Miniproposals

Miniproposal: 245 Date Filed: 3/31/1999 Title: Dependence of Main Chamber Recycling on Plasma Density First Author: Maxim Umansky Session Leader: Brian Labombard (shots 1-19)

Engineering Operator Run Comment

Mossesian/Silva

Session Leader Plans

Physics Operators Plans

Session Leader Summaries

Entered: Jul 7 2004 03:49:20:367PM

Author: To Be Determined

Session Leader's summary of run 990519 MP#245 - Dependence of Main Chamber Recycling on Plasma Density Physics Operator: Mossessian, Wolfe Session Leader: LaBombard Purpose: See if the regime of strong main chamber-wall recycling persists in very low core plasma density discharges. Plan: First try to run some very low density 0.8 MA ohmic discharges (NL04 < .2?!) and then do a density scan. Result: Plasma operation started in the mid afternoon (shot#9), owing to some power supply problems. We were successful in setting up reproducible discharges with NL04 around 0.35x10^20 m^-2. We got one discharge at NL04 ~ 0.2 (shot#10) by turning the gas off but it had a lot of run-aways. This got nearly everyone into an excited state. To avoid the population inversion and the runaways, we kept NL04 above 0.35 for the remaining 5 plasma shots of the run. There was no time to do the density scan. Combinations of flapper closed (open), then open (closed) after 0.9 or 1.0 sec were run. The FSP and ASP probes were triggered to insert at 0.75, 0.95, and 1.15 seconds. By shot #18, the probes were optimized for deepest insertion depth and should have reached the last-closed flux surface. There appeared to be a problem with the automatic data analysis of the divertor probe data, with most I-V fits reporting an error. The camac data for these probes are not saturated so fitted density and Te values may be recoverable. Perhaps the high Te on the target does not allow a true ion saturation to be achieved with the -100 volt bias. This will be sorted out later. The key measurements for this miniproposal were considered to be: (1) Compare midplane and divertor neutral pressures with flapper open/closed Q: Does the flapper influence the midplane pressure more at lower densities? If so then this would imply that main-chamber recycling becomes less important relative to divertor recycling a low plasma densities: A: No the flapper does not influence the midplane pressure at all at lower densities. It still does influence the divertor neutral pressure, although to a lesser degree (~25% drop in divertor pressure when flaps open compared to 50% drop at high NL04). (2) Measure parallel flows to divertor with scanning Mach probes and compare it to the ionizations in the main chamber from H-alpha/Ly-alpha measurements. Q: Does the profile-integrated parallel flow to the divertor become comparable to the total number of ionizations in the main chamber at low densities. (Recall Maxim's observation that ionizations in the main chamber can become a factor 10 HIGHER than the flow to the divertor at high NL04). A: Don't know yet. However, we should have some good Mach probe data. Also, Rejean's new Lyman-alpha profile measurements should provide some important information here. Shots: Shot#09 - NL04=0.6, no flappers, no FSP/ASP Shot#10 - NL04=0.2, hard x-rays, flapper opened at 0.9 sec - no effect on pressures. Shot#11 - NL04=0.36, flapper closed then opened at 0.9 sec - divertor pressure drops Shot#12 - NL04=0.36, flapper closed then opened at 1.0 sec - no change in divertor pressures, ASP/FSP at .75, .95, 1.15 Shot#13 - NL04=0.36, flapper closed then opened at 1.0 sec, ASP/FSP at .75, .95, 1.15 Shot#15 - NL04=0.36 Injection at .85 sec causes pressure drop in divertor. Flapper open then closed at 1 second. Divertor pressure increases when flapper closes, ASP/FSP at .75, .95, 1.15 Shot#18 - NL04=0.35, flapper open then closed at 1 sec - increase in divertor pressure. No change in midplane pressure. ASP/FSP at .75, .95, 1.15, best insertion depths for scanning probes

Physics Operator Summaries

Entered: Jul 7 2004 04:37:01:160PM

Author: To Be Determined

Physics operator summary for run 990519 Experiments: MP#245 "Dependence of Main Chamber Recycling on Plasma Density" - SL LaBombard MP#242 "Effect of Right Gap on Mid-Plane Pressure" - SL Pitcher - planned but not executed. SL: B. Labombard PO: D. Mossessian/S. Wolfe Summary: Run was delayed due to commutation curcuit problems. First 8 shots are tests. Shot 9 is a copy of 990429027 with nl04 programmed to 6e19. Then in attempt to get lowest possible density the C-side gas valve was disabled and shot 10 had nl04 = 2e19 causing hard x-rays problem. The density was increased after that and following shots ran at 4e19. We had a few duds, possibly because sparkers were turned off. After the run, Jim Irby checked on why the sparker (which normally provides pre-ionization and may prevent duds) was not firing today or yesterday. It was turned off. He turned it back on and took a test shot, and it worked as usual. It should be on for tomorrow's run. Scorecard: 7 plasmas 0 fizzles 3 dud ---------------------------------------------------------------------------- 990519009 Plasma. nl04=6e19 as requested. Flapper was requested to open at .9 sec but was not functionning. For next shot hybrid DISABLE C-side valve - turn off fueling. Lowered Br0 offset to 0.002 from 0.003 990519010 Plasma. nl04=2e19. Runaway problems. Increase target to 4e19. 990519011 Program nl04 4e19, turned off pulse_gas3 after .3 sec Plasma, nl04=3.6e19. 990519012 Same density. Increased gas at .3 sec trying to get rid of the density minimum at that time. Flappers moved to 1. sec. Plasma, nl04=3.6e19. No effect on Ne minimum @ .3 sec. 990519013 Same density. Increased gas at .3 sec. Moved ZXL up 5 mm. Plasma, nl04=3.6e19. 990519014 No PCS change. Dud. Steve thinks the prepuff is low. Increase prepuff to 22 msec. 990519015 Plasma. 3.6e19. shot 17: tweaked pre-puff and BR_0 and got another dud shot 18: Put Br0 back and tweaked Bz by making IC_EF4 more positive by 15Amps got a good plasma shot 19: Tried to drop the density by 1.0e19 got another dud.

Session Leader Comments
May 19 1999 03:03:44:887PM	990519009	Brian Labombard	Plan for first half of tuesday's run: MP#245 "Dependence of Main Chamber Recycling on Plasma Density" Purpose: See if the regime of strong main chamber-wall recycling persists in very low core plasma density discharges. Plan: First try to run some very low density 0.8 MA ohmic discharges (NL04 < .2?!) and then do a density scan. Discharge cleaning: No ECDC. Base pressure is presently in the mid -9 range. The walls are degassed well enough now. Shot # 9 No probes firing. Flapper did not go. NL04 = .64 G_side = .028 mtorr Next shot get flappers. Turn off gas.
May 19 1999 03:25:07:107PM	990519010	Brian Labombard	Shot#10 Got NL04= 0.2. G_side=.008 mtorr, B_bottom= .6 mtorr So compression ratio is still roughly 100. Flapper went at 0.9 sec but no change in pressures. Too many hard x-rays. Raising density to 0.4.
May 19 1999 03:35:41:043PM	990519011	Brian Labombard	Shot#11 Got NL04= 0.4. G_side=.018 mtorr, B_bottom= 1.3 -> 0.8 mtorr when flapper opens. Next shot repeat with scanning probes firing .75, .95, 1.15 sec.
May 19 1999 03:54:56:593PM	990519012	Brian Labombard	Shot#12 Got NL04= 0.37 G_side=.013 mtorr, B_bottom= 1.1 mtorr Flapper makes no difference. Next shot repeat with tweak of x-point Z.
May 19 1999 04:15:59:547PM	990519013	Brian Labombard	Shot#13 Got NL04= 0.35 G_side=.014 mtorr, B_bottom= 1.15 mtorr at 1 second. Next shot repeat with flapper open then closed at 1 sec.
May 19 1999 04:51:31:090PM	990519015	Brian Labombard	Shot#15 Got NL04= 0.35. Injection at .85 sec causes pressure drop in divertor. Flapper open then closed at 1 second. Divertor pressure increases when flapper closes. Next shot repeat. Flapper open then closed at 1 sec.
May 19 1999 05:52:32:077PM	990519018	Brian Labombard	Shot#18 Got NL04= 0.35. G_side= .015 mtorr, B_bot=.8 mtorr Flapper closing at 1 sec causes increase in divertor pressure. No change in midplane pressure. Next shot try for lower density with flapper open, closed at 0.8 sec and open at 1.0 sec.

Physics Operator Comments
May 19 1999 07:43:20:547AM		Dmitri Mossessian	PCS load from 990429027 Coldstart OK. Engineering Setup for 9905019: Load from 990429027. NO OVERNIGHT ECDC. TF uder hybrid control. Gas setup: B-top - 6 psi of D2 Hybrid enabled B-side lower - 1 psi of Ar Hybrid DISABLED B-side upper - as is HYBRID DISABLED C-side - 30 psi D2 Hybrid enabled J-bottom - as is Hybrid DISABLED ECE,VUV gate valves enabled. Experiments: MP#245 "Dependence of Main Chamber Recycling on Plasma Density" - SL LaBombard MP#242 "Effect of Right Gap on Mid-Plane Pressure" - SL Pitcher
May 19 1999 12:02:54:280PM		Dmitri Mossessian	Run delayed because of the commutation curcuit problems
May 19 1999 02:40:36:263PM	990519008	Dmitri Mossessian	OH test shot.
May 19 1999 03:05:52:217PM	990519009	Dmitri Mossessian	Plasma. nl04=6e19 as requested. Flapper was requested to open at .9 sec but was not functionning. For next shot hybrid DISABLE C-side valve - turn off fueling. Lowered Br0 offset to 0.002 from 0.003
May 19 1999 03:13:33:357PM	990519010	Dmitri Mossessian	Plasma. nl04=2e19. Runaway problems. Increase target to 4e19.
May 19 1999 03:29:56:497PM	990519011	Dmitri Mossessian	Program nl04 4e19, turned off pulse_gas3 after .3 sec Plasma, nl04=3.6e19.
May 19 1999 03:46:08:077PM	990519012	Dmitri Mossessian	Same density. Increased gas at .3 sec trying to get rid of the density minimum at that time. Flappers moved to 1. sec. Plasma, nl04=3.6e19. No effect on Ne minimum @ .3 sec.
May 19 1999 04:12:14:327PM	990519013	Dmitri Mossessian	Same density. Increased gas at .3 sec. Moved ZXL up 5 mm. Plasma, nl04=3.6e19.
May 19 1999 04:30:48:093PM	990519014	Dmitri Mossessian	No PCS change. Dud. Steve thinks the prepuff is low. Increase prepuff to 22 msec.
May 19 1999 04:39:18:437PM	990519015	Dmitri Mossessian	Plasma. 3.6e19.
May 19 1999 04:56:40:450PM	990519016	Dmitri Mossessian	No PCS changes. Dud. Steve Wolfe will take over now.
May 19 1999 05:11:11:750PM	990519017	Steve Wolfe	shot#17: Wolfe taking over as Physop for the last half-hour (after a dud on shot #16) Raise pre-puff to 24 msec, lower BR-0 by .5mT; could stand a little more Bz, but just change two things for now. Note that the sparker is not running (since yesterday); could be causing duds. Another Dud. Next shot, try increasing Bz (EF4 15amps positive)
May 19 1999 05:25:55:717PM	990519018	Steve Wolfe	shot#18: Br0 back to .002 (from .0015) and IC_ef4 from -1275 to -1260. plasma ok. 3.4e19 Next shot drop the density to 3e19
May 19 1999 05:39:55:590PM	990519019	Steve Wolfe	shot#19: drop the density to 3e19 dud. We seem to be much more prone to duds, probably because of the lack of sparker for pre-ionization. End of Run.

Engineering Operator Comments
Shot	Time	Type	Status	Comment
1	07:18:14:530AM	Test	Bad	cycle test appears to be hung up
2	07:45:00:263AM	Test	Ok	cycle test ok
3	09:14:44:183AM	Test	Bad	OH2 comm test no power
4	10:15:58:683AM	Test	Bad	OH2 u comm test
5	01:32:46:327PM	Test	Bad	OH2U Commutation Test
6	02:02:18:343PM	Test	Bad
7	02:13:55:640PM	Test	Ok	OH2 comm test/ u,l both fired
8	02:35:20:560PM	Test	Ok	OH2U,L 10KA comm test
9	02:44:57:763PM	Plasma	Ok	no faults/plasma
10	03:01:52:903PM	Plasma	Ok	No Faults
11	03:21:19:857PM	Plasma	Ok	Plasma
12	03:40:14:590PM	Plasma	Ok	NO Faults
13	04:01:08:467PM	Plasma	Ok	No Faults
14	04:18:55:967PM	Plasma	Ok	No power supply faults
15	04:34:14:420PM	Plasma	Ok	No Faults
16	04:52:23:670PM	Plasma	Ok	No faults
17	05:06:09:060PM	Plasma	Ok	No Faults
18	05:19:22:623PM	Plasma	Ok	No faults
19	05:36:43:420PM	Plasma	Ok	No Faults