Alcator C-Mod Run 950301 Information

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Miniproposals
Miniproposal:077a
Date Filed: 2/2/1995
Title:ICRF Heating in L-mode Plasmas
First Author:Yuichi Takase
Session Leader:Steve Golovato (shots 1-30)

Operators
Session leader(s):Steve Golovato
Physics operator(s):Earl Marmar
Engineering operator(s):Vinny Bertolino,Joe Daigle

Engineering Operator Run Comment
icrf l-mode

Session Leader Plans

Physics Operators Plans

Session Leader Summaries
Entered: Jul 7 2004 03:49:12:320PM
Author: To Be Determined
run summary - 950301
---------------------

SL: golovato
PO: marmar
EO: bertolino/daigle

This run was a continuation of MP77A which began with the run on 950203.
We did a power scan at several densities at the standard current of 800kA
on 950203. This run proposed to do the same thing at 600kA and 1.0MA.
We succeeded in getting a scan at 660kA and one density at 1.1MA. We were
plagued by a number of problems which should be described in the physics
operator summary. We got 24 plasmas in 30 attempts but many had severe
runaway problems and/or early disruptions. The good shots were 9, 14,16-25,
26,28. The conditions with current in MA and density in units of nl04/1,e20 cm-2
were:
shot 9 ; .725 ; 1.1
shots 14,16-25 ; .660 ; .5,.7,1.2
shots 26,28 ; 1.1 ; 1.2

We had problems with the d-port system, probably in the transmission line near
the antenna, which limited the power to only a few hundred kW. Howver, e-port
ran well up to 1.8 MW. The power limitation did not impede the run goals because
we typically went into H-mode above 1 MW anyway. Good L-mode power scans will have
to wait for the reverse field run next month, where presumably the thesholds will
be higher. We did reduce the outer gap by 3mm from 1.2 to .9 cm on shot 18 and
the inner gap from 1.5 to 1 cm on shot 24 in order to raise the H-mode thresholds.
It wasn't clear that the thresholds went up substantially. Rather than getting
three rf power levels per shot, we usually got only one, the lowest, in L-mode.
Shot 20 gave a good indication of the threshold with a 150 kW chamge in power
leading to H-mode at 0.660MA and nl04=0.5 e20. Shots 26 and 28 at 1.1MA and
nl04=1.2e20 dithered into H-mode at each sawtooth crash, indicating that we
were right on the edge at around 1.2MW. Also, the gaps tended to get smaller
when we went from .660 to 1.1MA although no PCS changes were made (operators
take note when doing current scans).

This run will provide additional information for the L-mode confinement database
with auxiliary heating. However the auxiliary power is not much greater than
the Ohmic power since we tend to go into H-mode when it is. It is probably
not productive to have another L-mode run until we've reversed the fields.

The session leader shot-to-shot summary can be found in the logbook under the
session_leader topic. Details on technical difficulties can be found in the
physics operator summary.

The shot summary was: 24 plasmas
4 fizzles
1 dud
1 test shot (data system)


Physics Operator Summaries
Entered: Jul 7 2004 04:36:53:270PM
Author: To Be Determined

ICRF L-Mode.
Density and current scans

PO Marmar
SL Golovato
EO Bertolino, Daigle

ECDC in D2 for 1.5 hours, ending at ~7:30 am.

There was a 45 minute delay waiting for the alternator to come up (oil temp
problem).

The early part of the run was plagued with dirty, runaway discharges.
Substantially raising the fill pressure helped with this problem, although
there was one bad runaway shot late in the run at P_fill=2.2e-5.

We got good shots at .7MA and .6MA and 2 good shots at
1.1MA. In spite of the miniproposal title, many of the shots showed signs of
H-Mode transitions. The E port antenna ran well, D port had a lot of problems;
see the physics operator's summary. The shot summary follows:


1 Data system test
2 Start from 950215027; nel 1.0e20, deriv gain on nel, fill 1.7e-5, plasma,
disrupt at 0.7
3 Lower early gas slightly, nel .7e20, lower deriv gain, fill 1.7e-5, bad shot
hards, disrupt at .2 MA
4 raise early gas slightly, fill 1.8e-5, bad hards
5 Ip to 0.5 MA, nel .75, still bad hard x-rays, disrupt at .5 s
6 fill 2.5e-5, fizzle
7 fill 2.2e-5, plasma, disrupt at .53, oscillating vertically before that
8 lower deriv gain on fast zcur (wire 3) after .45 s, tweak early gas, fill
2.2e-5, disrupt at .5 s
9 reload shot 2, lower Ip to .7MA, good shot, H-mode around 1 s (ELMy)
10 raise Ip to 0.8MA, nel 1.5e20, fizzle
11 fill 2.1e-5, retry, hards, disrupt at .34 s
12 fill 2.3e-5, retry, better, disrupt at .45 s
13 Ip .6 MA, nel .9e20, fill 2.3e-5, fizzle
14 fill 2.2e-5, good shot
15 Br0 offset from 7e-3 to 6.5-3 in segment 1, dud, OH1 rogowski failed, big
Bz at t=0
16 retry, good shot,
17 lower nel to .7e19, good, got .8e19 during H-modes
18 move RCUR out by 1.5 mm to 0.6695 during flat-top, enable Argon puff, good,
big injection of something at 1.0 s
19 nel 5e19, good, got 6e19
20 no changes, good, some hards
21 nel 1.2e20, tweak early gas, good, disrupt on rampdown, sharkfin, no hards
22 lower nel_04 after 1.05 s, good, still finning
23 repeat, good
24 nel_04 to .7e20, RCUR in 2.5 mm, CLEARIN decrease 5 mm, good
25 repeat, good
26 nel to 1.1e20, Ip to 1 MA, good, disrupt on rampdown at .45 MA, OH1 problem
at 1.2 s, lost R position control (went in)
27 repeat, bad hards, early disrupt
28 fill 2.3e-5, tweak early gas up, good, disrupt on rampdown at .7 MA, same
OH1 problem
29 change early nl_04 in segment 2 to match density at .1 s, ne_04 to 1.5e20,
fizzle
30 repeat, 1 MA disrupt at start of flat top, EF2's railed, early density
probably too high.

29 plasma attempts, 4 fizzles, 1 bus rogowski dud, 24 plasmas.

Session Leader Comments
Mar 1 1995 09:04:47:740AMSteve Golovatorun 950301

goals -

continue L-mode confinement (MP77) parameter scans

typically 2-3 rf powers per shot, 3-4 densities per scan
at a given current.

(1) finish density scan at 800ka, going to higher density (nl04=1.8e20)

(2) density scans at 600ka, then 1ma.

starting with shot 950215027, from last L-mode run. shot has current
flattop to 1.4s to get three rf powers and some oh only before
and after. rf steps are 700-850ms, 850-1000ms, 1000-1150ms. the
rf power steps will be 1, 2, and 3 MW if possible. we will
try to get a FSP scan at as many conditions as possible. the outer
gap is smaller than usual, 1cm, to try to prevent H-modes.

Mar 1 1995 09:40:44:400AMSteve Golovatoshot 950301001 - nl04-1.e20
plasma, disrupted at .7s. ef1l problem.

Mar 1 1995 09:40:56:710AM950301001Steve Golovatoshot 950301001 - nl04-1.e20
plasma, disrupted at .7s. ef1l problem.

Mar 1 1995 09:47:43:740AM950301002Steve Golovatoshot 950301002 - i had shot numbers mixed up, shot 001 was a data system
test, all entries for shot 001 apply to shot 002.

Mar 1 1995 09:46:36:400AM950301003Steve Golovatoshot 950301003 - lower density, nl04=.77e20.

not quite a fizzle, 200ka, 140ms.

Mar 1 1995 10:06:14:360AM950301004Steve Golovatoshot 950301004 - early dispruption, hards again. dirty machine.

Mar 1 1995 10:19:09:540AM950301005Steve Golovatoshot 950301005 - went to .5MA, nl04=.6e20.
hards again, ran a little longer.

Mar 1 1995 10:33:08:700AM950301006Steve Golovatoshot 950301006 - fizzle at last. raised fill to 2.5e-5 to get rid
of hards.

Mar 1 1995 10:45:44:630AM950301007Steve Golovatoshot 950301007 - fill to 2.2e-5. hards gone but disrupted at .55s
got to current, density requested.

Mar 1 1995 11:12:25:420AM950301008Steve Golovatoshot 950301008 - plasma, god start but lose vertical control as last
shot around .5s

Mar 1 1995 11:26:25:050AM950301009Steve Golovatoshot 950301009 - reloaded shot 2 to segment 2 and lowered Ip a little,
to .7MA.

plasma. good shot, got rf power. 725ma, 1.1e20, h-modes at 2MW,
d-port tripped out.

Mar 1 1995 11:30:50:900AM950301010Steve Golovatoshot 950301010 - Ip to .8MA, nl04 to 1.5e20.
fizzle.

Mar 1 1995 11:53:32:750AM950301011Steve Golovatoshot 950301011 - hards, but only small reduction in fill, 2.2 to 2.1

Mar 1 1995 11:54:32:030AM950301012Steve Golovatoshot 950301012 - plasma. disrupted at .46s.

Mar 1 1995 12:01:13:990PM950301013Steve Golovatoshot 950301013 - give up on running at .8ma, high density.
go to next Ip of .6ma and do density scan starting at nl04=.9e20
fizzle.

Mar 1 1995 12:10:40:770PM950301013Steve Golovatoshot 950301013 - give up on running at .8ma, high density.
go to next Ip of .6ma and do density scan starting at nl04=.9e20
fizzle.

Mar 1 1995 12:26:31:380PM950301014Steve Golovatoshot 950301014 - plasma. full shot with rf. .66, 1.2, 1.8MW steps.

Mar 1 1995 01:01:41:030PM950301015Steve Golovatoshot 950301015 - dud. no oh1 rogowski signal.

Mar 1 1995 01:17:43:320PM950301016Steve Golovatoshot 950301016 - try again. good plasma.
h-mode at 1.7MW. only L-mode power at 1MW.

Mar 1 1995 01:35:01:920PM950301017Steve Golovatoshot 950301017 - lower density nl04=.7e20.
good plasma.

Mar 1 1995 02:14:19:300PM950301018Steve Golovatoshot 950301018 - moved rcur out by 1.5mm to reduce outer gap, avoid
h-modes if possible. also added argon puff for this shot.
good plasma, L-mode data at 1MW and 1.4MW.

Mar 1 1995 02:14:23:770PM950301018Steve Golovatoshot 950301018 - moved rcur out by 1.5mm to reduce outer gap, avoid
h-modes if possible. also added argon puff for this shot.
good plasma, L-mode data at 1MW and 1.4MW.

Mar 1 1995 02:38:09:230PM950301019Steve Golovatoshot 950301019 - go to lower density, nl04=.5e20
good shot, went into h-mode at 1.1MW.

Mar 1 1995 02:48:51:660PM950301020Steve Golovatoshot 950301020 - getting hards at this low density.
h-mode threshold between .94 and 1.1 kw.

Mar 1 1995 03:04:50:680PM950301021Steve Golovatoshot 950301021 - going to higher density, nl04=1.2e20.
no h-modes at this density at up to 1.2MW.

Mar 1 1995 03:28:56:970PM950301022Steve Golovatoshot 950301022 - good plasma, similar to last shot.

Mar 1 1995 03:28:28:250PM950301023Steve Golovatoshot 950301023 - getting high power out of e-port, now adding
d-port power. (d-port has been at low power since shot 19)

Mar 1 1995 03:40:59:070PM950301024Steve Golovatoshot 950301024 - bacl to nl04=.7e20, but reduced inner gap from
1.5 to 1cm.
good plasma, h-mode at 1.4MW, not clear that smaller inner gap
has reduced threshold.

Mar 1 1995 03:48:27:050PM950301025Steve Golovatoshot 950301025 - good plasma.

Mar 1 1995 04:12:32:320PM950301026Steve Golovatoshot 950301026 - going to 1MA, 1.2e20. dithering h-modes above
1.5MW.

Mar 1 1995 04:20:33:580PM950301027Steve Golovatoshot 950301027 - hards, oh2l had problems, early disruption.

Mar 1 1995 04:39:00:110PM950301028Steve Golovatoshot 950301028 - good shot, dithering starts between 1.07 and 1.17MW.

Mar 1 1995 04:44:19:550PM950301029Steve Golovatoshot 950301029 - go to nl04=1.5e20
fizzle.

Mar 1 1995 04:57:40:090PM950301030Steve Golovatoshot 950301030 - disruption at .666s

Physics Operator Comments

Engineering Operator Comments
ShotTimeTypeStatusComment
108:44:38:860AMTestOkdata system only
209:28:56:430AMPlasmaBadef1 comm fault
309:41:30:520AMPlasmaOkno faults
409:53:07:340AMPlasmaOkno faults
510:09:53:800AMPlasmaOkoh2u comm fault and tf ioc after disruption
610:30:23:160AMPlasmaOkno faults
710:42:29:480AMPlasmaOkoh2u comm fault after disruption
810:59:08:690AMPlasmaOkoh2l comm fault after disruption
911:14:13:320AMPlasmaOkno faults
1011:29:13:520AMPlasmaOkno faults
1111:38:18:240AMPlasmaOkno faults
1211:49:25:820AMPlasmaOkno faults
1311:59:46:200AMPlasmaOkno faults
1412:09:13:510PMPlasmaOkno faults
1512:21:44:770PMPlasmaOkno faults
1601:04:01:560PMPlasmaOkno faults
1701:19:26:070PMPlasmaOkNo Faults.
1802:03:25:490PMPlasmaOkNo Faults.
1902:25:07:550PMPlasmaOkNo Faults.
2002:37:13:550PMPlasmaOkNo Faults.
2102:48:22:410PMPlasmaOkNo Faults.
2203:01:54:210PMPlasmaOkNo Faults.
2303:14:21:080PMPlasmaOkNo faults.
2403:28:06:770PMPlasmaOkNo Faults.
2503:40:50:040PMPlasmaOkNo Faults.
2603:56:07:440PMPlasmaOkOH1 > 1SCR not conducting
2704:12:38:400PMPlasmaOkOH2L comm fault.
2804:24:58:210PMPlasmaOkMore than one SCR not conducting OH1
2904:40:07:880PMPlasmaOkNo Faults.
3004:51:37:730PMPlasmaOkComm fault OH1 & OH 2 L