Alcator C-Mod Run 950411 Information

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Miniproposals
Miniproposal:
Date Filed:
Title:
First Author:
Session Leader:Rejean Boivin (shots 1-43)
Miniproposal:108
Date Filed: 3/23/1995
Title:Examine Up-down Neutral Density and Forbidden Line Asymmetry during Reversed
First Author:John Rice
Session Leader:John Rice (shots 1-43)

Operators
Session leader(s):Rejean Boivin,John Rice
Physics operator(s):Steve Wolfe
Engineering operator(s):Vinny Bertolino,Vinny Bertolino,Frank Silva

Engineering Operator Run Comment
Wolfeman

Session Leader Plans

Physics Operators Plans

Session Leader Summaries
Entered: Jul 7 2004 03:49:13:320PM
Author: To Be Determined

The main goals of run 950411 were to look at neutral effects both in
the CX flux and in Argon radiation in the reversed configuration.

We started with the X point (Grad B is up) directed towards the divertor.
We spent about 14 shots before getting something and then we obtained a fair
number of good shots, enough to obtain a good scan in Hirex and PCX. The
required density of 5e19 was not always obtained and very bizarre density
time traces were seen instead, all in the neighborhood though.

After the first part was reasonably completed (see summary further down),
we switched the X point UP. We spent many shots with little success.


Summary

001 : Tuesday test shot
002-014 : fizzles or very short
015 : 0.7 sec. long
016 : Fiz.
017-019 : Good
020 : Short plasma
021-024 : Good
025 : Fizzle
026-029 : Good plasmas

Reverse X point

030 : Short plasma
031 - 040 : Fizzle
041 - 043 : Good plasmas, last one with HARDS


So, it's too bad we didn't get many points today, it looked like we were on to
something interesting. But we got some.

***************************************************************************
By the way, people should be aware that the ECE was scanning up/down and
consequently the chain of data analysis, ECE, Zeff, neutron, etc etc could
be severely disrupted.
**************************************************************************

John mentions that the forbidden lines asymetry switched with the Grad B
direction. On his point of vue, it seems that the neutral density asymetry
stayed down with the Xpoint down.

On the CX point of view, it seems that the flux has a local minimum
no matter what configuration near the midplane. An increase in flux
is observed at some distance from the midplane. Also it seems that Ti
was higher than similar discharges (e.g. 950307 or 950322).



Also thanks for the engineering team, they've done a great job today.
And thanks to Steve Wolfe. Actually I am surprised he still has all his
hair, with those plasma attempts.

Physics Operator Summaries
Entered: Jul 7 2004 04:36:53:787PM
Author: To Be Determined
Physics Operator Summary for 950411

MP#103A CX Flux
MP#108 Up-Down neutral
SL: Boivin,Rice
PO: Wolfe
EO: Bertolino/Silva/Bertolino

The plan was to start with 800 kA, low density (5-6 X10 ^19 NL04) discharge
with lower X point. Repeat 10 -15 times without any change. Scan HIREX, PCX
McPherson, maybe ECE and others. Then change to upper x-point and repeat. It
didn't go that easily. We were plagued by an unreasonable number of fizzles at
the beginning and end of the run, and some difficulty controlling the density
at the low levels desired. Adequate data was obtained for the lower x-point,
but only 2 reasonable shots for the upper x-point.

I started with a prepared shot consisting of:
Segment 1 from 950407038 (startup with EF1s tweaked to get rid of bad curvature.)
Segment 2 from 950307034, flipped and adjusted for reverse field
Segment 3 from 950322004, flipped and adjusted for reverse field (upper x-point)
For the lower x-point, segment 2 was on, for the upper x-point, segment 3 was
on.

We began the run with 11 straight fizzles. I spent shots 2-9 tweaking up the
startup from Friday. One thing I tried was adjusting the EF1's first by 50A
and then by 100A, in the belief that the field index might be too positive,
leading to radial instability. Unfortunately, I had the sign wrong, so I was
making it more positive rather than less. I didn't realize this until Shot 11,
after I reloaded a segment 1 from Thursday, with the large negative index;
this almost went but bounced outside. Shot 12 had higher fill (2.5e-5) and
ran, but disrupted at 540, and still had a bounce problem in startup. At shot
15, I changed the seg 1 RCUR offset from 1000. to 500., which may or may not
have been the right tweak, but it ran. On shot 17 I finally made a V_OH1 tweak
after 20msec; this seemed to give a reasonable breakdown which survived for
17-30, with one fizzle on 25 due to a power supply problem.

Shots 18-29 were more or less what Rejean and John wanted for the first scan.
There were problems with the density jumping back and forth between 5e19 and
6.5e19 several times during many of these shots. This may have been
correlated with the appearance of the upper x-point in the vessel, or with
proximity to the inner nose. On many of these, we also had a problem with EF1U
going to its voltage rail. Argon puffs of 50msec width ran ok, but 60msec led
to disruption (#20).

On shot 30 we tried to go to upper x-point; this shot disrupted at .7 sec,
apparently from dirt or Moly from the upper strike points. We then started a
long unpleasant sequence of dirty disruptive discharges followed by multiple
fizzles. Almost all of the fizzles bounced outside. Tweaks to the startup
fields and gas failed. Finally, on shot 41 I reloaded the segment 1 from #30,
and it went. Shots 41 and 42 were good upper null shots (41 better than 42).
Shot 43, still at a fill of 2.5e-5, had serious hard x-rays, and may not be
useable.

Problems (other than a ridiculous number of fizzles)
-----------------------------------------------------
Shot #25 had some sort of problem on OH2L. It looked like it might have been
single-phasing, but Vinnie said all the gate pulses were there. At any rate it
was oscillating at 60HZ and did not get to its normal current by a long way.
The shot fizzled with a very late breakdown. The next shot was ok, with no
remedial action taken.

Shot #27 had a TORVAC gas fill target problem, similar to one that happened a
few weeks ago. The fill was set to 2.5e-5, but PARAGON managed to translate
the target improperly, and we ended up with 6.5e-5. Fortunately, Rejean caught
it before the shot went and we backed out. John Goetz brought up the Paragon
screen and determined that the target was being improperly translated into
bits. It turned out that the way to fix this was to change the value of the
exponent in the target (changing the mantissa didn't help); once this was
done, the proper translation was applied, and changing it back worked
correctly.

The Thursday startup seemed to work as long as we didn't get disruptions, and
made it through some of those, but is not robust. Almost all the fizzles were
outside bouncers.

For lower null discharges we were getting into trouble with the EF1U voltage
rail. Some playing with waveforms and gains on RXU seemed to affect it, though
not in the way I expected. More careful analysis of what was going on on
#22-27 may shed some light on this problem.

Scorecard: 43 shots. 22 plasmas. 20 fizzles. 1 test




Session Leader Comments
Apr 11 1995 08:24:26:930AM950411001Rejean BoivinUsual tuesday morning test shot. Next one, plasma attempt.
Go for it Steve!

Apr 11 1995 11:56:45:260AM950411017Rejean BoivinShot got almost all the way through. We will get scanning next shot.

Apr 11 1995 11:57:48:660AM950411018Rejean BoivinThings are getting very good. PCX is scanning, Hirex on the way too.
Holding ECE scan a little bit for getting startup all tuned up.

Apr 11 1995 11:58:46:600AM950411019Rejean BoivinVery nice, I think we got what we needed. Shot 20 should be the same.

Apr 11 1995 12:12:52:730PM950411020Rejean BoivinWell, John got his Argon, just a tad too much, Yeah right!

Apr 11 1995 12:14:06:170PM950411021Rejean BoivinAlmost all the way through but the flattop is good.

Apr 11 1995 12:26:46:750PM950411022Rejean BoivinAlmost all the way through but the flattop is good. Still working
on the ramp down.

Apr 11 1995 12:50:59:660PM950411023Rejean BoivinGot a glitch on the density on this shot. May not be able to save
this one for the scan.

Apr 11 1995 01:05:44:370PM950411024Rejean BoivinGood shot, got a little bit farther out in time. Still a curious
event/transition at ~0.7 sec.

Apr 11 1995 02:14:51:030PM950411027Rejean BoivinVery good shot, we will go for 2 more good ones and switch to X point
UP.

Apr 11 1995 02:34:13:470PM950411029Rejean BoivinOk shot, density a bit high and then disruption at 1 sec.

Next shot, attempt X point up.

Apr 11 1995 02:55:07:320PM950411030Rejean BoivinX point up. Start-up looking ok, maybe some crud entering the
plasma and disrupted it.

Apr 11 1995 02:56:55:750PM950411031Rejean BoivinFizzzzzzzllllllllle

Apr 11 1995 03:13:38:460PM950411032Rejean BoivinThis shot has been awarded the title of the ugliest shot on C-Mod.
But eh, we are not picky...

Apr 11 1995 03:27:17:110PM950411033Rejean BoivinFize-L. Try again

Apr 11 1995 03:27:41:650PM950411034Rejean BoivinFize-L. Is gas the problem?

Apr 11 1995 03:37:34:830PM950411035Rejean BoivinWell shot 032 got almost beaten up by this one. Quite ugly
still. We'll pass on that one. LAsted about 0.5 sec.

Apr 11 1995 05:42:32:210PM950411041Rejean BoivinVery nice plasma, density very flat at 5e19, maybe a small injection
in the middle. Wished we had those all along!!!!

Apr 11 1995 05:43:19:540PM950411042Rejean BoivinAnother nice one. more injections but still. A suspicious drop
in H alpha and rise in density around 0.65 seconds.

Apr 11 1995 05:43:52:190PM950411043Rejean BoivinRunaway! It's the last shot!
Hards, may be recoverable for some aspects/times.

Physics Operator Comments
Apr 11 1995 07:50:26:800AMSteve WolfeMP#103A CX Flux
MP#108 Up-Down neutral
SL: Boivin,Rice
PO: Wolfe
EO: Bertolino

Physics Run plan:
Start with 800 kA, low density (5-6 X10 ^19 NL04) discharge
lower X point. Repeat 10 -15 times without any change. Scan HIREX, PCX
McPherson, maybe ECE and others.

If things are going well we will then move to X point up,
same conditions. That should complete the day.

Apr 11 1995 07:51:17:750AMSteve WolfeMP#103A CX Flux
MP#108 Up-Down neutral
SL: Boivin,Rice
PO: Wolfe
EO: Bertolino

Run plan for 950411 (operational details)

Engineering setup from 950407038
A-side plenum filled to 19psi D2
B-side lower plenum to 4psi Argon

Start from a prepared shot (user9:[wolfe.mds.shots.hybrid.pcs]pcs_950411901.*)
with the following characteristics:

Segment 1 from 950407038. Tweak startup until it works, then
stop tweaking until it ceases to work.

Segment 2 based on 950307034, suitably flipped and massaged for
reverse-field operation. Try using EF2_by_EF4 control once shot established;
if it makes things worse, then punt. Adjust gaps, density, etc. to taste
(Rejean and John's taste, that is). Try to run constant shots.

If we get to the upper x-point portion of the run, use segment 3 of the
same prepared shot, based on 950322004, also suitably flipped and massaged.
Tweak this up as indicated, and try for another set of constant shots.

Apr 11 1995 08:23:56:110AM950411001Steve WolfeShot 950411001

Tuesday morning test will include EF1's, along with EFC and OH's.

Test looks ok.

Apr 11 1995 08:36:35:450AM950411002Steve WolfeShot 950411002

First plasma attempt.
Fill=1.8e-5
50msec. wide Ar puff
Gatevalves: ECE,TCX,PCX,Mo,VUV

Fizzle.
Late bd. 11msec
CII @.004
Ugly null, nothing like 38 from Friday!

Apr 11 1995 08:49:58:580AM950411003Steve WolfeShot 950411003

Change Br from .001 to 0.
IC_EF4 from 1215 to 1230.

Fizzle
Extremely late bd. 19msec!!
Null doen't look bad, except field comes in too slowly?

Apr 11 1995 09:01:29:910AM950411004Steve WolfeShot 950411004

IC_EF1U & L from 4600 to 4550: Undo a little of the dB/dR fix from Friday

Fizzle. BD at 12 msec
I'm tempted to reload SEG 1 from 950406014.
Null looks ok, index a little positive still.
Try a blind Br tweak.

Apr 11 1995 09:09:58:680AM950411005Steve WolfeShot 950411005

Br offset to +0.0005
Fizzle. BD at 9msec, got to 40kA and bounced.
Ran outside.

Apr 11 1995 09:17:15:150AM950411006Steve WolfeShot 950411006

Raise fill to 2.2e-5. No other changes
Didn't go, still a fizzle.
Very similar, late bd (9msec) then bounces outside.

Apr 11 1995 09:30:57:270AM950411007Steve WolfeShot 950411007

Another .5mT on Br (to .001)
Fizzle- bd at 6.75msec, still bounced outside, and maybe down?
Restrike almost makes it.

Apr 11 1995 09:39:44:540AM950411008Steve WolfeShot 950411008

Back to 1215 on EF4. (from 1230)
Try to start with a bit more negative field.

Fizzle - BD still at 6.6msec, no bounce, current rise is poorer.

Apr 11 1995 09:47:23:260AM950411009Steve WolfeShot 950411009

Take another 50A off EF1 currents (to 4500)

Still fizzles! Late bd again: 17msec
Field still comes in late.

See if a setup from thursday works any better!

Apr 11 1995 09:57:14:610AM950411010Steve WolfeShot 950411010

Import segment 1 from 950406014. This one has EF1s at 4800; I've been
going the wrong way? I thought I was undoing part of the index change
from Friday, but in fact I was making it more radially unstable. I forgot
Bz is negative.

Still fizzles, but got a breakdown at 6.6msec, and it bounces with 40kA

Apr 11 1995 10:08:25:880AM950411011Steve WolfeShot 950411011

Drop EF4 from 1200 to 1185.

Fizzle. Bd at 5.7msec, bounces at 20msec
ECE shows signal across the whole field.
RCUR looks like its caught it, then suddenly loses it outside.

Apr 11 1995 10:25:38:210AM950411012Steve WolfeShot 950411012

Raise fill to 2.5e-5. No wire tweaks.

Started, but disrupted early (540msec)
Bounced late in startup (29msec)
The disruption looks like excess radiation. Begins to rise around 330.

Apr 11 1995 10:36:17:500AM950411013Steve WolfeShot 950411013

Drop Ar pulse width to 40msec
Fizzle. BD at 5.6msec, hesitates, then bounces
Rides inside, then jumps quickly out.

Apr 11 1995 10:43:14:550AM950411014Steve WolfeShot 950411014

No changes. Still fizzled.
We're not there yet!
Similar, bounces earlier.

Apr 11 1995 10:57:36:980AM950411015Steve WolfeShot 950411015

Change RCUR offset from 1000 to 500.

Started, but disrupted early again. Made it to .7sec
density is a little low (4e19 insterad of 5e19)
CLEARIN is a little low.

Apr 11 1995 11:07:44:240AM950411016Steve WolfeShot 950411016

Raise NL_04 to 6e19, lose early spike up to 9e19.
INcrease CLEARIN by 4mm

Fizzle again. That wasn't supposed to happen, the previous startup
looked good.
This one bounced again. Very similar to 14.

Apr 11 1995 11:18:35:370AM950411016Steve WolfeShot 950411017

Reduce OH1 voltage between 20 and 35msec

That one made it longer, just into rampdown.
Looks like the high density program in rampdown killed that one.

Apr 11 1995 11:18:44:540AM950411017Steve WolfeShot 950411017

Reduce OH1 voltage between 20 and 35msec

That one made it longer, just into rampdown.
Looks like the high density program in rampdown killed that one.

Apr 11 1995 11:39:36:620AM950411018Steve WolfeShot 950411018

Get rid of late density rise
Increase CLEARIN by 2mm early, 4mm late.
Increase Ar puff back to 50msec

Made it to 1.2sec.
Startup looks very ragged.

Apr 11 1995 11:52:40:000AM950411019Steve WolfeShot 950411019

INcrease NL04 gain at .52sec from 4 to 6
Tweak the rampdown some.
Drop fill to 2.2e-5

Ran nicely to 1.4sec.
Still dropping density a bit.

Apr 11 1995 12:04:21:370PM950411020Steve WolfeShot 950411020

INcrease Ar puff to 60msec
Extend density flattop into rampdown (RF will fire at 1.0sec)

Disrupted early, .56sec
2pi gets to > 500 before it disrupts.
Snipes says there is a locked mode.

Apr 11 1995 12:20:10:830PM950411021Steve WolfeShot 950411021

Put Ar pulse width back to 50msec

Disrupted in rampdown, 1.1sec.

Apr 11 1995 12:30:20:670PM950411022Steve WolfeShot 950411022

Draw RXU moving out by 1cm(what it's doing anyway)

Disrupted at 1.1sec again.

Apr 11 1995 12:43:45:040PM950411023Steve WolfeShot 950411023

Slow down RCUR rampdown
MOve RXU out by more after .8sec

Still disrupting on rampdown
EF1U is worse. Maybe I'm going the wrong way on RXU.

Apr 11 1995 12:58:54:220PM950411024Steve WolfeShot 950411024

Reload RXU from #21
Last one did something funny on the density, went down then up.
I think it may be related to the upper x-point behavior

Made it to 1.14;
Density dip is at a different time, around 0.7 sec

Apr 11 1995 01:26:27:300PM950411025Steve WolfeShot 950411025

Raise PG3 V-program after .5sec in Segment 2
Reduce gain on RXU by factor of 2

Fizzle. Here we go again
Late breakdown 13 msec
Looks like a power supply problem.
Null basically isn't. OH2L has big ripple.

Apr 11 1995 01:40:15:030PM950411026Steve WolfeShot 950411026

Repeat, to see if the OH2 problem is still there.
Raise PG3 V-program after .5sec in Segment 2
Reduce gain on RXU by factor of 2

This time it made it to 1.4sec.
EF1U is still railing, maybe worse.
Density is still a bi-level
Note: Change of fill from 2.5 to 2.2 never was implemented.

Apr 11 1995 02:09:33:190PM950411027Steve WolfeShot 950411027

Raise gain on RXU to 20/sec
The appearance of the upper null is the only thing that seems to
correlate at all.
Pressure went to 6.8e-5 in INIT, and TORVAC thought it was ok.
Goetz finally "fixed" it by changing the exponent, which got it to
put the right number in the lookup table, then changing it back.

Ran ok. Density back down to 5e19 at .66sec, stays down.
EF1U still in trouble after .8sec
Leave it alone, since its running

Apr 11 1995 02:18:26:400PM950411028Steve WolfeShot 950411028

No changes.
Rejean says two more good ones and we'll try the upper x-point.
Copy pulse gas and NL_04 waveforms into segment 3 in preparation

Ran ok. NL_05 back to 6e19.

Apr 11 1995 02:32:45:540PM950411029Steve WolfeShot 950411029

No changes.
Disrupted at 1.0sec
This one had EF1 getting in trouble earlier.
Density excursion goes higher, but we'll live with it.

Apr 11 1995 02:50:17:990PM950411030Steve WolfeShot 950411030

Go to upper x-point. Switch off seg2 and on Seg 3.

Disrupted at .7sec
Looks resistive.

Apr 11 1995 02:58:54:080PM950411031Steve WolfeShot 950411031

Raise density to 0.7e20; see if it just needs to clean up.
Fizzle. CII is high, it looks like it chokes early.

Apr 11 1995 03:09:22:430PM950411032Steve WolfeShot 950411032

Repeat with density at 0.7e20
Looked very dirty. Disrupted at 400msec
Disrupting repeatedly from the start.
Bounced outside at 28msec

Apr 11 1995 03:18:38:710PM950411033Steve WolfeShot 950411033

Repeat with density at 0.7e20. It may just need to clean up.
fizzle. Bounces at 25msec

Apr 11 1995 03:25:10:620PM950411034Steve WolfeShot 950411034

Repeat.

Still bouncing outside.

Apr 11 1995 03:36:34:750PM950411035Steve WolfeShot 950411035

Raise A-side plenum pressure back to 19psi.
Another dirty disruptive one. Dies at.46

Apr 11 1995 03:46:36:420PM950411036Steve WolfeShot 950411036

Drop NL04 back to .6e20, slow down rise
Drop early seg 2 gas puff.

fizzle- lowering the fill wasn't the answer.
Another bouncer!

Apr 11 1995 03:46:53:770PM950411036Steve WolfeShot 950411036

Drop NL04 back to .6e20, slow down rise
Drop early seg 2 gas puff.

fizzle- lowering the fill wasn't the answer.
Another bouncer!

Apr 11 1995 03:56:58:010PM950411037Steve WolfeShot 950411037

Move segment 1 gas puff earlier by 2msec
Fill back to 2.5e-5

Another fizzle. still bouncing outside.

Apr 11 1995 04:10:29:050PM950411038Steve WolfeShot 950411038

try putting segment 1 RCUR offset back to 1000.
Another fizzle. Bounces earlier, almost recovers.
Check on RCUR calibration. Zero-crossing was in channel 4 of ECE,
now in channel 3. That would say this is better?

Apr 11 1995 04:11:20:780PM950411038Steve WolfeShot 950411038

try putting segment 1 RCUR offset back to 1000.
Another fizzle. Bounces earlier, almost recovers.
Check on RCUR calibration. Zero-crossing was in channel 4 of ECE,
now in channel 3. That would say this is better?

Apr 11 1995 04:26:40:950PM950411039Steve WolfeShot 950411039

Reduce OH1 voltage between 15 and 20msec.
Just the same!

Apr 11 1995 04:35:25:410PM950411040Steve WolfeShot 950411040

Keep RCUR gain high in Seg 1 and draw waveform to stay flat at .66
I'm runnning out of things to try

No help. Try reloading shot 30 segment 1.

Apr 11 1995 04:44:49:660PM950411041Steve WolfeShot 950411041

Import seg1 from shot 30 which did start ok.

Well, at least it started up.
Disrupted at 1.17sec
Density looks good at 5.5e19

Apr 11 1995 04:56:38:260PM950411042Steve WolfeShot 950411042

Repeat.
Disrupts at 1sec
Some injections, density rises and H-alpha drops after one at .57 sec
Possible H-mode?

Apr 11 1995 05:10:07:930PM950411043Steve WolfeShot 950411043

Try for one last shot. No changes.
Hard x-rays, disrupts at 0.85sec.

Engineering Operator Comments
ShotTimeTypeStatusComment
108:21:11:150AMTestOkcoax test
208:31:15:770AMPlasmaOkno faults
308:41:38:510AMPlasmaOkno faults
408:55:46:390AMPlasmaOkno faults
509:04:37:410AMPlasmaOkno faults
609:13:59:810AMPlasmaOkno faults
709:25:19:490AMPlasmaOkno faults
809:34:37:570AMPlasmaOkno faults
909:43:00:670AMPlasmaOkno faults
1009:53:11:440AMPlasmaOkno faults
1110:01:25:180AMPlasmaOkno faults
1210:12:07:550AMPlasmaOkno faults
1310:28:35:310AMPlasmaOkno faults
1410:37:56:340AMPlasmaOkno faults
1510:47:12:830AMPlasmaOkno faults
1611:02:00:190AMPlasmaOkno faults
1711:13:20:760AMPlasmaOkno faults
1811:30:00:000AMPlasmaOkno faults
1911:46:35:040AMPlasmaOkno faults
2011:58:28:460AMPlasmaOkno faults
2112:10:12:770PMPlasmaOkno faults
2212:23:07:020PMPlasmaOkno faults
2312:37:45:680PMPlasmaOkno faults
2412:49:02:700PMPlasmaOkno faults
2501:04:49:670PMPlasmaOkno faults
2601:27:51:940PMPlasmaOkno faults
2701:43:49:000PMPlasmaOk
2802:15:35:820PMPlasmaOkno faults
2902:27:49:720PMPlasmaOk
3002:40:12:910PMPlasmaOk
3102:54:05:590PMPlasmaOkpower supply operation flawless
3203:04:00:350PMPlasmaOk
3303:12:35:480PMPlasmaOk
3403:22:16:130PMPlasmaOk
3503:32:00:080PMPlasmaOk
3603:42:49:180PMPlasmaOk
3703:53:48:770PMPlasmaOk
3804:03:06:010PMPlasmaOk
3904:14:15:110PMPlasmaOk
4004:29:32:970PMPlasmaOk
4104:39:44:750PMPlasmaOk
4204:50:31:760PMPlasmaOk
4305:02:03:130PMPlasmaOk