Alcator C-Mod Run 1050428 Information

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Miniproposals
Miniproposal:410
Date Filed: 1/19/2005
Title:Extension of pedestal scalings
First Author:Jerry Hughes
Session Leader:Jerry Hughes (shots 1-34)

Operators
Session leader(s):Jerry Hughes
Physics operator(s):Bill Rowan
Engineering operator(s):Bill Cochran,Bill Byford,Gary Dekow

Engineering Operator Run Comment
MP#410, Day 1

Session Leader Plans
Entered: Apr 27 2005 01:01:14:927PM
Author: Jerry Hughes
Session Leader plan for 1050428 (MP410, Day 1)

This run will collect edge profile data over a range of Bt, Ip, with
RF power varied during each shot. We are looking to get multiple L-H
transitions, with good H-modes, in a given discharge. We will evaluate
pedestal parameters in both EDA and ELM-free plasmas (and ELMy if we
get them), including the tranisent phase of inital H-mode development.

A. Begin by loading 1050426022 (Bt=5.4 T, Ip=1.05MA).
RF request: flat 2MW from 0.6-0.8s
flat 3MW from 0.9-1.1s
flat 4MW from 1.2-1.4s
B. Run a series of shots using same RF scheme, but with different Ip,
Bt. Adjust target nl04 and RF power levels as needed.
~2 shots: 5.4T, 0.9MA (q95~4.3)
~2 shots: 5.4T, 1.2MA (q95~3.2)
~2 shots: 5.4T, 0.6MA (q95~6.4)
~2 shots: 5.4T, 0.4MA (q95~9.6)
~2 shots: 4.4T, 0.9MA (q95~3.5)
~2 shots: 4.4T, 0.6MA (q95~5.2)
~2 shots: 4.4T, 0.4MA (q95~7.8)
~2 shots: 6.2T, 1.2MA (q95~3.7)
~2 shots: 6.2T, 1.5MA (q95~2.9)
~2 shots: 6.2T, 0.9MA (q95~4.9)
~2 shots: 6.2T, 0.6MA (q95~7.3)
Then, if we're feeling good:
~2 shots: 5.4T, 1.5MA (q95~2.6)
~2 shots: 4.4T, 1.2MA (q95~2.6)
~2 shots: 6.2T, 1.8MA (q95~2.4)

SL reserves the right to play with these exact parameters and the
ordering of shots. D2 puffing may be requested during H-mode, to
evaluate its effect on pedestals/confinement.

Essential diagnostics: Thomson, GPC, TCI, bolometry, PCI. Will use GPI
camera to image background D-alpha, and will probably want to adjust
gains on the Xybion camera on the fly.


Physics Operators Plans
Entered: Apr 27 2005 03:54:10:333PM
Author: Bill Rowan
Engineering setup for Thursday, 28 Apr 2005

MP#410 Extension of pedestal scalings

Session leader: Jerry Hughes
Physics operator: Bill Rowan

ECDC in D2 at 2e-4 Torr overnight at 60 C

Run begins at 09:00 and ends at 17:00.

We will start with a standard fiducial (1050427003) with 2 MW of rf
The gatevalves should be setup to toggle closed --- bypass at 160 clicks

A-coil configuration: normal [+Dtop -Dbot -Jtop +Jbot] and enabled.

Gas Setup:
fill B-Top with 6 psi D2 Hybrid enabled (PG4)
fill B-side lower with 2 psi Ar Hybrid disabled (PG1)
leave B-side upper with whatever Hybrid disabled
fill B-main (C-side) with 40 psi D2 Hybrid enabled (PG3)

fill NINJA with 10 psi D2 but leave disabled

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

ICRF Setup: All transmitters in run on at 8:30

***************************************
Starting around 05:00 lower hybrid conditioning is planned before the
run. This activity should stop at 08:00 and ECDC should be started
and run for 30 minutes.
***************************************

Session Leader Summaries
Entered: Apr 28 2005 06:03:53:843PM
Author: Jerry Hughes
Summary of run 1050428. MP410: Extension of pedestal scalings
SL: J. Hughes
PO: W. Rowan

This run was in support of MP410, which explores the scalings of
pedestal parameters in various H-mode regimes, particulary during the
evolving phase immediately following the L-H transition. H-modes were
triggered multiple times in a given discharge, with current and
toroidal field varied between discharges throughout the day. The
nominal fields sought were 4.4, 5.4, and 6.2T, with currents ranging
from 0.4 to 1.5MA (or even higher). The target density was scaled
proportionally with current, such that the Greenwald density in L-mode
was comparable on each shot. Square pulses of RF at power levels
varying from 2 to 5MW were dialed up on most shot. We were looking for
good T_e and n_e pedestal data from edge Thomson scattering at 60Hz
supplemented by the scanning A-port probe. Background D-alpha was also
sought from the GPI camera, for neutral profile analysis.

After an initial fizzle, we had several successful discharges. Shots
2,3 had essentially the same plasma parameters and shape that
has been run earlier this week for performance evaluation. Shot 2 used
the RF square pulses called for in the MP, while shot 3 used the
fiducial RF waveforms. The paramater scan began on shot 4. Good data
were obtained in 600kA discharges at the three target values of Bt
(7,10,11,14--18). There is no obvious trend in pedestal parameters
with Bt at this current, but John Rice was watching the rotation, and
observed more counter-current V_phi at lower fields. This trend is
opposite that observed at 800kA.

A foray into the nether regions of current resulted in two shots
(19,20) at 400kA, 4.4T. Densities were very low, and impurities
became a problem on the lower Ip shots. Though RF behaved admirably,
the plasmas were of poor quality. The 400kA shots had high Zeff, high
H/D fraction, and underwent sawtooth suppression, resulting in very
low central temperatures after RF turn-off. J. Rice reported large
quantities of Mo as the run went into the afternoon.

We were plagued with a number of duds and a fizzle throughout the
day, which slowed us down. But by late afternoon, we were able to
proceed to the higher currents called out in the run plan. Zeff was
lower, and H/D came back down to below 5%. The field scans at 0.9MA
(4,22,26,27) and at 1.2MA (28--33) were accomplished; there were no
obvious pedestal trends as a function of Bt, but this will be examined
more carefully. Pedestal density scaled linearly with Ip, as before,
though the absolute density levels, as with the prior runs of this
campaign, were generally higher than the previous scaling work would
predict. Most H-modes were short and brutish. Steady EDAs were
hard to come by, though higher q and lower n_e helps. A wealth of data
was acquired, and will require a great deal of detailed analysis.

There were some notable faulty shots. Shot 5 had no Thomson data due
to a laser failure. Shot 6 detatched badly and disrupted, because,
upon dropping I_p from 0.9 to 0.6MA, we neglected to lower target
density accordingly. We disrupted shot 34 at 1.5MA before any H-modes
were obtained. There were fizzles on shots 1,25, and shots
8,9,12,13,21,23,24 were duds. The ASP finished burning out around
shot 14, unfortunately. The Xybion camera got good data, and RF
performed well, though it had the expected trouble coupling at
parameter combinations outside our usual range. Ultimately, the
points obtained in the Ip-Bt scan were:
4.4 T @ 0.4, 0.6, 0.9 MA
5.4 T @ 0.6, 0.9, 1.2 MA
6.2 T @ 0.6, 0.9, 1.2 MA
These were most of the points requested for Day 1 of MP410.

Many thanks to PO Rowan and EO Dekow; RF operators Wukitch and Y. Lin;
and Biewer, Hubbard, LaBombard, Terry, L. Lin and Edlund for manning
their diagnostics!

Tabular Summary:
Shot Bt Ip Comment
001 Fizzle
002 5.4 1.05 Good
003 5.4 1.05 Good, fiducial.
004 5.4 0.9 Good
005 5.4 0.9 No TS
006 5.4 0.6 Detatchment
007 5.4 0.6 Good
008 Dud
009 Dud
010 5.4 0.6 Good, but disrupted.
011 5.4 0.6 Good
012 Dud
013 Dud
014 4.4 0.6 Good, GPI saturates at beginning of 2nd RF pulse
015 4.4 0.6 Good, GPI saturates at beginning of 2nd RF pulse
016 4.4 0.6 Good, GPI saturates at beginning of 2nd RF pulse
017 6.2 0.6 Good
018 6.2 0.6 Good, Marr put in D2 at ~1s
019 4.4 0.4 Good
020 4.4 0.4 Good
021 Dud
022 5.4 0.9 Good
023 Dud
024 Dud
025 Fizzle
026 6.2 0.9 Good
027 4.4 0.9 Good
028 5.4 1.2 Good, but needs more power
029 5.4 1.2 Good
030 5.4 1.2 Good
031 6.2 1.2 Good
032 6.2 1.2 Good
033 6.2 1.2 Good
034 6.2 1.5 Disrupted in L-mode

Physics Operator Summaries
Entered: Apr 29 2005 09:52:24:837AM
Author: Bill Rowan
Physop Report for Run 1050428. April 28, 2005.

MP#410 Extension of pedestal scalings

Session leader: Jerry Hughes
Physics operator: Bill Rowan

Results
Generally, the machine ran well. It was easy to transition to H-mode.
There were several duds during the run. For these, the pressures and breakdown
fields looked okay. Raising and lowering the pressure did not have
a lasting impact. ECDC-between-shots worked once but not the second time.
There were no further duds after a small change in BR_0 for shot 026.

The low current shot 011 required a change in the lower x-point to avoid exposing
the floor of the divertor to high heat flux.

The fiducial is not the first shot but shot 003.


Score Card
Plasmas 25 002,003(fiducial),004,005,006(Disrupted@1s),007,
010(Disruption@1s),011,014,015,016,017,018,019,
020,022,026,027,028,029,030,031,032,033,034(disruption@0.8s)
Fizzles 2 001,025
Duds 6 008,009,012,013,021,023,024
Total 34

Session Leader Comments
Apr 28 2005 09:02:05:870AM1050428001Jerry HughesFizzle
Apr 28 2005 09:24:18:650AM1050428002Jerry HughesThis shot was supposed to be a fiducial, but we got my RF waveform instead.
No H-mode at 2MW, 2 H-modes, at 3 and 4MW. Looks rather ELM-free.
Apr 28 2005 09:51:27:667AM1050428003Jerry HughesThis was the fiducial. Some H-modes during RF ramp and plateau. Looks like some QC mode is showing its
face.
Next shot: 0.9MA, 5.4T
Apr 28 2005 10:04:00:700AM1050428004Jerry Hughes0.9MA 5.4T.
Got H-modes on all 3 RF pulses. Some faulting on RF.
Positive ID of QC mode from Liang Lin.
Next shot: lengthen RF pulses somewhat.
Apr 28 2005 10:18:59:963AM1050428005Jerry Hughes0.9MA 5.4T.
Shot was good. No TS data, unfortunately. Need to keep moving.
Next shot: 0.6MA, 5.4T, same RF
Apr 28 2005 10:26:12:103AM1050428006Jerry Hughes0.6MA 5.4T.
Forgot to lower target density. Detatchment at 0.57s. Eventual disruption.
Next shot: lower target density to 6e19.
Apr 28 2005 10:47:19:510AM1050428007Jerry Hughes0.6MA 5.4T.
A good shot. 3 H-modes, but RF is lower than requested.
Next shot: Repeat.
Apr 28 2005 10:57:13:290AM1050428008Jerry HughesDud
Apr 28 2005 11:22:33:807AM1050428009Jerry HughesDud
Apr 28 2005 11:28:46:463AM1050428010Jerry HughesIp=0.6, Bt=5.4
This shot started out well, but disrupted around 1.01s. Looks like outer strike point
could be culprit. PO is changing the X-point location for next shot.
Apr 28 2005 11:42:30:213AM1050428011Jerry HughesIp=0.6, Bt=5.4
That's a good one. 3 H-modes at different powers. Last one a little ratty.
Pedestal data look good. GPI and PCI look good. QC mode is there.
Next shot: Go to 4.4T
Apr 28 2005 12:01:13:480PM1050428012Jerry HughesDud
Apr 28 2005 12:23:26:073PM1050428013Jerry HughesDud
Apr 28 2005 12:40:30:433PM1050428014Jerry HughesIp=0.6MA, Bt=4.4T
A successful shot. H-modes on 2nd and 3rd RF pulses. 1st pulse gives density rise,
but not clearly an H-mode, judging by pedestals.
Next shot: repeat
Apr 28 2005 12:40:58:760PM1050428015Jerry HughesIp=0.6MA, Bt=4.4T
Essentially identical to shot 14.
Next shot: Change Bt to 6.2T
Apr 28 2005 12:52:59:713PM1050428016Jerry HughesIp=0.6MA, Bt=4.4T
Was supposed to be 6.2T. Ended up with a shot nearly identical to 14,15.
There is a repeated burst of light on the GPI at around 0.9s on 014--016, when
the second RF pulse starts. Camera saturates, then returns to normal before H-mode
temrinates.
Next shot: Change Bt to 6.2T. We mean it this time.

Apr 28 2005 01:26:04:860PM1050428017Jerry HughesIp=0.6MA, Bt=6.2T
Good. 3 H-modes, somewhat more EDA-ish.
Next shot: Repeat, but Marr will add a D2 puff around 1.05s

Apr 28 2005 01:31:52:923PM1050428018Jerry HughesIp=0.6MA, Bt=6.2T
Very similar to 017.
Next shot: Bt=4.4T,0.4MA, lower target nl to 4e19

Apr 28 2005 01:36:47:330PM1050428019Jerry HughesIp=0.4MA, Bt=4.4T
A few short H-mode, with very low Wp, as expected. Some pedestal data is obtained in H-mode.
Pretty low ne_PED, of course.
Next shot: Repeat. Marr will puff into the third RF pulse, somewhere around t=1.35
Apr 28 2005 01:51:11:080PM1050428020Jerry HughesIp=0.4MA, Bt=4.4T
RF was better. There are some H-mode pedestals on the 3rd pulse, followed by a huge
Te collapse after the H-L. Did Marr's puff help RF coupling?
Next shot: Raise Bt to 5.4T
Apr 28 2005 02:10:37:987PM1050428021Jerry HughesDud.
Quit the low Ip portion and reload shot 4. Use nl04~9e19. This should keep
the L-mode Greenwald ne consistent.
Apr 28 2005 02:32:43:300PM1050428022Jerry HughesIp=0.9MA, Bt=5.4T
Basically a repeat of shot 4, with a slightly lower target. Not especially more radiative,
but the H-modes are shorter. RF has fewer trips. The data are okay.
Next shot: Raise Bt to 6.2T
Apr 28 2005 02:58:45:300PM1050428023Jerry HughesDud
Next shot: Try again.
Apr 28 2005 02:58:54:593PM1050428024Jerry HughesDud
Next shot: Try again.
Apr 28 2005 03:14:38:860PM1050428025Jerry HughesFizzle
Apr 28 2005 03:36:41:080PM1050428026Jerry HughesThere's our plasma.
Ip=0.9MA, Bt=6.24
3 H-modes.
Next shot: Bt-->4.4
Apr 28 2005 03:45:29:987PM1050428027Jerry HughesIp=0.9MA, Bt=4.44
Some transient H-modes on 2nd, 3rd RF pulse.
Next shot: Ip=1.2MA, Bt=5.4T, target nl=1.2e20
Apr 28 2005 03:55:46:690PM1050428028Jerry HughesIp=1.2, Bt=5.4
No RF from D-port. Only 1 H-mode. Want more power.
Next shot: Repeat, with all RF antennas.
Apr 28 2005 04:08:25:907PM1050428029Jerry HughesIp=1.2, Bt=5.4
D worked partially on this shot. More H-modes, more pedestal data. Pretty much the
same as shot 28. Pedestal pressure gradient is large, as expected from high Ip. Te
is not exceptionally high, presumably due to high density.
Next shot: Bt=6.2. Yijun Lin will try to give me a little more Prf.
Apr 28 2005 04:18:32:690PM1050428030Jerry HughesIp=1.2, Bt=5.4
Field change didn't go through, so we got more data at 5.4.
Next shot: Bt=6.2, I hope.
Apr 28 2005 04:34:13:140PM1050428031Jerry HughesIp=1.2, Bt=6.24
All the RF went in. H-modes at 4 and 5MW. Good pedestal data.
Wp relatively low, given the parameters. High Prad.
Next shot: repeat.
Apr 28 2005 04:52:08:453PM1050428032Jerry HughesIp=1.2, Bt=6.24
Ditto last shot.
Next shot: Ip-->1.5MA
Apr 28 2005 04:57:12:550PM1050428033Jerry HughesIp=1.2, Bt=6.24
PCS isn't working as it should. It didn't accept the change to 1.5MA.
Next shot: Ip-->1.5MA
Jun 23 2005 12:07:21:097PM1050428034Jerry HughesHey! There's an H-mode on this shot that I didn't notice before, at 0.79s. RF doesn't stay on long enough to sustain it. But there is one TS pulse at 0.793.

Physics Operator Comments
Apr 28 2005 08:11:39:917AMBill RowanLoad the fiducial shot from 1050427

Load from 1050427036
Load at 28-Apr-2005 08:10:07.00
Open tree /home/rowan -1
Open tree done

Apr 28 2005 08:40:39:057AMBill Rowan
Argon puff, PG1 set to zero
Argon valve disabled

Changed the argon fill on PG1 to 1 psi
John has asked for 60 ms but this will not happen for the fiducial shot

ECDC ran all night
LH conditioning occurred as planned
ECDC was run following the LH conditioning

Apr 28 2005 09:06:25:200AM1050428001Bill Rowan
Fizzle

pressure higher than for the shot that was loaded
reduce the gas from 20 ms to 18 ms
Apr 28 2005 09:18:51:150AM1050428002Bill RowanAttempted the fiducial. The RF was set for the MP and not for the fiducial so will take the fiducial again.

Next shot. Ramped RF for the fiducial.
Apr 28 2005 09:41:59:103AM1050428003Bill RowanPlasma. Successful fiducial.

Next shot.
Open the gatevalve for the rest of the run
0.9 MA
Reduced prefill by 1 ms to 17 ms
Apr 28 2005 09:59:32:040AM1050428004Bill Rowan004. Plasma. 0.9 MA

Next shot. No changes in DPCS
Optimize RF pulses
Apr 28 2005 10:03:24:243AM1050428004Bill Rowan
Enable PG1 (ar). 60 ms at 1 psi
Apr 28 2005 10:14:02:700AM1050428005Bill Rowan
005. Plasma. 0.9 MA

Next shot.
0.6 MA
Apr 28 2005 10:25:14:993AM1050428006Bill Rowan006. Plasma. Disrupted at 1.0s

Next shot
nl_04 reduced to 0.6e+20
Apr 28 2005 10:41:29:400AM1050428007Bill RowanPlasma. 0.6 MA, nl_04=0.7e+20 before h-mode

Next shot
Reduce A-coil to approximately 1000A at the beginning
Reduce the Ar pulse length to 50 ms (PG1)
Apr 28 2005 10:53:17:510AM1050428008Bill Rowan
Dud

Next shot.
Increase the prefill by 2 ms from 17 ms to 19 ms
Apr 28 2005 11:11:55:980AM1050428009Bill Rowan
Dud

Next shot.
Increase the prefill by 2 ms from 19 ms to 21 ms
Apr 28 2005 11:25:28:667AM1050428010Bill Rowan010. Plasma. Disruption at 1 s

Next shot. Move RXL out by 1 cm
Apr 28 2005 11:39:52:620AM1050428011Bill RowanPlasma.

Next shot.
Change TF. Reduce to 4.4 T, TF current = -120777
Apr 28 2005 12:04:53:730PM1050428012Bill Rowan012. Dud

Next shot.
Reduce prefill by 1 ms
Apr 28 2005 12:17:33:603PM1050428013Bill RowanDud


Next shot.
Reduce prefill 1 ms. Moving back toward the pressure
range used for 1050427
Apr 28 2005 12:31:23:777PM1050428014Bill RowanPlasma
BT = 4.5T

Next shot. Repeat
Apr 28 2005 12:40:58:010PM1050428015Bill RowanPlasma

Next shot. BT=6.2T
TF current = -173610


Apr 28 2005 12:43:24:167PM1050428015Bill Rowanreset TF limit to 180


Apr 28 2005 12:50:47:200PM1050428016Bill RowanPlasma
BT = 4.5 T again.

Next shot. reloaded the TF change
Apr 28 2005 01:05:18:987PM1050428017Bill Rowan017. Plasma
BT = 6.2T

Next shot. Repeat
Apr 28 2005 01:22:32:940PM1050428018Bill RowanPlasma

Next shot.
ip = 0.4 MA
BT = 4.4 T
Apr 28 2005 01:24:20:470PM1050428018Bill Rowannl_04=4e+19
Apr 28 2005 01:36:10:953PM1050428019Bill RowanPlasma

Next shot. Repeat
Apr 28 2005 02:08:29:157PM1050428021Bill Rowan
021. Dud

ECDC for 10 minutes before the next shot

Next shot.
Reload seg 3 of shot 1050428004
Reduce nl_04 to 0.9e+20



Apr 28 2005 03:00:46:750PM1050428024Bill Rowan024. Dud

Next shot.
Increase prefill by 3 ms to 21 ms
topped up b-top plenum pressure to 6psi from 5.12 psi
Apr 28 2005 03:15:40:440PM1050428025Bill Rowan
025. Fizzle

Next shot.
Increase the prefill by 1 ms to 22 ms
Decreased BR_0 from -0.0005 to -0.0009
Apr 28 2005 03:26:30:720PM1050428026Bill RowanPlasma

Next shot.
BT = 4.4 T
TF current = -120777
Apr 28 2005 03:40:53:157PM1050428027Bill Rowan027. Plasma

Next shot.
BT = 5.4 T
tf current = -150000
IP = 1.2 MA
Apr 28 2005 03:42:58:843PM1050428027Bill Rowannl_04 = 1.2e+20
Apr 28 2005 03:55:25:470PM1050428028Bill Rowan
028. Plasma

Next shot.
Reduce prefill by 1 ms to 21 ms
Apr 28 2005 04:05:17:237PM1050428029Bill RowanPlasma
1.2 MA
nl_04=1.2e+20


Next shot.
BT = 6.2 T
TF current = -173610
Apr 28 2005 04:16:20:987PM1050428030Bill Rowan030. Plasma
Bt = 5.4 T

Next shot
Reload the TF
Apr 28 2005 04:30:56:830PM1050428031Bill RowanPlasma
BT = 6.2T

Next shot.
Repeat
Apr 28 2005 04:46:43:487PM1050428032Bill RowanPlasma

Next shot.
IP = 1.5 MA
Apr 28 2005 04:56:53:237PM1050428033Bill RowanPlasma

Next shot
nl_04 = 1.3e+20
Apr 28 2005 05:08:19:203PM1050428034Bill Rowan Plasma. disruption

last shot

Engineering Operator Comments
ShotTimeTypeStatusComment
108:59:58:573AMPlasmaOk
209:12:54:683AMPlasmaOk
309:25:44:463AMPlasmaOk
409:48:22:683AMPlasmaOk
510:04:30:103AMPlasmaOk
610:18:25:840AMPlasmaOk
710:33:13:307AMPlasmaOk
810:46:23:433AMPlasmaOk
911:00:51:340AMPlasmaOk
1011:13:37:823AMPlasmaOk
1111:31:24:777AMPlasmaOk
1211:54:16:120AMPlasmaOk
1312:08:24:980PMPlasmaOk
1412:20:55:183PMPlasmaOk
1512:33:35:887PMPlasmaOk
1612:46:11:120PMPlasmaOk
1712:59:05:710PMPlasmaOk
1801:13:00:657PMPlasmaOk
1901:28:45:877PMPlasmaOk
2001:42:06:500PMPlasmaOk
2101:55:59:500PMPlasmaOk
2202:19:04:190PMPlasmaOk
2302:31:46:033PMPlasmaOk
2402:53:36:407PMPlasmaOk
2503:06:28:157PMPlasmaOk
2603:19:04:377PMPlasmaOk
2703:32:50:377PMPlasmaOk
2803:45:32:500PMPlasmaOk
2903:59:22:877PMPlasmaOk
3004:12:42:080PMPlasmaOk
3104:25:13:050PMPlasmaOk
3204:39:42:033PMPlasmaOk
3304:52:14:203PMPlasmaOk
3405:06:06:987PMPlasmaOk