Alcator C-Mod Run 960807 Information

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Miniproposals
Miniproposal:147
Date Filed: 7/15/1996
Title:Enhanced Startup Techniques (Higher Pre-charge and Parallel EF4)
First Author:Ian Hutchinson
Session Leader:Ian Hutchinson (shots 1-33)
Miniproposal:159a
Date Filed: 7/29/1996
Title:Restart Operation: August 1996
First Author:Steve Wolfe
Session Leader:Ian Hutchinson (shots 1-33)

Operators
Session leader(s):Ian Hutchinson,Ian Hutchinson
Physics operator(s):Robert Granetz
Engineering operator(s):Frank Silva

Engineering Operator Run Comment
high precharge/hutch/granetz/silva

Session Leader Plans

Physics Operators Plans

Session Leader Summaries
Entered: Jul 7 2004 03:49:15:867PM
Author: To Be Determined
Run Summary from Session Leader 960807

Four plasmas obtained, 3 with paralleled EF4s demonstrate the viability
of the scenario. Finally at the end of the day, the TF trip problem came
back. Closed down to work on that.

We observed several duds following a plasma.
Plasmas were 8, 17, 24, and 31.

Still very dirty. Need more discharge cleaning.
See the physop log for more gory details.


Physics Operator Summaries
Entered: Jul 7 2004 04:36:56:410PM
Author: To Be Determined
Physics operator's summary for run 960807.

MP 159A and 147 -- Re-start machine, and use higher pre-charge.

SL: I. Hutchinson
PO: R. Granetz
EO: F. Silva

Today's run will again try to get good plasmas after the 5-month shutdown.
The initial attempts at this during the past 2 days have not yet yielded
any more than 0.2 s long discharges. The main difference today is that
there was 12 hours of ECDC in D2 overnight. We will also continue to use
higher pre-charge on the OH's and EF1's.

Summary: Well, this run was only marginally better than the previous two
days. We managed to get plasmas today with EF4's in both series
and parallel configurations, but the null seems to be marginal.
In an effort to beat this, I raised the field to 6 tesla on
shot 030, and we got the best plasma so far on shot 031. This,
however, was followed by two TF crowbars, almost certainly due to
paralleling the EF4's. We gave up early today, so that discharge
cleaning and troubleshooting could proceed. There were five plasma
shots today: #003, 008, 017, 024, and 031. Shot 031 had 0.7 MA and
lasted 0.37 s.

Scorecard: 5 plasmas
16 fizzles
12 duds (2 due to TF crowbar with parallel EF4's)
----------
33 total

Run plan:

Start from yesterday's shot 960806032. Bang away until we get good
operation. Tweaks to the null and the initial pressure will be done
for psychological purposes. The primary difference between the previous
two days and today is that we finally got a lot of ECDC done last night.

Engineering setup for Wednesday 07 Aug 1996:

Discharge cleaning in deuterium overnight. We need as much as possible.
Start with the same resistors and PLC settings as we ended with yesterday.
All gas plenums and valves should also be setup identical to yesterday.
Ditto for the gate valves.

Use engineering settings from shot 960806032. This shot had higher
pre-charge on the OH's and EF1's.

Detailed shot log:

Shot 01 -- Fizzle. OH1 faulted. Null is fair. Try again, no changes

Shot 02 -- Fizzle. OH1 faulted. Null is only so-so. Carbon light is
down about a factor of 2 from yesterday. On Steve's suggestion,
I will reduce pre-pulse gas puff duration from 18 to 16 ms for
next shot.

Shot 03 -- Plasma. Ip=0.5 MA, disrupted at 0.15 s. Carbon continues to
drop. No changes for next shot. Will it be a dud?

Shot 04 -- Dud. Null is unchanged. Repeat with no changes.

Shot 05 -- Dud. Increase the pre-pulse gas puff duration from 16 back to
18 ms (measured across the 100 volt flattop) for the next shot.

Shot 06 -- Dud. For the next shot, increase Bz by 1 mT (by adding +15 amps
to EF4 from t=-1 to 0 s).

Shot 07 -- Fizzle. For the next shot: reduce pre-pulse gas puff from 18
to 15 ms.

Shot 08 -- Plasma. Getting a little better. Reasonably nice current
rise. Ip=0.65 MA, disrupted at 0.23 s. X-point is being formed
at 0.2 s. For the next shot, raise the pre-pulse puff duration
from 15 to 18 ms, in the hopes of preventing a dud.

Shot 09 -- Fizzle (not a dud!) For the next shot, decrease pre-pulse gas puff
duration from 18 to 15 ms again.

Shot 10 -- Dud. For the next shot: increase pre-pulse gas puff back up
to 18 ms, increase Bz another 1 mT, and reduce density demand from
nl_04=1.0 to 0.8e20 m-2.

Shot 11 -- Fizzle. Breakdown was a little later. For the next shot, tweak
both Bz and the gas puff a bit back toward the previous settings.
Also, move OH1 and OH2 crowbar times back from 0.2 to 0.12 s.

Shot 12 -- Dud. For the next shot, raise pre-pulse gas puff duration from 17
to 20 ms (length of 100 volt flattop).

Shot 13 -- Fizzle. No changes for next shot.

Shot 14 -- Fizzle. For next shot reduce Bz by another 0.5 mT, which will bring
it back to the value used on shot 008. Also reduce gas puff by 1 ms

Shot 15 -- Fizzle.

We are going to change gears here and try paralleling the EF4 coils. Re-load
segment 1 from shot 960806036 from yesterday, but cut in half the EF4 pre-
programmed voltage for t <= 0 s.

Shot 16 -- Dud. Null looks similar to previous shot. Next shot: change
Bz by -1 mT (for no good reason).

Shot 17 -- Plasma (with EF4 coils in parallel). Ip=0.71 MA, with a fast
disruption at 0.20 s. The shot went vertically unstable (up).
For the next shot, increase early gas valve programming (on PG3) and
increase pre-pulse puff duration by 1 more ms.

Shot 18 -- Fizzle. Next shot: delay the CLEARIN outward movement.

Shot 19 -- Fizzle. Next shot: increase pre-pulse gas puff duration by 2 ms.

Shot 20 -- Fizzle. Next shot: decrease pre-pulse gas puff duration by 5 ms (so
it will be 3 ms shorter than shot 018.

Shot 21 -- Dud. Guess the pressure was too low. Let's go back to longer
pre-pulse gas puffs. For the next shot, the 100 V flattop will
be 26 ms long.

Shot 22 -- Fizzle. No changes for the next shot.

Shot 23 -- Fizzle. Next shot, reduce pre-pulse gas puff duration to 20 ms
(length of 100 volt flattop).

Shot 24 -- Plasma. Very disruptive. Ip=0.3 MA, duration=0.26 s. For the
next shot, decrease the early pulse gas voltage programming.

Shot 25 -- Dud. Next shot, increase PG4 puff to 24 ms.

Shot 26 -- Dud. Next shot: increase Bz by 1 mT

Shot 27 -- Fizzle. Next shot, tweak OH1 pre-programmed voltage around t=0 so
that there's a little more early loop voltage.

Shot 28 -- Fizzle. Next shot, reduce pre-pulse puff to 20 ms.

Shot 29 -- Dud. This sucks. Next shot, raise toroidal field from 5.25 to
6.0 tesla. Hopefully this will make plasma initiation easier.

Shot 30 -- Fizzle. Btor didn't get to flattop until 0.1 s. Next shot, reduce
pre-pulse puff to 18 ms, and start TF 0.1 s earlier.

Shot 31 -- Plasma, best shot so far. Ip=0.68 MA, terminated by a disruption
at 0.37 s. Next shot: no changes.

Shot 32 -- Dud, due to TF tripping out at -0.76 s. Could this be the
parallel EF4 problem rearing its ugly head again? Repeat with
no changes.

Shot 33 -- Dud, again due to the TF crowbarring at -0.76 s. Looks like its
the parallel EF4 problem.

The session leader has decided to stop the run and have the engineers start
looking into the TF/EF4 problem again.

End of run.

Session Leader Comments
Aug 7 1996 10:41:30:170AM960807010Robert GranetzShot 10 -- Dud. For the next shot: increase pre-pulse gas puff back up
to 18 ms, increase Bz another 1 mT, and reduce density demand from
nl_04=1.0 to 0.8e20 m-2.

Aug 7 1996 10:52:25:790AM960807011Robert GranetzShot 11 -- Fizzle. Breakdown was a little later. For the next shot, tweak
both Bz and the gas puff a bit back toward the previous settings.

Aug 7 1996 10:56:06:380AM960807011Robert GranetzAlso for the next shot, move OH1 and OH2 crowbar times back from 0.2 to 0.12 s.

Aug 7 1996 10:58:53:650AM960807012Robert GranetzShot 12 -- Dud. For the next shot, raise pre-pulse gas puff duration from 17
to 20 ms (length of 100 volt flattop).

Aug 7 1996 11:19:30:170AM960807013Robert GranetzShot 13 -- Fizzle. No changes for next shot.

Aug 7 1996 11:26:25:710AM960807014Robert GranetzShot 14 -- Fizzle. For next shot reduce Bz by another 0.5 mT, which will bring
it back to the value used on shot 008. Also reduce gas puff by 1 ms

Aug 7 1996 11:42:55:480AM960807015Robert GranetzShot 15 -- Fizzle.

We are going to change gears here and try paralleling the EF4 coils. Re-load
segment 1 from shot 960806036 from yesterday, but cut in half the EF4 pre-
programmed voltage for t <= 0 s.

Aug 7 1996 12:10:43:850PM960807016Robert GranetzShot 16 -- Dud. Null looks similar to previous shot. Next shot: change
Bz by -1 mT (for no good reason).

Aug 7 1996 12:23:19:890PM960807017Robert GranetzShot 17 -- Plasma (with EF4 coils in parallel). Ip=0.71 MA, with a fast
disruption at 0.20 s. The shot went vertically unstable (up).
For the next shot, increase early gas valve programming (on PG3) and
increase pre-pulse puff duration by 1 more ms.

Aug 7 1996 12:32:50:920PM960807018Robert GranetzShot 18 -- Fizzle. Next shot: delay the CLEARIN outward movement.

Aug 7 1996 12:37:51:010PM960807019Robert GranetzShot 19 -- Fizzle. Next shot: increase pre-pulse gas puff duration by 2 ms.

Physics Operator Comments
Aug 7 1996 08:37:34:700AMRobert GranetzMP 159A and 147 -- Re-start machine, and use higher pre-charge.

SL: I. Hutchinson
PO: R. Granetz
EO: F. Silva

Today's run will again try to get good plasmas after the 5-month shutdown.
The initial attempts at this during the past 2 days have not yet yielded
any more than 0.2 s long discharges. The main difference today is that
there was 12 hours of ECDC in D2 overnight. We will also continue to use
higher pre-charge on the OH's and EF1's.

Aug 7 1996 08:38:04:550AMRobert GranetzRun plan:

Start from yesterday's shot 960806032. Bang away until we get good
operation. Tweaks to the null and the initial pressure will be done
for psychological purposes. The primary difference between the previous
two days and today is that we finally got a lot of ECDC done last night.

Engineering setup for Wednesday 07 Aug 1996:

Discharge cleaning in deuterium overnight. We need as much as possible.
Start with the same resistors and PLC settings as we ended with yesterday.
All gas plenums and valves should also be setup identical to yesterday.
Ditto for the gate valves.

Use engineering settings from shot 960806032. This shot had higher
pre-charge on the OH's and EF1's.

Aug 7 1996 09:03:24:130AM960807001Robert GranetzShot 01 -- Fizzle. OH1 faulted. Null is fair. Try again, no changes

Aug 7 1996 09:15:55:920AM960807002Robert GranetzShot 02 -- Fizzle. OH1 faulted. Null is only so-so. Carbon light is
down about a factor of 2 from yesterday. On Steve's suggestion,
I will reduce pre-pulse gas puff duration from 18 to 16 ms for
next shot.

Aug 7 1996 09:27:37:060AM960807003Robert GranetzShot 03 -- Plasma. Ip=0.5 MA, disrupted at 0.15 s. Carbon continues to
drop. No changes for next shot. Will it be a dud?

Aug 7 1996 09:42:44:300AM960807004Robert GranetzShot 04 -- Dud. Null is unchanged. Repeat with no changes.

Aug 7 1996 09:59:18:010AM960807006Robert GranetzShot 06 -- Dud. For the next shot, increase Bz by 1 mT (by adding +15 amps
to EF4 from t=-1 to 0 s).

Aug 7 1996 10:06:30:660AM960807007Robert GranetzShot 07 -- Fizzle. For the next shot: reduce pre-pulse gas puff from 18
to 15 ms.

Aug 7 1996 10:19:37:230AM960807008Robert GranetzShot 08 -- Plasma. Getting a little better. Reasonably nice current
rise. Ip=0.65 MA, disrupted at 0.23 s. X-point is being formed
at 0.2 s. For the next shot, raise the pre-pulse puff duration
from 15 to 18 ms, in the hopes of preventing a dud.

Aug 7 1996 10:28:51:790AM960807009Robert GranetzShot 09 -- Fizzle (not a dud!) For the next shot, decrease pre-pulse gas puff
duration from 18 to 15 ms again.

Aug 7 1996 12:47:22:440PM960807020Robert GranetzShot 20 -- Fizzle. Next shot: decrease pre-pulse gas puff duration by 5 ms (so
it will be 3 ms shorter than shot 018.

Aug 7 1996 12:53:13:390PM960807021Robert GranetzShot 21 -- Dud. Guess the pressure was too low. Let's go back to longer
pre-pulse gas puffs. For the next shot, the 100 V flattop will
be 26 ms long.

Aug 7 1996 01:00:27:930PM960807022Robert GranetzShot 22 -- Fizzle. No changes for the next shot.

Aug 7 1996 01:16:44:880PM960807023Robert GranetzShot 23 -- Fizzle. Next shot, reduce pre-pulse gas puff duration to 20 ms
(length of 100 volt flattop).

Aug 7 1996 01:26:07:960PM960807024Robert GranetzShot 24 -- Plasma. Very disruptive. Ip=0.3 MA, duration=0.26 s. For the
next shot, decrease the early pulse gas voltage programming.

Aug 7 1996 01:43:24:230PM960807025Robert GranetzShot 25 -- Dud. Next shot, increase PG4 puff to 24 ms.

Aug 7 1996 01:46:11:500PM960807026Robert GranetzShot 26 -- Dud. Next shot: increase Bz by 1 mT

Aug 7 1996 01:57:22:810PM960807027Robert GranetzShot 27 -- Fizzle. Next shot, tweak OH1 pre-programmed voltage around t=0 so
that there's a little more early loop voltage.

Aug 7 1996 02:05:30:430PM960807028Robert GranetzShot 28 -- Fizzle. Next shot, reduce pre-pulse puff to 20 ms.

Aug 7 1996 02:31:29:580PM960807029Robert GranetzShot 29 -- Dud. This sucks. Next shot, raise toroidal field from 5.25 to
6.0 tesla. Hopefully this will make plasma initiation easier.

Aug 7 1996 02:38:36:550PM960807030Robert GranetzShot 30 -- Fizzle. Btor didn't get to flattop until 0.1 s. Next shot, reduce
pre-pulse puff to 18 ms, and start TF 0.1 s earlier.

Aug 7 1996 03:01:50:820PM960807031Robert GranetzShot 31 -- Plasma, best shot so far. Ip=0.68 MA, terminated by a disruption
at 0.37 s. Next shot: no changes.

Aug 7 1996 03:14:57:740PM960807032Robert GranetzShot 32 -- Dud, due to TF tripping out at -0.76 s. Could this be the
parallel EF4 problem rearing its ugly head again? Repeat with
no changes.

Aug 7 1996 03:41:19:250PM960807033Robert GranetzShot 33 -- Dud, again due to the TF crowbarring at -0.76 s. Looks like its
the parallel EF4 problem.

The session leader has decided to stop the run and have the engineers start
looking into the TF/EF4 problem again.

End of run.

Engineering Operator Comments
ShotTimeTypeStatusComment
107:30:50:880AMTestOkoh1 comm fault
209:08:10:160AMTestOkoh1 comm fault
309:21:33:720AMTestOkno faults
409:33:21:780AMTestOkno faults
509:43:08:250AMTestOkno faults
609:51:29:640AMTestOkno faults
710:02:20:770AMTestOkno faults
810:12:32:720AMTestOkno faults
910:22:04:880AMTestOkno faults
1010:35:54:630AMTestOkno faults
1110:45:12:820AMTestOkno faults
1210:56:11:180AMTestOk
1311:10:05:400AMTestOkno faults
1411:20:39:570AMTestOkno fault
1511:32:27:660AMTestOkoh1 comm fault
1612:00:22:420PMTestOk
1712:12:14:030PMTestOk
1812:24:32:620PMTestOk
1912:33:38:460PMTestOk
2012:41:04:690PMTestOk
2112:48:52:230PMTestOk
2212:55:41:720PMTestOkComm Fault OH1
2301:08:36:790PMTestOkComm Fault OH1
2401:18:16:820PMPlasmaOk
2501:30:09:230PMPlasmaOk
2601:39:51:740PMPlasmaOkCopmm Fault OH1
2701:51:05:830PMPlasmaOkComm Fault OH1
2802:02:12:090PMPlasmaOk
2902:16:52:510PMPlasmaOkComm Fault OH1
3002:32:06:080PMPlasmaOkComm Fault Bypass cab oh2u
3102:47:02:180PMPlasmaOk
3203:10:11:520PMPlasmaBadTF C-Bar
3303:25:32:720PMPlasmaBadtf crowbar