Miniproposals

Miniproposal: 086 Date Filed: 2/2/1995 Title: Ohmic H Modes at Low q First Author: Joseph Snipes Session Leader: Joseph Snipes (shots 1-41)

Engineering Operator Run Comment

low q h modes snipes goetz

Session Leader Plans

Physics Operators Plans

Session Leader Summaries

Entered: Jul 7 2004 03:49:12:240PM

Author: To Be Determined

Low q Ohmic H-modes 940214 - Valentine's Day Engineer in Charge: Frank Silva Physics Operator: John Goetz Session Leader: Joseph Snipes The purpose of this run is to determine H-mode threshold scalings at low q as a function of density. The low toroidal field startup was developed on 950201 to breakdown at about 3.4 T. So, the run will begin with a flattop TF of 3.5 T at 0.85 MA. The line integrated density will begin at 6 x 10^19 m^2. Then we will vary the density down and then up looking for limits to the H-mode threshold. Depending on the results, we may increase the current up to 0.9 MA or even 1 MA to reach still lower q though care should be taken to try to avoid low q disruptions. The run went reasonably well, though the discharges were plagued by disruptions near q(95) = 3. The power systems all worked beautifully despite these disruptions and gave us no trouble throughout the day. The computer systems also worked well except for a CAMAC problem with the neutron diagnostics that meant there was no neutron data throughout the run. The machine proved to be quite finicky to low q plasmas. Startup is more difficult. We had a total of 33 plasmas, 6 fizzles, and two power supply tests. Certainly the low field reduces TF cooldown time so that more shots can be run in a day. However, almost all shots disrupted before 1.1 sec at nearly full current. Getting by q=3 both on the way up and on the way down proved difficult. One suggestion to try to go through quickly did not work very well. Care must be taken before the plasma is well diverted, so it would be advisable for a future run to try to lengthen the discharge and ramp the current very very gradually though q=3 both on the way up and on the way down and wait until after about 0.5 sec to pass through q(95)=3. Still, we did get some interesting physics done today. There were several fairly long ELM-free H-modes, the best being triplets on shots 13 and 14. The H-L transitions at higher density give a good indication of the H-mode "hysteresis" in the power threshold. Overall, threshold values of the P/(nBS) coefficient were in the range of 0.02 to 0.03, which is typical for C-Mod and better than our previous ELM-free results, indicating that the machine was fairly well conditioned. We also lowered q still further down to 2.7 by raising the current to 0.85 MA with successful ELM-free shots on 22 and 23. Shot 23 set a high density record for ohmic ELM-free H-mode at a density of nl = 1.28 x 10^20 m^-2. Afterward, however, the discharges became unstable perhaps because the moly radiation became too large. One suggestion was to provide density feedback during segment 1 in relation to the plasma current so that you don't get too little or too much density for a given current. It seems that the density was not rising fast enough during the early phase of the discharge and the hot edge plasma at low q was sputtering more moly than usual. This should be corrected in future runs. Finally, the last few shots returned to 0.7 MA and moderate density to fill in some more density points. They did not achieve good H-modes, with only ELMy or even dithering behavior. This indicates that the wall conditions deteriorated during the day either because the walls were loaded with gas or impurity radiation became a problem. This will need to be analyzed in more detail. A Li pellet was injected into shots 35 and 41 at 0.8 sec and 1.1 sec, respectively and into the wall on shots 38 and 40 because the plasma disrupted before the injector fired. Spectroscopy measurements indicate that there was a fair amount of Li in the plasma during startup even before the first pellet was injected, apparently left over from Friday's PEP mode run where some 50 odd pellets were injected. So, it may be that Li helped improve the early H-mode shots, but that after all of the disruptions we had, the later shots no longer had the benefit of Li wall conditioning. Henceforth, we should schedule H-mode runs after Li pellet injection runs! These tantalyzing results also strongly indicate a need to revisit MP038 - Li conditioning and Ohmic H-modes perhaps by first injecting a large number of Li pellets into the machine and then looking at how the H-mode behavior changes after ceasing to inject Li pellets. Shotlist 1 - Power supply test shot 2 - Repeat 3 - Plasma, disrupted at 0.4 sec 4 - Plasma, disrupted at 0.4 sec 5 - Fizzle 6 - Plasma, disrupted at 0.4 sec 7 - Plasma, disrupted at 0.5 sec 8 - Fizzle 9 - Increased TF to 103 kA because we were not getting the 99 kA requested. Plasma, disrupted at 0.6 sec. 10 - Decent shot at Ip = 0.725 MA. Short H-mode 0.515-0.545,1.02-1.06 s 11 - Fizzle 12 - Fizzle 13 - Good shot! Several ELM-free H-modes, disrupted at 1.09 s 14 - Good shot! Several ELM-free H-modes, disrupted at 1.07 s, P/(nBs) = 0.02 to 0.03 15 - Fizzle 16 - Lower density to 5 x 10^19 m^-2. Dithering from 0.6 to disruption at 1.1 sec, P/(nBs) = 0.05 yet no H-mode. 17 - Raise density to 8 x 10^19 m^-2. Disrupted at 0.45. 18 - Good shot. ELM-free H-modes at 0.45-0.56, 0.7-0.85 sec 19 - Raise nl to 1 x 10^20 m^-2. Short H-mode from 0.96-1.05 s. 20 - Good shot with Ar. Short ELMy H-mode 0.96-1.01, ELM-free 1.01-1.05 s 21 - Raised nl to 1.1 x 10^20 m^-2. High recycling. No H-mode. 22 - Raised Ip to 0.85 MA and lowered nl to 1 x 10^20 m^-2. ELM-free H-modes from 0.9-0.95 and 0.98-1.03 sec. 23 - Raised nl to 1.1 x 10^20 m^-2. ELM-free H-mode 0.97-1.01 sec. 24 - Raised nl to 1.2 x 10^20 m^-2. Disrupted at 0.64 sec. Too much gas. 25 - Short H-mode early. Lowered nl to 7 x 10^19 m^-2. Disrupted at 0.65 sec. 26 - Disrupted again at 0.65 sec. 27 - Short H-mode early. Turned off Ar. Disrupted again at 0.63 sec. 28 - Short H_mode from 0.45-0.57 sec. Turned Ar back on. Disrupted again at 0.61 sec. 29 - Return to shot 23 programming but with nl = 7 x 10^19 m^-2. Disrupted at 0.64 sec. 30 - Short ELMy H-mode early. Disrupted at 0.66 sec. 31 - Disrupted at 0.64 sec. 32 - Fizzle 33 - Disrupted at 0.6 sec. 34 - Disrupted at 0.41 sec with faster current rise. 35 - Reduced current to 0.72 MA. Med Li pellet at 0.8 sec. Disrupted at the Li pellet. ELMy and short ELM-free H-modes 0.45 - 0.75 s. 36 - Good shot. Disrupted late at 0.95 s due to too strong density feedback and too large of a gas puff. ELMy and short ELM-free H-modes from 0.45 - 0.85 sec. 37 - Lowered gain on density feedback after 0.4 sec. ELMy H-mode from 0.43 - 0.46 sec and from 0.52 - 0.85 sec. 38 - Good shot. ELMy H-mode from 0.54 - 0.984 sec. Med Li at 1.1 sec. 39 - Disrupted at 0.6 sec due to no density. Feedback gain was too low. 40 - Increased density feedback gain to 4 during flattop. Disrupted at 0.52 sec. 41 - Good shot. Dithering throughout most of the shot from 0.43-1.1 s.

Physics Operator Summaries

Entered: Jul 7 2004 04:36:53:190PM

Author: To Be Determined

Physics operator summary for 950214 EO: Silva/Bertolino/Daigle PO: Goetz SL: Snipes Run 950214 was in support of Mini-Proposal #086 - Ohmic H-modes at Low q. The goal of this mini-proposal is to characterize the H-modes achieved at various densities and currents in plasmas with low safety factor. Program for this run: - Setup a lower SN discharge with Bt=3.5T, Ip=0.85MA, and NL_04=0.6e20 - Vary the density and characterize the quality of the H-modes achieved - Raise the current to 0.9 and/or 1.0MA and repeat This program was not completely carried out. See the Session Leader's summary to find out the details of the physics aspects of the run. Plasmas with Ip greater than 0.7MA were difficult if not impossible to obtain, so the program could not be completed. Some things discovered today: 1) It was very difficult today to run past the qpsi=3 barrier today. Only two shots ran completely with qpsi<3. All other attempts to cross the barrier were swatted back with gusto. Fast current ramps, slow current ramps, and stairstep current ramps were tried with no avail. In order to begin the program, a SN plasma with Ip=0.7MA and Bt=3.5T was used - this plasma has a qpsi ~ 3.1. A density scan was performed at this current. Some tweaks were made to the x-point controllers and their drawn waveforms until an acceptable lower SN was obtained (See shots 007->021). Running with moderate to high density with low q is possible. The qpsi=3 barrier was passed with NL_04 > 1.0e20 but not with NL_04 = 0.7e20 (see shots 022-033). 2) Breakdown was very reliable today. After getting the correct toroidal field setting for 3.5T, all but two plasma attempts had a current rise. There is a slight offset in what gets typed into the PLC and what actually appears on the bus, so be careful when asking for a specific current. The two attempts that fizzled did not form a current channel and can be attributed to too much gas, either prefill or puff. 3) There were problems today with the current rise, but mostly after 0.1sec. The molybdenum levels were quite high and tweaking of the segment 1 puff and the density ramp rate in segment 2 were the tools used to beat back the evil invader. As discussed in the notes for 950210, it may be necessary to have density feedback in segment 1 so that slight changes in plenum pressure do not result in loss of control of the early moly influx. 4) Most disruptions today followed this scenario: magnetics looked fine -> H-mode activity -> ramping Halpha signal (with oscillation) -> disruption. Spectroscopy corner indicates that there were no MARFEs to speak of today and the EDGE group reports that the inner divertor was attached for the first time ever. What these facts have to do with operation are yet to be determined. Does this have anything to do with the H-mode quality, the inability to get past qpsi=3? Engineering, computing, and diagnostics today: Engineering was excellent today. No power supply problems, no breaker pulls, no nothin. And to the suprise of all, DAQ1 troubles disappeared today and there were no complaints about diagnostics. Scorecard: 41 shots = 33 plasmas + 6 fizzles + 2 p.s. test Shot summary for Run 950214 coldstart hybrid - all matrices respond 2 hours of He ECDC prior to the run Load segment 1 of 950201020 into segment 1 Load segment 2 of 941221003 into segment 2 Waveforms match across segments Recalculate predictors in segment 2 Offset on RCUR in segment 2 is 8000 NL_04 = 0.6e20 until 1.0 sec IP = -820000 Slow down CLEARIN ramp and delay I gain until 0.375sec Lower the P gain on ZCUR(W2) during rampdown to prevent faults to the PF supplies P_0 = 2.5e-5 Shot change result ____ _____ ______ 1 OH and EF3 test OH1 rogowski integrator reset 2 OH test looks o.k. 3 see above plasma - disr. @ 0.41 chopper working hard 4 load gains from 950210030 in both plasma - disr. @ 0.41 ZCUR wires; P_0=2.2e-5 exact same undetermined problem 5 delay CLEARIN until 0.5sec; remove fizzle - no current rise some PG3 @ 0.1sec hits something @ .016 6 P_0=2.0e-5 plasma - disr. @ .402 at qpsi=3 ?!!? 7 IP=-680000 to change qstar plasma - disr. @ .508 qpsi->3 8 slow down IP ramp rate - flattop @ 0.5 fizzle - no current at all ZXU=+.04 9 TF current = 103kAmps; BR_0 offset is plasma - disr. @ 0.59 7.0mT; RXU P gain=2 qpis->3 10 RXU P gain=4; slow IP ramp until 0.6 plasma - all the way down qpsi~3.1; n/ncrit=1 11 no changes fizzle - no current channel 12 lower first two points of PG3 to 42V; fizzle - no current channel CLEARIN=0@0.5; +2.5e-3@1.; RXU=-.04 Br a little positive 13 BR_0 offset = 6.5mT plasma - disr. @ 1.09 don't know why; RF?!? 14 no changes plasma - disr. @ 1.07 upper x-pt coming in?? 15 NL_04=0.5e20; stairstep off ZXU and ZXL fizzle - no current channel 16 BR_0 offset = 6.0e-3 plasma - disr. @ 1.03 low density disruption?? 17 NL_04=0.8e20; PG3 volts to 45 early plasma - disr. @ 0.45 too much gas? too much MARFE? 18 NL_04 reaches max @ 0.55 plasma - disr. @ 1.02 >0.2MA halo current 19 NL_04=1.0e20 plasma - all the way down puff of gas helps it down 20 hyb. enable B_SIDE_LOWER plasma - all the way down 21 NL_04=1.1e20 plasma - disr.@1.24 - shark fin 22 NL_04=1.0e20; IP=-850000 plasma - disr @ 1.09 turn on chopper gains more slowly qpsi=2.7 - disrupt @ qpsi=3 23 NL_04=1.1e20; slow down IP rampdown plasma - disr. @ 1.04 24 NL_04=1.2e20; speed up IP rampdown plasma - disr. @ 0.638 MARFEing phenomena 25 NL_04=0.7e20 plasma - disr. @ 0.632 26 P_0=1.8e-5 plasma - disr. @ 0.645 why? 27 lower P gain on NL_04 to 4 @ 0.5; plasma - disr. @ 0.625 PG3=25V; remove B_SIDE_LOWER hyb. en. 28 lower P gain on NL_04 to 2 @ 0.4; plasma - disr. @ .612 lower PG3 from .05 on in seg.1 enable B_SIDE_LOWER 29 reload 950214023; P_0=2.2e-5; plasma - disr. @ .638 NL_04=0.7e20 current rise better 30 more PG3 between .05 and .1sec plasma - disr. @ .664 31 even more PG3; P_0=2.5e-5 plasma - disr. @ .645 32 increase density and IP ramp rates fizzle - no current channel 33 P_0=2.2e-5; step on ZXU gains earlier plasma - disr. @ .583 qpsi=3; good current rise 34 make IP ramp straight to 0.85MA plasma - disr. @ .407 35 draw IP to -680000 plasma - disr. @ .805 Li pellet @ .8 36 no changes plasma - disr. @ .953 37 lower P gain on NL_04 to 2 @ 0.4sec plasma - disr. @ .979 much smaller gas puff after leaving H-mode 38 lower P gain on NL_04 to 0.5 @ 0.6sec plasma - disr. @ 1.06 density on preprogramming long ELMy H-mode 39 P gain on NL_04=1 @ 0.5sec; plasma - disr. @ 0.58sec PG3=0 after 0.5sec very low density 40 P gain on NL_04=2 after 0.6sec; plasma - disr. @ 0.522 PG3=17V after 0.5sec terrible startup 41 NL_04=0.9e20 plasma - disr. @ 1.18 pellet induced death

Session Leader Comments
Feb 14 1995 08:31:17:720AM		Joseph Snipes	The purpose of this run is to determine H-mode threshold scalings at low q as a function of density. The low toroidal field startup was developed on 950201 to breakdown at about 3.4 T. So, the run will begin with a flattop TF of 3.5 T at 0.85 MA. The line integrated density will begin at 6 x 10^19 m^2. Then we will vary the density down and then up looking for limits to the H-mode threshold. Depending on the results, we may increase the current up to 0.9 MA or even 1 MA to reach still lower q though care should be taken to try to avoid low q disruptions.
Feb 14 1995 09:13:25:200AM	950214003	Joseph Snipes	Shot 3 Got plasma, but it disrupted at 0.4 sec apparently because of too high a derivative gain on the fast vertical position ZCUR.
Feb 14 1995 09:31:30:250AM	950214004	Joseph Snipes	Shot 4 Got plasma, but it disrupted at 0.4 sec again.
Feb 14 1995 09:31:54:480AM	950214005	Joseph Snipes	Shot 5 Fizzle!
Feb 14 1995 09:50:03:160AM	950214006	Joseph Snipes	Shot 6 Another disruption at 0.4 sec. Wolfe claims that it is a q=3 disruption. So we will lower the current by 0.1 MA and try again.
Feb 14 1995 10:09:36:600AM	950214007	Joseph Snipes	Shot 7 Another disruption at 0.5 sec. Try lowering the rate of rise of Ip and moving the upper X point up out of the machine.
Feb 14 1995 10:33:04:880AM	950214009	Joseph Snipes	Shot 9 Increased TF current request to 103 kA because we were not getting the 99 kA that we requested. Disrupted at 0.6 sec. EFIT q(95) is about 3.1 at these disruptions. Try reducing the rate of rise of the current again to flattop at 0.6 sec.
Feb 14 1995 10:45:27:010AM	950214010	Joseph Snipes	Shot 10 Decent shot. Short ELMy H-mode from 0.515 to 0.545 sec.
Feb 14 1995 11:31:37:370AM	950214013	Joseph Snipes	Shot 13 Good shot! Several ELM-free H-modes with large density rises that then make the plasma revert to L-mode.
Feb 14 1995 11:32:58:520AM	950214014	Joseph Snipes	Shot 14 Good shot! Several ELM-free H-modes with large density rises that then make the plasma revert to L-mode. Got good fast scanning probe data as well.
Feb 14 1995 11:56:27:470AM	950214016	Joseph Snipes	Shot 16 Good shot! Lowered nl to 5 x 10^19 m^-2. Dithering from 0.6 sec until the disruption at 1.1 sec.
Feb 14 1995 12:02:51:600PM	950214017	Joseph Snipes	Shot 17 Disrupted at 0.45 sec. Appears that the density feedback overdid it as the plasma went diverted. We will try reducing the rate of rise of the density to match that of the current.
Feb 14 1995 12:33:46:390PM	950214018	Joseph Snipes	Shot 18 Good shot! ELM-free H-modes from 0.45-0.56 and 0.7-0.85 sec.
Feb 14 1995 12:38:29:330PM	950214019	Joseph Snipes	Shot 19 Good shot! Raised nl to 1 x 10^20 m^-2. ELM-free H-mode from 0.96-1.05 s at nl = 1.1 x 10^20 m^-2. P/(nBS) = 0.024.
Feb 14 1995 12:46:11:530PM	950214020	Joseph Snipes	Shot 20 Good shot! Ar added and did not make much difference. Short ELMy and then ELM-free H_mode; ELMy from 0.96-1.01 s, ELM-free from 1.01-1.05 sec.
Feb 14 1995 12:58:02:720PM	950214021	Joseph Snipes	Shot 21 Raised nl to 1.1 x 10^20 m^-2. High recycling. No H-mode.
Feb 14 1995 01:20:53:650PM	950214022	Joseph Snipes	Shot 22 Raised Ip to 0.88 MA, lowered nl to 1.0 x 10^20 m^-2. Good shot! ELM-free H-modes from 0.9-0.95 and 0.98 - 1.03 sec.
Feb 14 1995 01:22:11:470PM	950214023	Joseph Snipes	Shot 23 Raised nl to 1.1 x 10^20 m^-2. Good shot! ELM-free H-mode from 0.97 - 1.01 sec.
Feb 14 1995 01:33:03:470PM	950214024	Joseph Snipes	Shot 24 Raised nl to 1.2 x 10^20 m^-2. Too much gas. Disrupted at 0.64 sec.
Feb 14 1995 01:43:09:150PM	950214025	Joseph Snipes	Shot 25 Lowered nl to 0.7 x 10^20 m^-2. Disrupted at 0.64 sec. ELMy H-mode from 0.49 to 0.57 sec despite the slow startup. Then, the gas valve went wide open and the plasma disrupted.
Feb 14 1995 01:53:24:720PM	950214026	Joseph Snipes	Shot 26 Try again with lower fill pressure at 1.8 x 10^-5 Torr. Disrupted again at 0.65 sec. Try turning off the Ar for the next shot.
Feb 14 1995 02:14:22:020PM	950214027	Joseph Snipes	Shot 27 No Argon. Disrupted again at 0.63 sec. So, it does not appear to be due to the Argon.
Feb 14 1995 02:24:46:640PM	950214028	Joseph Snipes	Shot 28 Lowered early gas puff. Turned Ar back on. Disrupted again at 0.61 sec.
Feb 14 1995 02:35:20:890PM	950214029	Joseph Snipes	Shot 29 Returned to shot 23 programming but with nl = 7 x 10^19 m^-2. Disrupted at 0.64 sec.
Feb 14 1995 03:13:41:940PM	950214031	Joseph Snipes	Shot 31 Disrupted at 0.64 sec.
Feb 14 1995 03:08:30:070PM	950214032	Joseph Snipes	Shot 30 Increased early gas puff. Disrupted at 0.66 sec. Short ELMy H-mode early.
Feb 14 1995 03:15:13:670PM	950214032	Joseph Snipes	Shot 32 Fizzle!
Feb 14 1995 03:27:01:230PM	950214033	Joseph Snipes	Shot 33 Lowered fill pressure to 2.2 x 10^-5 Torr. Disrupted at 0.6 sec. Appears to be a q psi = 3 problem again. One idea was to pass through q = 3 faster. So, we will increase the rate of rise of Ip. I don't expect it to work, but at this point, we'll try it.
Feb 14 1995 03:39:19:100PM	950214034	Joseph Snipes	Shot 34 Disrupted earlier at 0.41 sec as I expected. Return to the lower current and fill in some moderate density points.
Feb 14 1995 04:03:42:090PM	950214035	Joseph Snipes	Shot 35 Return to 0.72 MA at 7 x 10^19 m^-2. Medium Li pellet at 0.8 sec. Disrupted at pellet. ELMy and short ELM-free H-modes from 0.45 - 0.75 sec.
Feb 14 1995 04:41:45:420PM	950214036	Joseph Snipes	Shot 36 Repeat without Li pellet. Disrupted at 0.95 sec due to too high density feedback and strong gas puff after H-L transition. H-modes from 0.45 - 0.85 sec.
Feb 14 1995 04:43:10:830PM	950214037	Joseph Snipes	Shot 37 Lowered gain on density feedback after 0.4 sec. ELMy H-mode from 0.43-0.46 sec and from 0.52 - 0.85 sec.
Feb 14 1995 06:23:57:910PM	950214038	Joseph Snipes	Shot 38 Good shot. ELMy H-mode from 0.43-0.46, then short ELM-free period, then long ELMy H-mode from 0.54 - 0.984 sec. Medium Li pellet (1.2 x 10^20 electrons) injected at 1.1 sec.
Feb 14 1995 06:25:53:590PM	950214039	Joseph Snipes	Shot 39 Turned down density feedback after 0.4 sec. Pre-programmed gas was also turned off and it led to a disruption at 0.6 sec because there was no density. The gain was too low on the density feedback.
Feb 14 1995 06:35:46:040PM	950214040	Joseph Snipes	Shot 40 Increased density feedback gain to 2 after 0.6 sec. Pre-programmed gas set to 17 V after 0.5 sec. Disrupted at 0.52 s.
Feb 14 1995 06:38:04:010PM	950214041	Joseph Snipes	Shot 41 Increased density to nl = 9 x 10^19 m^-2. Medium Li pellet at 1.1 sec. Disrupted just after pellet at 1.18 sec. Dithered for most of the discharge from 0.43 - 1.1 sec.
Feb 14 1995 06:42:15:320PM	950214041	Joseph Snipes	The run went very well from the engineering side with no time or shots lost due to engineering problems other than two test shots at the beginning of the day. Well done! Goetz also did a decent job of keeping the fizzles down, though the low field startup was certainly more difficult. There were a total of 33 plasmas, 6 fizzles, and two power supply tests. Computer systems also worked very well today with no failures other than a CAMAC problem with the neutron diagnostics that meant we have no neutron data today.
Feb 14 1995 07:22:33:710PM	950214041	Joseph Snipes	From the physics side, we succeeded in getting some interesting results, though we were plagued by disruptions thoughout the day usually near q(95)=3. Some of these were also caused by the density feedback going wide open and flooding the machine with gas. Nonetheless, we achieved a fair amount of the goals of this run at one current of 0.72 MA and 3.5 T over a range of densities. The thresholds were in the range of P/(nBS) = 0.02 to 0.03, which is similar to previous results, but better than our previous ohmic ELM-free H-modes.
Feb 14 1995 07:29:17:810PM	950214041	Joseph Snipes	The low density limit at low q was found to be again at about 5 x 10^19 m^-2 or about 1 x 10^20 m^-3, similar to both ohmic and ICRF results at 5.3 T. Sawteeth were absent at the lowest density and very strong dithering was observed even on the plasma current (shot 16). The high density limit was much higher at low q being about 1.3 x 10^20 m^-2, compared to 8 x 10^19 m^-2 at 5.3 T. So, this might be a good regime for trying to combine radiative divertor regime with H-mode.

Physics Operator Comments
Feb 14 1995 08:15:47:760AM		John Goetz	Run 950214: Mini-Proposal #086 - Ohmic H Modes at Low q Characterize H-modes at low safety factor under conditions of varying density and plasma current. Run Plan Helium ECDC to cleanse the walls of helpful deuterium Lower SN plasma with Bt=3.5T, Ip=0.85MA, and nel=0.6e20 Vary the density and characterize the quality of the H-modes Raise the current to 0.9MA and/or 1.0MA Start from: Load 950201020 segment 1 into segment 1 ( low field startup ) Load 941221003 segment 2 into segment 2 Recalculate predictors in segment 2 Check waveforms across the segment switch Offset on RCUR = 8000 IP=-820000 and NL_04=0.6e20 until 1.0sec Slow down CLEARIN ramp and delay I gain until 0.375sec Lower the gains on ZCUR(W2) during rampdown
Feb 14 1995 08:50:35:930AM		John Goetz	Run 950214: Coldstart hybrid - all matrices respond
Feb 14 1995 08:47:50:510AM	950214001	John Goetz	Shot 950214001: OH and EF3 test Results: looks like the OH1 rogowski integrator didn't reset
Feb 14 1995 08:50:06:050AM	950214002	John Goetz	Shot 950214002: OH test Results: looks o.k.
Feb 14 1995 09:10:20:540AM	950214003	John Goetz	Run 950214003: first shot o' the day Results: Plasma - disrupts @ 0.41 current rise is slow 0.5MW of unintentional RF power - very radiative Chopper working hard to hold vertical position
Feb 14 1995 09:26:15:850AM	950214004	John Goetz	Run 950214004: Load gains from 950210030 in ZCUR(W2) and ZCUR(W3) to optimize the vertical position control P_0=2.2e-5 Results: Plasma - disrupts @ 0.41 disrupts at exactly the same time nothing untoward on any of the power supplies seems to coincide with the end of the ramps for ZXL and CLEARIN
Feb 14 1995 09:36:20:560AM	950214005	John Goetz	Run 950214005: delay end of CLEARIN ramp until 0.5sec remove some volts from PG3 around 0.1sec Results: fizzle hits something @ .016 no current channel formation - current rise very slow
Feb 14 1995 09:48:20:810AM	950214006	John Goetz	Run 950214006: P_0=2.0e-5 Results: Plasma - disrupts @ .402 Seems to be associated with qstar=3.0
Feb 14 1995 10:05:33:630AM	950214007	John Goetz	Run 950214007: IP=-680000 to try and change the qstar Results: plasma - disr. @ .508 qstar just approaching 3 still an upper x-point
Feb 14 1995 10:15:04:740AM	950214008	John Goetz	Run 950214008: slow down IP ramp - reach flattop @ 0.5 ZXU = +.04 Results: fizzle no current rise at all scatterplot says Br is 1mT too low
Feb 14 1995 10:31:30:890AM	950214009	John Goetz	Run 950214009: Bt=103kAmps BR_0 offset is 7.0mT (was 6.0mT) RXU P gain = 2 ( was 1 ) Results: plasma - disr. @ 0.59 Bt=3.5T qpsi->3
Feb 14 1995 10:44:50:430AM	950214010	John Goetz	Run 950214010: slow IP ramp until 0.6sec RXU P gain = 4 ( was 2 ) Results: plasma - all the way down - Ip=0.7MA qpsi~3.1; n/ncrit=1 made it through whatever stability boundary was in the way error on RXU is now near zero
Feb 14 1995 10:55:09:020AM	950214011	John Goetz	Run 950214011: no changes Results: fizzle - no current channel formation no Halpha burnout
Feb 14 1995 11:08:12:530AM	950214012	John Goetz	Run 950214012: lower first two points of PG3 to 42V CLEARIN = 0@0.5; +2.5e-3@1.0 RXU = -.04 (these two are to keep the SL happy with the eq. ) Results: fizzle - no current channel Br a little too positive
Feb 14 1995 11:18:51:530AM	950214013	John Goetz	Run 950214013: BR_0 offset = 6.5mT Results: plasma - disr. @ 1.09 n/ncrit=1 disruption unexplained; RF junk?!?!
Feb 14 1995 11:29:40:100AM	950214014	John Goetz	Run 950214014: no changes Results: plasma - disr. @ 1.07 n/ncrit=1 upper x-point coming in ??
Feb 14 1995 11:42:15:380AM	950214015	John Goetz	Run 950214015: NL_04=0.5e20 stairstep off gains on ZXU and ZXL Results: fizzle - two bounces - no current channel Br too positive (from scatterplot and fluxplot)
Feb 14 1995 11:55:00:640AM	950214016	John Goetz	Run 950214016: BR_0 offset = 6.0e-3 Results: plasma - disr. @ 1.03 low density disruption?? dithering everywhere
Feb 14 1995 12:02:46:830PM	950214017	John Goetz	Run 950214017: NL_04 = 0.8e20 PG3 early volts back to 45V Results: plasma - disr. @ 0.45 rubs on something during crossover too much gas? - too much MARFE?
Feb 14 1995 12:19:47:060PM	950214018	John Goetz	Run 950214018: NL_04 reaches flattop @ 0.55 Results: plasma - disr. @ 1.02 >0.2MA of halo current on this shot three Halpha bumps - first one at 0.99
Feb 14 1995 12:35:02:360PM	950214018	John Goetz	Run 950214018: this wasn't >0.2MA - Horne was looking at the divertor shunts, not the rogowskis - the black mark is removed
Feb 14 1995 12:31:15:260PM	950214019	John Goetz	Run 950214019: NL_04 = 1.0e20 Results: plasma - all the way down large puff due to H-mode right before ramp down may have helped this one ramp down
Feb 14 1995 12:49:56:100PM	950214020	John Goetz	Run 950214020: hybrid enable B_SIDE_LOWER Results: plasma - all the way down very bad startup - Ip reverses @ 0.2sec, but the plasma recovers - looks like MARFE phenomena
Feb 14 1995 12:59:03:530PM	950214021	John Goetz	Run 950214021: NL_04=1.1e20 Results: plasma - disr. @ 1.24 - shark fin
Feb 14 1995 01:12:29:890PM	950214022	John Goetz	Run 950214022: NL_04=1.0e20 IP=-850000@0.6 (add a point of 0.6MA @ 0.45) turn chopper gains on more slowly Results: plasma - disrupts @ 1.09 qpsi=2.7, but the disrupts occurs when qpsi=3
Feb 14 1995 01:21:47:440PM	950214023	John Goetz	Run 950214023: NL_04=1.1e20 slow down IP rampdown Results: plasma - disrupts @ 1.04 qpsi->3 - disrupts earlier than 022
Feb 14 1995 01:32:01:080PM	950214024	John Goetz	Run 950214024: NL_04=1.2e20 speed down IP rampdown Results: plasma - disrupts @ 0.638 MARFEing phenomena - gas full on, but the plasma isn't taking it
Feb 14 1995 01:43:26:160PM	950214025	John Goetz	Run 950214025: NL_04=0.7e20 Results: plasma - disrupts @ 0.632 terrible startup again - bumps something early
Feb 14 1995 01:53:36:500PM	950214026	John Goetz	Run 950214026: P_0=1.8e-5 Results: plasma - disrupts @ .645 passes thru qpsi=3 at about 0.6sec
Feb 14 1995 02:15:37:620PM	950214027	John Goetz	Run 950214027: lower P gain on NL_04 to 4 @ 0.5 PG3 = 25V remove hybrid enable from B_SIDE_LOWER Results: plasma - disrupts @ 0.625 terrible startup again short H-mode then density troubles
Feb 14 1995 02:36:44:220PM	950214028	John Goetz	Run 950214028: lower P gain on NL_04 to 2 @ 0.4 lower PG3 in segment 1 (around .06+) Results: plasma - disr. @ .612 still a bad current rise - very radiative
Feb 14 1995 02:38:14:580PM	950214029	John Goetz	Run 950214029: reload 950214023 P_0=2.2e-5 NL_04=0.7e20 Results: plasma - disr. @ .638 current rise better - moly radiation less still disrupts after leaving H-mode and an oscillation in Halpha begins
Feb 14 1995 02:48:04:870PM	950214030	John Goetz	Run 950214030: more PG3 between .05 & .1sec Results: plasma - disr. @ .664 a little better on the startup shot lasts a little longer
Feb 14 1995 03:00:26:490PM	950214031	John Goetz	Run 950214031: even more PG3 between .05 & .1sec P_0=2.5e-5 Results: plasma - disr. @ .645 current rise has slowed down - don't want anymore seg1 gas
Feb 14 1995 03:08:51:190PM	950214032	John Goetz	Run 950214032: increase density ramp rate in seg2 increse IP ramp rate before pause Results: fizzle - no current channel formed - Halpha bounce
Feb 14 1995 03:27:03:880PM	950214033	John Goetz	Run 950214033: P_0=2.2e-5 step on ZXU gains earlier Results: plasma - disr. @ .583 qpsi=3 very nice current and density rises though
Feb 14 1995 03:39:08:220PM	950214034	John Goetz	Run 950214034: IP current ramp straight to 0.85MA Results: plasma - disr. @ .407 qpsi around 3 for a while
Feb 14 1995 03:52:42:920PM	950214035	John Goetz	Run 950214035: draw IP to -680000 Results: plasma - disr. @ .804 Li pellet fired at 0.8sec did it in
Feb 14 1995 04:19:13:670PM	950214036	John Goetz	Run 950214036: no changes Results: plasma - disr. @ .953 same Halpha behavior - a slow rise after coming out of H-mode followed by death
Feb 14 1995 04:20:09:350PM	950214037	John Goetz	Run 950214037: lower P gain on NL_04 to 2 after 0.4sec Results: plasma - disr. @ .979 density feedback better - much smaller puff of gas after leaving H-mode
Feb 14 1995 04:31:13:330PM	950214038	John Goetz	Run 950214038: lower P gain on NL_04 to 0.5 after 0.6sec Results: plasma - disr. @ 1.06 density just riding along on preprogrammed voltage long ELMy H-mode period
Feb 14 1995 04:45:01:030PM	950214039	John Goetz	Run 950214039: P gain on NL_04 to 1 after 0.5sec Results: plasma - disr. @ 0.58 very low density - not enough feedback to overcome no volts from PG3
Feb 14 1995 04:58:04:140PM	950214040	John Goetz	Run 950214040: P gain on NL_04 to 2 after 0.6sec PG3=17V after 0.5sec Results: plasma - disr. @ 0.522 terrible startup - bad current rise and density rise
Feb 14 1995 05:27:41:420PM	950214041	John Goetz	Run 950214041: NL_04 = 0.9e20 more PG3 between 0.05 to 0.1 Results: plasma - disr. @ 1.18 - death by Li pellet made it through for no apparent reason

Engineering Operator Comments
Shot	Time	Type	Status	Comment
1	08:22:58:130AM	Test	Bad	oh1 rog traces ?? bad
2	08:47:22:150AM	Test	Ok	oh co=ax test
3	08:55:48:860AM	Plasma	Ok	no faults
4	09:10:17:940AM	Plasma	Ok	no faults
5	09:26:21:530AM	Plasma	Ok	no faults
6	09:37:15:230AM	Plasma	Ok	no faults
7	09:49:25:130AM	Plasma	Ok	no faults
8	10:04:46:420AM	Plasma	Ok	no faults
9	10:16:40:650AM	Plasma	Ok	nofaults
10	10:32:04:890AM	Plasma	Ok	No Faults.
11	10:46:13:320AM	Plasma	Ok	no faults
12	10:56:53:120AM	Plasma	Ok	no faults
13	11:07:06:190AM	Plasma	Ok	no faults
14	11:18:13:860AM	Plasma	Ok	no faults
15	11:30:42:710AM	Plasma	Ok	no faults
16	11:41:52:890AM	Plasma	Ok	no faults
17	11:54:24:730AM	Plasma	Ok	no faults
18	12:05:03:970PM	Plasma	Ok	no faults
19	12:19:34:990PM	Plasma	Ok	no faults
20	12:32:16:510PM	Plasma	Ok	no faults
21	12:48:42:670PM	Plasma	Ok	no faults
22	01:00:38:820PM	Plasma	Ok	no faults
23	01:11:29:890PM	Plasma	Ok	No Faults.
24	01:22:42:660PM	Plasma	Ok	No Faults.
25	01:32:32:740PM	Plasma	Ok	No Faults.
26	01:42:17:290PM	Plasma	Ok	No Faults.
27	01:53:38:480PM	Plasma	Ok	No Faults.
28	02:15:32:340PM	Plasma	Ok	no faults
29	02:28:26:670PM	Plasma	Ok	No Faults.
30	02:39:29:540PM	Plasma	Ok	No Faults.
31	02:49:04:450PM	Plasma	Ok	No Faults.
32	03:02:25:710PM	Plasma	Ok	No Faults.
33	03:13:34:480PM	Plasma	Ok	No faults.
34	03:26:46:850PM	Plasma	Ok	No Faults.
35	03:42:09:120PM	Plasma	Ok	No Faults.
36	03:54:53:630PM	Plasma	Ok	No faults.
37	04:07:13:860PM	Plasma	Ok	No Faults.
38	04:19:51:570PM	Plasma	Ok	No Faults.
39	04:34:58:290PM	Plasma	Ok	No Faults.
40	04:45:37:220PM	Plasma	Ok	No Faults.
41	04:58:51:720PM	Plasma	Ok	No Faults.