Alcator C-Mod Run 990921 Information

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Miniproposals
Miniproposal:230
Date Filed: 1/15/1999
Title:Effect of Divertor Baffling on Confinement, Thresholds
First Author:Spencer Pitcher
Session Leader:Spencer Pitcher (shots 1-25)

Operators
Session leader(s):Spencer Pitcher
Physics operator(s):Dmitri Mossessian
Engineering operator(s):Frank Silva

Engineering Operator Run Comment
MP#230/Mossessian, Silva

Session Leader Plans

Physics Operators Plans

Session Leader Summaries
Entered: Jul 7 2004 03:49:21:460PM
Author: To Be Determined

MP 230: The Effect of Divertor Baffling on H-mode Power Threshold

Plan:

We will use standard 0.8 MA, 5.4 T discharges with a variety of
target plasma densities (nl04 = 0.7 to 1.4) to investigate
the H-mode power threshold. RF heating will be programmed to give
slow linear ramps. Identical discharges will be run, first with
flaps closed for the entire discharge and then a comparison
discharge with flaps open. Trace amounts of argon and helium
will be used to investigate divertor screening.

Summary:

The machine ran very well. RF also ran quite well, after spending
a shot or two at new densities to tune..good RF ramps generally
attained. The flappers appear to have no measurable effect on
the H-mode threshold (within an error of around 10%). Identical
discharges were run with and without the flapper. As usual,
with flapper open at moderate to high density, the divertor
neutral pressure is reduced by a factor of ~ 2, with no measurable
effect on the midplane pressure. The results cannot address
whether main chamber neutrals affect confinement.

---------------------------------------------------------------------

The best shot comparisons are:

nl04 shot shot (flaps open)

0.7 20,22 21
0.9 4 5
1.1 9 10
1.4 16 15

During the day the flapper power supply got progressively
sicker, so that for shots 24, 25 it is unclear to what
degree the flaps were open. Detailed analysis of the flapper
waveforms could possibly determine this.

Detailed shot summary below.

---------------------------------------------------------------------


***shot 2
flaps closed
nl04 = 0.94, good RF ramp, good EDA
Pthr = 0.92 MW

***shot 3
repeat, flaps closed, RF tuning changed a little
nl04 = 0.96, good RF ramp, good EDA
Pthr = 1.03 MW

***shot 4
repeat, flaps forced closed, RF tuning not touched
chromex 6678 (reasonable signal), helium thru AB limiter

nl04 = 0.92, good RF ramp, good EDA
Pthr = 1.03 MW

***shot 5
repeat, flaps open, RF tuning not touched
chromex 6678 (increase slit), helium thru AB limiter

nl04 = 0.94, good RF ramp, good EDA
Pthr = 1.03 MW......no measurable effect of flapper on threshold

***shot 6
repeat, flaps closed, RF tuning not touched
chromex 6678, helium thru AB limiter

RF finger problem!...not a good ramp, lower power

***shot 7
repeat, flaps closed, RF tuning not touched

RF problems...not a very good ramp.
Discharge is a nice example of hysteresis....ie raise
power over threshold and then drop power below and it
stays in EDA H-mode.

***shot 8
raise density, nl04 = 1.1, reduce right gap, flaps closed
not bad RF ramp....will try to improve for next shot

***shot 9
repeat, flaps closed

***shot 10
repeat, flaps open

***shot 11
raise density, nl04 = 1.4, flaps open
RF ramp ok, no H-mode, right gap increasing during shot

next shot....fix right gap, increase power, change RF tuning

***shot 12
flaps open, brief ELM-free H-mode, Pthr = 1.04 MW

***shot 13
flaps closed, good RF ramp, no H-mode!

***shot 14
repeat, flaps open, drop density to nl04 = 1.3
no plasma

***shot 15
repeat, flaps open
Pthr = 1.4 MW, nl04 = 1.4
good RF ramp

***shot 16
repeat, flaps closed

***shot 17,18
no plasma

pause to take ninja test shot # = 2129

***shot 19
flaps closed, drop density to nl04 = 0.7

RF ramp not that good, Pthr = 1.2 MW, nel04 = 0.84

***shot 20
flaps closed, Pthr = 0.96 MW, nl04 = 0.8

***shot 21
flaps open, Pthr = 0.72 MW, nl04 = 0.77

***shot 22
flaps closed, Pthr = 0.9 MW, nl04 = 0.72
kaiser helium to inner wall

end of threshold study

***shot 23
long, steady RF pulse...got 3 EDA periods
flapper open

***shot 24
tune up RF, very long steady-state EDA...very nice
flapper open

***shot 25
repeat
flapper starts open and closes quickly at t = 1.1 s
(flappers take 32 ms to close)
flapper power supply appears to be drooping










Physics Operator Summaries
Entered: Jul 7 2004 04:37:09:333PM
Author: To Be Determined
Physics operator summary for run 990921:

______________________________

Run Plan for 990921:

SL: S.PItcher
PO: D.Mossessian

Setup Power Supplies from Shot 990920003

Two Hours of ECDC in D2 prior to run.

Gas setup: Fill B-Top with 6 psi D2, Hybrid Enabled
Fill B-side lower with 1 psi Ar, Hybrid Enabled
Fill B-side upper with 6 psi H2, Hybrid DISABLED
Fill C-Side with 30 psi D2, Hybrid Enabled
J-Bottom as is, Hybrid DISABLED

ECE and VUV valves enabled, if no vacuum problems

Run plan:

Run in support of MP#230 Flapper Effect on Thresh.

_____________________________________________


Summary:

Our "toroidal chamber with magnetic windings" ran very well today.
First shot was OH and B_side_upper gas tests - all went OK.
Then out of 24 shots there was 2 fizzles, first (990921014) was probably because of
the previous shot disruption, second (990921018) was for unknown reason. There was a problem with
TCI nl_04 on shot 14. On shot 990921017 there was a CAMAC initialization problem.

Scorecard:

25 shots
2 fizzles
0 duds
1 test

______________________________________________________
990921001 OH test and B_side_upper test.
Pulse gas 2 programmed for 50 msec pulse at .6 sec
OH's OK.

For next shot: Load 990915003, .8 MA, 5.4 T, no ECE sweep, n0=0.9e20

990921002 Good shot.
RF ramps up to 2 MW. EDA from .75 to 1.45 interrupted by an injection at 1.28.

For next shot: Extend TF current flattop to 1.5 sec.

990921003 Good shot.
RF ramps up to 2 MW. EDA from .8 to 1.5.

For next shot: No PCS changes.

990921004 Good shot.
RF ramps up to 2 MW. EDA from .8 to 1.5.

For next shot: No PCS changes.

990921005 Good shot.
RF ramps up to 2 MW. EDA from .8 to 1.5.

For next shot: No PCS changes.

990921006 Good shot. Two very small H-modes

For next shot: No PCS changes.

990921007 Good shot.
EDA from .8 to 1.5 sec. E port RF has problems.

For next shot: Set target density to 1.1e20
Changed RCUR in attempt to hold right gap at 1 cm rom .5 sec

990921008 Plasma. EDA from .8 to 1.5 sec with large injection at 1.3 sec.
RF E and D ramp up to 2 MW.

For next shot: No changes

990921009 Plasma. Long EDA. RF ramps up to 2MW and then J-port adds another noisy .5 MW.
Right gap constant at 1 cm from .5 to 1.2 sec.

For next shot: no changes

990921010 Plasma. Long EDA.

For next shot: set target density to 1.4e20. Increased pulse_gas_3

990921011 Plasma. Density 1.5e20. RF ramps up to 1.6 MW, no H mode.
Right gap is moving up from 1 cm to 1.5 cm.

For next shot: Program rampdown of the right gap trying to keep
it at 1 cm.

990921012 Plasma. RF ramps to 1 MW. ELM-free H mode from .8 to 1 sec.

For next shot: no changes

990921013 Plasma. Density 1.4e20. Disrupted at 1.2 sec - large injection.
RF ramps to 2 MW. No H mode.

For next shot: drop density to 1.3e20

990921014 Fizzle. No TCI signal.

For next shot: no changes

990921015 Plasma. EDA H mode from .9 to 1.5. RF ramps up to 2.3 MW

For nex shot: no change.

990921016 Plasma. EDA H mode from .9 to 1.5. RF ramps up to 2.3 MW

For nex shot: set density to 0.7e20. Reduce gas a little.

990921017 Camac initialization problem. Returned to RECOOL from INIT.
Do "no power" shot.

990921018 Fizzle. Bz looks a little high.

For next shot: Drop EF4 current by 15 A.

990921019 Plasma. Density .8e20. E port RF faults, but D and J ramp up to 2 MW.
ELM-free H mode from .84 to 1 sec, EDA from 1.2 to 1.5 sec.

For nesxt shot: no changes

990921020 Plasma. Multiple ELM free H modes

For nesxt shot: no changes

990921021 Plasma. Density .8e20. Multiple ELM free H modes

For nesxt shot: no changes

990921022 Plasma. Density .8e20. Multiple ELM free H modes

For nesxt shot: set density to 1.0e20, adjusted RCUR for right gap.

990921023 Plasma. Density didn't quite get to 1.e20.
Two ELM free H modes and one EDA.
RF at 1 MW. Right gap constant at 1 cm.

For nesxt shot: change nl_04 and gas puff a little to get target density.

990921024 Plasma. Density 1.e20 at .5 sec. Then steady state EDA for 1 sec.
RF const at 2 MW.

For next shot: no changes

990921025 Plasma. Steady state EDA from .5 to 1.5 sec.

Session Leader Comments
Sep 21 1999 09:22:43:090AM990921002Spencer Pitcherflaps closed
nl04 = 0.94, good RF ramp, good EDA
Pthr = 0.92 MW
Sep 21 1999 09:37:11:623AM990921003Spencer Pitcherrepeat, flaps closed, RF tuning changed a little
nl04 = 0.96, good RF ramp, good EDA
Pthr = 1.03 MW
Sep 21 1999 09:54:02:373AM990921004Spencer Pitcherrepeat, flaps forced closed, RF tuning not touched
chromex 6678 (reasonable signal), helium thru AB limiter

nl04 = 0.92, good RF ramp, good EDA
Pthr = 1.03 MW
Sep 21 1999 10:11:34:983AM990921005Spencer Pitcherrepeat, flaps open, RF tuning not touched
chromex 6678 (increase slit), helium thru AB limiter

nl04 = 0.94, good RF ramp, good EDA
Pthr = 1.03 MW......no measurable effect of flapper on threshold
Sep 21 1999 10:27:14:187AM990921006Spencer Pitcherrepeat, flaps closed, RF tuning not touched
chromex 6678, helium thru AB limiter

RF finger problem!...not a good ramp, lower power
Sep 21 1999 11:10:40:187AM990921007Spencer Pitcherrepeat, flaps closed, RF tuning not touched

RF problems...not a very good ramp.
Discharge is a nice example of hysteresis....ie raise
power over threshold and then drop power below and it
stays in EDA H-mode.
Sep 21 1999 11:11:34:840AM990921008Spencer Pitcherraise density, nl04 = 1.1, reduce right gap, flaps closed
not bad RF ramp....will try to improve for next shot
Sep 21 1999 11:21:37:403AM990921009Spencer Pitcherrepeat, flaps closed
Sep 21 1999 12:10:17:920PM990921010Spencer Pitcherrepeat, flaps open
Sep 21 1999 12:13:16:530PM990921011Spencer Pitcherraise density, nl04 = 1.4, flaps open
RF ramp ok, no H-mode, right gap increasing during shot

next shot....fix right gap, increase power, change RF tuning
Sep 21 1999 01:52:56:170PM990921012Spencer Pitcherflaps open, brief ELM-free H-mode, Pthr = 1.04 MW
Sep 21 1999 01:53:31:733PM990921013Spencer Pitcherflaps closed, good RF ramp, no H-mode!
Sep 21 1999 01:53:56:000PM990921014Spencer Pitcherrepeat, flaps open, drop density to nl04 = 1.3
no plasma
Sep 21 1999 01:54:27:170PM990921015Spencer Pitcherrepeat, flaps open
Pthr = 1.4 MW, nl04 = 1.4
good RF ramp
Sep 21 1999 03:18:50:500PM990921016Spencer Pitcherrepeat, flaps closed
Sep 21 1999 03:19:13:983PM990921017Spencer Pitcherno plasma
Sep 21 1999 03:20:00:967PM990921018Spencer Pitcherno plasma

pause to take ninja test shot # = 2129
Sep 21 1999 03:48:52:090PM990921019Spencer Pitcherflaps closed, drop density to nl04 = 0.7

RF ramp not that good, Pthr = 1.2 MW, nel04 = 0.84
Sep 21 1999 03:49:28:297PM990921020Spencer Pitcherflaps closed, Pthr = 0.96 MW, nl04 = 0.8
Sep 21 1999 04:15:39:140PM990921021Spencer Pitcherflaps open, Pthr = 0.72 MW, nl04 = 0.77
Sep 21 1999 04:23:43:890PM990921022Spencer Pitcherflaps closed, Pthr = 0.9 MW, nl04 = 0.72
kaiser helium to inner wall

end of threshold study
Sep 21 1999 06:31:01:327PM990921023Spencer Pitcherlong, steady RF pulse...got 3 EDA periods
flapper open
Sep 21 1999 06:31:20:030PM990921024Spencer Pitchertune up RF, very long steady-state EDA...very nice
flapper open
Sep 21 1999 06:31:52:090PM990921025Spencer Pitcherrepeat
flapper starts open and closes quickly at t = 1.1 s
(flappers take 32 ms to close)
flapper power supply appears to be drooping

Physics Operator Comments
Sep 21 1999 08:57:59:840AMDmitri MossessianRun Plan for 990921:

SL: S.PItcher
PO: D.Mossessian

Setup Power Supplies from Shot 990920003

Two Hours of ECDC in D2 prior to run.

Gas setup: Fill B-Top with 6 psi D2, Hybrid Enabled
Fill B-side lower with 1 psi Ar, Hybrid Enabled
Fill B-side upper with 6 psi H2, Hybrid DISABLED
Fill C-Side with 30 psi D2, Hybrid Enabled
J-Bottom as is, Hybrid DISABLED

ECE and VUV valves enabled, if no vacuum problem.

________________________

MP 230: The Effect of Divertor Baffling on H-mode Power Threshold

We will use standard 1 MA, 5.4 T discharges with a variety of
target plasma densities (nl04 = 0.6 to 2.0) to investigate
the H-mode power threshold. RF heating will be programmed to give
slow linear ramps. Identical discharges will be run, first with
flaps closed for the entire discharge and then a comparison
discharge with flaps open. Trace amounts of argon and helium
will be used to investigate divertor screening.

____________________________________


Load PCFS from 990920019, 1MA, 5.4 T (with ECE sweep at 1sec), n0=1.0e20

_________________________________________

Cold start OK. Load clean.

Sep 21 1999 09:04:36:983AM990921001Dmitri MossessianOH test and B_side_upper test. Pulse gas 2 programmed for 50 msec pulse
at .6 sec

OH's OK.

For next shot Session leader requested shot 990915003 to be loaded.

Load 990915003, .8 MA, 5.4 T, no ECE sweep, n0=0.9e20
Sep 21 1999 09:18:40:263AM990921002Dmitri MossessianGood shot.

RF ramps up to 2 MW. EDA from .75 to 1.45 interrupted by an injection at 1.28.

For next shot: Extend TF current flattop to 1.5 sec.
Sep 21 1999 09:32:53:060AM990921003Dmitri MossessianGood shot.

RF ramps up to 2 MW. EDA from .8 to 1.5.

For next shot: No PCS changes.
Sep 21 1999 09:51:54:937AM990921004Dmitri MossessianGood shot.

RF ramps up to 2 MW. EDA from .8 to 1.5.

For next shot: No PCS changes.
Sep 21 1999 10:17:05:513AM990921005Dmitri MossessianGood shot.

RF ramps up to 2 MW. EDA from .8 to 1.5.

For next shot: No PCS changes.
Sep 21 1999 10:28:04:827AM990921006Dmitri MossessianGood shot.

RF fault.

For next shot: No PCS changes.
Sep 21 1999 10:41:58:653AM990921007Dmitri MossessianGood shot.

EDA from .8 to 1.5 sec E port RF has problems.

For next shot: Set target density to 1.1e20
Sep 21 1999 11:03:25:937AM990921008Dmitri MossessianBefore shot 8: Changed RCUR in attempt to hold right gap at 1 cm rom .5 sec

Plasma. EDA from .8 to 1.5 sec with large injection at 1.3 sec.
RF E and D ramp up to 2 MW.

For next shot: No changes
Sep 21 1999 11:24:18:170AM990921009Dmitri MossessianPlasma. Long EDA. RF ramps up to 2MW and then J-port adds another noisy .5 MW.
Right gap constant at 1 cm from .5 to 1.2 sec.

For next shot: no changes
Sep 21 1999 11:58:21:733AM990921010Dmitri MossessianPlasma. Long EDA.

For next shot: set target density to 1.4e20. Increased pulse_gas_3
Sep 21 1999 12:10:25:687PM990921011Dmitri MossessianPlasma. DEnsity 1.5e20. RF ramps up to 1.6 MW, no H mode.
Right gap is moving up from 1 cm to 1.5 cm.

For next shot: Program rampdown of the right gap trying to keep
it at 1 cm.
Sep 21 1999 12:25:17:967PM990921012Dmitri MossessianPlasma. RF ramps to 1 MW. ELM-free H mode from .8 to 1 sec.

For next shot: no changes
Sep 21 1999 12:49:29:810PM990921013Dmitri MossessianPlasma. Density 1.4e20. Disrupted at 1.2 sec - large injection.
RF ramps to 2 MW. No H mode.

For next shot: drop density to 1.3e20
Sep 21 1999 01:50:27:090PM990921014Dmitri MossessianFizzle. No TCI signal.
Sep 21 1999 01:51:36:217PM990921015Dmitri MossessianNo PCS changes was made for this shot.

Plasma. EDA H mode from .9 to 1.5. RF ramps up to 2.3 MW

For nex shot: no change.
Sep 21 1999 02:09:52:810PM990921016Dmitri MossessianPlasma. EDA H mode from .9 to 1.5. RF ramps up to 2.3 MW

For nex shot: set density to 0.7e20. Reduce gas a little.
Sep 21 1999 02:44:33:890PM990921017Dmitri MossessianCamac initialization problem. Returned yo RECOOL from INIT.

Do "no power" shot.
Sep 21 1999 02:47:14:780PM990921018Dmitri MossessianFizzle. Bz looks a little high.

For next shot: Drop EF4 current by 15 A.
Sep 21 1999 03:28:29:497PM990921019Dmitri MossessianPlasma. Density .8e20.
E port RF faults, but D and J ramp up to 2 MW.
ELM-free H mode from .84 to 1 sec, EDA from 1.2 to 1.5 sec.

For nesxt shot: no changes
Sep 21 1999 03:46:14:590PM990921020Dmitri MossessianPlasma. Density .8e20.
Multiple ELM free H modes

For nesxt shot: no changes
Sep 21 1999 03:56:25:670PM990921021Dmitri MossessianPlasma. Density .8e20.
Multiple ELM free H modes

For nesxt shot: no changes
Sep 21 1999 04:17:39:123PM990921022Dmitri MossessianPlasma. Density .8e20.
Multiple ELM free H modes

For nesxt shot: set density to 1.0e20, adjusted RCUR for right gap.
Sep 21 1999 04:38:45:577PM990921023Dmitri MossessianPlasma. Density didn't quite get to 1.e20.
Two ELM free H modes and one EDA.
RF stays at 1 MW. Right gap constant at 1 cm.

For nesxt shot: change nl_04 and gas puff a little to get target density.

Sep 21 1999 04:50:07:420PM990921024Dmitri MossessianPlasma. Density 1.e20 at .5 sec. Then steady state EDA for 1 sec.
RF const at 2 MW.

For next shot: no changes

Sep 21 1999 05:15:15:373PM990921025Dmitri MossessianPLasma. Steady state EDA from .5 to 1.5 sec.

Engineering Operator Comments
ShotTimeTypeStatusComment
108:57:35:170AMTestOkOH1, OH2u,l ok, no pulse B side upper
209:07:23:297AMPlasmaOkno faults/plasma
309:25:29:450AMPlasmaOkno faults/plasma
409:42:25:797AMPlasmaOk(null)
509:59:31:153AMPlasmaOkno faults/plasma
610:18:22:123AMPlasmaOkno faults/plasma
710:34:20:310AMPlasmaOkno faults/plasma
810:54:39:750AMPlasmaOk(null)
911:10:39:640AMPlasmaOk(null)
1011:29:15:357AMPlasmaOk(null)
1111:58:38:390AMPlasmaOk(null)
1212:15:11:170PMPlasmaOk(null)
1312:34:52:857PMPlasmaOk(null)
1412:53:55:750PMPlasmaOk(null)
1501:42:09:950PMPlasmaOk(null)
1601:58:30:560PMPlasmaOk(null)
1702:16:16:717PMPlasmaOk(null)
1802:38:17:107PMPlasmaOk(null)
1903:12:26:623PMPlasmaOk(null)
2003:28:21:030PMPlasmaOk(null)
2103:47:14:827PMPlasmaOk(null)
2204:08:41:780PMPlasmaOk(null)
2304:25:12:263PMPlasmaOk(null)
2404:43:28:653PMPlasmaOk(null)
2505:02:12:590PMPlasmaOk(null)