Miniproposals

Miniproposal: 096 Date Filed: 3/7/1995 Title: Lithium Conditioning in Ohmic and ICRF H Modes First Author: Joseph Snipes Session Leader: Joseph Snipes (shots 1-38)

Engineering Operator Run Comment

snipe hutch

Session Leader Plans

Physics Operators Plans

Session Leader Summaries

Entered: Jul 7 2004 03:49:12:880PM

Author: To Be Determined

MP096 Lithium Conditioning and H-modes Engineer in Charge: Frank Silva Physicist in Charge: Ian Hutchinson Session Leader: Joseph Snipes The purpose of the run is to test the hypothesis that a coating of lithium on the walls of the vessel improves conditions for H-modes. A couple of discharges in conditions where we expect H-modes will begin the run (nl = 7 x 10^19 m^-2 Ip = 0.8 MA, BT = 5.3 T). Then, we will spend up to several hours of discharges injecting Li pellets to put down as much lithium as possible in a few hours, using the Li emission as a guide to determine when or if the level of lithium in the plasma saturates. For these conditioning discharges, the current will be reduced to 0.7 MA. When the Li conditioning is complete, the current will be returned to 0.8 MA and we will scan the density for H-modes to see if the H-mode behavior has changed. If the duration of H-modes increases or the H factors increase, this will indicate that lithium conditioning can improve H-mode performance. If there is little change in the duration or quality of the H-modes, then the experiment will show that even many monolayers of lithium do not improve H-mode conditions in C-Mod. Shot 1 started by copying 950329012 with some modifications to the current rise, RCUR changed to new algorithm with 8 mm offset, density set to 7 x 10^19 m^-2. We then immediately took out the FSP controller and turned on the X point controllers. Overall, the machine ran very well with only a short delay for cooling problems. The power supplies worked excellently. There were 38 Li pellets injected between shots 8 and 22. Ohmic H-modes were not observed before or after injecting Li pellets. There were a few weak ICRF H-modes observed before Li was injected and there was one good ICRF H-mode on shot 950331038 that had several L-H-L transitions. Overall, the result seems to be clear that the lithium pellets did not improve H-mode conditions neither by lowering the threshold nor by increasing the H factors. The one good ICRF H-mode had an H factor of 1.2, which is O.K. in comparison with previous ICRF H-modes, but is not a very high H factor compared to low q ohmic H-modes. Some good data was also obtained using the Li pellet viewing camera to determine the Li pellet cloud tilt angles for q profiles. Overall, it was a successful run albeit with a rather negative result in that lithium did not improve the H-modes. Shot 1: Disrupted at 0.54 sec at change over to FSP controller 2: Now on X point controllers. Disrupted at 1.2 sec. 3: Fizzle 4: Good shot. Short RF H-mode 0.9-1.0 sec with 0.45 MW 5: Good shot. RF H-mode from 0.9 - 1.0 sec. 6: Raised nel to 8 x 10^19 m^-2. Short RF H-mode 0.9 - 1.0 sec 7: Another short RF H-mode 0.9 - 1.0 sec. 8: Li pellets at 0.45 (small) and 0.6 (med). Disrupted at 0.62 sec. 9: Li pellets at 0.45 (small), 0.6 (med), and 0.8 (med). Disrupted at 0.82 sec. 10: Li pellets 0.45,0.6,0.8,1.0 (large). Disrupted at 1.01 sec. 11: No pellets. Gate valve not enabled. Otherwise a good shot. 12: Disrupted at 0.46 sec after first small pellet! 13: Disrupted after 3rd pellet at 0.81 sec. 14: Raised nel to 9 x 10^19 m^-2. Good shot. Li at 0.45,0.8, 1.0 sec. 15: Li at 0.6, 0.8, 1.0 sec. Good shot. 16: Li at 0.45, 0.6, 0.8 sec. Good shot. 17: Li at 0.6 sec. Disrupted at 0.69 sec. 18: Li at 0.6, 0.8, 1.0 sec. Good shot. 19: Li at 0.45, 0.8, 1.0 sec. Disrupted at 1.04 sec. 20: Li at 0.45,0.6,0.8,1.0 sec. Good shot. 21: Li at 0.45,0.6,0.8,1.0 sec. Good shot 22: Ip = 0.8 MA, nel = 7 x 10^19 m^-2. No H-mode. Li at 1 sec. Disrupted at 1.09 sec. 23: Good shot. Short RF H-mode from 0.95 - 1.0 sec. 24: Good shot. No H-mode. Lower RF 25: nel = 9 x 10^19 m^-2. Good shot. Dithering from 0.4 - 1.1 sec. 26: Good shot. Weak RF H-mode from 0.75 - 1.0 sec. 27: Nel set to 1 x 10^20 m^-2. Good shot. No H-mode. 28: Ip = 0.9 MA, dithering from 0.9 - 1.1 sec. 29: Repeat. Dithering from 0.8 - 1.1 sec. 30: O.K. shot. Dithering 0.5 - 0.95 sec, no H-mode. Disrupted at 1.05 sec. 31: Ip = 0.9 MA, nel = 8 x 10^19 m^-2. Weak RF H-mode 0.5 - 1.0 sec. 32: Repeat without RF. No H_mode. 33: nel = 7 x 10^19 m^-2. Some moly injections. No H-mode. 34: Ip = 1 MA, nel = 8 x 10^19 m^-2. Some dithering 1.12 - 1.24 sec. 35: nel = 9 x 10^19 m^-2. Some dithering from 1.12 - 1.25 sec. 36: Gas turned off at 0.8 sec. No H-mode. 37: nel = 1.4 x 10^20 m^-2. ICRF not turned on due to finger trouble. 38: Good ICRF H-mode from 0.72 - 1.04 sec. taue up to 45 msec.

Physics Operator Summaries

Entered: Jul 7 2004 04:36:53:723PM

Author: To Be Determined

Physop Summary 950331 H-modes and Lithium SL Snipes PO Hutch EO Silva/Bertolino Summary _______ After a few setup shots, a lot of Li pellets were injected. The conditioning was considered complete at shot 23. Thereafter H-modes were sought, largely without success. If anything, the Li conditioning appears to make getting H-modes harder. But who knows what other influences are at work. Personal view: This is a massive nail in the Li H-mode coffin. (That Vampire will probably never die, though). As a side effort, an EF4 controller to keep EF2 from railing was developed. The controller is called EF2_by_EF4. By shot 27 this was sufficiently tuned as to give good EF2 current centering. This helps a lot to avoid VDEs due to EF2 problems. It is HIGHLY RECOMMENDED that this controller be used from here on. __________________ Shots 34-38 were pristine 1MA shots with excellent ramp-downs. Shot 38 was a very nice cycling H-mode with 1 MW RF. Scorecard: 35 plasmas in a row. _________ Shot,Duration(s),Ipmax(MA) Shot,Duration(s),Ipmax 1 0.568 0.835 2 1.196 0.841 3 0.000 0.029 4 1.190 0.848 5 1.219 0.843 6 1.238 0.841 7 1.348 0.835 8 0.633 0.740 9 0.828 0.740 10 1.016 0.735 11 1.402 0.737 12 0.462 0.727 13 0.825 0.732 14 1.391 0.737 15 1.353 0.737 16 1.361 0.740 17 0.694 0.737 18 1.477 0.735 19 1.045 0.727 20 1.446 0.732 21 1.489 0.732 22 1.099 0.830 23 1.305 0.833 24 1.552 0.835 25 1.482 0.830 26 1.513 0.830 27 1.497 0.825 28 1.497 0.918 29 1.573 0.926 30 1.055 1.073 31 1.087 0.936 32 1.600 0.926 33 1.610 0.934 34 1.610 1.024 35 1.610 1.027 36 1.576 1.024 37 1.444 1.019 38 1.472 1.027 Finished summary for 950331 Total of 38 shots. 38 shots. 37 plasmas. 1 fizzles. 0 duds. Fizzle = gt 17 lt 50kA. Details. _______ Fill 2.0 1 Pla Disruption caused by the FSP turn on. Removed FSP restored the RXL gain 2 Pla Fixed disruption 3-9 Hutch away for a while see SL. Fill 1.7 10 Pla Disrupts at 1.02s. Repeat. 11 Pla Pellets did not fire. Gate valve not enabled. Repeat. 12 Pla Disrupts at .46s, first pellet. Xrays on TV at disruption. Can't see an obvious reason. Repeat 13 Pla Disrupt at .81s. Put in a new EF2_by_EF4 wire, with zero gain on line 13. This controls the EF4 current to achieve a desired EF2. Raise nl04 to .9. 14 Pla Ran to 1.35s. Repeat 15 Pla Three nice pellets. 16 Pla Ditto Present EF4 controller is such that +ve error gives +ve voltage. EF2_by_EF4's polarity needs to be such that if EF2 is too high, EF4 is decreased, i.e. moved in the same direction we want EF2 to move. For zero drawn, so that EF2 is more negative than programmed, EF2 is giving a positive A_out error, which would raise EF4 for a positive controller. Correct. Value 0.9, time constant 1. Predictor is 0.5*EF2U+0.5*EF2L. Tweak Clearin to ramp down slightly quicker. Delay due to cooling hitch, entry to fix the TV. Enter cell and fix camera. 17 Pla Disrupts at 0.69s. Only got the 0.6s pellet. EF2 L zeros there. Lower EF4 current to 1900 from 2300A. 18 Pla Runs to 1.47s. Three pellets and several Mo injections. Turn on EF2_by_Ef4 gain to 0.2 at .5s Slightly more gas at .05-.1 sec. (Small change) 19 Pla Disrupts at 1.03s. Got the .45s pellet, not the .6s. RF fired. EF2 kept well away from its rail. Early Mo drops. Program EF2_by_EF4 to ramp later. 20 Pla Good ramp down. $pellets. E2/4 gain to 0.4. 21 Pla EF2L zeroed at 1.05s but we survived. Four pellets. Plenum pressure had dropped to 16.7 put back to 18. E2/4 gain to 1. Ip to 800 kA. nl04 0.7e20. 22 Pla Pellet at 1s. Disrupts at 1.1s, due to EF2L zeroing. Kept on RXL/ZXL till 1.1s instead of 1. Argon 20ms at 90V. E2/4 to gain 2. Ip programmed more rounded in the late rise. Fill to 1.9e-5 23 Pla disrupts at 1.3s. VDE dus to excessive n/n_c. Hmode during RF pulse at end. Drop ZXL gain in ramp down. Program ZXL up in down ramp. Drop IC_EF4 gain to 3. during .5-1.0s. 24 Pla No hmode. Ramped down nicely. nl04 to .9e20. IC_EF4 gain to 2. Maintain RXU at -.035 to end of flat top. 25 Pla Signs of dithering. Ramp-down to 1.48s EF2/4 ramp down much slower. EF2/4 gain to 4 nl04 to 0.8e20. Removed RXU glitch .9 to 1.s which may be responsible for the signs of vertical instability. 26 Pla Runs to 1.5s. Dithering. nl04 to 1.e20 EF2/4 gain switched on at .25s. Start clearin ramp at .95 s to avoid instability. 27 Pla to 1.5s. Instability signs gone. Ip to 900kA. 28 Pla Ran to Program clearin more negative at 1.5s. ZXL to -.005 from -.003 during flat top. 29 Pla Fine shot. Rampdown even better. Ip to 1MA. 30 Pla Disrupts at 1.06s. Hairy edge of instability throughout, but this is not a VDE. Lots of radiation from RF. Halo warning. Ip to 0.9MA nl04 to .8e20 RCUR to .663 from .661. 31 Pla Disrupts at 1.07 due to a strange gas effect associated with RF turn off. RF is givng a lot of Mo. Removed the density glitch at 1.s 32 Pla Lovely ramp down. No H-mode. Tiny tweak to current rise. Try to avoid the EF2 rail Fill to 1.7 to help the hesitant Ip rise. nel4 to .7e20 zxl to -.01 from -.005 Init failure. Cycled round. 33 Pla Long. No H-mode. Ip=1MA Nl04=.8e20. 34 Pla Ran down fine. No H-Mode. nl04 to 0.9e20 zxl to -.015 Argon off. 35 Pla Fine. No H-mode. Turn gas off at 0.8s through nl04 programming. Reenable Argon. 36 Pla Big Mo injection at .55s. Nl04 to 1.4e20. RF on. 37 Pla No RF but a good density 1.5. Sharkfin on rampdown. Repeat. 38 Pla Very nice H-mode shot. 1.2 MW RF. This one's a `keeper'!

Session Leader Comments
Mar 30 1995 11:02:36:830PM		Joseph Snipes	MP096 Lithium Conditioning H-mode Run Ohmic and ICRF Session Leader: Joseph Snipes This run will test the hypothesis that a coating of lithium on the walls of the vessel improves conditions for H-modes. A couple of discharges in conditions where we expect H-modes will begin the run (nl = 7 x 10^19 m^-2 Ip = 0.8 MA, BT = 5.3 T). Then, we will spend up to several hours of discharges injecting Li pellets to put down as much lithium as possible in a few hours, using the Li emission as a guide to determine when or if the level of lithium in the plasma saturates. For these conditioning discharges, the current will be reduced to 0.7 MA. When the Li conditioning is complete, the current will be returned to 0.8 MA and we will scan the density for H-modes to see if the H-mode behavior has changed.
Mar 30 1995 11:09:18:050PM		Joseph Snipes	For shot 1, we are starting with shot 950329012 with some modifications. The density will be set to 7 x 10^19 m^-2, RCUR was changed to include an offset of 8000 using the latest algorithm and the waveform was shifted out by 8 mm to correct for this. The current rise was modified slightly. A spike was added to the density waveform at 1 sec to avoid disruptions in the rampdown. The FSP and STRKPSI programming were left untouched.
Mar 31 1995 08:51:48:390AM	950331001	Joseph Snipes	Shot 1 Disrupted at about 0.54 sec at the change to the FSP controller. Return to X point controllers for shot 2.
Mar 31 1995 08:53:14:490AM	950331002	Joseph Snipes	Shot 2 Disrupted at about 1.2 sec during rampdown. No sign of H-mode except perhaps a small one at the gas puff at 1 sec.
Mar 31 1995 09:03:41:290AM	950331003	Joseph Snipes	Shot 3 Fizzle!
Mar 31 1995 09:14:20:630AM	950331004	Joseph Snipes	Shot 4 Prefill set to 1.7 x 10^-5 Torr. Good shot. Disrupted at 1.2 sec. Short ICRF H-mode from 0.9 - 1.0 sec with 0.45 MW of RF.
Mar 31 1995 09:24:46:470AM	950331005	Joseph Snipes	Shot 5 Good shot. RF H-mode from 0.9 - 1.0 sec.
Mar 31 1995 09:48:31:300AM	950331006	Joseph Snipes	Shot 6 Raised nel to 8 x 10^19 m^-2. Another short RF H-mode 0.9 - 1.0 sec, now with 0.8 MW.
Mar 31 1995 10:01:39:940AM	950331007	Joseph Snipes	Shot 7 Kept ZCUR at -2 cm during the rampdown in an attempt to eliminate the disruption in rampdown. A bit better, disrupted at 1.35 sec. Again a short RF H-mode from 0.9 - 1.0 sec.
Mar 31 1995 10:18:54:040AM	950331008	Joseph Snipes	Shot 8 Ip set to 0.7 MA, nel to 7 x 10^19 m^-2. Four Li pellets to be injected at 0.45 (small), 0.6 (med), 0.8 (large), and 1.0 (med) sec. Disrupted at 0.62 sec after second Li pellet.
Mar 31 1995 10:30:09:360AM	950331009	Joseph Snipes	Shot 9 Try again. Disrupted at 0.82 sec after third pellet.
Mar 31 1995 10:37:51:990AM	950331010	Joseph Snipes	Shot 10 Try again. Better. Got 3 pellets. Disrupted on large pellet at 1.0 sec.
Mar 31 1995 10:53:16:110AM	950331011	Joseph Snipes	Shot 11 Try again. LPI gate valve was not enabled. No pellets. Otherwise a good shot.
Mar 31 1995 11:05:29:200AM	950331012	Joseph Snipes	Shot 12 Try again. Disrupted at first small pellet.
Mar 31 1995 11:18:13:340AM	950331013	Joseph Snipes	Shot 13 Try again. Disrupted at 0.8 sec after 3rd pellet.
Mar 31 1995 11:26:22:710AM	950331014	Joseph Snipes	Shot 14 Raised nel to 9 x 10^19 m^-2. Got 3 pellets at 0.45 (small), 0.8 (med), and 1.0 (large). Pellet at 0.6 sec was missing. Good shot.
Mar 31 1995 11:45:30:200AM	950331015	Joseph Snipes	Shot 15 Got 3 pellets at 0.6 (small), 0.8 (med), and 1.0 (large). Good shot.
Mar 31 1995 11:49:23:030AM	950331016	Joseph Snipes	Shot 16 Got 3 pellets at 0.45 (small), 0.6 (med), and 0.8 (med). Good shot.
Mar 31 1995 12:36:20:030PM	950331017	Joseph Snipes	Shot 17 Short delay due to cooling problem. Li pellet camera repaired. Got 3 pellets at 0.6 (med), and 0.8 (med) and 1.0 sec. Good shot.
Mar 31 1995 12:40:38:440PM	950331018	Joseph Snipes	Shot 18 Got 3 pellets at 0.6 (med), and 0.8 (med) and 1.0 sec. Good shot.
Mar 31 1995 12:50:48:990PM	950331019	Joseph Snipes	Shot 19 Got 3 pellets at 0.45 (small), and 0.8 (med) and 1.0 sec. Disrupted at 1.04 s.
Mar 31 1995 01:22:16:390PM	950331020	Joseph Snipes	Shot 20 Got 4 pellets at 0.45 (small), 0.6 (med), 0.8 (med) and 1.0 sec. Disrupted at 1.44 s.
Mar 31 1995 01:20:39:740PM	950331021	Joseph Snipes	Shot 21 Got 4 pellets at 0.45 (small), 0.6 (med), 0.8 (med) and 1.0 sec. Disrupted at 1.49 s.
Mar 31 1995 01:36:52:360PM	950331022	Joseph Snipes	Shot 22 Ip set to 0.8 MA, nel to 7 x 10^19 m^-2. No H-mode. Lots of Moly injections. Li pellet at 1 sec. Disrupted at 1.09 sec.
Mar 31 1995 01:44:53:040PM	950331023	Joseph Snipes	Shot 23 Good shot. Short RF H-mode from 0.87 - 0.96 sec.
Mar 31 1995 02:03:30:600PM	950331024	Joseph Snipes	Shot 24 LPI gate valve does not close properly. So, there may be no more pellets today. No H-mode. Moly levels rather high.
Mar 31 1995 02:26:58:420PM	950331025	Joseph Snipes	Shot 25 Nel set to 9 x 10^19 m^-2. Good shot. Dithering from 0.4 - 1.1 sec.
Mar 31 1995 02:32:53:970PM	950331026	Joseph Snipes	Shot 26 Nel set to 8 x 10^19 m^-2. Good shot. Weak dithering H-mode from 0.75 - 1.0 sec.
Mar 31 1995 02:41:53:590PM	950331027	Joseph Snipes	Shot 27 Nel set to 1 x 10^20 m^-2. Good shot. No H-mode.
Mar 31 1995 02:54:15:780PM	950331028	Joseph Snipes	Shot 28 Ip set to 0.9 MA. Good shot. Some dithering, no H-mode.
Mar 31 1995 03:06:35:060PM	950331029	Joseph Snipes	Shot 29 Good shot. Some dithering 0.8 - 1.1 sec, no H-mode.
Mar 31 1995 03:14:03:010PM	950331030	Joseph Snipes	Shot 30 O.K. shot. Dithering 0.5 - 0.95 sec, no H-mode. Disrupted at 1.05 sec. Halo current warning above 150 kA.
Mar 31 1995 03:30:43:740PM	950331031	Joseph Snipes	Shot 31 Ip set to 0.9 MA, nel = 8 x 10^19 m^-2. Decent shot. Disrupted at 1.08 sec. Ugly RF near H-mode from 0.5 - 1.0 sec. Try without RF under the same conditions.
Mar 31 1995 03:47:54:930PM	950331032	Joseph Snipes	Shot 32 Repeat without RF. No H-mode.
Mar 31 1995 03:57:14:090PM	950331033	Joseph Snipes	Shot 33 nel set to 7 x 10^19 m^-2. No RF asked for. No H-mode.
Mar 31 1995 04:14:42:490PM	950331034	Joseph Snipes	Shot 34 nel set to 8 x 10^19 m^-2. Ip = 1 MA. No RF asked for. No real H-mode, some dithering from 1.12 - 1.24 sec.
Mar 31 1995 04:26:22:980PM	950331035	Joseph Snipes	Shot 35 Raised nel to 9 x 10^19 m^-2. Lowered ZXL by another 0.5 cm. Turned off Argon gas. Dithering from 1.1 - 1.25 sec.
Mar 31 1995 04:43:03:220PM	950331036	Joseph Snipes	Shot 36 Turned off A side gas at 0.8 sec. No H-mode.
Mar 31 1995 05:21:18:640PM	950331037	Joseph Snipes	Shot 37 nel set to 1.4 x 10^20 m^-2. RF not turned on due to finger trouble.
Mar 31 1995 05:20:31:620PM	950331038	Joseph Snipes	Shot 38 nel set to 1.4 x 10^20 m^-2. RF turned on at 0.5 sec to 1.0 sec. Great shot. ICRF H-mode from 0.73 - 1.04 sec. Several H-L-H transitions with an H factor up to 1.2 and taue up to about 45 msec.

Physics Operator Comments

Engineering Operator Comments
Shot	Time	Type	Status	Comment
1	08:29:32:440AM	Plasma	Ok	no faults
2	08:41:56:830AM	Plasma	Ok	no faults
3	08:54:50:530AM	Plasma	Ok	no faults
4	09:04:10:080AM	Plasma	Ok	no faults
5	09:15:07:800AM	Plasma	Ok	no faults
6	09:33:18:600AM	Plasma	Ok	no faults
7	09:49:34:730AM	Plasma	Ok	no faults
8	10:06:20:620AM	Plasma	Ok	no faults
9	10:18:53:220AM	Plasma	Ok	no faults
10	10:31:24:630AM	Plasma	Ok	no faults
11	10:42:50:940AM	Plasma	Ok	no faults
12	10:54:32:470AM	Plasma	Ok	no faults
13	11:05:08:260AM	Plasma	Ok	no faults
14	11:15:45:010AM	Plasma	Ok	no faults
15	11:27:17:020AM	Plasma	Ok	no faults
16	11:42:25:270AM	Plasma	Ok	noi faults
17	12:17:46:020PM	Plasma	Ok	no faults
18	12:28:32:100PM	Plasma	Ok	no faults
19	12:39:39:160PM	Plasma	Ok	no faults
20	12:54:48:320PM	Plasma	Ok	no faults
21	01:09:32:700PM	Plasma	Ok	no faults
22	01:21:37:100PM	Plasma	Ok	no faults
23	01:36:31:430PM	Plasma	Ok	no faults
24	01:50:17:950PM	Plasma	Ok	no faults
25	02:03:37:790PM	Plasma	Ok	no faults
26	02:15:57:030PM	Plasma	Ok	no faults
27	02:28:50:890PM	Plasma	Ok	no faults
28	02:41:03:810PM	Plasma	Ok	no faults
29	02:55:18:830PM	Plasma	Ok	no faults
30	03:06:24:130PM	Plasma	Ok	no faults
31	03:18:08:610PM	Plasma	Ok	no faults
32	03:31:56:830PM	Plasma	Ok	no faults
33	03:44:55:390PM	Plasma	Ok	no faults
34	04:00:37:240PM	Plasma	Ok	no faults
35	04:15:41:690PM	Plasma	Ok	no faults
36	04:29:26:520PM	Plasma	Ok	no faults
37	04:42:41:200PM	Plasma	Ok	no faults
38	04:53:35:900PM	Plasma	Ok	no faults