Alcator C-Mod Run 1050520 Information

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Miniproposals
Miniproposal:298a
Date Filed: 5/20/2002
Title:C-Mod Plasma Startup
First Author:Jim Irby
Session Leader:Jim Irby (shots 1-35)

Operators
Session leader(s):Jim Irby
Physics operator(s):Robert Granetz
Engineering operator(s):Andy Pfeiffer,Gary Dekow,Ed Fitzgerald

Engineering Operator Run Comment
Recovery from vacuum opening Nominal MP #298A: C-Mod Startup Session lea

Session Leader Plans

Physics Operators Plans
Entered: May 20 2005 09:06:48:380AM
Author: Robert Granetz
Engineering setup for Friday, 20 May 2005

Recovery from vacuum opening
Nominal MP #298A: C-Mod Startup

Session leader: TBD
Physics operator: R. Granetz

Overnight ECDC in D2, 2.e-4 torr; Bake at 60 C.

Run begins at 09:00 and ends at 17:00.

Power systems as on 1050519033 (0.9 MA, 5.4 T vanilla plasma)

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 with whatever Hybrid disabled
fill B-main (C-side) with 40 psi D2 Hybrid enabled (PG3)
NINJA not used today

Torvac setup: machine gate valves to remain open during and after shot.

Enable the following gate valves, assuming no vacuum problems:
ECE, VUV, Z-bolo shutters

Necessary diagnostics: titanium monitoring, video monitors, H/D ratio

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ICRF Setup: All transmitters in run on at 08:30.

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Run plan: Carry on trying to get the machine back into normal operation after
last week's vacuum break. If it does approach normal operation,
then load the 1 MA fiducial and start applying RF power.

Session Leader Summaries

Physics Operator Summaries

Session Leader Comments

Physics Operator Comments
May 20 2005 09:06:25:350AM1050520001Robert GranetzFizzle. Really weak.

Next shot: reduce pre-fill to 25 ms (from 30 ms)
May 20 2005 09:20:15:270AM1050520002Robert GranetzFizzle. Better. Still need the current to rise a little faster.

Next shot: reduce pre-fill another 2 ms. Leave fields alone for now.
May 20 2005 09:41:52:053AM1050520003Robert GranetzPlasma. Good shot. 0.9 MA. Good startup. Very few dust specks on the video
images. H/(H+D)=7%

Next shot: load the 1 MA, 5.4 T fiducial, except reduce nl_04 to 0.5e20 m-2
May 20 2005 09:49:00:147AM1050520004Robert GranetzFizzle. Another really weak one. Fill pressure was noticeably higher than
on previous (plasma) shot.

Next shot: reduce pre-fill another 3 ms.
May 20 2005 10:07:56:787AM1050520005Robert GranetzPlasma. Good 1 MA, 5.4 T fiducial-like shot. nl_04 is 0.8e20 m-2, with is higher than
programmed, so we must still be outgassing a lot. No RF on this shot. Clean videos.
H/(H+D)=8%. Titanium concentration in plasma is low.

Next shot: no PCS changes. Turn on some RF power.
May 20 2005 10:13:21:803AM1050520006Robert GranetzFizzle. Pre-fill pressure came up again, although not as much as after plasma shot 3.

Next shot: reduce pre-fill another 2 ms (to 18 ms).
May 20 2005 10:26:02:100AM1050520007Robert GranetzDud. Pre-fill pressure looks reasonable, but I guess I'll raise it a tiny amount.

Next shot: add just 1 ms to the pre-fill pulse.
May 20 2005 10:37:35:600AM1050520008Robert GranetzAnother dud. Give up...add the gas back in.

Next shot: raise pre-fill by 3 ms (to 22 ms), even though this will probably make
the current rise too slow.
May 20 2005 10:51:47:850AM1050520009Robert GranetzDud.

Next shot: add 3 more ms to pre-fill (to 25 ms). Also tweak up the Br by 0.3 mT.
May 20 2005 11:08:42:147AM1050520010Robert GranetzFizzle. Not clear what I should adjust, if anything.

Next shot: repeat, no changes.
May 20 2005 11:20:08:147AM1050520011Robert GranetzDud. I hate to raise the pre-fill more, but I guess we have to.

Next shot: increase pre-fill pulse by another 3 ms (to 28 ms).
May 20 2005 11:41:08:177AM1050520012Robert GranetzPlasma. Good 1 MA shot. Short H-mode. Target density is still higher than requested.
Prf=about 1 MW. H/(H+D)=9-10%.

Next shot: no changes.
May 20 2005 11:52:18:867AM1050520013Robert GranetzFizzle. Null looks good.

Next shot: Ian and Steve suggest reducing the RCUR offset in segment 1 by 1000 (from 2500
to 1500)
May 20 2005 12:04:28:880PM1050520014Robert GranetzFizzle. The null doesn't look so good after that RCUR offset change.

Next shot: undo the RCUR offset change (set it back to 2500).
May 20 2005 12:13:25:740PM1050520015Robert GranetzFizzle.

Next shot: Br0 tweak
May 20 2005 12:28:24:570PM1050520016Robert GranetzFizzle. Stronger.

Next shot: put the RCUR offset tweak back in (2500 -> 1500).
May 20 2005 12:41:05:163PM1050520017Robert GranetzDud.

Next shot: undo the Br0 tweak. It's about time to just take my hands off and bang away
until the machine fixes itself.
May 20 2005 12:56:52:897PM1050520018Robert GranetzPlasma. Good shot. 1 MA. Late H-mode. Prf=1-2 MW. H/(H+D)=10-11%.
Startup still doesn't look very robust.

Next shot: take 1 ms off pre-fill (seemed to be needed after previous full-length
plasmas today).
May 20 2005 01:07:20:490PM1050520019Robert GranetzFizzle.

Next shot: no changes, but after that we'll start between-shot ECDC.
May 20 2005 01:28:42:037PM1050520020Robert GranetzPlasma. Good shot. Prf up to 2.5 MW. H/(H+D)=11-12%. It seems to be creeping up.

We'll be doing ECDC between shots for at least the next hour.

Next shot: no changes.
May 20 2005 01:48:53:257PM1050520021Robert GranetzFizzle. Weak one.

Between-shot ECDC.

Next shot: modify ZXU late in the flattop so that the plasma doesn't come
close to being double null (at Bruce's request).
May 20 2005 02:00:51:477PM1050520022Robert GranetzFizzle. Looks identical to the last shot.

Between-shot ECDC.

Next shot: no changes.
May 20 2005 02:18:33:300PM1050520023Robert GranetzPlasma. Good 1 MA shot. Numerous short little H-modes. SSEP was quite constant
over the entire flattop. Prf up to 2 MW. H/(H+D)=10%.

Between-shot ECDC.

Next shot: no changes.
May 20 2005 02:29:11:967PM1050520024Robert GranetzFizzle. Pre-fill pressure was much higher on this startup. Maybe we need to wait
longer after the ECDC is stopped.

Between-shot ECDC.

Next shot: no changes.
May 20 2005 02:44:02:460PM1050520025Robert GranetzFizzle. Pre-fill pressure is high again. Null is okay.

Between-shot ECDC. This will be the last time I do this today.

Next shot: play with pre-fill pulse...reduce by 2 ms.
May 20 2005 03:05:41:233PM1050520026Robert GranetzPlasma. H/(H+D)=9-10%.

No between-shot ECDC.

Next shot: no changes.
May 20 2005 03:10:31:340PM1050520027Robert GranetzFizzle.

Next shot: no changes.
May 20 2005 03:28:16:567PM1050520028Robert GranetzDud. Nice null.

Next shot: add 2 ms back to the pre-fill.
May 20 2005 03:42:33:013PM1050520029Robert GranetzPlasma. DNB fired into this plasma. That's the first time for the long-pulse beam.
It actually reduced the pressure in the chamber prior to the pre-fill pulse.

Next shot: no changes. Try firing the beam into the plasma again.
May 20 2005 03:54:47:697PM1050520030Robert GranetzPlasma. Two in a row. Many little H-modes, as on previous plasmas today. Peak Wth is around 100 kJ,
also similar to previous H-modes today. H/(H+D)=11%. Prf about 2 MW. Really
clean on the divertor video image (JANT) for the first time today.

Next shot: no changes. Try firing the DNB again.
May 24 2005 08:23:47:870AM1050520031Robert GranetzFizzle. Everything's the same. DNB fired into the post-fizzle chamber.

Next shot: no changes. DNB will fire again. Li pellet injection may also
fire after t=1.4 s.
May 20 2005 04:23:25:890PM1050520032Robert GranetzPlasma. Good shot. 2 MW RF. Pre-RF density was finally down at the requested level
of nl_04=0.5e20 m-2 for the first time today. DNB fired at t=0.5 s. Li pellet didn't
fire. H/(H+D)=13%.

Next shot: no changes.
May 20 2005 04:36:17:150PM1050520033Robert GranetzPlsama. Good shot. Many little H-modes. Prf up to 3 MW, sort of. DNB fired at t=0.5 s.
H/(H+D)=14%.

Next shot: raise nl_04 to 0.8e20 m-2.
May 20 2005 04:49:07:817PM1050520034Robert GranetzFizzle.

Next shot: no changes. Last shot of the day.
May 20 2005 05:00:02:687PM1050520035Robert GranetzFizzle. Late breakdown. DNB fired into post-fizzle chamber again.

End of run.

Engineering Operator Comments
ShotTimeTypeStatusComment
109:03:08:617AMPlasmaOk
209:16:11:070AMPlasmaOk
309:28:46:460AMPlasmaOk
409:41:19:553AMPlasmaOk
509:55:43:880AMPlasmaOk
610:08:39:007AMPlasmaOk
710:21:12:897AMPlasmaOk
810:33:45:380AMPlasmaOk
910:46:11:930AMPlasmaOk
1010:58:52:553AMPlasmaOk
1111:16:31:927AMPlasmaOk
1211:29:10:647AMPlasmaOk
1311:41:44:537AMPlasmaOk
1411:54:26:570AMPlasmaOk
1512:08:12:380PMPlasmaOk
1612:23:06:897PMPlasmaOk
1712:35:51:757PMPlasmaOk
1812:48:44:147PMPlasmaOk
1901:01:26:490PMPlasmaOk
2001:14:34:490PMPlasmaOk
2101:37:08:083PMPlasmaOk
2201:51:51:130PMPlasmaOk
2302:08:41:860PMPlasmaOk
2402:22:42:547PMPlasmaOk
2502:38:10:913PMPlasmaOk
2602:53:52:440PMPlasmaOk
2703:06:32:747PMPlasmaOk
2803:19:18:820PMPlasmaOk
2903:32:33:127PMPlasmaOk
3003:45:12:810PMPlasmaOk
3103:57:41:603PMPlasmaOk
3204:15:54:987PMPlasmaOk
3304:28:27:827PMPlasmaOk
3404:44:53:787PMPlasmaOk
3504:57:24:533PMPlasmaOk