Alcator C-Mod Run 1000407 Information

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Miniproposals
Miniproposal:
Date Filed:
Title:
First Author:
Session Leader:Ian Hutchinson (shots 1-18)

Operators
Session leader(s):Ian Hutchinson
Physics operator(s):Dmitri Mossessian
Engineering operator(s):Gary Dekow

Engineering Operator Run Comment
Startup and conditioning

Session Leader Plans

Physics Operators Plans

Session Leader Summaries

Physics Operator Summaries
Entered: Jul 7 2004 04:37:10:287PM
Author: To Be Determined
Physics operator summary for run 1000407:

MP ? -- Startup and conditioning with normal field direction

SL: I. Hutchinson
PO: D. Mossessian
EO: G. Dekow
_______________________

Summary:

The goal of this run was to use the newly-installed cameras
to try to locate whatever is sticking into the plasma and causing the short
disruptive shots we have been getting this week. The results were better than was expected.
Ten out of 18 plasmas made it all the way to the rampdown, disrupting at 1.87 sec.
There were very many large injections in all plasmas, but they are overwhelmingly Mo
and the new videocameras show multiple injections coming from various places on
the machine's walls but do not show anything sticking into the plasma.
Ian's suggestion that plasmas were killed in the rampup phase by an excessive amount of gas
was tested and proved correct. 1.87 sec long plasmas were obtained by lowering the demand for
gas puff in the startup phase and lowering target line average density to 5e19 m^-2. There were
several disruptions because of large injections or too much gas at the beginning. On shot
a poloidal B coil went bad and we lost control of the plasma. After the coil was repaired there
were two more disruptions and we ended the day with a nice long plasma. Throughout the day I
played with EF2 programming, inner gap and positions of upper and lower x-points around 1.8 sec
in vain attempt to obtain disruption-free rampdown (see details below). All the little tweaks
seem to be happily ignored by the plasma, as I suspected before.
______________________________

Scorecard:

shots 18
plasmas 18
fizzles 0
______________________________


Engineering Setup:

Overnight ECDC in deuterium, stopping 1 hour prior to the run.

Power system setup as on 1000406001

Gas setup - fill B-top with 6 psi of D2 Hybrid enabled
fill B-side lower with 1 psi of Ar Hybrid DISABLED
leave B-side upper as is Hybrid DISABLED
fill C-side with 30 psi of D2 Hybrid enabled
leave J-bottom as is Hybrid DISABLED


Load from shot 1000406017 (typical 0.8 MA, 5.2 T, normal field direction)
___________________________________


Details:


1000407001 Plasma, disrupted at 0.34 sec.

Ian thinks that there's too much gas.

For next shot: lowered pulse_gas3 at .05 sec from 80 to 40 V.
Also lowered density target from 1e20 to 7e19 and programmed
for slower density rise between 0 and 0.5 sec.

1000407002 Plasma, disrupted at 0.6 sec. Lots of large injections.
Density is rising faster than it should.

For next shot: Lowered target to 5e19.

1000407003 Full plasma to 1.86 sec. Many injections, but it survives.

For next shot : no PCS changes

1000407004 Full plasma to 1.87 sec. Lots of injections

For next shot : no PCS changes

1000407005 Full plasma to 1.87 sec. Lots of injections.

For next shot : no PCS changes

1000407006 Full plasma to 1.87 sec. Many injections. Disruption at 1.87 sec may be
connected to the fact that EF2 is programmed to go to 0

For next shot : reprogram EF2_by_EF4 to stay at 2000 A up to 1.68 sec and
go to 1000 A at 2sec.

1000407007 Full plasma to 1.87 sec. Seems to have fewer injections.
No changes in rampdown - still disrupts at 1.87.

For next shot : no PCS change

1000407008 Full plasma to 1.87 sec.

For next shot : Increase CLEARIN between 1.7 and 1.9 sec by 5 mm

1000407009 Disrupted at .37 due to large injection.

For next shot : no PCS change

1000407010 Long plasma, disrupts at 1.87 sec .
Inner gap is large enough now, but the plasma is going upper diverted
at the end.

For next shot : pull ZXU 5 mm up around 1.85 sec

10004070011 Long plasma, disrupts at 1.86 sec .
Plasma stays lower diverted to the end.

For next shot : pull ZXL up around 1.85 sec. Increased target density to 8e19

1000407012 Disrupted at 0.4 due to large injection

For next shot : no PCS change

1000407013 Disrupted at 0.23 due to very large injection or, may be, to much gas again.

For next shot : lower target density back to 5e9

1000407014 Long, nice plasma with fewer injections after .3 sec.

For next shot : drop pulse_gas3 at .15 sec trying to get rid of the
first large bump in radiated power. Also pulled ZXL more up after 1.7 sec.

1000407015 Disruption at .32 sec - lost signal from BP23 coil and, consequently, lost
control of the plasma.

Granetz went in and connected a spare coil to Hybrid instead of the bad one.

For next shot: no PCS change

1000407016 VDE disruption at 0.61 sec

For next shot: no PCS change

1000407017 Disrupted at 0.19. Very large injection at .07

For next shot: no PCS change

1000407018 Long plasma, ended at 1.69 Lots of injections


Session Leader Comments

Physics Operator Comments
Apr 7 2000 09:50:14:390AMDmitri MossessianPlan:

Plasma run will begin at 10:00

MP ? -- Startup and conditioning with normal field direction

Engineering Setup:
------------------
Overnight ECDC in deuterium, stopping 1 hour prior to the run.

Power system setup as on 1000406001

Note: Fizzle detector should be on from t=0.080 to 1.7 s

Gas setup - fill B-top with 6 psi of D2 Hybrid enabled
fill B-side lower with 1 psi of Ar Hybrid DISABLED
leave B-side upper as is Hybrid DISABLED
fill C-side with 30 psi of D2 Hybrid enabled
leave J-bottom as is Hybrid DISABLED


The goal of this run is to use the newly-installed cameras
to try to locate whatever is sticking into the plasma and causing the short
disruptive shots we have been getting this week.

Load from shot 1000406017 (typical 0.8 MA, 5.2 T, normal field direction)

9:45 am:

PCS load from 1000406017, load/clean

Coldstart OK.
Apr 7 2000 10:32:58:357AM1000407001Dmitri MossessianPlasma, disrupted at 0.34 sec.

Ian thinks that there's too much gas.
So we lowered pulse_gas3 at .05 sec from 80 to 40 V.
Also lowered density target from 1e20 to 7e19 and programmed
for slower density rise between 0 and 0.5 sec.
Apr 7 2000 10:46:08:483AM1000407002Dmitri MossessianPlasma, disrupted at 0.6 sec.

Lots of large injections. Density is rising faster than it should.
Lowered target to 5e19.
Apr 7 2000 10:58:43:060AM1000407003Dmitri MossessianFull plasma to 1.86 sec. Many injections, but it survives.

For next shot : no PCS changes
Apr 7 2000 11:18:44:217AM1000407004Dmitri MossessianFull plasma to 1.87 sec. Lots of injections

For next shot : no PCS changes
Apr 7 2000 11:40:06:200AM1000407005Dmitri MossessianFull plasma to 1.87 sec. Lots of injections. We'll keep cleaning up.

For next shot : no PCS changes
Apr 7 2000 12:33:34:983PM1000407006Dmitri MossessianFull plasma to 1.87 sec. Many injections. Disruption at 1.87 sec may be
connected to the fact that EF2 is programmed to go to 0

For next shot : reprogram EF2_by_EF4 to stay at 2000 A up to 1.68 sec and
go to 1000 A at 2sec.
Apr 7 2000 12:34:47:013PM1000407007Dmitri MossessianFull plasma to 1.87 sec. Seems to have fewer injections.
No changes in rampdown - still disrupts at 1.87.

For next shot : no PCS change
Apr 7 2000 12:41:39:467PM1000407008Dmitri MossessianFull plasma to 1.87 sec. Same as shot 7.

For next shot : Increase CLEARIN between 1.7 and 1.9 sec by 5 mm
Apr 7 2000 12:58:26:810PM1000407009Dmitri MossessianDisrupted at .37 due to large injection.

For next shot : no PCS change
Apr 7 2000 01:22:06:717PM1000407010Dmitri MossessianLong plasma, disrupts at 1.87 sec .
Inner gap is large enough now, but the plasma is going upper diverted
at the end.

For next shot : pull ZXU 5 mm up around 1.85 sec
Apr 7 2000 01:36:02:890PM1000407011Dmitri MossessianLong plasma, disrupts at 1.86 sec .
Plasma stays lower diverted to the end.

For next shot : pull ZXL up around 1.85 sec. Increased target density to 8e19
Apr 7 2000 01:50:37:233PM1000407012Dmitri MossessianDisrupted at 0.4 due to large injection

For next shot : no PCS change
Apr 7 2000 02:13:52:420PM1000407013Dmitri MossessianDisrupted at 0.23 due to very large injection or, may be, to much gas again.

For next shot : lower target density back to 5e9
Apr 7 2000 02:34:30:013PM1000407014Dmitri MossessianLong, nice plasma with fewer injections after .3 sec.

For next shot : drop pulse_gas3 at .15 sec trying to get rid of the
first large bump in radiated power. Also pulled ZXL more up after 1.7 sec.
Apr 7 2000 03:22:12:450PM1000407015Dmitri MossessianDisruption at .32 sec - lost signal from BP23 coil and, consequently, lost
control of the plasma.

Granetz went in and connected a spare coil to Hybrid instead of the bad one.

For next shot: no PCS change
Apr 7 2000 03:41:55:890PM1000407016Dmitri MossessianVDE disruption at 0.61 sec

For next shot: no PCS change
Apr 7 2000 03:52:16:590PM1000407017Dmitri MossessianDisrupted at 0.19. Very large injection at .07

For next shot: no PCS change
Apr 7 2000 04:05:20:153PM1000407018Dmitri MossessianLong plasma, ended at 1.69 Lots of injections

Engineering Operator Comments
ShotTimeTypeStatusComment
110:14:05:687AMPlasmaOk
210:34:45:107AMPlasmaOk
310:52:53:340AMPlasmaOk
411:13:23:327AMPlasmaOk
511:33:05:140AMPlasmaOk
611:53:11:090AMPlasmaOk
712:13:12:670PMPlasmaOk
812:32:11:310PMPlasmaOk
912:51:17:200PMPlasmaOk
1001:07:49:890PMPlasmaOk
1101:26:45:967PMPlasmaOk
1201:45:22:890PMPlasmaBadOH1 Fault
1302:02:49:187PMPlasmaOk
1402:18:37:107PMPlasmaOk
1502:43:29:013PMPlasmaOk
1603:26:05:000PMPlasmaOk
1703:45:03:590PMPlasmaOk
1803:59:16:030PMPlasmaOk