upper set). Digitized raw sensor signals, filtered signal that reach the FPGA, signals from the FPGA, and current in control coils. Will analyze data to see how it is consistent with mode control algorithm and filters. We tried several gain settings on the analog boards to see at what point crunch amplifiers are overdriven. More work needs to be done, including checking polarity of control coils and current shunts, (spatial) phase shifting of output signals.

Wednesday April 21 02 51 Alex Klein 42271-42315 FPGA testing
Yesterday, fixed polarity issues with current shunts. Also took many shots with sine wave driving things instead of sensors (no plasmas), to measure overall system transfer function. Today, verified control coil polarities and then ran toroidal phase shift scan on bottom-midplane FPGA group with all signals looking very nice. Took shots at 0,45,90,135 and 180 degrees toroidal shift. Will analyze data. Hope to wire in remaining FPGA groups by end of week.

Thursday April 29 09 53 A. Klein 42326-42434 wiring/repair/configure
The FPGA global mode control system is installed and functioning. All analog boards, FPGA wiring details, control coil current shunt polarities, crunch amplifiers, control coil polarities, sensor coil polarities, coil integrities, etc are fixed, configured, functioning, verified. Now ready to apply feedback to RWM plasmas at various spatial phase angles using 20 sensors/coils configured in 4 groups of 5.

Thursday April 29 05 07 D. Maurer, Alex K. 42438-42457 mode control testing
Applied DFT FPGA mode control with all available coils. Only covered 2 spatial phase angles for feedback: 0 and -85 degrees. Will require much analysis to see actual effects on the plasma, and much analysis to see what effects should be acting on the plasma.

Friday April 30 04 33 Maurer none
Bias probe reinstalled and bellows assembly leak checked this week. Opened gate valve to chamber this afternoon. Pressure rise was maximum of about 6e-7 Torr and composed mostly of H2O. The bake has been on for over an hour and the base pressure is already down to 2.8e-8 Torr. We will continue baking over the weekend.

Thursday May 6 04 54 stillits 42464-42519 clean-up shots.
Clean-up shots were taken with RPFB and biased probe turned on.

Friday May 7 04 53 stillits 42520-42591 clean-up shots. Clean-up shots were taken with the biased probe and RPFB (R=94 cm and R=93 cm) turned on.

Monday May 10 03 43 stillits 42592-42605 H-modes (Biased probe + RPFB)
In our attempt to create H-modes, we ran the biased probe with RPFB. However, after a few shots, the biased probe arched. We measured a high-voltage short between the tip of the probe and ground. The probe has been pulled out, and the gate valve has been closed.

Tuesday May 11 05 39 Alex Klein 42607-42630 Global Mode Control
Initially, trouble with basement digitizer. Ch 2 on 8210#2 in basement appears to be out, switched VF bank signal to Ch3. Then, developed discharges to yield q* < 3 at start, then slowly ramp through q*=3.
Ran several shots with FPGA mode control ON at t=2 msec, off at t=3.5 msec for 0 and 180 degree spatial phase shifts.
Did not run radial position control, will do so tomorrow.

Wednesday May 12 05 18 Alex K 42631-42668 FPGA mode control
Performed gain scan on FPGA system: It had been slightly overdriven previously (increasing gain caused no increase in crunch amp current). Reduced FPGA gain setting and found gain setting which causes max crunch amp output (5-7 amperes)for typical plasmas.
Ran with radial position control, with goal of keeping plasmas alive as long as possible while slowly ramping through edge q =3 from below. Found m =2 tearing modes to dominate everything at 4 msec, resulting in disruptions. While FPGA feedback was on at various times for many shots, these may not be too meaningful...
Plans now have changed: perhaps run through edge =3 quickly and from above, to look for RWM before tearing modes dominate ? Did some discharge development in this direction.

Friday May 14 10 15 Alex Klein 42669-42722 FPGA model control
Spent a while developing discharge with aggressive OH ramp, such that edge q runs through 3 from the outside early on in the shot. Got to the point where RWM consistently observed between t=2 and t= 3 msec as edge q dipped below 3.
With this type of shot, then ran with FPGA mode control. Control output gated on between t=1.5 and 3.5 msec. Took data at 45 degree spatial phase shift increments for FPGA output. Have at least two shots at each angle with RWM.
Will have to look at data carefully to be able to say reasonable things about mode control. The RC filters and digital integration, as well as control coil inductances are causing control coil output to be dominated by low frequencies, and phase between sensors and controls highly susceptible to frequency as well.
Puff valve: For unknown reason, puff valve required to be open for 2.2 msec to get comparable gas levels as existed earlier in the day with valve opening only for 1.2 msec. Battery on valve checked out fine (235V), gas lines were all open with adequate pressure….There may be something wrong with the puff valve.

Friday May 21 03 49 Alex Klein 42723-42747 Mode Control
Again used discharges where plasma current ramp = agressive, edge q comes from the outside and rapidly dips below '3', giving rise to RWM early on in the shot. Very clear and reproducible RWM's.
With FPGA mode control algorithm now using much reduced integration time (~15 micro-secs), determined what spatial angle to dial into DFT to have 90 degree spatial phase shift between N=1 sensor mode and N=1 control mode. Took many shots at this setting with and without FPGA running. Consistently had 90 degree phase relationship.
Saw evidence that at "+" 90 degrees, feedback system excites N=1 mode. Fairly reproducible increase in sensor mode amplitude and lower mode rotation rates when FPGA is on, vs. when it is off.
Then, adjusted DFT angle by 180 degrees, to attempt "-" 90 degree feedback, should be suppression of RWM. No clear results. Mode amplitude looks always similar, regardless of wether FPGA is on or not.
Why? -> Consistenly had NO fixed phase relationship between control and sensor coils, i.e. phase is all over the place. Mode rotation rates seem high.
Will now do more rigourous analysis, with some objective method for quantifying data.

Thursday June 3 04 46 Alex K. 42748-42792 FPGA mode control Picked up where we left off 2 weeks ago. Plasma behaved exactly the same, without any tweaking required (edge q comes to 3 quickly, from the outside). Took many shots with spatial phase angle close to 0 degrees, and many shots with phase angle near 180. Cursory glance: RWM looks about the same for the two types. Will require more analysis to say anything meaningful. Then drove control coils with function generator going into analog boards, to explore gain and saturation limits in crunch amplifiers. Then with p[lasmas: began gain scan (at spatial phase angle ~90 degrees), will continue tomorrow and perform gain scan at phase angle ~ -90 degrees.
Friday June 4 04 43 Alex K. 42793-42817 FPGA mode control Hose for ignitron cooling burst, flooded basement. Fixed and cleaned up in the morning. Then continued gain scan from yesterday, at approx. +90 degree spatial phase shift and -90 degree target phase shift. Nearly finished, cua900 computer acting up... Gain scan should be complete after about 20 more shots (to be done next week).
Monday June 7 02 34 Maurer/Rivera
The OHEL bank is back up and running... The fpga is being programed for this weeks latency tests. The run will start tomorrow.

Wednesday June 9 03 56 Alex K. 42829-42871 FPGA mode control
Yesterday, ignitron cooling water hose had burst and flooded basement (again), therefor no runs. Today: With the usual discharge (see past several run reports): Finished gain scan at spatial phase angle which causes mode suppression. Then: Implemented FPGA program which has select-able latency in multiples of 10.2 microseconds, while keeping looprate/sample-rate the same. Took shots at 10, 50, 100, 200 microsecond latencies. It will require lengthy analysis to expose small effect, judging by quick look at the data.

Monday June 21 05 29 stillits 42873-42894 clean-up shots + biased probe
In the first 13 shots the biased probe was not turned on. In these shots the plasma was cold, lasted between 3-4ms, and the plasma current reached 10 kA. The loop voltage was fairly constant ~ 12 in each of these shots. From shot#42887 the biased probe was turned on. The biased probe voltage was increased from 0V to 350 V in 50V-steps. Saturation was reached at 300-350 V in which I_sat = 100-150 A. We saw a few more spikes in the loop voltage (~ 12), and from SXR the plasma was a bit hotter (but not much). However, there is a lot of noice in SXR, for example, so it is not easy to say anything about spikes in SXR. The RPFB was not turned on in any of the shots because of problems with the hot decks on the LANL. Tomorrow we will continue taking clean-up shots with the biased probe on.

Tuesday June 22 05 24 stillits 42895-42931 clean-up shots + biased probe
Clean-up shots were taken. The biased probe (BP) was slowly ramped up to 300V (it looks more like 200 V on the scope), and at 300 V the BP-current was 100 A. The plasmas created lasted for 3-4ms, and the plasma currents were ~10 kA. The signals are very noisy, so it is not very easy - by looking at the SXR-signals - to say anything about how hot the plasmas were, but the spikes in the loop-voltage seem to be absent in some of the last shots. The RPFB was not on because of problems with the LANL, but Nick is working on it. We will continue taking clean-up shots tomorrow.

Wednesday June 23 05 21 stillits 42966-43011 clean-up shots + biased probe
Clean-up shots were taken. The biased probe (BP) was slowly ramped up from 100 V to about 300V, and at 300V the BP-current was ~100 A. The plasmas lasted for ~ 4 ms and plasma current ~ 10kA. There are no spikes in the loop-voltage indicating the BP is clean. Furthermore, as soon as the BP is turned on (at 2ms), the loop-voltage remains constant (~ 10) or decreases indicating the plasma is getting heated (the plasma current ramp is 2.5 MA/s). SXR indicates a hot plasma but it is difficult to say because of noice. The RPFB was not turned on, but Nick is working on the LANL.

Thursday June 24 05 00 Alex K. 43012-43076 FPGA open loop runs
Coerced the machine to produce the types of discharges I have been using for a while now, with agressive current ramp, edgq q approaching 3 from above early in the shot... Spent the day running "open loop" experiments: All 20 control coils were energized with a set of signals that were out of phase with each other such as to drive a m=3, n=1 helical pertubation around the tokamak. At a certain time during the pulse, the polarity of the signals was reversed. (Phase Flip Experiments) Initially (in the morning), I had the pertubation propagate downwards poloidally as the toroidal angle was advanced (along plasma current). Saw little or no mode locking at several frequencies (between 4 and 8 kHz). Then I switched helicity, and found mode locking (between sensor coils and control coils) for a range of frequencies. This means presumably that perturbations are tied to the electron fluid. Can now analyze data to measure plasma response to phase flip of magnetic perturbation, also looks like I can measure plasma amplification of resonant perturbations.

Friday June 25 04 21 Alex K. 43078-43107 open loop, closed loop
In the morning, I continued the open loop experiments: Driving a 3-1 helical perturbation with the mode control coils. In these cases, I reversed the toroidal direction of the driving waves (now parallel to the plasma current) and tried both types of helicity at several frequencies (4-8 kHz). No phase locking at all was observed, in fact, very regular phase slipping is seen. Thus, the kink modes in HBT are definately such that perturbations propagate in the direction of the electron fluid motion, along the magnetic field. The velocity of the modes seems be on par with the electron fluid velocity as calculated from density estimates and current measurements. In the afternoon I implemented FPGA feedback with an improved algorithm that partially fixes phase shifts in the transfer functions from sensor coils to control coils. Dramatic results: Unambiguous feedback when the phase between sensors and control coils is -90 degrees, to the point where it is dificult to tell if there's a mode present at all on the Rogowski coils. In additon, there is unambiguous negative feedback when the phase shift is arranged to be +90 degrees, very loud RWM (or whatever they are) are observed. Without feedback, medium RWM seen. Many shots were taken, each one definately shows the effect upon first glance, without requiring statistical analysis. The transfer functions of a feedback system seem to be surprisingly important.

Tuesday June 29 04 02 stillits/maurer 4343108-43124 Biased probe
The biased probe (BP) was tested. With BP inserted 3 cm into the plasma, an IV-characteristic was obtained with I_sat = 45-50 A at V = 250 V (the BP voltage was increased to 350 V with no sign of increased BP current). There was no sign of impurities by looking at the loop-voltage (too much noice on SXR). Tomorrow we will perform an IV-scan by obtaining IV-characteristics at different positions of BP in the plasma.

Wednesday June 30 04 50 stillits/maurer 43153-43174 Biased probe
We had BP positioned at 1 cm and 5 cm from the edge of the plasma (it was positioned at 3 cm yesterday) to obtain IV-characteristics. The voltage was increased from 100V to 350 V in 50V-steps. For 1 cm, I_sat was 30 A, and for 5 cm it was 55 A. In the 5 cm case I_sat was reached at 100V-150 V, and in the 1 cm case I_sat was reached at 200V - 250V.
Thursday July 1 04 41 Alex K. 43175-43202 Mode control debugging
Was going to run latency experiments, spent the day chasing down bugs and problems instead. Output signals from the crunch amps on bottom poloidal group are not what they should be. Input signals as seen by digitizer are what they should be. Verified that FPGA module works as it should, and analogboard output stage performs properly as well. Took some plasma shots as part of the bug-chasing work, no good data. Hope to fugure this out tomorrow.

Thursday July 8 05 05 Alex K. 43242-43249 Mode control debugging
The analog boards/rack seem to be fixed after Nick R. worked on it on the bench. All channels are working except for one output signal on one of the bottom control lines (Channel 3B C3). It is a very bizzarre problem that can't easily be diagnosed/explained. Just as I was getting to the bottom this, the CAMAC data aqcuisition failed, presumably because the basement rack is overheating - the air conditioner in the basement is down, Jim A. is on the job of getting it repaired.

Tuesday July 13 05 50 A. Klein 43262-43288 Mode control debugging
Still had problems with one group of output signals - but I think I finally figured out the problem. Will test tomorrow and hopefully everything will be working. Developed discharges also: while the typical type of shot used previously for mode control studies appeared once in a while, it was not as reproducible and robust today as before. Will continue tomorrow, and hopefully run latency experiments.

Wednesday July 14 05 16 A. Klein 43288-43319 latency in mode control
All signals behave properly now. It took a while to get the target plasma, but then the old mode control shot (aggressive current ramp, edge q comes in to 3 and hovers there for a while, slow freq 3-1 oscillations visible) appeared. Ran feedback with 10, 60,110,160,210 microsecond latency in system. Data looks interesting. Every shot from 43302 to 43319 is relevant, no dud shots (which is nice for the operator). Will now have to analyze the data more thoroughly.

Thursday July 15 05 01 stillits 43320-43349 biased probe + RPFB
The LANL and the triple probe are working again. We inserted the biased probe (BP) 5 cm into the plasma, and slowly increased the BP-voltage from 100 V to 300 V. The max. BP-current was 50A-100A. We used RPFB to position the plasma at 94 cm (from 3 to 10 msec), which was fairly successfull. In a couple of shots, for example shot# 43346, we saw huge inboard edge densities up to 6-8*10^18 m^-3. However, we have to smooth the signals before we com