Alcator C-Mod Run 941122 Information

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Miniproposals
Miniproposal:
Date Filed:
Title:
First Author:
Session Leader:Robert Granetz (shots 1-28)

Operators
Session leader(s):Robert Granetz
Physics operator(s):Steve Wolfe,Robert Granetz,Steve Horne
Engineering operator(s):Joe Daigle

Engineering Operator Run Comment
first plasmas

Session Leader Plans

Physics Operators Plans

Session Leader Summaries
Entered: Jul 7 2004 03:49:11:303PM
Author: To Be Determined




941122 Orthogonal controllers + work on startup.
Granetz, Horne, Daigle + Hutch, Wolfe, ... (all the usual suspects).

We didn't get to orthogonal controllers due to various difficulties
with the prepared shots. However we were successful in loading and running the
preparatory shot, which was a diverted shot from spring of 1994, with reorganized
wires in segment 2. This shot ran till the segment switch; by moving the switch to .1 sec
(and defeating a nasty PCS bug, see notes for shot 6) we were able to get our
first diverted shots for this campaign (9,10).
After 6 fizzles where we adjusted fill and OH1 voltage to reduce the plasma current rise,
we got another plasma (17); some fussing and fiddling followed; I believe the
diverted plasmas kicked up some crud which affected our startup
We finished with four nice diverted plasmas (25,26,27,28).

I suggest either 27 or 28 as a starting point for tomorrow,
depending on your RCUR preference.
Density feedback should be turned back on,
or the gas preprogramming should be tweaked, for
either of these.

PCS operator notes -- if you use EDIT CONTROLLER, be aware that for your changes
to be accepted you have to OK th screen you typed at, but ALSO ok the little
spreadsheet-like screen with the controller edit and call buttons.
This screen likes to hide itself away behind the main PCS screen,
for some unknown reason.
It would also be a good idea to verify FACTORS to make sure we've wiped out the
effects of the PCS bug reported yesterday.

PS -- we have lost some magnetics -- trying to compensate
tonight.
SFH.

Statistics:

2 Duds (one due to OH2L fault)
13 Fizzles (many with 50+ kA)
13 Plasmas (3 disrupted before rampdown began)

Run starts:
We fixed the tree to recover from the PCS bug discovered yesterday.

1 fill 1.1 e -5
Fizzle

2 fill 1.4e-5 Fizzle

3 fill .8e-5 Recalculated wires 1-4, 7 to repair damage created by yesterday's PCS bug.
Plasma. br is quite negative.

4 Raise br offset from 4.5 to 5.5 e-3.
Load Ian's shot 12, segment 2, to segment 2. This has reorganized wires.
Segment switch at .3 sec.
Plasma, disrupted at segment switch.

5. Plasma, died shortly after switch at .3.

6. Move switch to .1, adjust rcur programming in segment 2 to blend in better.
Plasma.
Switch didn't move; very wierd shot.
A PCS bug was suspected. We opened the cell to allow Irby to check
cooling on the Bragg cell (water interlock opened; turned out to be a bubble
in the flowmeter) and looked for the PCS bug. It turned out that the A matrix assembly
should have depended on the segment switch time, and didn't. (That is, if the matrix is
stale compared to the switch time it should be recomputed.) The PID and M were correct.
This bug has existed for a long time, but the conditions to tickle it
have never occurred before. It was fixed as we waited for cooling. The wait was longer
than usual due to EF1U cooling being set to nearly off.
FILL at 1.e-5 for next shot.

7. fizzle.

8. Plasma. Disruption at about .4. PCS bug seems to be fixed.
Still riding on RF limiter though; move RCUR in by 1 cm.
disrupts at .4 sec.

9. Good shot. First diverted shot.
Repeat.
10 Good diverted shot.
11 fizzle
12 fizzle; current rise too fast. Raise fill to 1.2e-5
13 fizzle. Raise fill to 1.6
14 Fizzle. Tweak oh1 V to reduce current rise.
15 Fizzle. Tweak oh1 voltage further
16 fizzle. Raise fill to 1.6e-5
17 Good plasma. Disrupted on rampdown, probably due to crud.
Drop fill too far to .8e-5
18 dud. Raise fill to 1.4e-5
19 OH2 L COMM FAULT; Jo D claims random event.
Then an init failure. There seems to be a consistent problem with
an engineering jorway,
20 fizzle. Raise fill to 1.6e-5
21 Plasma; disruption on rampdown. The disruption happens as rampdown starts,
just as plasma touches inner wall. Crud injection precedes disruption.
Fill to 1.2e-5; also reduce gas puff after .8 sec. Also adjust
CLEARIN to reduce elongation during
rampdown.
22 Plasma. Density feedback has been working just fine.
Rampdown goes to 200 KA or so. Divertor guys sasay that the scrapeoff
layer is heating up; divertor must be cleaning up.
Program density down starting at .8 sec.
23 50 ka fizzle. Big CII peak. Raise fill from 1.2 to 1.4 e -5.
24 Very similar, but CII peak is later and less. Assume cleanup, no changes.
25 Plasma. Still disrupts at 1.1 sec. Reduce density trace.
26 Nice plasma, but density still too high. NL_07 isn't working right. Turn off density
feedback for next shot.
27 Nice plasma, rampdown.
Move rcur in 1 cm to keep plasma off of RF limiter.
28 Plasma. Hard X-rays, disruption at 1.05 sec.
Moving rcur did keep a nice outer gap, but we don't divert till
around 600 msec.

Run ends.


Physics Operator Summaries

Session Leader Comments
Nov 22 1994 08:53:44:520AM941122001Robert GranetzFizzle.

Nov 22 1994 08:57:13:960AM941122001Robert GranetzNext shot, increase pre-fill to 1.4e-5 torr. No other changes.

Nov 22 1994 09:02:40:260AM941122001Robert GranetzGoal for today's run: MP65

Implement Ian's new orthogonal shape controllers.

Start with shot 941121033 from yesterday, with a fill pressure of 1.1e-5 torr
of deuterium. (It was done yesterday with p=1.5e-5, but we've ECDC'd
overnight.

There's also another problem with the PCS software, for which a fix was made
last night, but which has not been implemented yet. We will implement the
fix after we get a plasma, then proceed to MP#65.

Nov 22 1994 09:03:13:470AM941122001Robert GranetzGoal for today's run: MP65

Implement Ian's new orthogonal shape controllers.

Start with shot 941121033 from yesterday, with a fill pressure of 1.1e-5 torr
of deuterium. (It was done yesterday with p=1.5e-5, but we've ECDC'd
overnight.

There's also another problem with the PCS software, for which a fix was made
last night, but which has not been implemented yet. We will implement the
fix after we get a plasma, then proceed to MP#65.

Nov 22 1994 09:20:39:800AM941122002Robert GranetzFizzle. Too much gas, I guess. There was also too much BR.

Next shot, lower pre-fill to 0.8e-5 torr.

Also, I'll activate the PCS bug fix prior to the next shot.

Nov 22 1994 09:39:32:320AM941122003Robert GranetzPlasma. Ip=-0.78 MA, duration=1.32 s. Good shot.

Next shot, increase Br by +0.001 T by increasing it's offset coefficient.
Tickle the scale factor PCS bug fix for the remainder of the first 8 wires,
and load in Ian's new orthogonal controllers into segment 2. This segment
turns on at t=0.3 s. Also increase pre-fill to 0.9e-5 torr.

Nov 22 1994 09:59:31:140AM941122004Robert GranetzDisruption, caused by the segment switch at 0.3 s. Ip=0.60 MA, duration=0.38 s
There were bad discontinuities in EF1U currents, as well as RCUR.

Next shot, move segment switch time earlier (from 0.3 to 0.1 s) and adjust
RCUR programming.

Nov 22 1994 10:16:41:060AM941122005Robert GranetzDisruption, bad one. Ip=-0.76 MA, duration=0.535 s. Halo currents were
small and balanced.

It looks like the segment switch did not change from t=0.3 s to 0.1 s.
Next shot (after verifying segment switch time) make sure PCS model is
definitely loaded (it is) and return RCUR programming to that of shot 4.

Nov 22 1994 10:31:56:030AM941122006Robert GranetzFizzle. There's evidence on the Aout scope that a switch occurred at 0.1 s,
but there's also evidence that something screwy also happens at 0.3 s (which
was the old switch time). Steve Horne is checking for PCS bugs.

Nov 22 1994 11:20:26:100AM941122006Robert GranetzA bug was found in PCS. Basically, when the segment switch time was changed,
the M-matrix and the PID's were re-loaded as required, but the A-matrix
re-loading software was not being called. Steve Horne has now fixed this.

A long (approx 1 hour) break has occurred, partly for figuring out PCS, but
also because Jim Irby needed access to the cell in order to correct a water
cooling problem with one of the TCI Bragg cells. This necessitated turning
off the LN2 cooling. Re-cooling the machine is causing much of the delay
before the next shot.

Nov 22 1994 11:51:02:440AM941122007Robert GranetzFizzle. But Ip=50 kA. Next shot, no changes.

Nov 22 1994 12:11:36:100PM941122008Robert GranetzPlasma. Disrupted at 0.43 s. Ip=0.65 MA, duration=0.43 s.
Plasma was against the outer limiter for the whole shot, even though RCUR was
set for 0.66 m.

For the next shot, turn off density feedback (which was inadvertently on) and
reduce RCUR demand from 0.66 to 0.67 m.

Nov 22 1994 12:12:30:310PM941122008Robert GranetzPre-fill was set to 1.0e-5 prior to this shot.

Nov 22 1994 12:13:20:300PM941122008Robert GranetzThis disruption went downward and had about 110 kA of lower halo current.

Nov 22 1994 12:28:13:940PM941122009Robert GranetzPlasma. Good shot. Ip=-0.80 MA, duration=1.26 s.
This shot diverted, which is what we wanted. X-ray centroid looked pretty
good on this shot.

Nov 22 1994 12:33:35:620PM941122009Robert GranetzNext shot, extend RCUR to 1.3 s. No other changes.

Nov 22 1994 12:46:52:200PM941122010Robert GranetzGood plasma, diverted, very similar to previous shot. Next shot, no
changes. We are waiting for Steve Horne and Steve Wolfe to verify that it's
okay to load in the new controllers.

Nov 22 1994 01:06:38:490PM941122011Robert GranetzFizzle. Try again, no changes. Still have problems loading in the new
predictors. Couldn't find the one we needed for RCUR in Ian's area.

Nov 22 1994 01:49:36:800PM941122012Robert GranetzFizzle. Next shot, raise pre-fill to 1.2e-5.

Nov 22 1994 01:50:59:080PM941122013Robert GranetzFizzle. Got 60 kA. Next shot, raise pre-fill to 1.4e-5.

Nov 22 1994 01:47:56:860PM941122014Robert GranetzFizzle. We got 60 kA this time. The current is rising too fast.

For the next shot, reduce the OH1 voltage by 100 volts around 0.024 s, without
changing it in the breakdown time (<0.015 s). This is to reduce the loop
voltage at that time by about 1 volt, in order to slightly slow down the
current ramp.

Nov 22 1994 02:14:14:560PM941122015Robert GranetzFizzle. 60 kA again. Next shot, reduce OH1 voltage over a little wider
time window.

Nov 22 1994 02:15:59:720PM941122016Robert GranetzFizzle. 60 kA again. The base pressure comes down to the 4e-7 range between
shots. Next shot, raise pre-fill to 1.6e-5 torr.

Nov 22 1994 02:21:50:860PM941122017Robert GranetzPlasma. Ip=0.8 MA, duration=1.12 s. Terminated by a disruption during
the rampdown.

Downward going disruption, with 90 kA of halo current.

Nov 22 1994 02:33:21:320PM941122017Robert GranetzThe base pressure is now 1.3e-6, rather than 4.7e-7, so for the next
shot, try lowering the pre-fill to 0.8e-5 torr.

Nov 22 1994 02:34:59:830PM941122018Robert GranetzDud. Raise pre-fill to 1.4e-5.

Nov 22 1994 02:40:59:370PM941122019Robert GranetzDud. OH2L failed prior to commutation. Next shot, no changes.

Nov 22 1994 03:12:34:970PM941122020Robert GranetzFizzle. Next shot, raise pre-fill to 1.6e-5 torr.

Nov 22 1994 03:25:14:120PM941122021Robert GranetzPlasma. Ip=0.8 MA, duration=1.11 s. Terminated by a disruption during the
rampdown again. Plasma is not being pushed hard enough against the inner
wall at the end of the shot. Also, the density is not decreasing at the end.

For the next shot, push plasma against inner wall earlier (using CLEARIN) and
reduce the gas puff voltage starting at 0.8 s.

Nov 22 1994 03:38:00:480PM941122022Robert GranetzGood plasma shot. Ip=-0.81 MA, duration=1.26 s. Density was still high at
the end. It turns out that density feedback was still enabled, but since
it's working, we'll leave it on. However, the programmed density will
start decreasing earlier for the next shot.

Nov 22 1994 03:46:24:910PM941122023Robert GranetzFizzle. 50 kA blip. Next shot, raise pre-fill to 1.4e-5.

Nov 22 1994 03:59:20:870PM941122024Robert GranetzFizzle. 50 kA blip. Next shot, no changes

Nov 22 1994 04:15:49:360PM941122025Robert GranetzPlasma. Ip=-0.8 MA, duration=1.10 s. Terminated by a disruption during the
rampdown. John Goetz reports that the large density was due to detachment.

Next shot, reduce density demand, and reduce pre-fill to 1.2e-5.

Nov 22 1994 04:28:34:010PM941122026Robert GranetzPlasma. Good shot. Ip=-0.80 MA, duration=1.21 s. Density is still
very high even at the end of the shot (nl05=0.9-1.0e20). Looks like there
was another poloidal detachment.

Nov 22 1994 04:38:02:350PM941122026Robert GranetzNext shot, turn off density feedback. Found a bug while trying to turn off
the density feedback.

Nov 22 1994 04:51:36:580PM941122027Robert GranetzPlasma. Very good diverted shot. Ip=-0.81 MA, duration=1.28 s. Current
ramped all the way down.

Next shot, program RCUR to be 1 cm further inside (from 0.65 to 0.64 m).

Nov 22 1994 05:08:40:410PM941122028Robert GranetzPlasma. Ip=-0.81 MA, duration=1.06 s. Disrupted just after rampdown started.
Don't know what caused the disruption.

End of run.

Physics Operator Comments
Nov 22 1994 08:25:58:290AMSteve WolfeRun of 11/22/94

Physics Operators: Granetz,Horne
Substituting atatart of run: Wolfe

Loaded SHot 33 from yesterday.
Dispatched coldstart, etc. Log file ok.

Engineering Operator Comments
ShotTimeTypeStatusComment
108:52:18:910AMPlasmaOkno faults
209:03:01:630AMPlasmaOkno faults
309:19:54:950AMPlasmaOkno faults
409:39:50:550AMPlasmaOkno faults
509:58:46:660AMPlasmaOkno faults
610:15:43:650AMPlasmaOkno faults
711:41:51:450AMPlasmaOk
811:52:04:250AMPlasmaOkso-so
912:12:29:860PMPlasmaOkno faults
1012:35:37:750PMPlasmaOkno faults
1112:49:09:940PMPlasmaOkNo faults.
1201:09:55:820PMPlasmaOkNo faults
1301:20:57:360PMPlasmaOkNo faults
1401:31:43:790PMPlasmaOkno faults
1501:48:38:800PMPlasmaOkNo faults
1602:01:20:360PMPlasmaOk
1702:12:01:680PMPlasmaOkNo faults.
1802:26:44:230PMPlasmaOkNO faults
1902:37:33:150PMPlasmaBadOH@L Comm fault.
2002:53:11:510PMPlasmaOkNo faults
2103:08:48:790PMPlasmaOkno faults
2203:26:57:060PMPlasmaOkNo faults
2303:39:41:810PMPlasmaOkno faults
2403:50:53:180PMPlasmaOkNo faults
2504:01:33:450PMPlasmaOkNo faults
2604:21:00:760PMPlasmaOkNo Faults
2704:39:55:980PMPlasmaOkNo Faults
2804:55:32:410PMPlasmaOkNo Faults.