Alcator C-Mod Run 930930 Information

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Miniproposals
Miniproposal:009
Date Filed: 7/14/1993
Title:Pellet Fueling Studies
First Author:Martin Greenwald
Session Leader:Martin Greenwald (shots 1-26)

Operators
Session leader(s):Martin Greenwald
Physics operator(s):Joseph Snipes
Engineering operator(s): Unknown

Engineering Operator Run Comment
pellet injector

Session Leader Plans

Physics Operators Plans

Session Leader Summaries

Physics Operator Summaries

Session Leader Comments
Sep 30 1993 09:27:20:260AMMartin Greenwald2nd Pellet Run
We will push current to about .6 MA and try to raise the density to its
limit - about 4.5e20.
We will be looking at P mode confinement and ablation physics.
The plasma TV is looking at continuum - should see
high central density.

Sep 30 1993 09:27:55:010AM930930001Martin GreenwaldFizzle.

Sep 30 1993 09:45:52:830AM930930002Martin GreenwaldGood shot at about .49 MA

Sep 30 1993 10:01:28:770AM930930003Martin GreenwaldFizzle

Sep 30 1993 10:19:12:170AM930930004Martin GreenwaldGood shot - some strong interaction with RF limiter - at 93 cm
(asked them to move it out 1 cm for next shot)

Sep 30 1993 10:43:08:520AM930930005Martin GreenwaldGood shot - .61 MA

Sep 30 1993 11:06:51:240AM930930006Martin GreenwaldFirst shot with pellet - at .5 sec
Moly injection at .285 sec
Shark fin after pellet.

Sep 30 1993 11:27:05:750AM930930007Martin Greenwald pellet - at .5 sec
Shark fin after pellet.

Sep 30 1993 11:40:37:910AM930930008Martin Greenwaldfizzle
- going into cell to fix tracker and drop gains on JT's Halpha

Sep 30 1993 12:25:50:210PM930930010Martin GreenwaldFire pellet 14 at .5 sec.
Density rise unkown - analysis problem

Sep 30 1993 01:02:35:270PM930930012Martin GreenwaldFizzle

Sep 30 1993 01:07:14:000PM930930013Martin GreenwaldDisrupts about 50 msec after pellet

Sep 30 1993 01:32:31:590PM930930014Martin GreenwaldFizzle

Sep 30 1993 02:22:48:370PM930930015Martin GreenwaldGood Shot with smaller pellet - shark fin after pellet

Sep 30 1993 02:12:26:360PM930930016Martin GreenwaldGood Shot with smaller pellet - shark fin after pellet

Sep 30 1993 02:23:04:590PM930930017Martin Greenwaldfizzle

Sep 30 1993 02:43:17:210PM930930018Martin Greenwaldfizzle

Sep 30 1993 03:08:36:690PM930930019Martin GreenwaldDecent start but multiple Mo injections after .45 sec
pellet at .5

Sep 30 1993 03:33:41:010PM930930020Martin GreenwaldFizzle

Sep 30 1993 03:33:56:540PM930930021Martin GreenwaldFizzle

Sep 30 1993 03:52:08:340PM930930022Martin GreenwaldPut in big pellet, disrupted shortly after pellet.
big mhd

Sep 30 1993 04:29:38:020PM930930024Martin GreenwaldDisruption at .37 - before pellet

Sep 30 1993 04:47:15:160PM930930025Martin GreenwaldSome runaways, disrupts at .82
Softs never recover

Sep 30 1993 04:54:48:510PM930930026Martin GreenwaldFizzle

Physics Operator Comments
Sep 30 1993 09:41:48:950AM930930001Joseph SnipesShot 1
Set prefill to 1.1 x 10**-5 Torr. Copied programming from 930928019.
Fizzle

Sep 30 1993 09:53:22:250AM930930002Joseph SnipesShot 2
One more time . . . This time successful.

Sep 30 1993 10:06:59:550AM930930003Joseph SnipesShot 3
Increased the gas puff a bit from 150 to 180 ms to try to flatten out the
density. Also increased the plasma current waveform from 500 to 600 kA.
Fizzle!

Sep 30 1993 05:14:28:520PM930930004Joseph SnipesShot 4
Good shot. But note problems as OH1 passes through zero around 250 ms.

Sep 30 1993 10:53:52:180AM930930005Joseph SnipesShot 5
Moved the RF limiter out from R=0.92 m to R=0.93 m to avoid the limiter
sparks. Increased the gas puff a bit from about 0.4 to 0.6 s.
Pretty good.

Sep 30 1993 11:00:57:470AM930930006Joseph SnipesShot 6
Decreased the gas puff a bit from 0.5 to 0.8 s.
Pellet at 0.5 s. Decent shot.

Sep 30 1993 11:18:28:610AM930930007Joseph SnipesShot 7
Pellet at 0.5 s. Decent shot.

Sep 30 1993 11:56:26:330AM930930008Joseph SnipesShot 8
Modified Ip waveform to program in the notch in the current that is being
forced by the delay in OH1 as it passes through zero so that the feedback
does not have to fight the power supplies, hopefully to eliminate the sudden
change in radial position and decrease in kappa from 250 to 400 ms.
Pellet at 0.5 s. Decent shot.

Sep 30 1993 11:57:14:700AM930930008Joseph SnipesShot 8
Previous comment was wrong! Fizzle!!

Sep 30 1993 12:00:32:220PM930930009Joseph SnipesShot 9
Reduced prefill to 1.0 x 10**-5 Torr. Good shot! Pellet at 0.5 s.

Sep 30 1993 12:19:20:510PM930930010Joseph SnipesShot 10
Changed RCUR programming from 0.68 m to 0.67 m.
Decent shot. Pellet at 0.5 s. Disrupted late.

Sep 30 1993 12:38:00:130PM930930011Joseph SnipesShot 11
Decent shot. Pellet at 0.5 s. Disrupted late.

Sep 30 1993 12:52:58:700PM930930012Joseph SnipesShot 12
Reduced gain on Wire 2 slow ZCUR from 4 to 2 after 700 ms.
Ti injection at 850 ms. Pellet at 0.5 s.
Fizzle!

Sep 30 1993 01:12:06:870PM930930013Joseph SnipesShot 13
Reduced prefill to 9.5 x 10**-6 Torr.
Ti injection at 850 ms. Pellet at 0.5 s.
Disrupted at 0.6 s.

Sep 30 1993 01:43:47:590PM930930014Joseph SnipesShot 14
Reduced prefill to 9.0 x 10**-6 Torr.
Reduced gain on slow ZCUR wire 2 from 4 to 2 from 0.4 s on out to help
stabilize the plasma after the pellet.
Ti injection at 850 ms. Pellet at 0.5 s.
Fizzle!

Sep 30 1993 01:50:23:050PM930930015Joseph SnipesShot 15
Increased EF4 current from 1150 to 1180 A before breakdown to raise Bz by
a couple mT.
Decent shot. Pellet at 0.5 s. Disrupted at 0.95 s.

Sep 30 1993 02:06:00:530PM930930016Joseph SnipesShot 16
No change. Decent shot. Pellet at 0.5 s. Ti at 0.85 s.

Sep 30 1993 02:23:30:880PM930930017Joseph SnipesShot 17
Prefill increased to 9.5 x 10**-6 Torr. Proportional gain on slow ZCUR
Wire 2 changed from 2 to 1 after 0.4 s. Plasma current waveform ramped up
throughout the pulse by 30 kA over about 0.4 s. Increased gas puff early
to raise the density slightly. Added a 20 ms 40V gas puff after 0.8 s.
Fizzle!

Sep 30 1993 02:38:21:630PM930930018Joseph SnipesShot 18
Prefill reduced to 9.0 x 10**-6 Torr. Reduced EF4U by 10 A before breakdown
to 1170 A. Fizzle!

Sep 30 1993 03:09:16:830PM930930019Joseph SnipesShot 19
Increased Chopper pre-programming voltage from 200 to 500 units. Dropped
initial gas puff from 60 to 55 V as before. Reduced EF4 by 20 A before
breakdown to bring it back to where it was earlier in the day.
Good shot! Pellet at 0.5 s .

Sep 30 1993 03:17:21:930PM930930020Joseph SnipesShot 20
Moved RCUR programming in to 0.66 m. Increased late gas pulse to 60 V at
0.8 s. Good shot. Pellet at 0.5 s. Ti at 0.75 s.

Sep 30 1993 03:38:57:130PM930930021Joseph SnipesShot 21
Put in a step in OH1 voltage from 0.25 to 0.35 s to reduce effect of zero
crossing on the current and position. Took out programming of the notch in
the plasma current at 0.25 s. Increased gas puff at 0.8 s to 80 V for 30 ms.
Huge gas influx before the shot. No breakdown!

Sep 30 1993 04:02:46:270PM930930022Joseph SnipesShot 22
One more time . . .
Disrupted shortly after pellet at about 0.58 s.

Sep 30 1993 04:04:20:270PM930930023Joseph SnipesShot 23
One more time . . .
Good shot! Small pellet at 0.5 s.

Sep 30 1993 04:30:45:630PM930930024Joseph SnipesShot 24
Increased voltage step on OH1 from 0.25 to 0.35 s from -250 to -350 V.
Also changed proportional gain on slow ZCUR wire 2 from 4 to 1 after 0.2 s.
Late gas puff at 0.8 s taken out.
Disrupted at 0.37 s apparently due to the step on OH1.

Sep 30 1993 04:44:09:380PM930930025Joseph SnipesShot 25
Took out OH1 point at 350 ms to ramp down the step at 250 ms. Put in 60 V
gas puff at 750 ms for 20 ms.
Better shot, but disrupted at about 0.85 s.

Sep 30 1993 04:55:29:890PM930930026Joseph SnipesShot 26
Took out gas puff at 0.75 s.
Fizzle!

Engineering Operator Comments
ShotTimeTypeStatusComment
109:21:37:990AMPlasmaOkno faults
209:39:06:590AMPlasmaOkno faults
309:55:29:030AMPlasmaOkno faults
410:11:55:440AMPlasmaOktf commutation failure in inversion
510:36:20:130AMPlasmaOkno faults
610:53:15:650AMPlasmaOkno faults
711:09:46:150AMPlasmaOkno faults
811:33:59:790AMPlasmaOkno faults
911:53:35:940AMPlasmaOkno faults
1012:13:04:660PMPlasmaOkno faults
1112:27:43:460PMPlasmaOkno faults
1212:43:50:520PMPlasmaOkno faults
1301:00:06:840PMPlasmaOkpf comm faults due to disruption
1401:30:16:340PMPlasmaOkno faults
1501:45:33:710PMPlasmaOkno faults
1602:00:56:390PMPlasmaOkno faults
1702:20:21:200PMPlasmaOkno faults
1802:35:02:500PMPlasmaOkno faults
1902:52:00:250PMPlasmaOkno faults
2003:12:12:080PMPlasmaOkno faults
2103:28:30:160PMPlasmaOkno faults
2203:43:56:510PMPlasmaOkno faults
2304:00:23:490PMPlasmaOkno faults
2404:17:17:570PMPlasmaOkno faults
2504:35:01:500PMPlasmaOkno faults
2604:51:35:980PMPlasmaOkno faults