Alcator C-Mod Run 1050524 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 1-32)

Operators
Session leader(s):Jim Irby
Physics operator(s):Ian Hutchinson,Steve Wolfe,Ian Hutchinson
Engineering operator(s):Andy Pfeiffer,Bill Byford,Bill Parkin

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

Session Leader Plans

Physics Operators Plans

Session Leader Summaries

Physics Operator Summaries
Entered: May 24 2005 05:20:28:380PM
Author: Ian Hutchinson

Summary



Today we transformed from a very unreliable startup to a rather reliable startup.
That seems to be a success. However, the RF is not reliable. D-port is spraying dust. One good thing, however, is that the dust spray does not seem to disrupt the plasma, except for the first shot where the gas load was very large.

The transformation of startup reliability accompanied some major changes to the initiation configuration, mostly the OH2 current was lowered from -27400 to -26300A. This has the effect of opening up the null somewhat, and making the field gradient more vertically stabilizing (implying less horizontally stabilizing). There were zero duds today. The last three shots together with shot 25 were all identical settings, and gave plasmas.

Scorecard


  Shot,Duration(s),Ipmax(MA),Result  Shot,Duration(s),Ipmax,Result
  |   01   1.510   1.084   Plasma  |   02   0.000   0.028   Fizzle  |
  |   03   0.000   0.029   Fizzle  |   04   0.000   0.027   Fizzle  |
  |   05   1.841   1.069   Plasma  |   06   0.000   0.025   Fizzle  |
  |   07   0.000   0.026   Fizzle  |   08   0.000   0.025   Fizzle  |
  |   09   0.000   0.031   Fizzle  |   10   1.849   1.073   Plasma  |
  |   11   0.000   0.026   Fizzle  |   12   1.800   1.069   Plasma  |
  |   13   0.000   0.026   Fizzle  |   14   1.953   1.073   Plasma  |
  |   15   0.000   0.027   Fizzle  |   16   1.939   1.072   Plasma  |
  |   17   0.000   0.026   Fizzle  |   18   1.863   1.075   Plasma  |
  |   19   1.960   1.074   Plasma  |   20   1.951   1.069   Plasma  |
  |   21   1.915   1.078   Plasma  |   22   1.958   1.077   Plasma  |
  |   23   1.961   1.077   Plasma  |   24   1.884   1.080   Plasma  |
  |   25   1.926   1.068   Plasma  |   26   1.934   1.070   Plasma  |
  |   27   1.874   1.075   Plasma  |   28   0.000   0.028   Fizzle  |
  |   29   No Ip                   |   30   1.939   1.072   Plasma  |
  |   31   1.876   1.076   Plasma  |   32   1.874   1.072   Plasma  |

Date 1050524:  32 shots.  19 plasmas.  12 fizzles.   0 duds.   1 System Error
        (Plasma = Ip gt 50.0 kA   Dud = H_alpha lt  0.40 V)
Total plasma duration: 35.80 s (exceeding -108 kA)




Session Leader Comments

Physics Operator Comments
May 24 2005 09:07:23:343AMIan HutchinsonContinuation of vent recovery. Attempts to fix the startup to be more reliable.

This weekend we had ECDC all weekend.
This morning we had some ICRF conditioning for a couple of hours so we have
10 minutes of ECDC before starting the run.
May 24 2005 09:15:10:360AM1050524001Ian HutchinsonPlasma to 1.5s.
Good breakdown. B_r starts at zero.
Density continuously rises till disruption. Gas was off. Therefore what we are seeing is from the walls. MKS B-bottom reaches 160mtorr before disruption.
Looks as if the gas comes from the ICRF antennas.

Lower nl04 to .6 from .8, hope to reduce the influx.
May 24 2005 09:47:31:270AM1050524002Ian HutchinsonFizzle.

EF4 to -1320A from -1340.
May 24 2005 09:57:51:813AM1050524003Ian HutchinsonFizzle. Low pressure.
Late breakdown at 8ms.
Some reasonable current visible.

Fill puff to 35ms from 28ms.
May 24 2005 10:09:57:497AM1050524004Ian HutchinsonFizzle.
Breakdown at 6ms. Pressure .04, I_gas to 10kA at 12ms.

Rcur offset to 500 from 1500 (in seg 1).
May 24 2005 10:24:10:990AM1050524005Ian HutchinsonPlasma till rampdown. MKS gauge reaches "only" 70mtorr. Dust seen on camera.
Late breakdown, at 8ms, but it goes because ramp rate of Bz is slower (presumably).

Br offset to .0005 from .000
May 24 2005 10:36:23:987AM1050524006Ian HutchinsonFizzle. Breakdown at 6.5ms and weak.

Revert to Br offset=0. Gas puff to 40ms from 35ms.
May 24 2005 10:48:35:920AM1050524007Ian HutchinsonFizzle. Breakdown at 6.5ms, weak current.

IC-OH2 to -27600 from -27400A
May 24 2005 11:19:47:453AM1050524008Ian HutchinsonFizzle

OH2 current to -28000A
EF4 to -1330A from -1320A.
May 24 2005 11:31:17:073AM1050524009Ian HutchinsonFizzle 20 kA. Breakdown at 6.3ms.

OH2 to 27000A
May 24 2005 11:49:25:897AM1050524010Ian HutchinsonPlasma to rampdown. MKS 20 mtorr till 1.5s; then rises. D and E are showing arcs even at low power.
Breakdown at 6ms. Slight outboard bounce.

OH2 to -26700A

May 24 2005 12:04:19:530PM1050524011Ian HutchinsonFizzle <10kA. Bz too low.

IC-EF4 to -1310 from -1330A
May 24 2005 12:16:28:480PM1050524012Ian HutchinsonPlasma to rampdown. MKS ramps up after 1.2s.
Outboard bounce on startup. Bz ramp rate very slow.

Rcur offset to 1500 from 500.
May 24 2005 12:32:07:600PM1050524013Ian HutchinsonFizzle. Breakdown late at 6.8ms. Weak current.

Gas puff to 35ms from 40ms
May 24 2005 12:44:44:937PM1050524013Ian HutchinsonFizzle. Breakdown late at 6.8ms. Weak current.

Gas puff to 35ms from 40ms
May 24 2005 12:44:42:640PM1050524014Ian HutchinsonPlasma to rampdown.
Late breakdown 6.8ms, but strong enough to go.

OH2 to -26500A
May 24 2005 01:06:14:320PM1050524015Ian HutchinsonFizzle. Breakdown still late 6.7ms.

OH2 to -26300A
May 24 2005 01:15:05:987PM1050524016Ian HutchinsonPlasma till rampdown. Breakdown at 5.8ms.

Gas puff to 30ms from 35ms.
May 24 2005 01:19:58:330PM1050524017Ian HutchinsonFizzle. Breakdown at 5.7ms. Weak current rise.

Hand over to Wolfe as physop.
May 24 2005 01:33:12:823PM1050524018Steve Wolfe
Shot #18: Ian claims that if I do nothing it will run this time.
So I'll try it. It worked. Plasma full length on the even shots
Breakdown at 5.7msec again, current rise still low. 

next shot: pg4 from 29ms to 25 msec (risking the first dud of the day)

May 24 2005 01:45:32:367PM1050524019Steve Wolfe
Shot #19:  pg4 from 29ms to 25 msec
plasma, that's two in a row for the first time today. 
Current rise looks about the same as shot#18

next shot: rcur offset back to 500

May 24 2005 01:59:49:550PM1050524020Steve Wolfe
Shot#20 : rcur offset from 1500 to 500 (as on #5)
Three in a row. Breakdown at 6.3msec, current rise
still slow. 
Fside pressure at 1.5sec=0.2mTorr again

next shot: rcur offset to 0

May 24 2005 02:14:32:107PM1050524021Steve Wolfe
Shot#21 : rcur offset from 500 to 0
plasma, that's four in a row; barely made it
though, I think I've gone too far with rcur offset.

next shot: rcur offset back to 500, increase v_oh1 and 2

May 24 2005 02:27:57:740PM1050524022Steve Wolfe
Shot#22 : rcur offset from 0 to 500 
v_oh1 from 100 to 150, v_oh2u=v_oh2l up by 10V
plasma. Current rise is still slow, this one may
have bounced outside a little?

next shot: rcur offset to 1500, pg4 down 2msec

May 24 2005 02:42:27:267PM1050524023Steve Wolfe
Shot#23 :rcur offset to 1500, pg4 down 2msec to 23msec
plasma. Current rise is a little better, breakdown 6.3msec

next shot: down another 2ms on pg4

May 24 2005 02:53:31:467PM1050524024Steve Wolfe
Shot#24: pg4 from 23 to 21msec
plasma. Better current rise, over 40kA at 15msec
breakdown still around 6.3msec, Ip/Bz above 6e6
p0 below .04mTorr. That's the best startup of the
day. See if it repeats.

next shot: repeat

May 24 2005 03:07:36:740PM1050524025Steve Wolfe
Shot#25: No PCS changes.
plasma. current rise is slower this time, though.
Breakdown a little earlier, ~5.6msec

next shot: More oh voltage

May 24 2005 03:18:34:440PM1050524026Steve Wolfe
Shot#26: V_OH1 up 50V (to 200), V_OH2u=V_OH2L up by 10V
plasma. Almost lost it on an outside bounce. Faster 
current rise, though not as fast as 24?

next: rcur offset to 2000

May 24 2005 03:29:31:950PM1050524027Steve Wolfe
Shot#27: rcur offset from 1500 to 2000
plasma, still a little too much for the Bz,
but no bounce. Breakdown a little later

Ian back in the chair

May 24 2005 03:46:17:383PM1050524027Ian HutchinsonPlasma. Late breakdown, 7.5ms, but went.

Raise Gas Puff to 25ms from 22ms.
May 24 2005 04:31:22:897PM1050524028Ian HutchinsonFizzle. Late breakdown again. Raising puff did not help that.

Reload shot 25.
May 24 2005 04:31:34:803PM1050524029Ian HutchinsonNo power shot.
May 24 2005 04:50:24:703PM1050524030Ian HutchinsonPlasma to rampdown. Breakdown much earlier: 4.8ms. Ragged Ip rise.
Lots of runaways.

No changes.
May 24 2005 04:53:25:107PM1050524031Ian HutchinsonPlasma. Slightly later breakdown. Much lower runaways.

No changes.
May 24 2005 05:02:55:620PM1050524031Ian HutchinsonPlasma to rampdown.

Engineering Operator Comments
ShotTimeTypeStatusComment
109:00:58:243AMPlasmaOk
209:20:42:493AMPlasmaOk
309:43:06:663AMPlasmaOk
409:55:44:407AMPlasmaOk
510:08:30:043AMPlasmaOk
610:21:13:617AMPlasmaOk
710:34:37:487AMPlasmaOk
810:47:07:950AMPlasmaOk
911:16:03:660AMPlasmaOk
1011:29:34:277AMPlasmaOk
1111:49:20:740AMPlasmaOk
1212:02:05:627PMPlasmaOk
1312:14:53:293PMPlasmaOk
1412:27:23:193PMPlasmaOk
1512:40:03:597PMPlasmaOk
1601:03:11:960PMPlasmaOk
1701:15:51:800PMPlasmaOk
1801:28:24:560PMPlasmaOk
1901:40:49:087PMPlasmaOk
2001:54:46:660PMPlasmaOk
2102:10:12:420PMPlasmaOk
2202:22:39:807PMPlasmaOk
2302:35:35:113PMPlasmaOk
2402:48:15:437PMPlasmaOk
2503:01:28:150PMPlasmaOk
2603:13:55:800PMPlasmaOk
2703:26:26:670PMPlasmaOk
2803:39:00:057PMPlasmaOk
2903:55:26:800PMTestBad
3004:27:40:447PMPlasmaOk
3104:40:40:690PMPlasmaOk
3204:54:00:950PMPlasmaOk