Alcator C-Mod Run 930921 Information

Miniproposals

Miniproposal:

Date Filed:

Title:

First Author:

Session Leader: Ian Hutchinson (shots 1-26)

Operators
Session leader(s):	Ian Hutchinson
Physics operator(s):	John Goetz
Engineering operator(s):	Joe Daigle,Frank Silva,Vinny Bertolino

Engineering Operator Run Comment
plasma, silva

Session Leader Plans

Physics Operators Plans

Session Leader Summaries

Entered: Jul 7 2004 03:49:08:790PM

Author: To Be Determined

Run of 930921
Hutchinson, Goetz, Horne
Silva, Bertolino, Daigle

Implementation of new PCS system with 8 Ip referenced channels.
X-point feedback control.

Plan:
1.Get plasma with the new configuration and try to make reproducible.
2.Turn on the feedback to zxl and Rxl and verify their control.
3.If all is stable. Put in the fast-scan probe. Increase the current.
4.Play arround with the zcur controller a bit to see if we can stabilize
better.

Score card:
6 duds
14 Fizzles
6 Plasmas
26 shots total.

Summary:
Plasmas were obtained by shot 7, once it was realized that a current centroid
controller doesn't work prior to breakdown, and we switched to a flux
controller. However, current ramps were very irreproducible as witnessed by
the large number of fizzles. The majority of the fizzles can readily be
attributed to unsatisfactory field configuration, mostly horizontal field
problems, occasionally vertical field. It is not really known why the null is
irreproducible.

Two beautiful shots were obtained: 19 and 20. Shot 20 was dramatically blown
away by RF impurity influx starting at 650ms when the RF turned on. On these
shots, the ZXL controller was on and appeared to be working. RXL was turned on
after 20 but no plasma current rises were subsequently obtained. No change was
made for 21 that could account for losing the current rise. This is another
anecdote to add to the disruption theory list. However, the horizontal field
was fairly bad, enough to explain things on its own.

Keeping the zcur controller on till up to 20ms was tried without obvious
effect. Instead Voltage tweaks on OH2 during the first 20 ms were tried. These
did not seem to fix the problem. They did more or less what was asked but the
irreproduciblity (in BR) continued. The EF1 resistor was increased to try to
reduce the destabilizing field gradient and hence the sensitivity to BR. It
was a small effect.

Extra filtering was put into the EFC feedback. Some progress was made in
exploring the way to improve vertical stabilization during the flattop.

Recommendation:
We still need to find out how to:
(1) Control BR during the first 20ms to avoid the BR reproducibility.
(2) Fix the Bz irreproducibility, or learn to live with it.
(3) Optimize the field structure to give robust current rise.
We know it is possible to get reproducible plasmas. We need to find out how to
get them again.

Detailed notes:
Shot Result
1 1st new PCS setup. Fingers crossed! p=1.2e-5 Dud
A problem with both sum and difference of OH2. Ip-zcur Aout
is increasingly negative. Oh2(U-L) is increasing. Flux z_edge is increasing.
a bug found in the software.Predictors were not being scaled and loaded
properly.
2 Hopefully fixed. Dud
Suspect the filament predictor is not working.
3 Loaded fluxihh on the zcur8 predictor which controls Oh2dif. Dud
Better control but needs more gain. There is also an offset. FluxIHH reads
zero when predictor is -1400. Hybrid approaches zero at commutation when
fluxihh is +1.e-2 Wb.
4 P8 to 5 from 2, P10 to 4 from 2. Did not fix offset. Dud
Looks much better controlled but to the wrong value because of the
offset, 1.2e-2 Wb. BR = -4 mT.
Shot 930916031 has +6mWb ofset at comm. This may be what we want.
5 Put -1600 times minus_1_volt to adjust offset. Dud
Currents much more balanced. Br= +1.5mT, fluxihh zcur=0. Got what we
asked for but need to compensate for the predictor's offset as well as the
hybrids. Offset gives -3.4mT per 1000 on minus_1_volt.
6 zcur8 offset to -1150. Very nearly got current 30 kA. Fizzle
7 zcur8 to -1050. Plasma
Some funny things on the vertical position early.
8 Adjusted zcur dropout to 10ms. raised the Ip gain to 4 from 2. Plasma
9 zcur S to -.02, VOH2 kept at -25V till .9s. VOH1 to 250V
at 52ms, this is to try to fix the R-position wobble.
EF2L S to 1600 at 160ms, to try to elongate earlier and to improve
the xpoint R position. Plasma
10 Turn on ZXL controller on EF1L with P=1, M=2e-3
(Implies 10V per cm at .5MA). OH1 to -300V at 50ms.
Increased gas late. Fizzle
Br=-1.5mT at breakdown. fluxihh +6mWb.
11 Added D=5 to zcur8, carried through to +10ms. Fizzle
12 zcur8 to -1350. Fizzle
13 moved EF2 programming 5ms later. It seemed to be strange. There is
also a current difference, ef2u-l=-60A before. Fizzle
14 EF2 programming to 2ms. Fizzle
15 EF2L lowered 50 A. Oh2s to -25V from -15 V at 5ms. p=1.5e-5. Dud
EF3 PS failed to work.
16 No change except for adding a 0.5ms filter on EFC afol. Fizzle
17 Ef4 to 1120 zcur8 kept on till 20ms. Plasma
runaways, bkdwn at 8ms.
18 zcur8 switched off at 0ms. Fizzle
250A ripple in oh2s
19 Turned off zcur8 D, Lowere Oh2U V to 15 V from 35V @ 3ms. Try to
remove the BR swing by hand. Derivative gain 9 on EFC3 Plasma
20 Oh2 V to -15V from -20V zxl gain to 2. RF .65 to .85s Plasma
Argon turned on. Looks as if the RF killed this shot.
21 rxl gain to P=1. (M=5e-3). Derivative gain on zcur2 to 3. Ef2U to 1700
from 1550. RF off. Fizzle
22 EF1 resistors to 91 mohm from 80. Tweaked ICef1 to match. Fizzle
23 Added 40A to EF4 1160. OH2U to 25V at 3ms. Fizzle
24 EF4 to 1140A. oh2L to -35V @ 5 ms (was -25). Fizzle
25 p=1.3e-5 EF4 to 1130A Fizzle
26 zcur8 P=2. Fizzle

Physics Operator Summaries

Session Leader Comments

Physics Operator Comments

Sep 21 1993 09:26:00:690AM John Goetz Today's run will test out the new PCS interface which has 8 Ip referenced
wires and 8 10V referenced wires. When the interface is working correctly,
the task of X-point control will be undertaken.

Sep 21 1993 09:56:33:610AM 930921001 John Goetz Shot 001:
No plasma - OH2's unbalanced

Trouble with loadables in PCS
Some wires had garbage on them.

For shot 002:
Fix code and try again

Sep 21 1993 10:12:50:160AM 930921002 John Goetz Shot 002:
No plasma
Radial field troubles

For shot 003:
New predictor loaded in for ZCUR (wire 8) - now using FLUXIHH
instead of FILAMENT

Sep 21 1993 10:23:38:650AM 930921003 John Goetz Shot 003:
No plasma
Almost a null
ZCUR (8) predictor almost to 0 just before commutation

For shot 004:
Raise gain on P_OH2U from 1.8 to 4.0
Raise gain on P_ZCUR(8) from 2 to 5.0

Sep 21 1993 10:37:13:300AM 930921004 John Goetz Shot 004:
No plasma
vacuum fields dominated by -4mT radial field
ZCUR(8) to 0 before commutation (gain increase worked)

For shot 005:
put an offset of -1600 on the -1V reference in the customized A
controller for ZCUR(8)

Sep 21 1993 10:51:43:220AM 930921005 John Goetz Shot 005:
No plasma
Radial field = +1.5mT (went too far with offset correction)

For shot 006:
change offset in ZCUR(8) predictor to -1150 (-4/5.5*1600)

Sep 21 1993 11:11:09:930AM 930921006 John Goetz Shot 006:
Fizzle
radial field ~0; null not the greatest

For shot 007:
tweak radial field a bit yet - offset on ZCUR(8) to -1050.

Sep 21 1993 11:33:13:150AM 930921007 John Goetz Shot 007:
Plasma - disruption at .796 - does not hold 500kA
Too much elongation late

For shot 008:
P_IP to 4.0 from 2.0 (try and hold current)
ZCUR turn off time now from 0.5 to 0.51

Sep 21 1993 11:55:04:200AM 930921008 John Goetz Shot 008:
Plasma - disruption at .825 - holds 460kA
still too much elongation late

For shot 009:
S_ZCUR = -.02
V_OH2's @ -25V until 0.9 (for less elongation)
V_OH1 to -250V @ .05 (to stop radial excursion)
IC_EF2L to 1500A @ .16 (from 750) to help pull out X-point

Sep 21 1993 12:13:26:600PM 930921009 John Goetz Shot 009:
Plasma - no disruption - holds 470kA and ramps down when told
some non-thermal on ECE early

For shot 010:
M_ZXL: V_EF1L = +2e-3
P_ZXL = 1. @ .2 (begin x-point control)
V_OH1 = -300 @ .05 (stop radial excursion)

Sep 21 1993 12:32:55:990PM 930921010 John Goetz Shot 009:
Fizzle
radial field = -2mT

For shot 011:
lengthen gain on P_ZCUR(8) until .01
turn on gain on D_ZCUR(8) at 5. until .01

Sep 21 1993 12:42:02:290PM 930921011 John Goetz Shot 011:
Fizzle
radial field = -2mT; change of gains succeeded in getting to the
wrong value more quickly

For shot 012:
change offset on A_ZCUR(8) to -1350.

Sep 21 1993 01:14:11:600PM 930921012 John Goetz Shot 012:
Fizzle
breakdown at .01; too late for Bz

For shot 013:
fiddled with IC_EF2 and V_EF2's near 0 to try and balance them

Sep 21 1993 01:23:25:600PM 930921013 John Goetz Shot 013:
Fizzle
breakdown at .008; very close to taking off

For shot 014:
moved EF2 voltage programming 3msec earlier to try and match
the EF2 currents at commutation

Sep 21 1993 01:44:08:170PM 930921014 John Goetz Shot 014:
Fizzle
almost went

For shot 015:
lower IC_EF2L by 50A to 1700A at commutation (make bigger null)
lower V_OH2's to -25 @.005 (from -15) (add more curvature to fields)
P_0 = 1.5e-5

Sep 21 1993 01:50:41:860PM 930921015 John Goetz Shot 015:
Dud
No EF3

For shot 016:
no changes

Sep 21 1993 01:58:52:240PM 930921015 John Goetz Shot 015:
Dud
No EF3

For shot 016:
no changes
filter on EFC AFOL changed; should allow more derivative gain eventually

Sep 21 1993 02:14:44:070PM 930921016 John Goetz Shot 016:
Fizzle
almost went; plasma thrown up and in

For shot 017:
IC_EF4 upped to 1120 from 1100 (try and up vertical field at breakdown)
P_ZCUR(8) left on until .02

Sep 21 1993 02:34:58:520PM 930921017 John Goetz Shot 017:
Plasma
475kA flat-top - successful rampdown
much hard x-ray and non-thermal signature on ECe

For shot 018:
P_ZCUR(8) on until 0. (try to understand Br control)
D_ZCUR(3) = 9 (chopper only - try to get rid of z-oscillations)

Sep 21 1993 02:58:03:360PM 930921018 John Goetz Shot 018:
Fizzle
some radial field; 250A ripple on OH2's

For shot 019:
remove D gain from ZCUR(8)
lower OH2U from 35V @ .003 to 15V (try to remove radial field)

Sep 21 1993 03:16:14:350PM 930921019 John Goetz Shot 019:
Plasma - nice current rise - 460kA flattop - good rampdown
flat density!

For shot 020:
P_ZXL = 2. (from 1.)
V_OH2 = -15 (from -20.) (more elongation early)
enable argon puffing
allow RF pulses from .65 to .85

Sep 21 1993 03:33:36:070PM 930921020 John Goetz Shot 020:
Plasma - nice current rise - 460kA flattop
RF cooling at .65 - disruption at .78

For shot 021:
P_RXL = 1. @.2 (turn on radial control of x-point)
IC_EF2U to 1700 @ .16 (was 1550) (to cleanup upper shape)
D_ZCUR(2) = 3.
no more RF

Sep 21 1993 03:57:01:050PM 930921021 John Goetz Shot 021:
Fizzle
EF1/OH2 ratio chewing up flux in the corners

For shot 022:
change EF1 commutation resistor to 90mOhm (from 80mOhm)
and tweak IC_EF1's at commutation

Sep 21 1993 04:10:17:260PM 930921022 John Goetz Shot 022:
Fizzle
late breakdown; some radial field; Bz too negative

For shot 023:
IC_EF4 to 1160 from 1120 (fix vertical field)
V_OH2U to 25V @ .003 (was 15) (fix OH2 imbalance)

Sep 21 1993 04:27:02:430PM 930921023 John Goetz Shot 023:
Fizzle
vertical field too positive this time
still some radial field

For shot 024:
IC_EF4 to 1140 from 1160 (fix vertical field)
V_OH2L to -35V @ .005 (was -25) (fix OH2 imbalance - possibly due to
inner divertor?)

Sep 21 1993 04:40:40:920PM 930921024 John Goetz Shot 024:
Fizzle
vertical field blip @ .006 ruins the breakdown

For shot 025:
IC_EF4 to 1130 from 1140 (fix vertical field)
P_0 = 1.3e-5

Sep 21 1993 04:56:15:330PM 930921025 John Goetz Shot 025:
Fizzle
serious ripple on OH2

For shot 026:
lower P gain on ZCUR(8) to 2. from 5. (test to see if ZCUR controller
has been driving OH2 wild)

Sep 21 1993 05:13:05:350PM 930921026 John Goetz Shot 026:
Fizzle
still a bad field null; still some radial field

Engineering Operator Comments

Shot Time Type Status Comment

1 09:13:07:620AM Plasma Ok no bd ps,s aok

2 09:57:01:330AM Plasma Ok no bd, oh1 fault

3 10:12:33:240AM Plasma Ok no faults

4 10:25:03:600AM Plasma Ok no faults -- no plasma yet

5 10:40:21:250AM Plasma Ok no faults

6 10:54:29:810AM Plasma Ok flash

7 11:12:19:860AM Plasma Ok no faults -- plasma!!

8 11:34:26:320AM Plasma Ok no faults

9 11:54:57:110AM Plasma Ok no faults -- plasma>1sec

10 12:13:31:970PM Plasma Ok oh1 xbar in inversion. single phase

11 12:33:36:230PM Plasma Ok breakdown, ps aok

12 12:45:02:900PM Plasma Ok bd ps,s aok

13 01:10:33:030PM Plasma Ok bd ps,s aok

14 01:26:22:260PM Plasma Ok oh1 fault

15 01:44:04:690PM Plasma Ok no ,ef3

16 01:59:47:950PM Plasma Ok Plasma shot fizzle No faults.

17 02:15:32:530PM Plasma Ok Plasma shot O.K.

18 02:35:39:820PM Plasma Ok no faults

19 02:58:54:720PM Plasma Ok goodshot

20 03:16:42:510PM Plasma Ok ok ps,s aok

21 03:34:08:260PM Plasma Ok no faults

22 03:59:41:560PM Plasma Ok fizsell, ps,s aok

23 04:11:52:840PM Plasma Ok ps,s ok

24 04:27:55:370PM Plasma Ok ps,s ok fizzel

25 04:42:26:410PM Plasma Ok fizzel ps,s aok

26 04:56:50:840PM Plasma Ok oh1 >1scr not conducting late in the shot

Physics Operator Comments
Sep 21 1993 09:26:00:690AM		John Goetz	Today's run will test out the new PCS interface which has 8 Ip referenced wires and 8 10V referenced wires. When the interface is working correctly, the task of X-point control will be undertaken.
Sep 21 1993 09:56:33:610AM	930921001	John Goetz	Shot 001: No plasma - OH2's unbalanced Trouble with loadables in PCS Some wires had garbage on them. For shot 002: Fix code and try again
Sep 21 1993 10:12:50:160AM	930921002	John Goetz	Shot 002: No plasma Radial field troubles For shot 003: New predictor loaded in for ZCUR (wire 8) - now using FLUXIHH instead of FILAMENT
Sep 21 1993 10:23:38:650AM	930921003	John Goetz	Shot 003: No plasma Almost a null ZCUR (8) predictor almost to 0 just before commutation For shot 004: Raise gain on P_OH2U from 1.8 to 4.0 Raise gain on P_ZCUR(8) from 2 to 5.0
Sep 21 1993 10:37:13:300AM	930921004	John Goetz	Shot 004: No plasma vacuum fields dominated by -4mT radial field ZCUR(8) to 0 before commutation (gain increase worked) For shot 005: put an offset of -1600 on the -1V reference in the customized A controller for ZCUR(8)
Sep 21 1993 10:51:43:220AM	930921005	John Goetz	Shot 005: No plasma Radial field = +1.5mT (went too far with offset correction) For shot 006: change offset in ZCUR(8) predictor to -1150 (-4/5.5*1600)
Sep 21 1993 11:11:09:930AM	930921006	John Goetz	Shot 006: Fizzle radial field ~0; null not the greatest For shot 007: tweak radial field a bit yet - offset on ZCUR(8) to -1050.
Sep 21 1993 11:33:13:150AM	930921007	John Goetz	Shot 007: Plasma - disruption at .796 - does not hold 500kA Too much elongation late For shot 008: P_IP to 4.0 from 2.0 (try and hold current) ZCUR turn off time now from 0.5 to 0.51
Sep 21 1993 11:55:04:200AM	930921008	John Goetz	Shot 008: Plasma - disruption at .825 - holds 460kA still too much elongation late For shot 009: S_ZCUR = -.02 V_OH2's @ -25V until 0.9 (for less elongation) V_OH1 to -250V @ .05 (to stop radial excursion) IC_EF2L to 1500A @ .16 (from 750) to help pull out X-point
Sep 21 1993 12:13:26:600PM	930921009	John Goetz	Shot 009: Plasma - no disruption - holds 470kA and ramps down when told some non-thermal on ECE early For shot 010: M_ZXL: V_EF1L = +2e-3 P_ZXL = 1. @ .2 (begin x-point control) V_OH1 = -300 @ .05 (stop radial excursion)
Sep 21 1993 12:32:55:990PM	930921010	John Goetz	Shot 009: Fizzle radial field = -2mT For shot 011: lengthen gain on P_ZCUR(8) until .01 turn on gain on D_ZCUR(8) at 5. until .01
Sep 21 1993 12:42:02:290PM	930921011	John Goetz	Shot 011: Fizzle radial field = -2mT; change of gains succeeded in getting to the wrong value more quickly For shot 012: change offset on A_ZCUR(8) to -1350.
Sep 21 1993 01:14:11:600PM	930921012	John Goetz	Shot 012: Fizzle breakdown at .01; too late for Bz For shot 013: fiddled with IC_EF2 and V_EF2's near 0 to try and balance them
Sep 21 1993 01:23:25:600PM	930921013	John Goetz	Shot 013: Fizzle breakdown at .008; very close to taking off For shot 014: moved EF2 voltage programming 3msec earlier to try and match the EF2 currents at commutation
Sep 21 1993 01:44:08:170PM	930921014	John Goetz	Shot 014: Fizzle almost went For shot 015: lower IC_EF2L by 50A to 1700A at commutation (make bigger null) lower V_OH2's to -25 @.005 (from -15) (add more curvature to fields) P_0 = 1.5e-5
Sep 21 1993 01:50:41:860PM	930921015	John Goetz	Shot 015: Dud No EF3 For shot 016: no changes
Sep 21 1993 01:58:52:240PM	930921015	John Goetz	Shot 015: Dud No EF3 For shot 016: no changes filter on EFC AFOL changed; should allow more derivative gain eventually
Sep 21 1993 02:14:44:070PM	930921016	John Goetz	Shot 016: Fizzle almost went; plasma thrown up and in For shot 017: IC_EF4 upped to 1120 from 1100 (try and up vertical field at breakdown) P_ZCUR(8) left on until .02
Sep 21 1993 02:34:58:520PM	930921017	John Goetz	Shot 017: Plasma 475kA flat-top - successful rampdown much hard x-ray and non-thermal signature on ECe For shot 018: P_ZCUR(8) on until 0. (try to understand Br control) D_ZCUR(3) = 9 (chopper only - try to get rid of z-oscillations)
Sep 21 1993 02:58:03:360PM	930921018	John Goetz	Shot 018: Fizzle some radial field; 250A ripple on OH2's For shot 019: remove D gain from ZCUR(8) lower OH2U from 35V @ .003 to 15V (try to remove radial field)
Sep 21 1993 03:16:14:350PM	930921019	John Goetz	Shot 019: Plasma - nice current rise - 460kA flattop - good rampdown flat density! For shot 020: P_ZXL = 2. (from 1.) V_OH2 = -15 (from -20.) (more elongation early) enable argon puffing allow RF pulses from .65 to .85
Sep 21 1993 03:33:36:070PM	930921020	John Goetz	Shot 020: Plasma - nice current rise - 460kA flattop RF cooling at .65 - disruption at .78 For shot 021: P_RXL = 1. @.2 (turn on radial control of x-point) IC_EF2U to 1700 @ .16 (was 1550) (to cleanup upper shape) D_ZCUR(2) = 3. no more RF
Sep 21 1993 03:57:01:050PM	930921021	John Goetz	Shot 021: Fizzle EF1/OH2 ratio chewing up flux in the corners For shot 022: change EF1 commutation resistor to 90mOhm (from 80mOhm) and tweak IC_EF1's at commutation
Sep 21 1993 04:10:17:260PM	930921022	John Goetz	Shot 022: Fizzle late breakdown; some radial field; Bz too negative For shot 023: IC_EF4 to 1160 from 1120 (fix vertical field) V_OH2U to 25V @ .003 (was 15) (fix OH2 imbalance)
Sep 21 1993 04:27:02:430PM	930921023	John Goetz	Shot 023: Fizzle vertical field too positive this time still some radial field For shot 024: IC_EF4 to 1140 from 1160 (fix vertical field) V_OH2L to -35V @ .005 (was -25) (fix OH2 imbalance - possibly due to inner divertor?)
Sep 21 1993 04:40:40:920PM	930921024	John Goetz	Shot 024: Fizzle vertical field blip @ .006 ruins the breakdown For shot 025: IC_EF4 to 1130 from 1140 (fix vertical field) P_0 = 1.3e-5
Sep 21 1993 04:56:15:330PM	930921025	John Goetz	Shot 025: Fizzle serious ripple on OH2 For shot 026: lower P gain on ZCUR(8) to 2. from 5. (test to see if ZCUR controller has been driving OH2 wild)
Sep 21 1993 05:13:05:350PM	930921026	John Goetz	Shot 026: Fizzle still a bad field null; still some radial field

Engineering Operator Comments
Shot	Time	Type	Status	Comment
1	09:13:07:620AM	Plasma	Ok	no bd ps,s aok
2	09:57:01:330AM	Plasma	Ok	no bd, oh1 fault
3	10:12:33:240AM	Plasma	Ok	no faults
4	10:25:03:600AM	Plasma	Ok	no faults -- no plasma yet
5	10:40:21:250AM	Plasma	Ok	no faults
6	10:54:29:810AM	Plasma	Ok	flash
7	11:12:19:860AM	Plasma	Ok	no faults -- plasma!!
8	11:34:26:320AM	Plasma	Ok	no faults
9	11:54:57:110AM	Plasma	Ok	no faults -- plasma>1sec
10	12:13:31:970PM	Plasma	Ok	oh1 xbar in inversion. single phase
11	12:33:36:230PM	Plasma	Ok	breakdown, ps aok
12	12:45:02:900PM	Plasma	Ok	bd ps,s aok
13	01:10:33:030PM	Plasma	Ok	bd ps,s aok
14	01:26:22:260PM	Plasma	Ok	oh1 fault
15	01:44:04:690PM	Plasma	Ok	no ,ef3
16	01:59:47:950PM	Plasma	Ok	Plasma shot fizzle No faults.
17	02:15:32:530PM	Plasma	Ok	Plasma shot O.K.
18	02:35:39:820PM	Plasma	Ok	no faults
19	02:58:54:720PM	Plasma	Ok	goodshot
20	03:16:42:510PM	Plasma	Ok	ok ps,s aok
21	03:34:08:260PM	Plasma	Ok	no faults
22	03:59:41:560PM	Plasma	Ok	fizsell, ps,s aok
23	04:11:52:840PM	Plasma	Ok	ps,s ok
24	04:27:55:370PM	Plasma	Ok	ps,s ok fizzel
25	04:42:26:410PM	Plasma	Ok	fizzel ps,s aok
26	04:56:50:840PM	Plasma	Ok	oh1 >1scr not conducting late in the shot