Alcator C-Mod Run 960125 Information

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Miniproposals
Miniproposal:132
Date Filed:12/20/1995
Title:ICRF H Mode Confinement With Boronized Walls
First Author:Steve Golovato
Session Leader:Steve Golovato (shots 1-33)

Operators
Session leader(s):Steve Golovato
Physics operator(s):Ian Hutchinson
Engineering operator(s):Frank Silva,Joe Daigle

Engineering Operator Run Comment
icrf h-mode

Session Leader Plans

Physics Operators Plans

Session Leader Summaries
Entered: Jul 7 2004 03:49:15:007PM
Author: To Be Determined

Run summary - 960125

SL: Golovato
PO: Hutchinson
EO: Silva/Daigle

Run 960125 - H-modes with bornized walls continued.

Goals - (1) re-establish results of run 960116
(2) go to higher plasma current, up to 1.2 MA
(3) density scan at higher current
(4) get FSP edge profiles in H-mode
(5) get Hirex Ti profile at best condition.

The run was plagued by spontaneous imourity influxes ("bricks") which hit the plasma
on many shots at various times, often around 0.8 sec. This led to early disruptions
and subsequent fizzles. The plasma could survive these events at higher for nl04
above 1.e20 but had difficulty below this. We never got a shot as good as last week
but got similar shots under similar conditions (see shots 4 ansd 7). A density
scan was achieved at 1.1 MA (see shots 12,14,16,18,20,21,28,29,30), although some
of these shots has rf trips. It has been subsequently found that there may be a
arcing problem in one of the feeds to the d-port antenna. The best shots were
under similar conditions to the best shots of last week, in particular shots
4,7,9,and 12, where the stored energy was 180-200 kJ, the neutron rate above 5.e13,
and the H-factor above 1.8. During this scan, several FSP scans were accomplished.
FSP control was tried for shots 5 and 6 and seemed to lead to interaction with
the nose when combined with the postion feedback control, so it was abandoned.
Because we lost so many shots because of impurity bricks, we never got to the
last goal of getting a more detailed Hirex profile.

The position feedback control may contribute to disruptions when an event such as an
impurity injection drops the plasma out of H-mode and leads to rf trips. If the rf
stays on during L-mode before tripping, the feedback will try to move the plasma away
from the antenna. It will continue this after the rf trips because it holds the
error constant during trips. We have now reduced the maximum error signal from the
feedback circuit for the polarity that moves the plasma away from the antenna by a
factor of 5-7.

For information on engineering problems and shot statistics, see the physics
operator summary. For shot-to-shot comments, see the logbook under the
session_leader topic.


Physics Operator Summaries
Entered: Jul 7 2004 04:36:55:910PM
Author: To Be Determined
Physop 960125. MP132 ICRF H-modes with Boron. MP134 SOL profiles with H-Mode.
____________________________________________________________________________
PO Hutch; SL: Golovato;

Summary
_______
A difficult run starting with a vent(!) but got quite a bit of probe data.
So, useful especially for the divertor and SOL H-mode data. No stored energy
records. Only about half of the plan was accomplished.
Got 1.1MA shots to run reliably. Failed to get FSP control to work but did
not spend much time on it because it did not seem to be needed.
Failed to get 1.2MA to run reliably. A disruption "out" led to backing down
to 1.1MA. Generally if these shots disrupted it was due to an obvious
impurity injection. Completed a density scan at 1.1MA but probably not directly
comparable with 960116 because of worse radiation.
Plagued throughout by Mo injections and radiative accumulations at a rate
approximately twice that of 960116025. It looks as if Boron is wasted for this
week. Tungsten lines were seen clearly on the McPherson. (Probe erosion).
Some large disruptions but very robust startup recovery from
disruptions. 1 fizzle due to operator error. One due to excessive dirt
stirred up.

Plan
____
Engineering setup.
Fill A-side (actually K-side) plenum with 20 psi of deuterium
Fill B-top plenum with 5 psi of deuterium.
Fill B-side-lower plenum with 2 psi of argon.
Enable hybrid control of A-side and B-top for start of run

Start with the engineering setup from shot 960116037, for an initial
fiducial shot.

RF ready to go on first shot.
Enable the ECE, VUV, Moly monitor, PCX, and TCX valves, assuming status of
each is okay.

Hopelessly Optimistic Run plan Total
1 Fiducial. 1
2 reload 950116025. But with RF notched off for 0.95-0.965s 2
3 try an FSP-controlled shot to demonstrate feasibility at 1MA 4
4 Raise Ip to 1.2 MA avoiding disruptions (ho ho!) 7
5 Do a density scan with RF and H-mode at 1.2MA 17
6 At a density near optimum, repeat enough shots to get Ti
profiles from hirex. Use these shots to get SOL profile
if necessary by using the FSP controller. 22
7 Add H to A-side Plenum till 23 psi (15%) and run some shots 27
8 Repeat at 1MA to get SOL and Ti profiles. 35
9 Relax!

Scorecard
_________
Shot,Duration(s),Ipmax(MA) Shot,Duration(s),Ipmax
1 1.502 0.812 2 0.000 0.005
3 0.000 0.021 4 1.706 1.024
5 1.206 1.095 6 0.832 1.019
7 1.705 1.021 8 0.301 0.753
9 1.105 1.140 10 0.763 1.220
11 1.703 1.114 12 1.701 1.117
13 0.824 1.329 14 1.702 1.117
15 1.612 1.114 16 1.611 1.112
17 0.789 1.127 18 1.584 1.109
19 1.509 1.104 20 1.547 1.107
21 1.704 1.114 22 0.806 1.254
23 0.890 1.226 24 0.000 0.029
25 1.317 1.114 26 0.857 0.812
27 1.520 0.812 28 1.702 1.112
29 1.704 1.114 30 1.705 1.112
31 0.000 0.026 32 0.771 1.205
33 0.554 0.998
Finished summary for 960125 Total of 33 shots.
33 shots. 29 plasmas. 3 fizzles. 1 duds.
Fizzle = gt 17 lt 50kA.

________________________________________________________________________
Details
_______
ECDC in D2 overnight. Shut down at 6am. Vacuum fault causes vent at 6:40.
Restart and pump down. 1.e-6 at 8:10am. We hope this was Helium.

In view of the vent, we had about 45minutes of ECDC till about 9:40.
Both ratiomatics seem to have died during whatever happened.

Load from 960116037.
1 Pla Fiducial. Ran OK. ELM free H-mode. Some small injections.

Load 950116025.
2 Alternator power supply failure.

3 Fiz (Repeat.) Found that fill pulse was much too long.

Extend all P pulses to 1.2s. For longer current pulse.
PID changes. RXL,ZXL,RXU (ZXU already kept on till 2s.)
Others are already kept on.
Fill pulse to 12ms.
4 Pla Ramp down ok. 2.5 MW. 175 kJ.

Load FSP on wire 9 from 951219021 and extend to 1.2s
Reduce zxl gain to 2 from .5s on, when FSP comes on.
RF notch removed, just going to turn off at 1s.
5 Pla Disrupts at 1.2s Giant injection at .8s. Fairly large Mo injection
at .08s messes up current rise.

Turn FSP gain off at 1.1s.
6 Pla Disrupts at 0.82s. Big Mo chunk again. Also at .5s.

Reload shot 4
7 Pla Ran all the way. It looks as if there is a subtle problem with the
FSP-controlled plasmas. ELM-free H-mode; Mo accumulates to >1.e16.

Repeat with probe inserted.
8 Pla Disrupts at .3 seconds due to vertical instability.

Remove the RXL ramp to -.005 at time .5 to .6. Set to 0 instead.
This should move the strikepoint up the divertor somewhat.
Draw Rcur out a little further during .15 to .35s. to stabilitze.
Ip to 1.1MA.

9 Pla Disrupts at end of flat top. Big injection at .76s. Another at
the end preceeds the disruption.

Fill puff to 14ms, in case we are getting runaways.
Pushed plasma out some more during .15 to .3s.
Raise ZXL to -.016 from -.02.
10 Pla Disrupts at .75s. Growing vertical instability. Not obvious why.

Raise nl04 to 1. from .7 to help keep radiation down.
Raise ZXL to -.01.
11 Pla Ramps down. Strong Density rise but a lot of radiation. 184MJ falling.

Repeat with probe.
12 Pla Better shot. 195MJ. Prad to 1.7MW.

Raise Ip to 1.2MA.
13 Pla Disrupts. 257kA halo. This disruption seems to be induced by the RF
feedback that pushes the plasma in when it faults. However, the
disruption is a thermal quench prior to vertical loss of position.
Seems to have a radiation spike at ,808s that leads to the disruption.

Reload 12.
14 Pla Good shot. 170kA. Plenty of radiation.

nl04 to 1.2. Removed the 1.-1.2s RCUR ramp that was not supposed to
be there.
15 Pla RF faults.

Argon enabled 2psi .285-.3s.
16 Pla Full RF. Many things responding to sawteeth. 175kJ.

Argon to .28-.3
nl04 to 1.4
17 Pla Disrupts due to Mo brick at .78s. RF then pushes plasma in.

Repeat
18 Pla Ok except for small initial injection. 173kJ

nl04 to 1.7
19 Pla Cyclic RF trips, and conrresponding plasma motion.

Tweaked Ip rise program to reduce the roll over.
20 Pla Fine 162kJ.

nl04 to 0.8 Tweak the current some more.
21 Pla RF trips. Ip looks better.

Tune Rf. Tweak Ip some more.
22 Pla Disrupts at .8s. No H-mode.

Repeat
23 Pla Disrupts at .88s. No H-mode.

nl04 to 1.
24 Fiz

Repeat
25 Pla Disrupts at 1.26s. 0.8MA. Short H-mode.

Fiducial. Reload shot 1.
26 Pla Disrupts at .853s. 0.8MA. Peceded by a brick at .842

Repeat.
27 Pla OK

Reload 25
28 Pla OK

nl04 to .9.
29 Pla OK

nl04 to .7
30 Pla OK. Mo injection at .11s. ELM-free during RF. 2pi integrates.

nl04 to .5
31 PSDud No TF.

32 Pla Disrupts at .75s. Sawteeth are suppressed from about .55s. Internal
disruption leads to inward motion, followed by vertical instability.

Load segment 2 from 960116025. To do a direct comparison.
33 Pla Brick at .51 leads to disruption at .55s.

Session Leader Comments
Jan 25 1996 10:05:40:030AM960125001Steve Golovato960125001 - fiducial. good h-mode.

Jan 25 1996 10:09:03:840AM960125002Steve Golovato960125002 - load shot 960116025, best shot of last h-mode run.
position feedback enabled. rf notched from .95-.965 sec for fsp scan

dud. almost no power supplies ran.

Jan 25 1996 10:16:26:810AM960125003Steve Golovato960125003 - try again.

fizzle.

Jan 25 1996 11:00:54:090AM960125004Steve Golovato960125004 - try again.

plasma. Te_gpc=4.3kev, wp=180kj, good h-mode but got h-alpha blob,
lower wp, slower nl rise after initial elm-free fast rise.

Jan 25 1996 11:02:54:910AM960125005Steve Golovato960125005 - go to 1.1 MA.

plasma, h-mode, big impurity influx at .8 sec.
1 ma disruption at 1.2 sec

Jan 25 1996 11:11:57:390AM960125006Steve Golovato960125006 - fsp control on for this shot and previous shot.

plasma. disrupted again, even earlier. h-mode until impurity
injection.

Jan 25 1996 11:41:30:460AM960125006Steve Golovato960125007 - fsp off for this shot. seems we're hitting nose with
combination of fsp control and position feedback.

plasma. looks a lot like shot 960116025, no h-alpha blob.

Te-gpc=4.9kev, 185kj, h-factor about 1.8-2.

Jan 25 1996 11:41:37:310AM960125007Steve Golovato960125007 - fsp off for this shot. seems we're hitting nose with
combination of fsp control and position feedback.

plasma. looks a lot like shot 960116025, no h-alpha blob.

Te-gpc=4.9kev, 185kj, h-factor about 1.8-2.

Jan 25 1996 11:42:52:130AM960125008Steve Golovato960125008 - trying for 1.1ma, this is the first attempt.

early disruption, .3sec.

Jan 25 1996 11:58:02:050AM960125009Steve Golovato960125009 - try again.

plasma, got 1.1ma. brick hit plasma at .8 sec again.
d-port hiiting voltage limit, lowering power for next shot.
was going to be a good shot, were at 190kj when brick hit.

Jan 25 1996 12:17:17:110PM960125010Steve Golovato960125010 - strike points a little low, may pull separatrix close
to bottom of outboard limiter. move strike points up.

plasma, disruption at .76sec, no h-mode.

Jan 25 1996 12:29:14:150PM960125011Steve Golovato960125011 - raise density,see if things work better.

plasma, good h-modes, both antennas tripping at voltage limit.
imurity influx at .85sec.

Jan 25 1996 12:45:40:640PM960125012Steve Golovato960125012 - repeat.

plasma, h-modes, no rf trips. 2.6MW.

Jan 25 1996 01:05:35:770PM960125013Steve Golovato960125013 - go to 1.2 MA.

plasma, disrupted at 815ka, high halo currents. back off.
feedback probably caused disruption. d-port tripped and we lost
h-mode, this caused feedback to increase outer gap.

Jan 25 1996 01:16:59:720PM960125014Steve Golovato960125014 - reload shot 12, 1.1MA.

plasma, looked like shot 12. start density scan.

Jan 25 1996 01:36:10:560PM960125015Steve Golovato960125015 - nl04 programmed to 1.2e20 from 1.e20.

plasma, h-mode, d-port overloaded.

Jan 25 1996 01:42:26:000PM960125016Steve Golovato960125016 - repeat to keep rf on.

plasma, h-mode, h-alpha blob. 2.5MW.
initial nl04=1.3

Jan 25 1996 01:54:02:570PM960125017Steve Golovato960125017 - rasie nl04 to 1.4e20.

plasma, disrupted at .8sec, after brick hits at .75sec.

Jan 25 1996 02:05:59:770PM960125018Steve Golovato960125018 - repeat.

plasma. h-mode. 2.6MW. final nl04=2.5

Jan 25 1996 02:24:58:640PM960125019Steve Golovato960125019 - higher target nl04=1.7e20.

plasma, in and out of h-mode when d-port trips out.

Jan 25 1996 02:35:27:630PM960125020Steve Golovato960125020 - repeat

plasma, loading high enough that feedback incresed outer gap to
maintain match. max nl04 during h-mode is about 2.5e20 independent
of initial density.

Jan 25 1996 02:58:53:480PM960125021Steve Golovato960125021 - going ot lower nl, nl04=.8e20

plasma, h-mode until rf trips. initial nl04 still 1.1e20.

Jan 25 1996 03:06:13:030PM960125022Steve Golovato960125022 - repeat

plasma, disrupts at .8sec no h-mode, e-port overload.

Jan 25 1996 03:23:41:230PM960125023Steve Golovato960125023 - repeat

plsama, disrupts at .85sec, rf ran but no h-mode at 2.5 MW.

Jan 25 1996 03:24:03:530PM960125024Steve Golovato960125024 - repeat

fizzle.

Jan 25 1996 03:25:05:860PM960125024Steve Golovato960125024 - return to nl04=1.e20 for this shot, not a repeat of last shot.

Jan 25 1996 03:38:45:320PM960125025Steve Golovato960125025 - repeat.

plasma, short h-mode. not running well. try a fiducial next.

Jan 25 1996 03:50:51:490PM960125026Steve Golovato960125026 - fiducial.

plasma, disrupted at .86sec. something is wrong,
another brick hit plasma.

Jan 25 1996 03:56:38:800PM960125027Steve Golovato960125027 - another fiducial.

plasma, good h-mode. no e-port rf.

Jan 25 1996 04:18:27:780PM960125028Steve Golovato960125028 - reload shot 25, nl04=1.e20, 1.1MA.

plasma, h-mode, some rf interupts.

Jan 25 1996 04:26:30:660PM960125029Steve Golovato960125029 - lower nl04=0..e20,

plasma, h-mode, some rf interupts.

Jan 25 1996 04:40:50:050PM960125030Steve Golovato960125030 - lower nl04=0.7e20,

plasma, h-mode, some rf interupts.

Jan 25 1996 04:44:38:220PM960125031Steve Golovato960125031 - lower nl04=0.5e20 (note that i am giving here the pcs
programming, not he actual density achieved inthe shot.

no tf.

Jan 25 1996 04:58:11:330PM960125032Steve Golovato960125032 - nl04=.5e20

plasma, brick at .77 sec.

Jan 25 1996 05:07:23:740PM960125033Steve Golovato960125033 - reload shot 960116025.

plasma, disrupted at .55 sec.

Physics Operator Comments

Engineering Operator Comments
ShotTimeTypeStatusComment
109:46:41:230AMPlasmaOk
210:04:51:110AMPlasmaBadAll Power supplies operating off alt. did not turn on.
310:14:59:410AMPlasmaOk
410:28:11:080AMPlasmaOk
510:45:50:920AMPlasmaOk
611:01:43:630AMPlasmaOk
711:12:39:390AMPlasmaOk
811:27:30:630AMPlasmaOkself powered fired OH2U &OH1 Bypass
911:42:31:760AMPlasmaOk
1012:03:59:200PMPlasmaOk
1112:17:12:980PMPlasmaOk
1212:28:45:330PMPlasmaOk
1312:46:59:700PMPlasmaOk
1401:05:47:620PMPlasmaOk
1501:18:25:650PMPlasmaOk
1601:30:15:540PMPlasmaOk
1701:44:16:750PMPlasmaOk
1801:57:28:830PMPlasmaOk
1902:08:58:010PMPlasmaOk
2002:22:45:030PMPlasmaOk
2102:36:18:090PMPlasmaOk
2202:50:31:540PMPlasmaOk
2303:02:24:460PMPlasmaOk
2403:15:28:520PMPlasmaOk
2503:28:23:500PMPlasmaOk
2603:40:12:900PMPlasmaOk
2703:51:08:820PMPlasmaOk
2804:05:31:200PMPlasmaOk
2904:17:44:870PMPlasmaOk
3004:30:44:310PMPlasmaOk
3104:42:58:820PMPlasmaBadNo TF pulse
3204:51:51:060PMPlasmaOk
3305:04:12:080PMPlasmaOk