Alcator C-Mod Run 1060718 Information

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Miniproposals
Miniproposal:418
Date Filed: 3/4/2005
Title:LH system commisioning
First Author:Stefano Bernabei
Session Leader:Ron Parker (shots 1-1)
Miniproposal:455
Date Filed: 5/26/2006
Title:Determination of LHCD efficiency
First Author:J. Randall Wilson
Session Leader:J. Randall Wilson (shots 2-10)

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

Engineering Operator Run Comment
MP#418 LH System Commissioning SL: Wilson/Parker PO: Parker

Session Leader Plans
Entered: Jul 17 2006 03:49:50:563PM
Author: Ron Parker
Session Leader Plan for Tuesday, July 18, 2006

MP 418 LH System Commissioning

SL: Wilson/Parker
PO: Parker

Run Plan

We will start with standard 5.4 T, 700 kA, low density (nel_04 ~ 0.3e20 m-3) L-Mode discharges. The plan is to operate at 60, 90 and 120 deg phasing (beginning with 90 deg) at ~ 500 kW to see if location of LH current can be varied as expected by theory and modeling. The principal diagnostic will be the hard X-Ray camera. A second scan will be performed at higher field, e.g., 6.5 T where penetration is better. If time and NSTAR permit, LH power will be increased to determine power handling capability of the system.

Physics Operators Plans
Entered: Jul 17 2006 05:09:45:693PM
Author: Ron Parker
Physop Plan and Engineering Setup for Tuesday, July 18 2006

MP#418 LH System Commissioning
SL: Wilson/Parker
PO: Parker

Run starts at 9:00 and ends (with luck) at 5:00

CORRECTION!!! ************RUN STARTS AT 8:00 AND ENDS EITHER AT 4:00
OR EARLIER IF NSTAR TELLS US TO GET OFFLINE***********************

NOTE: With hot weather continuing, we may get shutdown early by NSTAR, or get last minute word that there will be no run at all. Stay tuned.

ECDC overnight in D2 at 2.e-4 Torr

Power systems as on 1060511001
A-coil configuration: normal [+Dtop -Dbot -Jtop +Jbot] and enabled.
C-coil Start=0.3sec, Invert=2.0sec

ICRF: Not required for this run

Gas Setup:
----------
fill B-top 6psi D2 Hybrid enabled (PG4)
fill B-side lower 1 psi Argon Hybrid Disabled (PG1)
fill B-side Upper as is, Hybrid Disabled (PG2)
fill B-main 40psi D2 Hybrid Enabled (PG3)


Enable ECE, VUV, Z-bolo shutter assuming no vacuum problems

Run Plan: We'll run standard 5.4 T, 700 kA low density (nel_04 ~ 0.3e20 m-3) L-mode discharges. Plan is to perform phase scans in order to confirm phase control of LH current density using primarily the hard X-Ray camera.

Session Leader Summaries

Physics Operator Summaries
Entered: Jul 18 2006 01:01:11:813PM
Author: Ron Parker
The run began at 8:00 due to anticipated early shutdown due to shedding of load by NSTAR because of high heat. In fact this occurred at noon.

A total of 10 shots were run, all useful from LH point of view. The power was increased to 600 kW absorbed, a mini-record. Shots 1-8 were at 90 deg phasing, and 9-10 were at 60 deg. Only about 150 ms of shot 10 was useful as this shot became disruptive. The goal here was to compare hard X-Ray profiles and energies for two phasings, and with the limited run time this was only partially achieved. More will be scheduled for the next run on July 20.

In an attempt to improve the coupling, shots 7-10 were run limited on the outboard limiter. With the higher density, at 90 deg phasing the reflection coefficient was ~ 15%, and at 60 deg phasing it increased to ~ 20%.

Shot 1 was loaded from May 11, 2006. F11 flux loop had died on May 18 and this was not taken into account by recalculating the magnetic predictors as requested by PCS notice -- operator error! Nevertheless, the shots ran well, with no disruptions until shot 9 where a disruption was caused by the pellet injector.

One item of concern was Shot 8 where the TF failed to regulate at 150 kA, instead regulating at 157 kA, or 5.7 T. Inspection of the control circuitry did not reveal any technical problems. For the remaining shots, the TF ran at the requested level.

Scorecard: 10 shots, no fizzles, no duds, 2 disruptions at least one of which due to pellet injection.

Session Leader Comments
Jul 18 2006 08:34:41:743AM1060718001J. Randall Wilsonfirst shot has short lh pulse at 1 sec
good reflection
Jul 18 2006 08:48:45:233AM1060718002J. Randall Wilson100 ms pulse at 0.7 sec
Jul 18 2006 09:10:23:477AM1060718002J. Randall Wilson100 ms pulse at 0.7 sec

jigh reflection need to push coupler in
Jul 18 2006 09:19:35:010AM1060718003J. Randall Wilson400 ms pulse

reflection much lower

1 dropeout
Jul 18 2006 09:38:47:457AM1060718004J. Randall Wilson400 ms pulse

reflection much lower

no dropouts 275 kW injected ~0.25 V drop
Jul 18 2006 09:54:59:460AM1060718005J. Randall Wilsonraise power

many trips

low density
Jul 18 2006 10:08:25:940AM1060718005J. Randall Wilsongood 340 kW

larger voltage drop
Jul 18 2006 10:31:28:633AM1060718007J. Randall Wilsongood 500 kW

larger voltage drop ~0.3 V
Jul 18 2006 10:45:23:280AM1060718008J. Randall Wilsongood 600 kW net 100 kW per klystron new record 1 trip early

larger voltage drop ~0.4 V
Jul 18 2006 11:55:24:587AM1060718009J. Randall Wilsonchange phase to 60 pure

good pulse at 350 kW nice ECE
Jul 18 2006 12:09:57:373PM1060718010J. Randall Wilsonraise power

ratty discharge after 0.83 s

Physics Operator Comments
Jul 18 2006 08:03:00:670AM1060718001Ron ParkerGood morning. We'll start Ohmic shots to warm up the machine while the LH system is tuned up.

Cell access for LH system at 8:00
Jul 18 2006 08:38:44:887AM1060718001Ron ParkerShot 1 ran OK, but LH fired on only 1 of 6 programmed pulses.
Jul 18 2006 08:50:11:763AM1060718002Ron ParkerShot 2 ran after an ugly startup.
Jul 18 2006 08:57:04:813AM1060718002Ron ParkerCell access to move coupler in to 1600 from 1625. Brian's position was at 3.5 mm, new position should be 1 mm behind LH limiter.
Jul 18 2006 09:30:06:450AM1060718003Ron ParkerShot 3 ran, with late startup. Bz is too negative, will raise IC_EF4U current from 1325 to 1300 A. LH pulse had one dropput, apparently due to arc before intermediate coupler.
Jul 18 2006 09:44:44:473AM1060718004Ron ParkerShot 4 ran well, now we'll start bringing LH power up. Loop voltage ~0.2 V at ~ 275 kW.
Jul 18 2006 10:04:37:400AM1060718005Ron ParkerShot 5 ran, but density was too low causing LH to trip (WG 13 reflected power) despite multiple retries. Next: Increase density to 4e19 cm-2.
Jul 18 2006 12:24:59:223PM1060718006Ron ParkerShot 6 ran Ok, pellet at 1.3 s. LH pulse went through after 1 trip at beginning.

LH computer needs to be rebooted, short delay. LH power ~ 340 kW, next increase to ~ 400 kW. Also reduce outer gap by ~ 1 cm.
Jul 18 2006 10:32:25:540AM1060718007Ron ParkerShot 7 ran well, LH power at ~ 480 kW net. Next try for ~600 kW.


Jul 18 2006 10:45:17:623AM1060718008Ron ParkerShot 8 ran well, and LH net power reached 600 kW. One trip in WG 3 but restrike succeeded. Next: Program for 60 deg phase, drop power to ~ 350 kW.
Jul 18 2006 11:22:39:183AM1060718008Ron ParkerThere is a problem with the TF current regulation -- last shot was at ~ 157 kA, not 150 as programmed. There is a delay while the regulator circuitry is inspected.
Jul 18 2006 12:12:46:047PM1060718009Ron ParkerShot 9 ran OK. No problem was found with TF, and it regulated at 150 kA for this shot.
Jul 18 2006 12:24:19:723PM1060718010Ron ParkerShot 10 disrupted, possibly contamination left over from previous disruption. There was about 150 ms of usable data for LH at ~ 80 kW/klystron. Need to repeat for next LH run.
Jul 18 2006 01:13:57:053PM1060718010Steve Wolfe
After shot #10 (final shot of the day) it was noted that
the shots from today used PCS setup from 1060511 before the 
flux loop F11 failure (see PO_SUMMARY), without recalculation 
of the magnetics predictors. Fortunately, the F11
loop seems not to have failed during the day, at least in an 
obvious way. However, these shots should not be used. 

After the run, I did a LOAD_INTO_MODEL from 1060707031, the 
last shot from previous operation. That should prevent accidental 
reuse of the startup tomorrow. I'll also notify tomorrow's physop.

Engineering Operator Comments
ShotTimeTypeStatusComment
108:24:48:817AMPlasmaOk
208:37:59:823AMPlasmaOk
309:14:08:540AMPlasmaOk
409:31:54:157AMPlasmaOk
509:48:50:973AMPlasmaOk
610:03:46:420AMPlasmaOk
710:19:48:910AMPlasmaOk
810:36:08:823AMPlasmaOk
911:50:24:180AMPlasmaOk
1012:04:32:387PMPlasmaOk