Alcator C-Mod Run 950215 Information

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Miniproposals
Miniproposal:077a
Date Filed: 2/2/1995
Title:ICRF Heating in L-mode Plasmas
First Author:Yuichi Takase
Session Leader:Yuichi Takase (shots 1-30)

Operators
Session leader(s):Yuichi Takase
Physics operator(s):Steve Horne
Engineering operator(s):Frank Silva,Joe Daigle

Engineering Operator Run Comment
ICRF Takase/Horne/Silva Daigle

Session Leader Plans

Physics Operators Plans

Session Leader Summaries
Entered: Jul 7 2004 03:49:12:257PM
Author: To Be Determined
MP077A ICRF Heating in L-Mode Plasmas
SL: Takase
PO: Horne
EO: Silva/Daigle

Plan:
1. Ip=0.8MA density scan (nel_04=0.5, 0.7, 1.1, 1.5)
2. Ip=0.4MA density scan (nel_04=0.5, 0.7, 1.1, 1.5)
3. Ip=1.1MA density scan (nel_04=0.5, 0.7, 1.1, 1.5)

Plan 1. was partially accomplished. The intended RF power steps were
0, 1, 2, and 3MW (150msec each). Plasma current flat-top was extended
to 1.25sec to accomodate this power programming. The outer gap was
reduced to 1cm to prevent H-modes. 3MW RF pulse was obtained on shots
12, 14, and 17, all at nel_04=1.1e20. The duration of the 3MW pulse
was limited by H-mode transitions. The maximum RF power levels were
1.5MW for lower densities (nel_04<=0.7e20) and 2MW for higher density
(nel_04=1.5e20).

Early in the run there were large amplitude (over 1MW peak-peak)
oscillations on the E-port RF power (and on D-port power to a lesser
extent). This was determined to be due to beating between the slightly
different frequencies used for the two transmitters (they talk to each
other through the plasma). We solved the problem by using a single RF
signal generator (as we have been until last week). The E-port antenna
and the transmitter ran very well today. D-port (which has been running
reliably until last week) had problems today, possibly arcing on the
antenna.

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

OH2 tests before the run (Shots 1-4)
Blew a bunch of fuses on shot 02 (switch in the wrong position,
and the interlock was bypassed!)

Loaded 950210022 for shot 05, changed density to nel_04=1.1e20.

Shot

05 Fiz OH2U (10:15am)
06 Pla no RF .85MA 1.1
07 Pla disr .85MA 1.1
08 Pla disr .85MA 1.1
09 Pla disr
10 Pla .85MA 1.1
11 Pla .85MA 1.1
12 Pla .85MA 1.1
13 Pla disr .85MA 1.1
14 Pla .85MA 1.1
15 Fiz
16 Pla .85MA 1.1
17 Pla .85MA 1.1
18 Pla .85MA 0.7
19 Pla .85MA 0.7
20 Pla .85MA 0.7
21 Pla .85MA 0.7
22 Dud
23 Pla .85MA 0.7
24 Pla .85MA 0.7
25 Pla disr .85MA 0.5
26 Pla disr .85MA 0.5
27 Pla .85MA 0.6
28 Pla .85MA 1.5
29 Pla disr .85MA 1.5
30 Pla .85MA 1.5

Physics Operator Summaries
Entered: Jul 7 2004 04:36:53:207PM
Author: To Be Determined
Run 950215; MP 77A.
Takase, Horne, Silva, Daigle.

Run had a late start due to OH2 supply modifications, blown fuses, other
problems. The modifications are advertised to give us more OH2 voltage.
I haven't checked this.

First plasma attempt was 5, a fizzle; shot 6 went.
Magnetics in segment 1 not touched all day. This seems like
a robust startup.
However plenum pressure should be watched; may have contributed to
fizzle on shot 15 and/or the wierd density behavior on shot 29.

Problems:
Reciprocating probe position trace unreliable; associated with rf,
but details unclear. Something broke starting shot 27 and probe didn't fire.
Various triggering problems were detected.

RF: E port ran well, D port erratic. 3 MW on shots 12,14,17.

Diagnostics -- apparently there's a plastic flange cover somewhere
in the ECE system which attenuates the signal, making it not very useful
for startup.

Score: Two fizzles, one dud (ps failure), 4 power tests, 23 plasmas.


Shot log:

load 950210022
Tweak NL and x-point programming

current limit oh1 to 26 ka
set knob in power supply

First two shots were tests. Second blew fuses in oh2L.
Tedious expedition to replace fuses.

Load, coldstart at 9:35

fill at 2.0e-5

shot
3 oh2 u forward gates. Open circuit

4 forward and reverse bridges , with the upper
and lower oh2. these are also open ckt tests
They were successful; OH2 at 25 ka might produce more than 100 v at 25 ka.
Up from 40 or so.

5 First plasma attempt. 10:10. OH2U fault?
fizzle. OH2 supplies tweaked.

6 Reduce fill to 1.4. Good shot, past the fizzle detector.

7. Drop lower x point 1 cm in a ramp. It ends up at -3 cm, 1 sec.
Argon on at 300 msec. This is a little scary.
Plasma, breaker pulled. Disr. at 1.02, vertical oscillation precedes so VDE.
h-mode at 800 msec. The elongation touches 1.8 at the disruption.

8. Move argon to 400 msec.
move rcur out 3 mm to reduce outer gap.
stop zxl ramp at -2.5 cm. Drop fast p gain from 3 to 2 at 1.0 sec.
Plasma, breakers pulled. Disrupts due to growing z oscillation.

9. Instead of dropping fast p at 1.0 sec, raise it from 3 to 4 there.
Tweak zxl
10 more msec argon.
Disruption at .48 sec due to power supply fault. Argon injection was coincidence, maybe.


10. No changes. Good shot.
The vertical quiver turns off at 1 sec. Move that switch back
to 330 msec. for next.

11. tweak upper and lower xpoints to satisfy recip probe.
Breakers tripped during rampdown. Shot ok otherwise.

12 zxl back down to -3 cm. Hope that the gain tweak on shot 10 is sufficient to hold it.
shot ran through rampdown. Elongation 1.8,; xpoint is way low. Unique shot.

13 RELOAD SHOT 11 PROBE GOES IN AT .55,.7,.85
EF2 railed, lost it at 500 msec.

14 raise ef4 current to 2500 A.
zxl up 5 mm, rxl in 3mm.
Good shot.

15 probe timing .65,.8,.95. Tweak slow z gains in rampdown to protect
oh2 supplies.
Fizzle.

16 fill to 1.7e-5.
Plasma. Went past fizzle detector; fuses blew on inversion at 1.7 sec.

17 Move fizzle detector to 1.6 sec. Shouldn't matter, but you never know.
Nice plasma, two fuses blown on rampdown.

18 Reduce nel to 7.e19.
Nice plasma, complete rampdown, no faults.

19 repeat
Good plasma shot.

20 repeat.
Good plasma shot, disrupted on rampdown.

21 adjust lower x-point to stay low during rampdown.
Minor density tweak during rampdown.
Plasma, no change from last shot.

22 Make the end_of_flat-top density spike bigger.
power supply fault (alternator) during precharge.

23 No change. Good shot, with rampdown.
24 see 23

25 Reduce nl to 5.e19.
Disrupts at .9 or so --

26 Repeat; disrupts earlier -- .6.

27 Raise nl to 6.e19
Worked, with rampdown.

28 nl 1.5e20
Nice shot. Sharkfin on rampdown.

29 Start density rampdown 50 msec earlier
Extend argon puff 10 msec
Very strange shot. Looked like a marf on the TV early;
after the current rises a bit the marf gets swallowed, leading to
a big density rise.

30 Slow down the nl ramp to deal with wierd density last shot.
Much better density control.


End run.


























Session Leader Comments
Feb 15 1995 10:21:26:070AM950215001Yuichi TakaseMP077A ICRF Heating in L-Mode Plasmas

Plan:
0.8MA density scan (nel_04=0.5, 0.7, 1.1, 1.5)
0.4MA density scan (nel_04=0.5, 0.7, 1.1, 1.5)
1.1MA density scan (nel_04=0.5, 0.7, 1.1, 1.5)

Shot 01: OH2 test

Feb 15 1995 10:22:48:420AM950215002Yuichi TakaseShot 02: OH2 test
Blew a bunch of fuses.
Switch was not in the correct position,
and the interlock was bypassed!

Feb 15 1995 10:23:15:830AM950215003Yuichi TakaseShot 03: OH2 test

Feb 15 1995 10:23:32:650AM950215004Yuichi TakaseShot 04: OH2 test

Feb 15 1995 10:25:00:830AM950215005Yuichi TakaseShot 05: Finally, plasma attempt (10:15am).
Loaded 950210022, nel_04=1.1e20
Fizzle, OH2U fault.

Feb 15 1995 10:56:01:550AM950215006Yuichi TakaseShot 06: Plasma (no RF)

Feb 15 1995 11:29:52:330AM950215007Yuichi TakaseShot 07: Plasma
D-port 1.0MW
E-port 1.5+/-0.5MW (large osc)

Feb 15 1995 11:30:15:500AM950215008Yuichi TakaseShot 08: Plasma
D-port 1.3MW
E-port 1.5+/-0.5MW (large osc)

Feb 15 1995 11:39:30:750AM950215009Yuichi TakaseShot 09: Early disruption
Still working on equilibrium

Feb 15 1995 12:16:16:870PM950215010Yuichi TakaseShot 10: Plasma
Still working on equilibrium.
Also working on RF power osc problem.

Feb 15 1995 12:17:22:930PM950215011Yuichi TakaseShot 11: Plasma
no D-port

Feb 15 1995 12:37:12:160PM950215012Yuichi TakaseShot 12: Plasma
RF 1MW(0.6-0.75s), 2MW(0.75-0.9s), 3MW(0.9-1.05s)
D-port tripped early.

Feb 15 1995 01:00:23:510PM950215013Yuichi TakaseShot 13: Plasma
going back to shot 011
Disrupted early

Feb 15 1995 01:12:56:680PM950215014Yuichi TakaseShot 14: Plasma
X point higher and in
P_RF = 1.0(0.7-0.85s), 2.0(0.85-1.00s), 3.0(1.00-1.15s)
D-port tripped early (at H-mode)

Feb 15 1995 01:15:59:480PM950215015Yuichi TakaseShot 15: Fizzle

Feb 15 1995 02:00:30:340PM950215016Yuichi TakaseShot 16: Plasma
D-port tripped early

Feb 15 1995 02:03:02:970PM950215017Yuichi TakaseShot 17: Plasma
Both tripped early (@ H-mode)
Lower density (nel_04=0.7) for the next shot.

Feb 15 1995 02:13:29:070PM950215018Yuichi TakaseShot 18: Plasma
D-port tripped early
nel_04=0.7e20

Feb 15 1995 02:53:04:200PM950215019Yuichi TakaseShot 19: Plasma
D-port tripped early
nel_04=0.7e20

Feb 15 1995 02:53:20:680PM950215020Yuichi TakaseShot 20: Plasma
D-port tripped early
nel_04=0.7e20

Feb 15 1995 02:55:59:560PM950215021Yuichi TakaseShot 21: Plasma
D-port tripped early
nel_04=0.7e20

Feb 15 1995 03:32:18:060PM950215022Yuichi TakaseShot 22: Dud (alternator problem)

Feb 15 1995 03:34:40:850PM950215023Yuichi TakaseShot 23: Plasma
D-port tripped early again.

Feb 15 1995 03:44:32:820PM950215024Yuichi TakaseShot 24: Plasma
D-port tripped early again.
Going to nel_04=0.5 for the next shot.

Feb 15 1995 04:21:01:440PM950215025Yuichi TakaseShot 25: Plasma (disrupted @ .93s)

Feb 15 1995 04:21:50:400PM950215026Yuichi TakaseShot 26: Plasma (disrupted @ .66s)

Feb 15 1995 04:23:40:730PM950215027Yuichi TakaseShot 27: Plasma
nel_04=0.6e20
D-port tripped early

Feb 15 1995 04:42:17:570PM950215028Yuichi TakaseShot 28: Plasma
nel_04=1.5e20
D-port tripped early

Feb 15 1995 04:55:28:260PM950215029Yuichi TakaseShot 29: Plasma
nel_04=1.5e20 (programmed)
Strange density jump @ 0.34s.

Feb 15 1995 05:06:15:990PM950215030Yuichi TakaseShot 30: Plasma
nel_04=1.5e20
P_RF=1.0(.7-.85s), 2.0(.85-1.15s)

Physics Operator Comments

Engineering Operator Comments
ShotTimeTypeStatusComment
108:18:31:390AMTestOkopen ckt oh test
208:27:21:410AMTestOkoh2 fault
309:46:26:230AMTestOkoh2 upper forward bridge test
410:00:26:680AMTestOktest ok
510:11:19:580AMPlasmaOkoh2 upper fault
610:32:29:310AMPlasmaOkno fault
710:52:12:950AMPlasmaOkcomm fault oh2l
811:10:08:000AMPlasmaOkoh2 comm fail plasma caused
911:28:12:150AMPlasmaOkcomm fault
1011:41:53:480AMPlasmaOkcomm faults
1112:01:01:920PMPlasmaOkcomm faults all 5 pf breaker supplies
1212:20:58:140PMPlasmaBadno faults
1312:41:57:020PMPlasmaOkoh2 U comm fault
1412:58:12:370PMPlasmaOkcomm faults all 5
1501:14:07:150PMPlasmaOkNo Faults.
1601:27:03:070PMPlasmaOkcomm fault OH2U&L OH1& EF1U
1701:52:32:030PMPlasmaOkComm fault oh2U&L
1802:07:04:410PMPlasmaOkNo Faults.
1902:18:09:880PMPlasmaOkno faults
2002:35:43:280PMPlasmaOkNO Faults.
2102:51:36:020PMPlasmaOkNo Faults.
2203:04:54:380PMPlasmaBadLoss Alt. Voltage.
2303:22:54:340PMPlasmaOkNo faults.
2403:33:43:860PMPlasmaOkNo Faults.
2503:45:49:820PMPlasmaOkNo Faults.
2603:58:46:170PMPlasmaOkNo Faults.
2704:09:37:810PMPlasmaOkNo Faults
2804:29:01:770PMPlasmaOkComm fault OH1, Oh2U&L, EF1 U&L
2904:42:18:340PMPlasmaOkcomm fault oh2l, oh1,ef1u
3004:58:42:010PMPlasmaOkNo Faults.