Miniproposals

Miniproposal: 421 Date Filed: 4/8/2005 Title: Obtaining Steady, Low Density H-Modes First Author: Martin Greenwald Session Leader: Martin Greenwald (shots 1-33)

Engineering Operator Run Comment

MP 421 - Steady, low density H-Modes SL: Greenwald PO: Marmar

Session Leader Plans

Entered: Jul 7 2005 04:20:23:320PM

Author: Martin Greenwald

MP 421 - Obtain steady, low-density h-modes Basically a repeat of 1050630 but with boronization Purpose: 1. Develop a method to lower the density of steady H-modes at normal current 2. Provide data on the scaling of the low density limit for the L/H transition 3. Explore ELM behavior at low collisionality Background and approach: Obtaining H-mode operation at low density is difficult because of the low density limit in the L-H threshold. Because a minimum density is required to make the transition, more gas is puffed into the target plasma than is desirable for lower density H-mode operation. The approach of this run is to enter H-mode at low current and low density, then to ramp up the current to normal operating levels. The figure from the MP shows proposed Ip and Prf waveforms Plan: Normal Bt, 5.3T, Standard plasma shape 1. Ip = 0.4 MA ramping to 0.8 as shown in MP figure RF power as shown, but lower power flat-top to about 2.0 MW start at nebar ~ 0.8 e20 adjust waveforms to optimize H-mode drop density shot by shot until low density l/h limit is reached 2. Ip to 0.2 MA repeat above, starting at lower density 3. Ip to 0.3 if time allows 4. Ip to 0.6 if time allows

Physics Operators Plans

Entered: Jul 7 2005 05:37:28:523PM

Author: Earl Marmar

Physop Plan 1050708 MP 421 - Steady, low density H-Modes SL: Greenwald PO: Marmar overnight boronization Engineering setup as on 1050630006, low current start-up A-coil configuration: normal [+Dtop -Dbot -Jtop +Jbot] and enabled. Gas Setup: fill B-Top with 6 psi D2 Hybrid enabled (PG4) fill B-side lower with 1 psi Ar Hybrid disabled (PG1) leave B-side upper alone fill B-main with 40 psi D2 Hybrid enabled (PG3) Enable the following: ECE and VUV gate valves, Z-bolo shutters ICRF Setup: transmitters in run-on at 8:30 Start from 1050630006, attempting to get into H-Mode at low density and current, then ramp the current and RF power up. The aim is to get high current, low density H-modes, which could make good targets for LHCD.

Session Leader Summaries

Entered: Jul 11 2005 01:10:44:770PM

Author: Martin Greenwald

For mp 421 We were able to make low density, low current H-modes but were not successful in ramping these up to full current. The low density limit did not seem to be much lower at low currents, however this was difficult to test, since the RF caused the density to rise. Generally the transition did not occur until nebar was in the range 0.9-1.1 These low density, low current discharges had very strong counter rotation - vphi was down below -50 km/sec ! This may connected to the difficulty in making the transition. It looked like the transition occured at about 0 km/sec; as before. Te95 at the transition was also high - typically in the range 200-250 eV. The best shot was 29 where we achieved a steady EDA H-mode with nebar down to 1.e20 at 0.38 MA; H98 = 1 At the L-H transition we have the following results: L-H PL/ Pnet/ Shot time nebar Ip PL nB Pnet nB Te95 02 1.04 1.99 0.91 2.1 0.20 1.7 0.18 190 04 0.79 1.73 0.91 1.7 0.25 1.6 0.24 180 05 0.48 1.38 0.45 1.2 0.19 1.0 0.16 190 06 0.46 1.28 0.45 1.2 0.22 1.1 0.21 160 07 0.45 1.24 0.45 1.4 0.28 1.2 0.25 190 08 0.45 1.13 0.45 1.4 0.31 1.2 0.29 200 09 none 1.2+ 0.45 2.0 >.28 1.7 >.25 >180 -35 10 none 1.2+ 0.45 1.9 >.3 1.6 >.26 >180 -15 11 none 0.9+ 0.45 2.0 >.35 1.5 >.15 >170 -30 12 none 1.2 0.45 1.9 >.3 1.5 >.26 >200 -20 14 0.88 1.15 0.58 2.1 0.33 1.2 0.20 150 15 0.53 1.22 0.45 1.5 0.21 1.3 0.19 150 -15 16 0.58 1.23 0.36 1.4 0.21 1.1 0.16 200 -15 17 0.58 1.26 0.33 1.5 0.22 1.0 0.15 110 -15 18 0.79 1.20 0.39 1.0 0.14 0.7 0.11 160 19 0.61 1.4 0.33 1.8 0.23 1.5 0.21 140 -20 21 0.63 1.27 0.33 1.8 0.26 1.5 0.21 190 22 0.65 1.17 0.33 2.0 0.30 1.6 0.25 190 -25 23 0.61 1.13 0.54 2.1 0.35 1.0 0.17 190 25 0.67 1.10 0.39 2.1 0.35 1.7 0.28 135 27 none 1.0 0.38 2.0 >.4 1.0 >.2 >170 <-30 * 29 0.66 1.0 0.38 1.2 0.22 0.9 0.16 140 Steady 30 0.64 1.20 0.39 1.0 0.16 0.7 0.10 145 -10 31 0.70 1.12 0.27 1.3 0.21 1.1 0.18 140

Physics Operator Summaries

Session Leader Comments
Jul 8 2005 09:07:36:237AM	1050708001	Martin Greenwald	fizzle
Jul 8 2005 09:27:58:580AM	1050708002	Martin Greenwald	Starting at higher current to degas after boronization 0.9 MA, target density 1.8e20 H-mode with H89 about 1.5
Jul 8 2005 09:34:21:690AM	1050708003	Martin Greenwald	fizzle
Jul 8 2005 09:50:32:830AM	1050708004	Martin Greenwald	Another shot at normal current - 0.9 MA density lower - target at 1.2e20 Power drops to 1 MW after brief excursion at 2-3 long H-mode
Jul 8 2005 10:09:26:363AM	1050708005	Martin Greenwald	Ip flat at 0.4 MA early H-mode - at about 0.5 seconds - lasts to about 0.7 target density to 0.85
Jul 8 2005 10:21:59:563AM	1050708006	Martin Greenwald	Current ramp added Good shot - early H-mode, at about 0.46 seconds target density down to 0.7, but goes to 1.15 with RF final H-mode density to 2.6e20 RF power at 1.6 early but drops to 1.3
Jul 8 2005 10:32:44:220AM	1050708007	Martin Greenwald	Good shot - first H-mode lasts longer Target density still at 0.7, goes into H-mode at 1.15 Final density goes to 2.6e20 Prad still low and not increasing
Jul 8 2005 10:44:15:300AM	1050708008	Martin Greenwald	Multiple H-modes Target density down to 0.65; 1.0 at L-H Radiated power up late some early hard xrays
Jul 8 2005 10:56:44:877AM	1050708009	Martin Greenwald	No early H-mode even with RF at 2 MW P/nBS at 0.4 early ne at L/H transition is 1.45 Prad low except for two large injections late - each kills the H-Mode
Jul 8 2005 11:07:11:893AM	1050708010	Martin Greenwald	Delayed start of Ip ramp (with same endpoint) Disrupts at 0.94 (maybe ramp too fast?) Radiated power going up fast No H-modes - though P/nBS goes to 0.4
Jul 8 2005 11:21:42:503AM	1050708011	Martin Greenwald	Target density down to 0.32 RF steady at 2 MW Lots of radiation No H-modes til very late
Jul 8 2005 11:39:55:393AM	1050708012	Martin Greenwald	Disrupts at 0.8 sec Target density to 0.5e20 Then flattops at 1 No H-modes - why not?? Edge Temperatures are hot
Jul 8 2005 11:45:28:520AM	1050708013	Martin Greenwald	Disrupts early - 0.6 sec Large Injection at 0.53 sec
Jul 8 2005 12:02:54:893PM	1050708014	Martin Greenwald	Multiple H-modes - none early OH density reaches 0.66 then rises to 1.1 before first H-mode Te edge above 200 eV at transition
Jul 8 2005 12:15:00:630PM	1050708015	Martin Greenwald	Raised density slightly Multiple H-modes again - include early one at 0.55 sec Density at L-H is 1.0e20 threshold Te near 200
Jul 8 2005 12:32:02:177PM	1050708016	Martin Greenwald	Initial Ip down a bit (we were aiming for 0.3 MA) Brief early H-mode at about 0.585 seconds impurities kill later H-modes
Jul 8 2005 12:45:33:127PM	1050708017	Martin Greenwald	Ip down to 0.33 MA Multiple H-modes, one early at about 0.6 sec Target density at 0.75 Rises to 1.0 at L-H transition Edge Te near 210 eV
Jul 8 2005 01:02:34:627PM	1050708018	Martin Greenwald	Ip starts at 0.32 Multiple H-modes - none early First H-mode is at 0.8 sec density at L-H ~ 1.e20 RF power data not available
Jul 8 2005 01:25:33:317PM	1050708019	Martin Greenwald	Multiple H-modes - one early at 0.62 sec current was a 0.33 RF data problem
Jul 8 2005 01:39:51:690PM	1050708020	Martin Greenwald	No power shot
Jul 8 2005 02:25:04:330PM	1050708021	Martin Greenwald	Early H-mode at 0.64 sec L-H at 1.1 sec
Jul 8 2005 02:40:55:690PM	1050708022	Martin Greenwald	Multiple H-modes First at 0.66 sec, density at 1.05e20
Jul 8 2005 02:48:24:050PM	1050708023	Martin Greenwald	Raise current to 0.55 Brief early H-mode at 0.62 sec, at transition density is at 0.93 Radiation is bad during H-modes
Jul 8 2005 03:04:28:940PM	1050708024	Martin Greenwald	MHD problem - locked mode Plasma thrashes badly at 0.8 seconds
Jul 8 2005 03:19:56:563PM	1050708025	Martin Greenwald	Ip flat at 0.38 No data on J-antenna, but RF power is probably flat at 2.5 MW long low density H-mode
Jul 8 2005 03:26:46:470PM	1050708026	Martin Greenwald	Another problem with MHD - locked mode? No H-modes
Jul 8 2005 03:42:25:690PM	1050708027	Martin Greenwald	Power ramped 1.5-2.5 Ip to 0.37 MA No H-modes Rotatation strongly counter-current
Jul 8 2005 03:54:40:860PM	1050708028	Martin Greenwald	MHD is back
Jul 8 2005 04:21:29:907PM	1050708029	Martin Greenwald	Steady v. low density H-mode Rotation near 0 m/sec
Jul 8 2005 04:41:35:127PM	1050708030	Martin Greenwald	Similar to previous shot - slightly higher density Ip ramped starting at 1.0 sec density rises and H-modes lost quickly L-H at about 200 eV - Vphi ~ 0
Jul 8 2005 04:40:52:470PM	1050708031	Martin Greenwald	Current to 0.26 Early H-mode (somewhere like .6-.7 sec) difficult to tell when the H-mode starts and stops but definitely lost during current ramp
Jul 8 2005 04:46:23:110PM	1050708032	Martin Greenwald	Disrupts early not clear if there are H-modes

Physics Operator Comments
Jul 8 2005 09:10:45:987AM	1050708001	Earl Marmar	start with I_p = 900 kA to evaluate post boronization conditions load from 1050630006, low current startup prepuff to 17 msec Ip target to -.9MA nl_04 target 5e19 fizzle fields look ok breakdown at about the right time lump on the H-alpha
Jul 8 2005 09:31:38:707AM	1050708002	Earl Marmar	reduce prepuff by 1 msec, to 16 msec plasma current rise looks good at startup Z-meter doesn't seem to burn out H-mode after 1.1 seconds, Prf ~ 2 MW low radiated power (~300 kW in H-mode)
Jul 8 2005 09:35:25:127AM	1050708003	Earl Marmar	reduce outer gap ~4 mm (increase RCUR 2 mm, and remove the late decrease) fizzle pressure is up a little at t=0
Jul 8 2005 09:55:41:283AM	1050708004	Earl Marmar	reduce prepuff 2 msec (to 14 msec) plasma H-mode RF power briefly 3 MW, then 1 MW through the H-Mode P_Rad up compared to shot 2, density is lower, F-side pressure lower
Jul 8 2005 10:09:23:393AM	1050708005	Earl Marmar	Ip to 400 kA straight across tweak RCUR between .8 and 1.4 seconds to try to keep the outer gap constant plasma better outer gap early H-mode? (around .5 seconds)
Jul 8 2005 10:18:13:063AM	1050708006	Earl Marmar	lower target nl_04 to 3e19 reduce post-breakdown segment 1 programmed puff to be 3 msec shorter ramp Ip from .4 to .8 MA between .6 and 1 sec. plasma early H-Mode, E-port gave up the ghost early
Jul 8 2005 10:34:17:767AM	1050708007	Earl Marmar	reduce the post-breakdown segment 1 puff by another 3 msec B-side upper, 1 psi neon, enabled B-side lower, 1 psi argon, enabled PG1 35 msec starting at .3 s (argon) PG2 30 msec starting at .3 s (neon) plasma early H-mode, lasts longer this time E-port still unhappy a few early hards on this one
Jul 8 2005 10:44:07:347AM	1050708008	Earl Marmar	no pcs changes plasma startup bounced early hards up some more 2 MW from J-port (E was off); various trips, in and out of H-mode
Jul 8 2005 11:00:35:580AM	1050708009	Earl Marmar	reduce prepuff 1 msec to 13 msec increase post-breakdown segment 1 puff by 2 msec plasma no bounce on startup; early hards are gone multiple H-modes
Jul 8 2005 11:06:15:783AM	1050708010	Earl Marmar	delay start of Ip ramp by .1 seconds, to begin at .7 increase neon puff to 35 msec, starting at 0.3 s plasma early disruption, during the current ramp from .4 to .8 MA
Jul 8 2005 11:24:08:893AM	1050708011	Earl Marmar	slow the .4 to .8 MA Ip ramp; target to reach .8 MA at 1.1 sec (instead of 1 sec) plasma got lower density (previous disruption outgassed the walls) big increase of radiated power around 1 second (John reports big moly signals)
Jul 8 2005 11:31:31:910AM	1050708012	Earl Marmar	nl_04 target to 4e19 plasma bouncy start, early hards disrupt at .7 seconds, big injections
Jul 8 2005 11:51:04:017AM	1050708013	Earl Marmar	tweak RXL to get out of the slot early plasma bouncy startup some hards earlier disrupt big injection around .5 s
Jul 8 2005 11:56:06:813AM	1050708014	Earl Marmar	add 2 msec to prefill puff (now 15 msec) tweak RXL to be slightly smaller at 0.5 s plasma bouncy startup, early hards are worse multiple late H-modes
Jul 8 2005 11:56:32:580AM	1050708015	Earl Marmar	Steve Wolfe taking over as physop for ~ 1 hour.
Jul 8 2005 12:12:47:877PM	1050708015	Steve Wolfe	Shot#15: Increase pg4 by 2ms (to 17ms) to try to reduce bouncy hards raise nl4 program from 4 to 5e19 plasma, no bounce, no hards. Early h-mode, but it has several H->L as the current increases. First H->L is at 0.935, which precedes crossover. Strike is back on the floor again; may have helped get the H-mode. Next: Reduce starting current to 300kA
Jul 8 2005 12:26:36:800PM	1050708016	Steve Wolfe	Shot#16: Reduce starting current to 300kA (seg1 and seg2) Delay second flattop from .11 to .12sec Change OH crowbar times from .08 to .06sec plasma full length, first plateau was only at 350kA, need to pull it down more. Early H-mode (?) but it loses it quickly The high gain(4) in seg1 only comes on at .086sec, so I need to either bring that on earlier or reduce the V next: try again
Jul 8 2005 12:45:00:630PM	1050708017	Steve Wolfe	Shot#17: Reduce V_oh1 to 0 after 50msec in seg1 Also in seg2 until .15sec, and from 150 to 100V from .2 to .4sec, ip gain from 4 to 8 at .356 plasma full length. Bouncy startup again, should have increased pg4 Ip is down to 320kA at 400, but comes back up. Should probably reduce the voltage all the way to 0.7sec next: increase pg4 another 2ms VOH1 to 50V from .2 to .7sec
Jul 8 2005 01:01:19:313PM	1050708018	Steve Wolfe	Shot#18: increase pg4 another 2ms VOH1 to 50V from .2 to .7sec plasma full length multiple h-modes First plateau is down to ~320kA and pretty flat. No bounce or hards this time. Doesn't get an H-mode early, or at least doesn't stay in H Next: Try a repeat with higher power
Jul 8 2005 01:18:46:237PM	1050708019	Steve Wolfe	Shot#19: Try a repeat with higher power plasma full length, bounce is back. RF problem (crowbar) and RF data problem (no cell data) Earl is back as physop
Jul 8 2005 01:45:19:720PM	1050708020	Earl Marmar	add another 1 ms to pre-fill puff (now 20 msec) data system problems during init no power cycle
Jul 8 2005 02:20:59:923PM	1050708021	Earl Marmar	no pcs changes plasma multiple h-modes
Jul 8 2005 02:39:46:033PM	1050708022	Earl Marmar	increase prefill puff another 1 msec (now 21 msec) increase neon puff by 10 msec to 50 msec plasma multiple H-modes
Jul 8 2005 02:52:44:750PM	1050708023	Earl Marmar	reload 1050708015 increase prefill puff to 21 msec increase early Ip flattop to 500 kA, then ramping up to 800 kA plasma multiple h-modes
Jul 8 2005 03:05:50:987PM	1050708024	Earl Marmar	.4 MA straight across lower a-coil current after .8 s plasma no h-modes sawteeth disappear around .7 seconds, then Z_eff goes up to about 4
Jul 8 2005 03:32:15:423PM	1050708025	Earl Marmar	reduce Ip to 350 kA add 1 msec to prefill puff plasma decent H-mode, seems steady
Jul 8 2005 03:33:18:800PM	1050708026	Earl Marmar	no pcs changes plasma mhd trouble around 1 second, then it seems to recover not clear if there was an h-mode
Jul 8 2005 03:41:34:703PM	1050708027	Earl Marmar	move rxl in to avoid the outer nose plasma no h-mode
Jul 8 2005 04:09:04:063PM	1050708028	Earl Marmar	try to increase elongation: ZXU 3 cm less positive nl_04 target to 4.5e19 plasma mhd lurch around 1 sec no obvious h-mode
Jul 8 2005 04:08:30:597PM	1050708029	Earl Marmar	no pcs changes plasma steady h-mode, ITER98y2 enhancement ~ 1
Jul 8 2005 04:09:30:283PM	1050708030	Earl Marmar	ramp current up to .8 MA between 1. and 1.4 sec
Jul 8 2005 04:43:43:940PM	1050708031	Earl Marmar	250 kA, ramping up after 1 second load from 1050708022 OH crowbars to .04 seconds OH voltages reduced in segment 1 and 2 (until 1 second) turn off a-coils Ip ramping to .8 MA between 1 and 1.4 s plasma H-mode into current ramp goes inner wall limited at crossover, and drops out of h-mode at that time
Jul 8 2005 04:52:17:690PM	1050708032	Earl Marmar	increase clearin between .85 and 1.3 seconds modify RCUR by half as much plasma disrupt during current ramp lost J-port around 1 second lurch to inner wall looks worse
Jul 8 2005 05:00:43:050PM	1050708033	Earl Marmar	reload shot 31 reduce Ip ramp, going up to 500 kA at 1.4 seconds plasma another disruption shortly into the current ramp, at 1.23 seconds

Engineering Operator Comments
Shot	Time	Type	Status	Comment
1	09:05:23:877AM	Plasma	Ok
2	09:19:33:927AM	Plasma	Ok
3	09:32:42:110AM	Plasma	Ok
4	09:45:06:753AM	Plasma	Ok
5	09:57:37:927AM	Plasma	Ok
6	10:10:02:160AM	Plasma	Ok
7	10:23:00:190AM	Plasma	Ok
8	10:35:29:753AM	Plasma	Ok
9	10:47:47:753AM	Plasma	Ok
10	11:00:02:487AM	Plasma	Ok
11	11:12:48:097AM	Plasma	Ok
12	11:25:15:970AM	Plasma	Ok
13	11:38:32:097AM	Plasma	Ok
14	11:51:23:987AM	Plasma	Ok
15	12:04:00:207PM	Plasma	Ok
16	12:19:20:567PM	Plasma	Ok
17	12:35:21:067PM	Plasma	Ok
18	12:48:04:767PM	Plasma	Ok
19	01:13:31:580PM	Plasma	Ok
20	01:33:15:737PM	Test	Ok	No power shot due to data acquistion problems
21	02:10:46:500PM	Plasma	Ok
22	02:26:28:940PM	Plasma	Ok
23	02:39:22:343PM	Plasma	Ok
24	02:52:41:190PM	Plasma	Ok
25	03:05:32:877PM	Plasma	Ok
26	03:18:25:690PM	Plasma	Ok
27	03:31:38:800PM	Plasma	Ok
28	03:45:45:953PM	Plasma	Ok
29	03:58:55:453PM	Plasma	Ok
30	04:11:53:063PM	Plasma	Ok
31	04:28:23:110PM	Plasma	Ok
32	04:42:21:440PM	Plasma	Ok
33	04:54:45:453PM	Plasma	Ok