Alcator C-Mod Run 990916 Information

Back to runs

Miniproposals
Miniproposal:237
Date Filed: 3/10/1999
Title:Scaling of Toroidal Rotation with Plasma Current
First Author:John Rice
Session Leader:John Rice (shots 1-12)
Session Leader:Earl Marmar (shots 13-18)

Operators
Session leader(s):John Rice,Earl Marmar
Physics operator(s):Ron Parker
Engineering operator(s):Frank Silva

Engineering Operator Run Comment
MP#237/Parker,Silva

Session Leader Plans

Physics Operators Plans

Session Leader Summaries
Entered: Jul 7 2004 03:49:21:240PM
Author: To Be Determined
Run summary for 990916, MP237, Toroidal Rotation during Plasma Current Scan

The purpose of this run was to determine the scaling of the rotation
velocity with plasma current, for otherwise constant target plasmas,
for H-mode discharges. The range of currents achieved was from 0.8 down to
.4 MA, however there was only one good shot at .4 MA due to difficulty
coupling 2 MW of ICRF power. The run was terminated early due to Floyd's
high humidity compromising the RF systems.

Physics Operator Summaries
Entered: Jul 7 2004 04:37:09:300PM
Author: To Be Determined
RUN SUMMARY 990916

The purpose of the run was to document scaling of toroidal rotation vs
plasma current in H-Mode. Although some data were collected, the run fell far
short of being an unqualified success. Two problems developed, both related to
hurricane Floyd. Because of the high humidity, transmitter 2 developed arcing
problems and became inoperable after shot 12. Thereafter only 1 MW was available
and this was insufficient to produce the reliable and high quality H-Modes
required for the scan. The second problem was concern over difficulties
personnel would have leaving PSFC late in the evening as the storm reached its
expected intensity. As a result it was dsecided to terminate the run at 3:00PM.

After shot 12, E. Marmar became Session Leader, taking over for J. Rice. The
purpose of the last 6 shots (shots 13-18) was to study Rf absorption efficiency
as a function of H/D ratio. Some difficulty was encountered in significantly
raising the H/D ratio using Pulse Gas Valve 2. Although the shots were useful,
the range of H/D variation was insufficient and additional shots will have
to be devoted to this study in a future run.

In spite of these problems, the machine ran exceptionally well with no fizzles
and only two disruptions, one occuring when the current was ramped down to 400
kA and the plasma was vertically instable. With some adjustment to shape (by J.
Goetz who had spelled R. Parker) the plasma became stable and no further
disruptions were encountered. The other disruption occurred due to a OH2 PS
fault.

A brief rundown of the shots follows:

Shots 1-3: Standard 800 kA plasmas, 2 MW RF H-Modes.

Shots 4-6: Current ramped down to 600 kA, 2 MW RF H-Modes

Shots 7-12: Various attempts to nail down the 400 kA point. Shots 007 and 010
disrupted, as discussed above. RF tripped out on other shots. Finally a good
400 kA shot was obtained in shot 12.

Shots 13-18: E. Marmar became Session Leader. (Transmitter 2 out of service.)
These shots were all run with ~ 1 MW RF from Trans 1. Current ~ 1 MA. No
further problems encountered, except difficulty bringing H/D ratio to
interesting levels with pulse valve 2.

Run Plan for Thursday 990916

MP#237 Ip Scaling of Rotation

Session Leader: J. Rice
Physics Operator: R. Parker

Setup Power Supplies from Shot 990915007

Two Hours of ECDC in D2 prior to run.

Gas setup: Fill B-Top with 6 psi D2, Hybrid Enabled
Fill B-side lower with 1 psi Ar, Hybrid Enabled
Fill B-side upper with 6 psi H2, Hybrid DISABLED
Fill C-Side with 30 psi D2, Hybrid Enabled
J-Bottom as is, Hybrid DISABLED

ECE and VUV valves enabled, if no vacuum problems

Run will begin with shot 990915007

We will scan Ip down to lowest reasonable levels and then scan it upwards
to get as wide range of Ip scaling of rotation as possible.



Session Leader Comments
Sep 16 1999 10:01:22:467AM990916001John Ricereran 990915007 with 2MW RF flat top
Sep 16 1999 10:02:20:090AM990916002John Ricesame, with 2MW RF flat top from .6 to 1.1 s
Sep 16 1999 10:02:55:310AM990916002John Ricesame, with 2MW RF flat top from .6 to 1.1 s and earlier TF ramp
Sep 16 1999 10:14:06:653AM990916004John Ricelower current to .6 MA and earlier TF ramp
Sep 16 1999 10:31:52:090AM990916005John Rice .6 MA and later RF pulse
Sep 16 1999 10:51:45:357AM990916006John Rice .6 MA
Sep 16 1999 11:07:37:467AM990916007John Rice .4 MA w/disruption
Sep 16 1999 11:30:10:437AM990916008John Rice .4 MA but RF tripped
Sep 16 1999 11:52:52:043AM990916009John Rice .4 MA but RF tripped again
Sep 16 1999 12:21:08:123PM990916010John Rice .4 MA, RF tripped again
Sep 16 1999 12:25:08:967PM990916011John Rice .4 MA, only D antenna
Sep 16 1999 12:43:58:700PM990916012John Rice .4 MA, good RF
Sep 16 1999 01:48:22:607PM990916013Earl MarmarOnly one transmitter available;

switching to H/D scan to assess RF absorption

1 MA

RF Tripped
Sep 16 1999 01:58:28:750PM990916014Earl Marmarretry

same RF trip; stays in H-Mode

H/D = .035
Sep 16 1999 02:14:12:937PM990916015Earl Marmarretry

RF stayed on

big increase in radiated power early in RF pulse

H/D = .035
Sep 16 1999 02:31:35:700PM990916016Earl Marmarpuff H_2 from B-side upper

100 msec puff, 100 volt, .609 < t < .709

RF power somewhat variable, but turn-off seems ok

H/D = .04
Sep 16 1999 03:23:20:030PM990916017Earl Marmarretry with 150 ms pulse on B side upper (.559 < t < .709)

~1 MW from E port

H/D ~ 0.04
Sep 16 1999 03:25:35:467PM990916018Earl Marmaradd another 100 ms to H_2 puff

It does not appear that the valve is opening.

H/D ~ 0.05

Increases in H from shot 16 on might be due to J-Port outgassing.

Physics Operator Comments
Sep 16 1999 09:22:51:840AM990916001Ron Parker
Shot 001

Shot ran as programmed (same settings as for 990915007)

No changes for the next few shots
Sep 16 1999 09:45:31:217AM990916002Ron ParkerShot 002

Reproduced shot 001

Shot ran well, good H-Mode, RF power ~ 2 MW (1&2)

TF ramp will be moved 50 msec earlier for next shot
Sep 16 1999 10:12:51:420AM990916003Ron Parker
Shot 003

Shot ran well, as programmed. TF ramp moved 50 msec earlier

Next shot will have current reduced to 600 kA. Also, TF ramp moved 100 msec earlier
Sep 16 1999 10:17:19:263AM990916004Ron Parker
Shot 004

Shot ran well, as programmed. RF turns on just as current flattops to lower value.

Next shot, same as 004, but RF will pulse 100 ms later.

Sep 16 1999 10:37:29:390AM990916005Ron ParkerShot 5

Ran as programmed. 600 kA H-mode, 2 MW RF.

Next shot will be a repeat of 005.
Sep 16 1999 11:02:16:670AM990916006Ron Parker
Shot 006

Ran as programmed.

John Goetz takes over as Phys Op.

Current for next shot will be programmed to 400kA.
ICEF4 = 2800A in segment 2
CLEARIN = -.014 in segment 2 (inner gap is getting big)
RCUR = .672 in segment2 (outer gap is getting big)


Sep 16 1999 11:25:11:187AM990916008Ron ParkerShot 007

Plasma - disrupts at 0.62s
inner gap of ~2.4cm and outer gap of ~2cm
n / n_crit ~ 1.5


Next shot:
CLEARIN = -.02 and RCUR = .675 to make smaller gaps
Sep 16 1999 11:40:13:090AM990916008Ron ParkerShot 008

Plasma
0.4MA, 0.9e19 on nl04
RF tripped
some strange happenings with the Dalpha during this shot

Next shot:
RCUR = 0.676 and CLEARIN=-.021
ZXL = -.011 (was -.005) because the x-point is ~1cm high
Sep 16 1999 11:53:44:217AM990916009Ron ParkerShot 009

Plasma
RF #2 tripped
same phenomenon on D_alpha as the last shot
outer gap ~ 1cm; inner gap ~ 1.8cm
got the x-point down to -38.5cm

Next shot:
no changes
Sep 16 1999 12:12:29:030PM990916010Ron ParkerShot 010:

Plasma
OH2 fault @ 0.86s, disruption @ 1.07s

Next shot:

try again
Sep 16 1999 12:30:15:107PM990916011Ron ParkerShot ran, but no power from MW 2.

Some problem with bringing up diagnostic signals.

Try again, next shot.

Parker taking over again as PhysOp, relieving Goetz who did an outstanding job
filling in.

Sep 16 1999 01:47:58:327PM990916012Ron Parker
Shot 12 was successful, with 2 MW coupled at 400 kA.

Shot 13 will be a repeat of shot 12.

Cell entry granted.

Change in plans: Transmitter 2 has arcing problem due to humidity.
Scan of current at 2 MW cannot be completed. Instead, we'll run 1 MW,
1 MA plasmas and study RF absorption vs. H/D ratio.

Session Leader is now E. Marmar

Sep 16 1999 01:49:13:687PM990916013Ron Parker
Shot 13

Ran as programmed. RF tripped. Will repeat, with TF wiggle taken out.
Sep 16 1999 01:57:36:140PM990916014Ron Parker
Shot ran OK.

RF tripped. Repeat shot, without changes.
Sep 16 1999 02:44:15:280PM990916015Ron Parker
Shot 15

Shot ran as programmed.
Sep 16 1999 02:47:28:327PM990916016Ron Parker
Shot 16

Shot ran OK. Modest increase in H/D ratio.

Next shot, H2 gas will be increased to 150 ms in pulse length (100 V)
Sep 16 1999 02:53:53:420PM990916017Ron ParkerShot 17

Ran as programmed. H/D ratio increased, only slightly.

J port pulsed to about 0.5 MW, from .5 to .7 s. E port pulses at about .75 s
at a level of about 1 MW, off at about 1.25 s.

H2 pulsed gas will be increased -- increase pulse 100 ms


Sep 16 1999 03:06:11:043PM990916018Ron Parker
Shot 18

Ran as programmed.

Run terminated with this shot because of concerns over storm (Floyd).

Engineering Operator Comments
ShotTimeTypeStatusComment
109:13:16:530AMPlasmaOk09:10 Interfer delay /no faults/plasma
209:32:55:920AMPlasmaOkno faults/plasma
309:51:11:890AMPlasmaOkno faults/plasma
410:11:14:950AMPlasmaOkno faults
510:29:08:577AMPlasmaOkno faults/plasma
610:48:20:623AMPlasmaOkno faults/plasma
711:06:08:217AMPlasmaOkno faults/disr.
811:25:08:687AMPlasmaOkno faults/disrupt
911:42:11:950AMPlasmaOk(null)
1012:00:23:000PMPlasmaOk(null)
1112:19:11:793PMPlasmaOk(null)
1212:38:20:310PMPlasmaOk(null)
1301:32:27:437PMPlasmaOkno faults/plasma
1401:47:53:840PMPlasmaOkno faults/plasma
1502:03:46:500PMPlasmaOkno faults/plasma
1602:21:37:950PMPlasmaOkno faults/plasma
1702:40:44:107PMPlasmaOkno faults/plasma
1803:00:10:500PMPlasmaOkno faults