Alcator C-Mod Run 1050331 Information

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Miniproposals
Miniproposal:418
Date Filed: 3/4/2005
Title:LH system commisioning
First Author:Stefano Bernabei
Session Leader:Stefano Bernabei (shots 1-33)
Session Leader:J. Randall Wilson (shots 1-33)

Operators
Session leader(s):Stefano Bernabei,J. Randall Wilson
Physics operator(s):Ron Parker
Engineering operator(s):Bill Cochran,Gary Dekow,Bill Parkin

Engineering Operator Run Comment
MP #418 Lower Hybrid Coupling Studies

Session Leader Plans

Physics Operators Plans
Entered: Mar 30 2005 05:21:21:033PM
Author: Ron Parker
Engineering Setup for Thursday, 31 March 2005

MP 418 Lower Hybrid Coupling Studies

Session Leader: Bernabei, Wilson
Physics operator: Parker

Overnight discharge clean in D2, bake at 60 C.

Run Begins at 09:00 and ends at 17:00

Power sytems as on 1050330

A-coils in standard configuration (lock mode suppression)
+Dtop -Dbot -Jtop +Jbot (same as 1050316)

Gas Setup:
fill B-top with 6 psi D2 hybrid enabled (PG4)
fill B-side lower with 2 psi Ar Hybrid enabled (PG1)
leave B-side upper with He3 Hybrid disabled
fill B-main (C-side) with 30 psi D2 Hybrid enabled (PG3)
leave J-bot Hybrid disabled (PG2)

Enable the following:
ECE gate valve, Z-bolo shutters
VUV gate valve

NO ICRF!!

Lower Hybrid 3 carts ready to pulse, -90 degree phasing.
Pulse length up to 20 msec power per klystron up to 20 kW

The run will focus on basic LH coupling studies. Plasma conditions will be routine,
5.6 T, 700 kA, single null. Lowish density. We may want to raise field to enhance
penetration.

The plan is to study coupling and any apparent plasma phenomena associated with LH
at 4 coupler positions; at each coupler position 4 phase decrements will be set, namely
-60, -90, -120 and -150 degrees.

Session Leader Summaries
Entered: Apr 1 2005 05:15:30:580PM
Author: J. Randall Wilson
We completed the shot list we hoped too.
Scans in phase at -60, -90, -120 and -150 degree phasing were performed with the lower hybrid coupler located 1, 3, and 5 mm behind (outboard of) the lower hybrid limiter
For the scans each klystron was requested to output 10 kW for 20 ms.
Data can be analyzed for the behaviour of teh reflection coeffient vs phase after more calibrations are completed (preliminary analysis can begin now)

As has been consistent from teh beginning of operations an arc like event was observed iin waveguide 16±1 of the top coupler. The strength of teh arc decreased as teh day progressed

At the end of the run power was increased in two steps to 20 kW/klystron at this level the event was similar in magnitude to the beginning of the run at half power.

Physics Operator Summaries
Entered: Mar 31 2005 05:59:19:683PM
Author: Ron Parker
The run was devoted to commissioning the LH system and was successful in this
regard. Injections from the antenna seemed to decrease during the day, and powers
up to 200 kW at the klystron were injected. A more or less constant discharge was
set up with Ip = 700 kA, nel4 = 0.5, B = 5.6 T. These discharges ran well, but
occasionally the breakdown seemed to shift relatively late, e.g., 7-8 ms and
this was usually followed by a dud.

In summary ,enough shots were run to accomplish the mini-proposal, except for the
reverse phasing which requires substantial time to set up. It would be best
to set this up off line and request ~ 10 shots at the beginning or end of a
run.

Scorecard: 33 shots, 3 fizzles, 3 duds and 27 full plasma shots.

Session Leader Comments
Mar 31 2005 10:44:50:957AM1050331008J. Randall Wilsonfirst shot with plasma and lh
20 ms pulse, arc in top row guide 16(?) after about 12 ms
-90 degree phasing
Mar 31 2005 11:18:38:990AM1050331011J. Randall Wilsonchnage phase by adding -60 and multiples
arc slightly less strong
Mar 31 2005 11:34:00:347AM1050331012J. Randall Wilsongood plasma and lh with incremental phasing +60 and multiples
Mar 31 2005 11:48:36:700AM1050331013J. Randall Wilsonchnage incremental phase to -120 and multiples
turn of klystron c2v4 to see if arc disappears
Mar 31 2005 11:57:50:460AM1050331014J. Randall Wilsonsame shot (no changes)
Mar 31 2005 12:14:58:347PM1050331015J. Randall Wilsonturn off klystron 9 and turn on klystron 8
phase increment still -120 and multiples
Mar 31 2005 12:30:55:213PM1050331016J. Randall Wilsonall klystrons on
0 incremental phasing
Mar 31 2005 12:56:29:883PM1050331017J. Randall Wilsonmove coupler into 1mm (was at 3mm)
-90 degree phasing, all klystrons
Mar 31 2005 01:15:29:520PM1050331018J. Randall Wilson+60 degree incremental phasing
Mar 31 2005 01:30:18:657PM1050331019J. Randall Wilsonincremental phase -60
Mar 31 2005 01:41:22:030PM1050331020J. Randall Wilson-120 degree incremental phasing
Mar 31 2005 01:55:37:260PM1050331021J. Randall Wilson-180 degree incremental phasing
Mar 31 2005 02:18:02:917PM1050331022J. Randall Wilsonmove coupler to -5mm (from -1)
keep phase at -180 incremental
Mar 31 2005 02:31:37:057PM1050331023J. Randall Wilson-90 pure phasing
Mar 31 2005 02:39:33:470PM1050331023J. Randall Wilsontrouble with lh control program
arc appears in second row!!
trying to recover lh data to understand what we did
Mar 31 2005 02:50:03:723PM1050331024J. Randall Wilsonrepeat -180 degree shot
lh model reset
Mar 31 2005 03:08:55:600PM1050331025J. Randall Wilson-90 degrees


Mar 31 2005 03:36:22:803PM1050331026J. Randall Wilson+60 degree incremental phase
data didnt take
Mar 31 2005 03:37:02:320PM1050331027J. Randall Wilsonrepeat +60
Mar 31 2005 03:43:50:083PM1050331027J. Randall Wilson+60
got data
Mar 31 2005 03:59:38:320PM1050331028J. Randall Wilson-60 degrees
Mar 31 2005 04:39:33:703PM1050331031J. Randall Wilson-60 degree
lower density
arc appears lessened
Mar 31 2005 04:46:44:123PM1050331032J. Randall Wilson-60 degree incremental
raise power to 15 kW/klystron
Mar 31 2005 05:00:12:937PM1050331033J. Randall Wilsonraise power request 20kW/klystron -90 degree phasing

Physics Operator Comments
Mar 31 2005 09:53:28:937AM1050331001Ron ParkerFirst shot was setup using engineering settings from 1050330001,
and plasma settings from shot 1050330007. It ran well, only disrupting on
current rampdown. LHRF did not fire due to faulty fizzle detector.
Mar 31 2005 09:55:22:670AM1050331002Ron ParkerShot 2 was similar to shot 001, however the density was extended throughout the pulse
at ~5e19 (nel4).

It ran well, again no Rf.
Mar 31 2005 09:56:38:260AM1050331003Ron ParkerShots continue to run well, no RF.
Mar 31 2005 09:59:21:653AM1050331004Ron ParkerShot 4 continued to run as programmed, 700 kA, nel4 ~ 5e19.
Fizzle detector for LHRF problem found and is being corrected.
Mar 31 2005 10:01:50:190AM1050331005Ron ParkerLHRF fizzle detector problem fixed, but plasma fizzled! (How did it know????)

Try again next shot, hopefully all systems working.

Mar 31 2005 10:15:39:083AM1050331006Ron ParkerAnother fizzle. Breakdown a little late. More fill?
Increase by 3 ms.
Mar 31 2005 10:30:12:607AM1050331007Ron ParkerThis time a dud -- wrong way on gas? next, reduce gas by 5ms.
Mar 31 2005 10:53:04:630AM1050331008Ron ParkerCoincidentally or not, plasma ran and LHRF did also.

Pictures of grill show breakdown in top row.
Mar 31 2005 10:55:27:113AM1050331009Ron ParkerShot 9 fizzled. Due to previous influx from LH antenna?

Next: repeat.
Mar 31 2005 11:14:25:500AM1050331010Ron ParkerAgain, a dud. The fill pressure is very low and it will be increased by

4 ms for next shot. The stray fields also look marginal, so they will
be tuned if we continue to have problems.

Try to reduce Bz by reducing EF4 by 15 Amps.
Mar 31 2005 11:32:58:660AM1050331011Ron ParkerPhew! Discharge came back, broke down at 5 ms.
We'll hold settings here ubtil we lose it.
Mar 31 2005 11:35:59:127AM1050331012Ron ParkerShot 12 ran OK. RF working and data being collected.
Mar 31 2005 11:51:21:993AM1050331013Ron ParkerShot 13 ran, but breakdown was again delayed until 7 ms. We may be
losing shot -- . Klystron 8 was shot off that time to reduce breakdown at
grill.
Mar 31 2005 12:02:34:617PM1050331014Ron Parker
Shot 14 ran, some flashes still coming out of grill. Turning off a different klystron.

Mar 31 2005 12:18:45:720PM1050331015Ron ParkerShot 15 ran OK, Gas increased slightly ( 1ms) to help earlier
breakdown.
Mar 31 2005 01:04:26:297PM1050331016Ron ParkerShot 16 ran well, breakdown OK.
Mar 31 2005 01:03:26:297PM1050331017Ron ParkerShot 17 went off well, after a cell opening.
Mar 31 2005 01:20:21:317PM1050331018Ron ParkerShots running well, LH data are being collected.
Continue with this shot.
Mar 31 2005 02:01:06:200PM1050331019Ron ParkerShot 19 went off well. Same shot.
Mar 31 2005 02:03:17:417PM1050331020Ron ParkerShot 20 ran well. Continue with same shot for LHRF scan.
Mar 31 2005 01:59:15:230PM1050331021Ron ParkerShot 21 went off well. Short break while grill is moved out to 5 mm
from limiter.
Mar 31 2005 02:27:40:337PM1050331022Ron ParkerShots keep repeating. No problems.
Mar 31 2005 02:44:48:567PM1050331023Ron ParkerShot 23 Ok, but LH phase messed up due to computer failure. Delay while computer
problem addressed.
Mar 31 2005 03:03:25:600PM1050331024Ron ParkerShot 24 was OK, data collected.
Mar 31 2005 03:02:36:257PM1050331025Ron ParkerShot 4 went off well, data collected.
Mar 31 2005 03:08:10:380PM1050331025Ron ParkerShots continuing to run, breakdown a bit late.
Mar 31 2005 03:41:06:397PM1050331026Ron ParkerShot 26 ran well --- but RF computer malfunctioned.
Mar 31 2005 03:41:52:177PM1050331027Ron ParkerShot 27 OK -- locked mode appearing?


Mar 31 2005 04:05:52:223PM1050331028Ron ParkerShot ran OK, but breakdown getting late.
Mar 31 2005 04:05:03:333PM1050331029Ron ParkerShot 28 was a dud. reload shot 19.
Mar 31 2005 04:19:00:200PM1050331030Ron ParkerShot ran, breakdown is prompt. This finishes the planned run for LHRF.

Now the denstiy will be reduced a bit and RF power increased, possibly
turning off the waveguides that have been breaking down.
Mar 31 2005 04:34:10:517PM1050331031Ron ParkerShot ran, density slightly reduced at time of LH pulse.
Mar 31 2005 05:52:55:023PM1050331032Ron ParkerShot ran well. RF injection is getting less intense on camera.
Mar 31 2005 05:54:00:023PM1050331033Ron ParkerShot ran well, breakdown getting late again.

Engineering Operator Comments
ShotTimeTypeStatusComment
109:03:40:500AMPlasmaOk
209:16:21:967AMPlasmaOk
309:29:39:490AMPlasmaOk
409:42:12:393AMPlasmaOk
509:54:59:137AMPlasmaOk
610:07:32:317AMPlasmaOk
710:21:33:010AMPlasmaOk
810:34:04:487AMPlasmaOk
910:50:09:297AMPlasmaOk
1011:02:57:537AMPlasmaOk
1111:15:35:097AMPlasmaOk
1211:28:48:023AMPlasmaOk
1311:42:02:543AMPlasmaOk
1411:54:48:197AMPlasmaOk
1512:11:18:660PMPlasmaOk
1612:26:04:497PMPlasmaOk
1712:53:06:013PMPlasmaOk
1801:12:03:770PMPlasmaOk
1901:25:07:243PMPlasmaOk
2001:37:42:843PMPlasmaOk
2101:52:14:823PMPlasmaOk
2202:15:34:680PMPlasmaOk
2302:29:01:290PMPlasmaOk
2402:47:36:893PMPlasmaOk
2503:00:16:007PMPlasmaOk
2603:17:04:273PMPlasmaOk
2703:33:58:790PMPlasmaOk
2803:49:35:897PMPlasmaOk
2904:02:15:677PMPlasmaOk
3004:14:46:550PMPlasmaOk
3104:28:14:130PMPlasmaOk
3204:43:46:060PMPlasmaOk
3304:56:24:400PMPlasmaOk