Alcator C-Mod Run 1050415 Information

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Miniproposals
Miniproposal:398
Date Filed: 1/10/2005
Title:Complete identity experiments with JET on error field locked mode thresholds
First Author:T.C. Hender
Session Leader:T.C. Hender (shots 1-18)
Session Leader:Steve Wolfe (shots 31-32)
Miniproposal:402
Date Filed: 1/14/2005
Title:Locked mode studies at different toroidal phase
First Author:Steve Wolfe
Session Leader:Steve Wolfe (shots 19-30)

Operators
Session leader(s):T.C. Hender,Steve Wolfe,Steve Wolfe
Physics operator(s):Earl Marmar
Engineering operator(s):Bill Byford

Engineering Operator Run Comment
MP#398 SL: Hender/Wolf PO: Marmar and MP#402 SL: Wolf

Session Leader Plans
Entered: Apr 14 2005 04:18:25:790AM
Author: T.C. Hender
MP#398 Complete identity experiments with JET on error field locked mode thresholds
SL: Hender/Wolfe

PO: Marmar


Run begins at 9:00 and ends at 13:00


Note: Acoil configuration (-Btop+Dbot+Gtop-Jbot)

RF Setup: NONE - no RF for this run.
---------------------------------------------------------------
Run Plan for MP#398:

q95=3.2 (I=0.81MA, B=4T, "JET shape") 1050310013 is a good reference
With ( -Btop+Dbot+Gtop-Jbot) trying to get LM data at low field (4T):

1. Repeat 1050310013 but with density of n114=1.e20. With 2kA square wave in A-coil from 0.8s to 1.28s. And then vary A-coil current up and down to refine LM threshold.

2. Repeat 1050310013 but with density of nl14=1.3e20. With 2kA square wave in A-coil from 0.8s to 1.28s. And then vary A-coil current up and down to refine LM threshold.


Go to -Bbot-Dtop+Gbot+Jtop


3. If 2. was successful repeat, if not repeat 1.


If time allows (possible but not too likely) try to get some 6.3T data but with -Bbot-Dtop+Gbot+Jtop

4. Repeat 1040413029 exactly. With 2kA square wave in A-coil from 0.8s to 1.28s. And then vary A-coil current up and down to refine LM threshold.
Entered: Apr 14 2005 08:28:53:617AM
Author: Steve Wolfe
Plan for Part 2 of 1050415
MP#402 "Locked mode studies with different toroidal phase"
SL: wolfe
PO: Marmar

The purpose of these experiments is to improve our characterization of the
C-Mod intrinsic error fields, and to investigate the dependence of the 2/1
locked mode threshold on the m=1 and m=3 sidebands. 

These experiments will be at 5.4T, while Hender's in the morning 
are at 4T, so the GPC2 grating may need to be adjusted between experiments. 
I'm assuming that GPC will have the 5.4T grating in place all day. 

Since we will be following Hender's MP#398 experiment, we will begin with
the Acoil tap configuration he ends with, which should be 
  ** [-Bbot -Dtop +Gbot +Jtop] rotated helical, phi= -104 degrees  **
This corresponds to setting 5A of Day 1 in the MP402 shot sequence.
Call this "option A". 

If Hender's run has gone too slowly, then we will still be in his starting
configuration, 
  ** [-Btop +Dbot +Gtop -Jbot] (anti-standard helical, phi=164 deg)  **
which corresponds to setting 6B in the Day1 MP402 shot sequence. 
Call this "option B" 

Note: Nominal intrinsic error field has phi~ -160 degrees.

We will try to maximize the data in each coil configuration before moving on
to the next. This plan therefore includes elements of both Day 1 and Day 2
from the MP402. 

1. Establish shot with 1MA, 5.4T, NL04=1.1e20, Acoil off (e.g. 1050412008, 
   tweak nl04 program).
   Verify that no intrinsic locked mode appears. If it does, raise
   NL04. [1-2shots] 
2. A) Program Acoil current to maximum (program 4000A, expect 3600A).[1 shot]
   B) If locked mode appears then reduce Acoil program to bracket the
   threshold. Otherwise, Reduce NL04 by 10% and try again. [1-3 shots]
   C) Program decreasing density (NL04 1.5->0.5e20) 
      set Acoil current=1600A (Option A) or 1360A (Option B). 
      (aiming for B21_app~4.4G), and determine locking density. [1-2 shots]
      Note: The Acoil program needs to be about 500A higher than the
       actual target value, so these should be programmed as ~"2100A" or
       "1860A" respectively. 
3. Reverse Acoil power supply leads
     Option A: [+Bbot +Dtop -Gbot -Jtop] (rotated helical, phi=76 degrees)  
     Option B: [+Btop -Dbot -Gtop +Jbot] (std. helical, phi=-16 degrees)
   A) Program 4000A in Acoil [1 shot]
   B) If locked mode appears, bracket the threshold. Otherwise, proceed to
   step C. [0-3 shots]
   C) Repeat 2C in this orientation [1 shot]
     Option A: Acoil current=1600A again
     Option B: Acoil current=1360A again
4. Change Acoil taps to [+Btop -Bbot -Gtop +Gbot] (rotated quadrupole, phi=-49
   degrees); this is step 2A of the MP402 Day1 program.
   A) Program Acoil for 4000A [1 shot]
   B) If locked mode appears, reduce Acoil current to bracket the
   threshold. [0-3 shots]
   C) Repeat 2C, but with Acoil current at 1660A. [1 shot]
5. Reverse Acoil power supply leads [-Btop +Bbot +Gtop -Gbot] (rotated 
   quadrupole phi= 131 degrees). This is step 2B of the MP402 Day 1 sequence.
   A) Program Acoil for 4000A [1 shot]
   B) If locked mode appears bracket the threshold [0-3shots]
   C) Run decreasing density shot with Acoil current = 1660A
   program) and determine locking density. [1 shot]

I don't expect to get past this point in a half-day, with tap
changes and disruptions. Actually, it would be doing well to 
get through step 3. If by some miracle we do get this far, then 
the next case would be the rotated dipole
[-Btop -Bbot +Gtop +Gbot] phi=-142 degrees. 
The acoil current for step C would be 3600A (program for max, 4000A). 

Physics Operators Plans
Entered: Apr 14 2005 04:59:51:007PM
Author: Earl Marmar
Physop plan for 1050415
PO Marmar

MP#398 JET locked mode identity (1/2day) SL: Hender
AND
MP#402 Locked modes at different phase(1/2 day) SL: Wolfe

The evening before the run, the machine will be backfilled with He (~500 Torr) for the DNB gatevalve and Thomson calibration.

After pumpdown, overnight ECDC in D2, P=2e-4 Torr (gauge), stopping by 7:00 am; vessel at 60 degrees C.

Run is scheduled to begin at 9:00 am, end at 5:00 pm


Gas Setup:
fill B-top with 6 psi D2 hybrid enabled (PG4)
fill B-side lower with 2 psi Ar Hybrid disabled (PG1)
leave B-side upper with He3 Hybrid disabled
fill B-main (C-side) with 30 psi D2 Hybrid enabled (PG3)
leave J-bot Hybrid disabled (PG2)

Power systems as on 1050414002
***NOTE: Acoil configuration (-Btop+Dbot+Gtop-Jbot)***

Enable the following:
ECE gate valve, Z-bolo shutters
VUV gate valve

RF Setup: NONE - no RF for this run.

Session Leader Summaries
Entered: Apr 15 2005 06:06:09:663PM
Author: Steve Wolfe
Run Summary for part 2 of 1050415
MP#402 "Locked mode studies at different toroidal phase"

This half-run begins the effort to improve the characterization
of the C-Mod intrinsic error fields and hopefully to identify
a sideband effect by comparing similar applied error fields
at different toroidal orientations using the newly available
Bbot coil. Today's experiments used the [-Bbot -Dtop +Gbot +Jtop]
orientation, which produces a "helical", mode spectrum with the
resonant 2/1 mode oriented at phi~ -104degrees. This 
configuration was also used for the JET-like experiments in the
morning run. 

We got off to a slightly late start, since we took some extra
shots on the morning experiment to try to get a higher field
point on the Bt scaling experiment. The first attempt on MP402
was at 2:10, and we began with a pair of duds. The first plasma
shot in this series was #21 at about 2:45PM. 

Despite the late start, we completed steps 1 and 2 of the run
plan. The threshold with this field configuration at 
nl04~1.15e20, 1MA, 5.4T is  Iacoil=2800A, Bapp=7.8G at 1.18sec 
and 2400A, Bapp=6.7G at 1.4 sec (shots #25 and 26). 
At Bapp=4.4G the threshold density is NL04=0.95e20 at t=1.03sec.  

These values will be compared to data in the standard "helical"
orientation and to other mode spectra, including "quadrupole"
and "dipole" in both our original orientations and "rotated"
examples employing the Bbot coil.  

We completed step 2 of the run plan by 4:45PM (2 hours from
our first plasma), including a couple of extra, pretty much
redundant, shots in refining the threshold and getting a more 
exact 4.4G point for comparison with other configurations. 
Since there was clearly not enough time to do the reverse 
polarity configuration called for in step 3, we went back
and took another try at the 6.3 T case of MP#398, though 
without success, as we got one fizzle and another early locked
mode, which may or may not have been induced by an almost 
simultaneous injection. 

Entered: Apr 18 2005 10:18:28:527AM
Author: T.C. Hender
This was fairly successful session. Good error field threshold data was obtained with the Acoil configuration Btop-Dbot-Gtop+Jbot at 4.1T (q95=3.2) in a JET identity match shape (key shots were 2, 3, 5 ad 7 which narrowly bracket the error field threshold). With the quadrature configuration -Bbot-Dtop+Gbot+Jtop it was found full A-coil current (3.7kA) was needed to make locked modes; having data from 2 quadrants should allow more accurate determination of the intrinsic error (at 4.1T). Some data was also obtained at 6.3T (where the 2004 JET identity experiments were conducted) though there were problems with early intrinsic locked modes forming at about 0.6s. With -Bbot-Dtop+Gbot+Jtop at 6.3T one shot (#12) at full A-coil current formed no locked mode, whereas at lower density (nl14=1.1e20) shot 14 formed a locked mode at 3.2kA (but during the ramp). There is certainly now enough data for an initial analysis of the Bt scaling; with Btop-Dbot-Gtop+Jbot the data obtained in this session at 4.1T can be compared with the extensive 2004 error field threshold dataset at 6.3T and with -Bbot-Dtop+Gbot+Jtop there is limited data at 4.1 and 6.3T.

Physics Operator Summaries
Entered: Apr 15 2005 05:10:27:163PM
Author: Earl Marmar
MP#398 JET locked mode identity (1/2day) SL: Hender
AND
MP#402 Locked modes at different phase(1/2 day) SL: Wolfe

PO: Marmar

The machine ran well today. There were many disruptions, with currents from 1 to 1.3 MA. Several of the 1.3 MA disruptions, which were at B_T=6.4 tesla, gave halo current warnings. Also we had 2 duds (19 and 20) after a number of these high current disruptions. Raising the fill pressure seemed to fix the problem for shot 21.

Shot 6 died at 100 kA, apparently due to an injection

Fizzles were also problem.

Early hard x-rays continue to be a problem on most shots.

There were no data system or power supply problems today.


After the run today, we plan to boronize. This will be the first boronization of the FY2005 comapaign.

Scorecard:

Plasmas 24
Fizzles 6
Duds 2

Total cycles 32


Session Leader Comments
Apr 15 2005 11:49:18:390AM1050415011Steve Wolfe
Cell access for Rick Murray to fix cooling 
on TCI Bragg cell, before shot#12.

Apr 15 2005 02:10:40:453PM1050415019Steve Wolfe
Shot#19: Go to MP402 program.
1. Establish shot with 1MA, 5.4T, NL04=1.1e20, 
   Acoil off (e.g. 1050412008, 
   tweak nl04 program).
   Verify that no intrinsic locked mode appears. If it does, raise
   NL04. [1-2shots] 
Leave A-coil in present configuration:
[-Bbot -Dtop +Gbot +Jtop]
Dud. 


Apr 15 2005 02:29:41:797PM1050415020Steve Wolfe
Shot#20: 
1. Establish shot with 1MA, 5.4T, NL04=1.1e20, 
   Acoil off (e.g. 1050412008, 
   tweak nl04 program).
   Verify that no intrinsic locked mode appears. If it does, raise
   NL04. [1-2shots] 
Leave A-coil in present configuration:
[-Bbot -Dtop +Gbot +Jtop]
 
Another dud.

Apr 15 2005 02:48:28:860PM1050415021Steve Wolfe
Shot#21: 
1. Establish shot with 1MA, 5.4T, NL04=1.1e20, 
   Acoil off (e.g. 1050412008, 
   tweak nl04 program).
   Verify that no intrinsic locked mode appears. If it does, raise
   NL04. [1-2shots] 
Leave A-coil in present configuration:
[-Bbot -Dtop +Gbot +Jtop]
 
Locked mode at 1.38sec, density had fallen to 0.86e20
It looks like we're about 20% above the intrinsic threshold at 1.05

next shot: raise nl04 to 1.1e20 and hold it flat, and 
run Acoil at 4000 program. 

Apr 15 2005 02:58:02:343PM1050415022Steve Wolfe
Shot#22:  raise nl04 to 1.1e20 and hold it flat, and 
run Acoil at 4000 program (flat from .6 to 1.5sec)
plasma into rampdown but had a locked mode
at 0.91sec, nl04=1.1e20, model total field=13.7G
Bapp=10.6 (Ia=3800A)

next shot: acoil program down to 2200A

Apr 15 2005 03:19:04:470PM1050415023Steve Wolfe
Shot#23:  acoil program down to 2200A
plasma to 1.7sec, no locked mode. Ia=2000A, Bapp=5.4G, Btot=10G
nl04=1.18e20.
There may be a hint of something at 1.48sec, sawteeth go
away before rampdown, no magnetic signature. 

next shot: acoil program to 3000A

Apr 15 2005 03:24:02:717PM1050415024Steve Wolfe
Shot#24: acoil program to 3000A
fizzle

Apr 15 2005 03:41:36:117PM1050415025Steve Wolfe
Shot#25: acoil program to 3000A
plasma full length. 
locked mode at 1.18sec. nl04=1.16e20
Ia=2800A, Bapp=7.8G, Btot ?= 11,6G

next shot: Acoil program to 2600A

Apr 15 2005 03:55:53:070PM1050415026Steve Wolfe
Shot#26:  Acoil program to 2600A
plasma into rampdown
locked mode at 1.40sec
IA=2400, Bapp=6.7G, Btot ?=10.9G

next shot: Acoil to 2400A

Apr 15 2005 04:02:12:040PM1050415027Steve Wolfe
Shot#27:  Acoil program to 2400A
 The result on shot#23 at 2200A was a bit ambiguous. 
fizzle

Apr 15 2005 04:19:21:587PM1050415028Steve Wolfe
Shot#28:  Acoil program to 2400A
 The result on shot#23 at 2200A was a bit ambiguous.
plasma to 1.7sec
No locked mode?, maybe the same kind of late sawtooth loss
at 1.48sec. 

next shot: Step 2C Acoil program to 1800A, density ramp
down after 0.8sec


Apr 15 2005 04:32:43:850PM1050415029Steve Wolfe
Shot#29:  Step (2C) Acoil program to 1800A, density ramp
down after 0.8sec

Disruption at 1.56sec
Locks at 1sec, NL04=9.5e19,IA=1500A, Bapp=4.1G

next shot: raise Acoil to 1900A

Apr 15 2005 04:58:26:337PM1050415030Steve Wolfe
Shot#30:  Step (2C) Acoil program to 1900A, density ramp
down after 0.8sec

plasma to 1.6 or so, locked mode at 1.03sec
Bapp=4.4G, Btot=8.4G, NL04=.95e20
That takes care of 2C

Next shot: Go back to shot#14

Apr 15 2005 04:54:44:117PM1050415031Steve Wolfe
Shot#31:  Go back to shot#14 (with higher plenum
pressure of 38psi) and try to finish off the MP#398
program for Tim. 

fizzle. That looks like Tim's run!

Apr 15 2005 05:17:50:647PM1050415032Steve Wolfe
Shot#32:  Go back to shot#14 (with higher plenum
pressure of 38psi) and try one more time to finish
off the MP#398 program for Tim. 

plasma disrupts at 1.20sec. Another early locked mode
at .62sec, amd density was near 1.2e20. I need to check
on Joe's signals to see if this is a delta-prime mode,
i.e. rotating before locking. I don't see why it is doing
this now and not last year.  There is a big injection
at that time, but it looks to me like the lock comes first;
they're almost simultaneous. 
Aside from the injection this is similar to 17. 


Physics Operator Comments
Apr 15 2005 09:14:32:283AM1050415001Earl Marmarload segment 1 from 1050414021
load segment 2 from 1050310013 (JET shape, 4 T, .8 MA)
0 the offsets for clearin and ip in segment 2
nl_04 target to 1.0e20
Acoil prog 2500 A square from 0.8 to 1.28 seconds

plasma

got a locked mode; disrupt at 1.27 s
Apr 15 2005 09:22:12:063AM1050415002Earl Marmarreduce A-coil demand to 1700 Amp

plasma into rampdown
Apr 15 2005 09:40:27:370AM1050415003Earl MarmarA-coil demand to 2100 Amp, same timing

plasma; locked mode & disruption
Apr 15 2005 09:52:02:990AM1050415004Earl Marmarnl_04 target to 1.3e20
A-coil demand to 2250, same timing

plasma; no sign of a locked mode
Apr 15 2005 09:59:24:440AM1050415005Earl MarmarA-coil demand to 2500 A, same timing

plasma; no sign of a locked mode

fill is creeping up
Apr 15 2005 10:11:42:887AM1050415006Earl MarmarReduce prefill puff by 1 msec to 20 msec
A-coil demand to 2750 A, same timing

got to almost 100 kA; looks like something fell in at ~22 msec, then it died.

Apr 15 2005 10:21:37:760AM1050415007Earl Marmarno pcs changes

plasma; locked mode; disruption
Apr 15 2005 11:01:46:417AM1050415008Earl MarmarA-coils to -Bbot-Dtop+Gbot+Jtop

plasma; locked mode; disruption
density is a tad low, and drooping
Apr 15 2005 11:06:11:797AM1050415009Earl MarmarA-coil program to 2800 A, same timing
tweak nl_04 program to get slightly higher, and avoid the droop

plasma, disrupt at end of flattop; no obvious locked mode
density is a bit higher, and doesn't droop
Apr 15 2005 11:25:40:970AM1050415010Earl MarmarA-coil program to 3300 A, same timing

plasma, disrupt at 1.41s; no sign of a locked mode
Apr 15 2005 11:33:26:203AM1050415011Earl MarmarA-coil program to 3600 A, same timing

plasma into rampdown; no sign of locked modes
Apr 15 2005 12:18:17:843PM1050415012Earl Marmarload segment 2 from 1040413024 (6.3 T, JET shape)
load segment 2 nl_04 wire from 1050415011
recalculate seg 2 Ip predictor to get the ROG-CD to ROG_FG change and 0 offset
0 offset in seg 2 CLEARIN
TF PLC limit raised to 180 kA
A-Coil program to 4000 A, on at 0.8, off at 1.3


short cell access for TCI before the shot

plasma; disrupt at end of flattop; no obvious locked mode


Apr 15 2005 12:17:43:533PM1050415013Earl Marmarcopy PG3 voltage programming from 1050415011 in to segment 2
reduce I_p demand to 1.280 MA
I_TF prog to -177.3 kA from -174.5
raise TF PLC limit to 185 kA

fizzle
Apr 15 2005 12:56:22:140PM1050415014Earl MarmarEF 4 current to -1355 A from -1345 A for t < 0
raise the OH1 PLC limits to +/-30 kA (from +/- 27 kA)

plasma; disrupt at end of flattop
Halo current warning.

Apr 15 2005 12:48:06:157PM1050415015Earl Marmartweak the early seg 2 nl_04, to try to get a little more density

fizzle
Apr 15 2005 01:23:38:690PM1050415016Earl Marmarreduce prefill puff by 2 msec to 18 msec
IC_EF4 another 10 A more negative for t < 0 (now -1365 A)
plasma; disrupt at .653, big injection, maybe an intrinsic locked mode

halo current warning
Apr 15 2005 01:36:39:940PM1050415017Earl Marmarincrease PG3 plenum pressure to 40 PSI (was down to ~27 psi from 30 at the start of the day)
tweak the early PG3 puff some more; try to avoid early marfe; puff less at .1 s, but puff more around .2 seconds.

plasma
early marfe is there, but doesn't kill it
got higher density
disrupt at 1.165 s; halo current warning
Apr 15 2005 01:53:46:157PM1050415018Earl Marmarraise early seg 2 PG3 voltage
increase early seg 2 nl_04 rise rate

plasma
disrupt at 0.23 s; too much gas; big marfe.
Apr 15 2005 02:11:34:813PM1050415019Earl Marmarimport segment 2 from 1050412008 into segment 2
nl_04 target to 1.1e20

decrease prefill puff by 1 msec to 17 msec

dud
Apr 15 2005 02:29:16:830PM1050415020Earl Marmaradd 2 msec to the prefill puff, now 19 msec
A-coils disabled (PLC)

dud
Apr 15 2005 03:02:19:530PM1050415021Earl Marmaradd 3 msec to prepuff, now 22 msec

plasma in to rampdown
Apr 15 2005 03:03:37:657PM1050415022Earl MarmarA-coils enabled, 4000 A

plasma; disrupt at start of rampdown
Apr 15 2005 03:26:54:113PM1050415023Earl Marmarreduce prefill puff by 1 msec, to 21 msec

A-coil prog to 2200 A

plasma into rampdown

Apr 15 2005 03:25:35:490PM1050415024Earl MarmarA-coil program to 3000 A

fizzle
Apr 15 2005 03:38:27:853PM1050415025Earl Marmarno pcs changes

plasma; disrupt at end of flattop
Apr 15 2005 03:51:01:553PM1050415026Earl Marmarreduce prefill puff by 1 msec, to 20 msec
A-coil program to 2600 A

plasma into rampdown
Apr 15 2005 04:04:24:257PM1050415027Earl MarmarA-coil program to 2400 A

fizzle
Apr 15 2005 04:20:28:913PM1050415028Earl Marmarno pcs changes

plasma into rampdown
Apr 15 2005 04:34:03:163PM1050415029Earl MarmarA-coil program to 1800 A
turn off PG3 at 0.8 seconds

plasma
disrupted early in rampdown
Apr 15 2005 04:45:42:197PM1050415030Earl MarmarA-coil program to 1900

plasma; disrupt at start of rampdown
Apr 15 2005 04:55:02:100PM1050415031Earl Marmarimport segment 2 from 1050415014 into segment 2; 6.3 T, JET shape

fizzle
Apr 15 2005 05:13:21:913PM1050415032Earl Marmaradd 1 msec to prefill puff to 21 msec

plasma; disrupt at 1.2 seconds;
big impurity injection at 0.6 seconds, right around time of locked mode onset.

Halo current warning.

Engineering Operator Comments
ShotTimeTypeStatusComment
109:03:17:397AMPlasmaOk
209:15:43:220AMPlasmaOk
309:28:10:763AMPlasmaOk
409:40:35:510AMPlasmaOk
509:52:54:707AMPlasmaOk
610:06:11:950AMPlasmaOk
710:18:31:963AMPlasmaOk
810:49:37:907AMPlasmaOk
911:02:46:263AMPlasmaOk
1011:16:55:627AMPlasmaOk
1111:29:15:423AMPlasmaOk
1211:55:19:297AMPlasmaOk
1312:16:19:593PMPlasmaOk
1412:28:40:190PMPlasmaOk
1512:45:39:610PMPlasmaOk
1612:58:05:267PMPlasmaOk
1701:25:04:813PMPlasmaOk
1801:49:22:297PMPlasmaOk
1902:07:55:983PMPlasmaOk
2002:20:33:000PMPlasmaOk
2102:36:02:500PMPlasmaOk
2202:50:15:580PMPlasmaOk
2303:08:15:470PMPlasmaOk
2403:20:49:360PMPlasmaOk
2503:35:21:010PMPlasmaOk
2603:47:52:400PMPlasmaOk
2704:00:44:193PMPlasmaOk
2804:13:16:163PMPlasmaOk
2904:25:47:960PMPlasmaOk
3004:38:18:023PMPlasmaOk
3104:50:59:350PMPlasmaOk
3205:03:20:867PMPlasmaOk