Alcator C-Mod Run 950209 Information

Miniproposals

Miniproposal: 076

Date Filed: 1/12/1995

Title: Raise plasma current to 1.2 MA

First Author: Robert Granetz

Session Leader: Robert Granetz (shots 1-32)

Operators
Session leader(s):	Robert Granetz
Physics operator(s):	Joseph Snipes
Engineering operator(s):	Frank Silva,Vinny Bertolino

Engineering Operator Run Comment
Increase plasma current to 1.2 MA without bad disruptions

Session Leader Plans

Physics Operators Plans

Session Leader Summaries

Entered: Jul 7 2004 03:49:12:210PM

Author: To Be Determined

Session leader's run summary for 950209.

SL: R. Granetz
PO: J. Snipes
EO: V. Bertolino

MP #076, Raise Ip to 1.2 MA while carefully monitoring disruption severity.

We managed to get one shot (950209029) at 1.2 MA, although the EF3 supply
faulted, resulting in a disruption with 200 kA of halo current. That was
our only high halo current disruption today. We also had several
non-disruptive shots at 0.9, 1.0, and 1.1 MA. See the following table of
high-current shots.

Note: These were all diverted deuterium plasmas at B=5.3 T. The ones from
the latter half of the run had kappa=1.7.

Nominal Shots Disrupted Disruption caused
Ip by power supply fault
-------------------------------------------------------------------------
0.9 MA 950209005 Yes Yes, EF1L
006 No
019 No
020 No

1.0 MA 007 No
008 No
010 Yes
011 Yes
021 No
027 Yes

1.1 MA 009 Yes
022 Yes Yes, OH1
023 No
024 Yes Yes, EF3
025 Yes Yes, OH1
026 No

1.2 MA 029 Yes Yes, EF3

Several general comments:

(1) We had numerous difficulties early in the run with power supplies
hitting their current and/or voltage limits. This was overcome by
decreasing the rate of current rise, resulting in shorter flattops.

(2) As we pushed to higher currents, numerous problems with power supplies
(specifically OH1 and EF3) occurred.

(3) A lot of optimization of power supply and plasma programming remains to
be done. For example, increase EF4 current so as to reduce the required
output from EF3 and the EF2's. Other possible optimizations: find the
best rate of current rise, and increase the duration of the flattop by
extending the length of the plasma shot.

Physics Operator Summaries

Entered: Jul 7 2004 04:36:53:160PM

Author: To Be Determined

MP076 - Discharge Development up to 1.2 MA
Engineers in Charge : Frank Silva and Vince Bertolino
Physicist in Charge : Joseph Snipes
Session Leader : Bob Granetz

Overall, the run was not very successful due to the power supplies
not being able to handle being pushed to their limits. There were failures in
OH1 and EF3 that cost us a large number of shots and the failure of EF3
finally ended the run early around 4:00 pm. Nonetheless, some progress was
made at developing high current discharges. Two shots were achieved above
1.1 MA without disruptions (shots 23 and 26). We also reached 1.2 MA on
shot 29 which disrupted late due to power supply problems. There were a
total of 32 shots, 22 plasmas, 8 fizzles, and two power supply test shots.

Shot,Duration(s),Ipmax(MA) Shot,Duration(s),Ipmax
1 0.000 0.021 2 1.441 0.851
3 0.000 0.032 4 0.549 0.724
5 0.869 0.931 6 1.446 0.936
7 1.438 1.029 8 1.449 1.029
9 1.019 1.122 10 0.505 1.174
11 0.613 1.249 12 0.000 0.024
13 0.427 0.864 14 0.000 0.037
15 0.000 0.034 16 0.000 0.042
17 0.471 1.016 18 1.438 0.851
19 1.452 0.936 20 1.442 0.936
21 1.459 1.029 22 1.018 1.208
23 1.457 1.122 24 1.127 1.125
25 1.015 1.161 26 1.441 1.127
27 0.557 1.037 28 0.000 0.026
29 0.990 1.210 30 0.000 0.024
31 0.000 0.008 32 0.000 0.005

Shotlist

1 Fizzle
2 Good shot ai 0.85 MA
3 Fizzle
4 Plasma, but EF1L fault led to a disruption at 0.55 sec at 0.4 MA
5 Plasma, but EF1L fault led to a disruption at 0.867 sec at 0.9 MA
6 Good shot with 0.93 MA
7 Enabled Ar. Good shot at 1.02 MA
8 Another 1.02 MA shot
9 Raised Ip to 1.12 MA, hit OH1 current limit and disrupted at 1.017 s
10 Disrupted at 0.5 sec. Hit EF2 current limits
11 Disrupted at 0.6 sec. Railed OH1 voltage
12 Fizzle
13 Disrupted at 0.4 sec perhaps due to impurity problems
14 Fizzle
15 Fizzle
16 Fizzle
17 Disrupts at 0.46 sec at 0.85 MA, lots of Moly injections
18 Reloading shot 2. Good shot at 0.85 MA
19 Raised Ip to 0.9 MA. Good shot.
20 Good shot at 0.9 MA
21 Raised Ip to 1 MA. Good shot.
22 Raised Ip to 1.1 MA. Disrupted at 1 sec due to OH1 fault
23 Good shot at 1.12 MA. Near H-mode threshold
24 Repeat. Disrupted at 1.12 sec after EF3 fault at 0.93 sec
25 Repeat. Disrupted at 1.005 sec after OH1 fault at 0.98 sec
26 Repeat. Good shot at 1.12 MA!
27 Tried to raise Ip to 1.2 MA, but disrupted at 0.5 sec perhaps by Moly
28 Fizzle
29 Got 1.2 MA, but EF3 failed at 0.92 sec, disrupted at 0.98 sec at 1 MA***
30 Fizzle
31 EF3 and EFC test shot. EFC worked, but EF3 inverted.
32 Another EF3 test shot. EF3 failed again. Run ends early to fix EF3.

Session Leader Comments

Feb 9 1995 08:30:49:720AM 950209001 Robert Granetz MP #076, Raise Ip to 1.2 MA while carefully monitoring disruption severity.

Start by loading a typical (non-disruptive) 0.8 MA shot from
yesterday, 950208024. Before running it though, decrease the elongation
a bit (1.67 to 1.60) to make VDE disruptions less likely. Keep invert
times at 1.7 s (1.6 s for the TF) for now.

Feb 9 1995 08:41:23:940AM 950209001 Robert Granetz Fizzle. Null needs adjusting.
Next shot, increase BR_0 by 0.001 T.

Feb 9 1995 08:52:16:870AM 950209002 Robert Granetz Shot 002: Plasma, good shot. BZ is at 0.001 T at breakdown. Monitor this.
Next shot: raise Ip to 0.9 MA.

Feb 9 1995 09:03:38:270AM 950209003 Robert Granetz Shot 003: Fizzle.
Next shot: increase RCUR from 0.660 to 0.667 in order to DECREASE
the elongation, and increase pre-fill from 1.6 to 1.8e-5 torr.

Feb 9 1995 09:16:46:280AM 950209004 Robert Granetz Shot 004: Plasma, but EF1L faulted at 0.35 s, which caused the shot to
have a 'soft' termination.
Next shot: no changes.

Feb 9 1995 09:40:17:450AM 950209005 Robert Granetz Shot 005: Plasma, Ip=0.92 MA, but EF1L faulted again at 0.7 s, causing
another 'soft' termination. (The current ramps down to 0.55 MA,
and then disrupts, with 100 kA of halo current.) Kappa has been
successfully reduced to 1.6.
Next shot: no changes.

Feb 9 1995 09:49:10:160AM 950209006 Robert Granetz Shot 006: Plasma, good shot, Ip=0.92 MA. Density came down really nicely.
Next shot: raise Ip to 1.0 MA.

Feb 9 1995 10:03:45:220AM 950209007 Robert Granetz Shot 007: Plasma, good shot, Ip=1.02 MA (and constant). Kappa is 1.65.
Next shot: no changes.

Feb 9 1995 10:18:29:250AM 950209008 Robert Granetz Shot 008: Plasma, good shot, Ip=1.02 MA. There were some hard x-rays on this
shot.
Next shot: raise Ip to 1.1 MA, increase pre-fill from 1.8 to 1.9e-5,
and move RCUR in by 1.5 mm (to increase outer gap).

Feb 9 1995 10:38:41:550AM 950209009 Robert Granetz Shot 009: Plasma, Ip=1.12 MA, hard disruption at 1.017 s. Current starts
to droop starting at 0.85 s. Halo_Upper was 90 kA. It turns
out that the OH1 PLC current limit was set at 20 kA, which is
too low.
Next shot: raise OH1 PLC limit to 26 kA.

Feb 9 1995 11:11:25:420AM 950209010 Robert Granetz Shot 010: Plasma, disrupted at 1.0 MA at 0.50 s. Ihalo_lower=1.26 kA.
Next shot: un-tweak small change made to clearin on the previous
shot, and increase EF4 a touch (to relieve EF3 a touch).

Feb 9 1995 11:29:38:420AM 950209011 Robert Granetz Shot 011: Plasma, disrupted at 0.61 s. We might be running into a voltage
limit on OH1, as well as current limits on the EF2's.
NEXT SHOT: re-load shot 008 (1.0 MA), but put in the RCUR change
made just after shot 008.

Feb 9 1995 11:41:19:410AM 950209012 Robert Granetz Shot 012: Fizzle. Null looks okay.
Next shot: no changes.

Feb 9 1995 11:54:29:880AM 950209013 Robert Granetz Shot 013: Plasma, disrupted at 0.42 s. We don't understand why. Seems to
be having problems early on.
Next shot: reduce pre-fill from 1.9 to 1.6e-5 torr.

Feb 9 1995 11:59:15:790AM 950209014 Robert Granetz Shot 014: Fizzle.
Next shot: increase pre-fill from 1.6 to 1.8e-5 torr.

Feb 9 1995 12:16:50:260PM 950209015 Robert Granetz Shot 015: Fizzle again.
Next shot: increase EF4 by a touch

Feb 9 1995 12:22:55:990PM 950209016 Robert Granetz Shot 016: Fizzle again.
Next shot: tweak RCUR gain.

Feb 9 1995 12:35:47:130PM 950209017 Robert Granetz Shot 017: Plasma, but disrupted at 0.46 s. Lots of molybdenum injections.
Next shot: re-load shot 002 (0.8 MA).

Feb 9 1995 12:53:00:520PM 950209018 Robert Granetz Shot 018: Plasma, nice shot. Ip=0.82 MA. Kappa=1.7, because the re-loaded
shot had RCUR mistakenly too far in.
Next shot: increase Ip to 0.9 MA and increase RCUR by 2 mm.

Feb 9 1995 01:08:44:210PM 950209019 Robert Granetz Shot 019: Plasma, nice shot. Ip=0.93 MA.
Next shot: repeat, except tweak down the early pulse gas.

Feb 9 1995 01:19:34:020PM 950209020 Robert Granetz Shot 020: Plasma, nice shot. Ip=0.93 MA. Initial current rise has been
rather slow today.
Next shot: raise Ip to 1.0 MA.

Feb 9 1995 01:32:02:250PM 950209021 Robert Granetz Shot 021: Plasma, nice shot. Ip=1.02 MA. Some molybdenum injections during
the current rampdown.
Next shot: raise Ip to 1.1 MA.

Feb 9 1995 01:54:19:950PM 950209022 Robert Granetz Shot 022: Plasma, disrupted at 1.016 s. Big moly injection at 0.7 s, which
may cause the EF2's to saturate. It may be that the disruption was
due to a fault with OH1.
Next shot: repeat.

Feb 9 1995 02:03:47:560PM 950209023 Robert Granetz Shot 023: Plasma, nice shot. Ip=1.12 MA. A few (smaller) moly injections.
Next shot: repeat.

Feb 9 1995 02:22:31:040PM 950209024 Robert Granetz Shot 024: Plasma, Ip=1.12 MA. Soft termination started at 0.94 s, possibly
due to a fault in EF3. There was no significant halo current
measured on any sensor.
Next shot: repeat.

Feb 9 1995 02:38:11:850PM 950209025 Robert Granetz Shot 025: Plasma, disrupted at 1.01 s. Ip=1.12 MA. Disruption probably
caused by an OH1 fault at 0.98 s. There were some moderate
molybdenum injections.
Next shot: repeat.

Feb 9 1995 02:46:23:340PM 950209026 Robert Granetz Shot 026: Plasma, nice shot. Ip=1.12 MA.
Next shot: raise Ip to 1.2 MA.

Feb 9 1995 03:02:28:050PM 950209027 Robert Granetz Shot 027: Plasma, disrupted at 0.554 s, maybe due to an impurity injection.
Current was only at 1.0 MA. Ihalo_lower=143 kA.
Next shot: repeat.

Feb 9 1995 03:29:52:520PM 950209028 Robert Granetz Shot 028: Fizzle.
Next shot: repeat.

Feb 9 1995 03:30:08:270PM 950209029 Robert Granetz Shot 029: Plasma, Ip=1.20 MA, EF3 faulted at 0.93 s, which caused a disruption
at 0.988 s. Ihalo_lower=200. kA! That's the first bad one.
Next shot: raise EF4 programming by 550 amps, in order to take
some of the load off of EF3 and EF2. No other changes.

Feb 9 1995 03:33:05:660PM 950209030 Robert Granetz Shot 030: Fizzle. No surprise.
Next shot; repeat.

Feb 9 1995 04:10:03:010PM 950209031 Robert Granetz Shot 031: Test of EF3 and EFC. EF3 faulted at a bus current of 10.5 kA.
Next shot: another test of EF3.

Feb 9 1995 04:21:19:050PM 950209032 Robert Granetz Shot 032: Another test of EF3. It faulted at 6 kA.

End of Run. Work on EF3.

Physics Operator Comments

Feb 9 1995 08:45:13:650AM 950209001 Joseph Snipes Shot 1
Fizzle!

Feb 9 1995 08:57:19:410AM 950209002 Joseph Snipes Shot 2
Good shot! Copied shot 950208024 and changed RCUR 3 mm outward to try to
reduce the elongation. However, the elongation was 1.7, a bit higher than
yesterday. Operator error. The RCUR was moved in instead of out. Try again
for shot 3.

Feb 9 1995 09:01:44:190AM 950209003 Joseph Snipes Shot 3
Ip raised to 0.9 MA.
Fizzle.

Feb 9 1995 09:24:56:770AM 950209004 Joseph Snipes Shot 4
RCUR changed to 0.67 m during the flattop. Prefill raised to 1.8 x 10^-5 Torr.
Bad shot. Got plasma, but there appears to be a power supply problem. Indeed
EF1L voltage oscillated single phase and crowbarred. Disruption at 0.55 sec
at 400 kA.

Feb 9 1995 09:33:25:710AM 950209005 Joseph Snipes Shot 5
Try again. EF1L failed. Reached 900 kA, then EF1 brought down the current
at about 0.7 sec. Finally disrupted at 0.867 sec with 540 kA of current.

Feb 9 1995 09:51:42:500AM 950209006 Joseph Snipes Shot 6
Try again. Good plasma! Got 0.93 MA of plasma current.

Feb 9 1995 10:09:09:210AM 950209007 Joseph Snipes Shot 7
Enabled argon gas puff at 300 msec for 24 msec. Ip raised to 1 MW. Also put
in a 15 kA upward ramp to 1 sec to try to avoid the droop in current that was
seen on shot 6.
Good 1.02 MA shot!

Feb 9 1995 10:14:26:790AM 950209008 Joseph Snipes Shot 8
Repeat. Good 1.02 MA shot! However, it looked worse than the previous shot.
Some hard x rays and moly are appearing.

Feb 9 1995 10:27:24:410AM 950209009 Joseph Snipes Shot 9
Moved RCUR in to 0.6655 m to try to increase the outer gap to avoid moly from
the outboard limiter. Raised prefill to 1.9 x 10^-5 Torr. Also noticed
that the deuterium gas pressure had dropped to about 13 pounds. It will be
raised to 17 pounds for this shot. Increased Ip to 1.1 MA. Disrupted.

Feb 9 1995 10:36:30:050AM 950209009 Joseph Snipes Shot 9
Moved RCUR in to 0.6655 m to try to increase the outer gap to avoid moly from
the outboard limiter. Raised prefill to 1.9 x 10^-5 Torr. Also noticed
that the deuterium gas pressure had dropped to about 13 pounds. It will be
raised to 17 pounds for this shot. Increased Ip to 1.1 MA. Disrupted at
1.1 sec with just over 1 MA of Ip.

Feb 9 1995 11:00:47:360AM 950209010 Joseph Snipes Shot 10
Try again. Shot 9 hit the OH1 current limit at 20 kA. We will raise it for
this shot to 26 kA. Also adjusted the EF4U programming to extend out to 1 sec.
It had been ramping down at 0.944 sec. Reduced RCUR to 0.6645 m to increase
outer gap. Ramped CLEARIN to zero at 0.257 sec rather than 0.37 sec. Also
increased EF3 current limit to 17 kA. Disrupted at about 0.5 sec.

Feb 9 1995 11:24:15:120AM 950209011 Joseph Snipes Shot 11
Reversed change made on shot 10 to CLEARIN so that it reached zero at 0.45 sec.
Also increased EF4U current to 2 kA throughout the flattop to try to remove
the demand on EF3 and EF2. Disrupted violently at 0.6 sec. It appears that
the OH1 voltage is railed at 400 V, so we need a slower ramp rate.

Feb 9 1995 11:35:22:730AM 950209012 Joseph Snipes Shot 12
Reloaded segment 2 from shot 8 to backtrack to 1 MA. Changed RCUR from 0.67
to 0.6655 m to take some heat off of the RF limiter.
Fizzle!

Feb 9 1995 11:53:26:780AM 950209013 Joseph Snipes Shot 13
Try again. Disrupted at 0.4 sec. Looks like a slow current rise. We may
have impurity problems or too high a prefill.

Feb 9 1995 11:59:19:410AM 950209014 Joseph Snipes Shot 14
Try reducing the prefill to 1.6 x 10^-5 Torr. Fizzle.

Feb 9 1995 12:05:39:070PM 950209015 Joseph Snipes Shot 15
Try increasing the prefill to 1.8 x 10^-5 Torr.
Fizzle!

Feb 9 1995 12:29:14:580PM 950209016 Joseph Snipes Shot 16
Increased EF4 current early to -1050 A from -1035 A. Changed the wrong
segment, segment 2. However, the startup looked a bit better anyway. Wolfe
suggests a fix Ian made for low field startup by increasing the RCUR gain
early from 0.01 to 0.04 sec from 4 to 9.5.

Feb 9 1995 12:38:02:990PM 950209017 Joseph Snipes Shot 17
Wolfe suggests a fix Ian made for low field startup by increasing the RCUR gain
early from 0.01 to 0.04 sec from 4 to 9.5. Disrupts violently at 0.46 sec at
about 0.85 MA.

Feb 9 1995 12:52:11:660PM 950209018 Joseph Snipes Shot 18
Reloading shot 2. Good shot.

Feb 9 1995 01:09:29:900PM 950209019 Joseph Snipes Shot 19
Raising Ip to 0.9 MA with a slow ramp to 0.915 at 1 sec. Reduced rate of
rise of Ip by a bit for the final 50 kA. Also increased RCUR to 0.662 m
from 0.66 m. Good shot.

Feb 9 1995 01:19:16:450PM 950209020 Joseph Snipes Shot 20
Reduced early gas puff in segment 1 by a small amount between 30 and 70 msec
to try to improve the current rise. Good shot.

Feb 9 1995 01:34:31:340PM 950209021 Joseph Snipes Shot 21
Increased Ip to 1 MA with a slow rate of rise so that it reaches 1 MA at 0.552
sec and ramps to 1.015 MA by 1 sec. Good shot.

Feb 9 1995 01:56:15:630PM 950209022 Joseph Snipes Shot 22
Increased Ip to 1.1 MA with a slow rate of rise so that it reaches 1.1 MA at
0.65 sec and ramps to 1.115 MA by 1 sec. Good shot, but disrupted at 1 sec
due to a fault in OH1.

Feb 9 1995 02:09:55:230PM 950209023 Joseph Snipes Shot 23
Try again. Reduced the initial gas puff a bit between 0.03 and 0.1 sec to
try to improve the current rise. Good shot at 1.12 MA!

Feb 9 1995 02:10:58:410PM 950209023 Joseph Snipes Shot 23
Try again. Reduced the initial gas puff a bit between 0.03 and 0.1 sec to
try to improve the current rise. Good shot at 1.12 MA! Dithering on H alpha.
Near the H-mode threshold.

Feb 9 1995 02:21:51:840PM 950209024 Joseph Snipes Shot 24
One more time . . . Violent disruption at 1.12 sec. EF3 fault at 0.93 sec.

Feb 9 1995 02:33:22:810PM 950209025 Joseph Snipes Shot 25
Try again. Another violent disruption. OH1 fault at 0.98 sec. Disrupted at
1.005 sec.

Feb 9 1995 02:46:10:660PM 950209026 Joseph Snipes Shot 26
One more once. Good shot at 1.12 MA!

Feb 9 1995 03:05:35:500PM 950209026 Joseph Snipes Shot 27
Raised Ip to 1.2 MA from 0.75 s to 1.0 s. Also decreased the rate of decay
of Ip after 1 sec. Disrupted violently at 0.5 sec.

Feb 9 1995 03:06:31:430PM 950209028 Joseph Snipes Shot 28
Fizzle!

Feb 9 1995 03:22:31:470PM 950209029 Joseph Snipes Shot 29
Got 1.2 MA, but EF3 failed at 0.92 sec and led to a disruption against the RF
antenna at 0.98 sec with nearly 1 MA of plasma current. 200 kA halo current
on lower halo rogowski.

Feb 9 1995 03:44:58:680PM 950209030 Joseph Snipes Shot 30
Try 1.2 MA one more time. Changed EF4 current from 1943 A to 2500 A during
the current flattop. Fizzle! EFC failed. Short delay to look into the
problem.

Feb 9 1995 04:07:11:670PM 950209031 Joseph Snipes Shot 31
EF3 and EFC test shot. EFC worked, but EF3 inverted again on its own. More
time needed to try to fix the problem.

Feb 9 1995 04:18:11:190PM 950209032 Joseph Snipes Shot 32
Another EF3 test shot. EF3 inverted again at only 6 kA. There are real
problems with EF3. Wolfe's idea is to bring EF4 up in proportion to Ip so
that it should be up to 3 kA during the flattop. So, I loaded that into
model in case we do get another shot.

Feb 9 1995 04:21:33:010PM 950209032 Joseph Snipes Run ending now to allow the engineers to fix the EF3 supply.

Feb 9 1995 04:38:00:940PM 950209032 Joseph Snipes Overall, the run was not very successful due to the power supplies not being
able to handle being pushed to their limits. There were failures in OH1 and
EF3 that cost us a large number of shots and the failure of EF3 finally ended
the run early around 4:00 pm. Nonetheless, some progress was made at
developing high current discharges. Two shots were achieved above 1.1 MA
without disruptions (shots 23 and 26). We also reached 1.2 MA on shot 29
which disrupted late due to power supply problems. There were a total of
32 shots, 22 plasmas, 8 fizzles, and two power supply test shots.

Engineering Operator Comments

Shot Time Type Status Comment

1 08:29:19:620AM Plasma Ok no faults, plasma

2 08:43:37:910AM Plasma Ok no faults, plasma

3 08:57:30:580AM Plasma Ok no faults

4 09:06:17:290AM Plasma Ok comm fail ef1L, plasma

5 09:25:34:050AM Plasma Bad ef1l comm fault

6 09:43:15:160AM Plasma Ok no faults

7 09:56:18:100AM Plasma Ok no faults

8 10:07:25:610AM Plasma Ok no faults

9 10:24:55:650AM Plasma Ok comm fail oh2L plasma

10 10:56:45:930AM Plasma Ok no faults

11 11:13:24:120AM Plasma Ok disruption induced comm faults

12 11:33:06:770AM Plasma Ok no faults

13 11:43:24:470AM Plasma Ok no faults

14 11:54:18:090AM Plasma Ok no faults

15 12:03:55:690PM Plasma Ok no faults

16 12:14:04:980PM Plasma Ok no faults

17 12:28:13:820PM Plasma Ok no faults

18 12:38:48:160PM Plasma Ok no faults

19 12:56:33:390PM Plasma Ok no faults

20 01:10:51:180PM Plasma Ok no faults

21 01:22:28:580PM Plasma Ok no faults

22 01:36:13:560PM Plasma Ok oh1 cond fault after disruption

23 01:58:38:750PM Plasma Ok no faults

24 02:10:39:700PM Plasma Ok no faults

25 02:23:07:480PM Plasma Bad conduction fail oh1

26 02:37:38:520PM Plasma Ok no faults

27 02:51:58:980PM Plasma Ok no faults

28 03:03:36:190PM Plasma Ok no faults

29 03:12:56:130PM Plasma Bad ef3 inverts early

30 03:29:48:540PM Plasma Bad no efc

31 03:59:41:760PM Test Bad ef3 dig sys fault at 10ka

32 04:12:33:900PM Test Bad ef3 fault

Session Leader Comments
Feb 9 1995 08:30:49:720AM	950209001	Robert Granetz	MP #076, Raise Ip to 1.2 MA while carefully monitoring disruption severity. Start by loading a typical (non-disruptive) 0.8 MA shot from yesterday, 950208024. Before running it though, decrease the elongation a bit (1.67 to 1.60) to make VDE disruptions less likely. Keep invert times at 1.7 s (1.6 s for the TF) for now.
Feb 9 1995 08:41:23:940AM	950209001	Robert Granetz	Fizzle. Null needs adjusting. Next shot, increase BR_0 by 0.001 T.
Feb 9 1995 08:52:16:870AM	950209002	Robert Granetz	Shot 002: Plasma, good shot. BZ is at 0.001 T at breakdown. Monitor this. Next shot: raise Ip to 0.9 MA.
Feb 9 1995 09:03:38:270AM	950209003	Robert Granetz	Shot 003: Fizzle. Next shot: increase RCUR from 0.660 to 0.667 in order to DECREASE the elongation, and increase pre-fill from 1.6 to 1.8e-5 torr.
Feb 9 1995 09:16:46:280AM	950209004	Robert Granetz	Shot 004: Plasma, but EF1L faulted at 0.35 s, which caused the shot to have a 'soft' termination. Next shot: no changes.
Feb 9 1995 09:40:17:450AM	950209005	Robert Granetz	Shot 005: Plasma, Ip=0.92 MA, but EF1L faulted again at 0.7 s, causing another 'soft' termination. (The current ramps down to 0.55 MA, and then disrupts, with 100 kA of halo current.) Kappa has been successfully reduced to 1.6. Next shot: no changes.
Feb 9 1995 09:49:10:160AM	950209006	Robert Granetz	Shot 006: Plasma, good shot, Ip=0.92 MA. Density came down really nicely. Next shot: raise Ip to 1.0 MA.
Feb 9 1995 10:03:45:220AM	950209007	Robert Granetz	Shot 007: Plasma, good shot, Ip=1.02 MA (and constant). Kappa is 1.65. Next shot: no changes.
Feb 9 1995 10:18:29:250AM	950209008	Robert Granetz	Shot 008: Plasma, good shot, Ip=1.02 MA. There were some hard x-rays on this shot. Next shot: raise Ip to 1.1 MA, increase pre-fill from 1.8 to 1.9e-5, and move RCUR in by 1.5 mm (to increase outer gap).
Feb 9 1995 10:38:41:550AM	950209009	Robert Granetz	Shot 009: Plasma, Ip=1.12 MA, hard disruption at 1.017 s. Current starts to droop starting at 0.85 s. Halo_Upper was 90 kA. It turns out that the OH1 PLC current limit was set at 20 kA, which is too low. Next shot: raise OH1 PLC limit to 26 kA.
Feb 9 1995 11:11:25:420AM	950209010	Robert Granetz	Shot 010: Plasma, disrupted at 1.0 MA at 0.50 s. Ihalo_lower=1.26 kA. Next shot: un-tweak small change made to clearin on the previous shot, and increase EF4 a touch (to relieve EF3 a touch).
Feb 9 1995 11:29:38:420AM	950209011	Robert Granetz	Shot 011: Plasma, disrupted at 0.61 s. We might be running into a voltage limit on OH1, as well as current limits on the EF2's. NEXT SHOT: re-load shot 008 (1.0 MA), but put in the RCUR change made just after shot 008.
Feb 9 1995 11:41:19:410AM	950209012	Robert Granetz	Shot 012: Fizzle. Null looks okay. Next shot: no changes.
Feb 9 1995 11:54:29:880AM	950209013	Robert Granetz	Shot 013: Plasma, disrupted at 0.42 s. We don't understand why. Seems to be having problems early on. Next shot: reduce pre-fill from 1.9 to 1.6e-5 torr.
Feb 9 1995 11:59:15:790AM	950209014	Robert Granetz	Shot 014: Fizzle. Next shot: increase pre-fill from 1.6 to 1.8e-5 torr.
Feb 9 1995 12:16:50:260PM	950209015	Robert Granetz	Shot 015: Fizzle again. Next shot: increase EF4 by a touch
Feb 9 1995 12:22:55:990PM	950209016	Robert Granetz	Shot 016: Fizzle again. Next shot: tweak RCUR gain.
Feb 9 1995 12:35:47:130PM	950209017	Robert Granetz	Shot 017: Plasma, but disrupted at 0.46 s. Lots of molybdenum injections. Next shot: re-load shot 002 (0.8 MA).
Feb 9 1995 12:53:00:520PM	950209018	Robert Granetz	Shot 018: Plasma, nice shot. Ip=0.82 MA. Kappa=1.7, because the re-loaded shot had RCUR mistakenly too far in. Next shot: increase Ip to 0.9 MA and increase RCUR by 2 mm.
Feb 9 1995 01:08:44:210PM	950209019	Robert Granetz	Shot 019: Plasma, nice shot. Ip=0.93 MA. Next shot: repeat, except tweak down the early pulse gas.
Feb 9 1995 01:19:34:020PM	950209020	Robert Granetz	Shot 020: Plasma, nice shot. Ip=0.93 MA. Initial current rise has been rather slow today. Next shot: raise Ip to 1.0 MA.
Feb 9 1995 01:32:02:250PM	950209021	Robert Granetz	Shot 021: Plasma, nice shot. Ip=1.02 MA. Some molybdenum injections during the current rampdown. Next shot: raise Ip to 1.1 MA.
Feb 9 1995 01:54:19:950PM	950209022	Robert Granetz	Shot 022: Plasma, disrupted at 1.016 s. Big moly injection at 0.7 s, which may cause the EF2's to saturate. It may be that the disruption was due to a fault with OH1. Next shot: repeat.
Feb 9 1995 02:03:47:560PM	950209023	Robert Granetz	Shot 023: Plasma, nice shot. Ip=1.12 MA. A few (smaller) moly injections. Next shot: repeat.
Feb 9 1995 02:22:31:040PM	950209024	Robert Granetz	Shot 024: Plasma, Ip=1.12 MA. Soft termination started at 0.94 s, possibly due to a fault in EF3. There was no significant halo current measured on any sensor. Next shot: repeat.
Feb 9 1995 02:38:11:850PM	950209025	Robert Granetz	Shot 025: Plasma, disrupted at 1.01 s. Ip=1.12 MA. Disruption probably caused by an OH1 fault at 0.98 s. There were some moderate molybdenum injections. Next shot: repeat.
Feb 9 1995 02:46:23:340PM	950209026	Robert Granetz	Shot 026: Plasma, nice shot. Ip=1.12 MA. Next shot: raise Ip to 1.2 MA.
Feb 9 1995 03:02:28:050PM	950209027	Robert Granetz	Shot 027: Plasma, disrupted at 0.554 s, maybe due to an impurity injection. Current was only at 1.0 MA. Ihalo_lower=143 kA. Next shot: repeat.
Feb 9 1995 03:29:52:520PM	950209028	Robert Granetz	Shot 028: Fizzle. Next shot: repeat.
Feb 9 1995 03:30:08:270PM	950209029	Robert Granetz	Shot 029: Plasma, Ip=1.20 MA, EF3 faulted at 0.93 s, which caused a disruption at 0.988 s. Ihalo_lower=200. kA! That's the first bad one. Next shot: raise EF4 programming by 550 amps, in order to take some of the load off of EF3 and EF2. No other changes.
Feb 9 1995 03:33:05:660PM	950209030	Robert Granetz	Shot 030: Fizzle. No surprise. Next shot; repeat.
Feb 9 1995 04:10:03:010PM	950209031	Robert Granetz	Shot 031: Test of EF3 and EFC. EF3 faulted at a bus current of 10.5 kA. Next shot: another test of EF3.
Feb 9 1995 04:21:19:050PM	950209032	Robert Granetz	Shot 032: Another test of EF3. It faulted at 6 kA. End of Run. Work on EF3.

Physics Operator Comments
Feb 9 1995 08:45:13:650AM	950209001	Joseph Snipes	Shot 1 Fizzle!
Feb 9 1995 08:57:19:410AM	950209002	Joseph Snipes	Shot 2 Good shot! Copied shot 950208024 and changed RCUR 3 mm outward to try to reduce the elongation. However, the elongation was 1.7, a bit higher than yesterday. Operator error. The RCUR was moved in instead of out. Try again for shot 3.
Feb 9 1995 09:01:44:190AM	950209003	Joseph Snipes	Shot 3 Ip raised to 0.9 MA. Fizzle.
Feb 9 1995 09:24:56:770AM	950209004	Joseph Snipes	Shot 4 RCUR changed to 0.67 m during the flattop. Prefill raised to 1.8 x 10^-5 Torr. Bad shot. Got plasma, but there appears to be a power supply problem. Indeed EF1L voltage oscillated single phase and crowbarred. Disruption at 0.55 sec at 400 kA.
Feb 9 1995 09:33:25:710AM	950209005	Joseph Snipes	Shot 5 Try again. EF1L failed. Reached 900 kA, then EF1 brought down the current at about 0.7 sec. Finally disrupted at 0.867 sec with 540 kA of current.
Feb 9 1995 09:51:42:500AM	950209006	Joseph Snipes	Shot 6 Try again. Good plasma! Got 0.93 MA of plasma current.
Feb 9 1995 10:09:09:210AM	950209007	Joseph Snipes	Shot 7 Enabled argon gas puff at 300 msec for 24 msec. Ip raised to 1 MW. Also put in a 15 kA upward ramp to 1 sec to try to avoid the droop in current that was seen on shot 6. Good 1.02 MA shot!
Feb 9 1995 10:14:26:790AM	950209008	Joseph Snipes	Shot 8 Repeat. Good 1.02 MA shot! However, it looked worse than the previous shot. Some hard x rays and moly are appearing.
Feb 9 1995 10:27:24:410AM	950209009	Joseph Snipes	Shot 9 Moved RCUR in to 0.6655 m to try to increase the outer gap to avoid moly from the outboard limiter. Raised prefill to 1.9 x 10^-5 Torr. Also noticed that the deuterium gas pressure had dropped to about 13 pounds. It will be raised to 17 pounds for this shot. Increased Ip to 1.1 MA. Disrupted.
Feb 9 1995 10:36:30:050AM	950209009	Joseph Snipes	Shot 9 Moved RCUR in to 0.6655 m to try to increase the outer gap to avoid moly from the outboard limiter. Raised prefill to 1.9 x 10^-5 Torr. Also noticed that the deuterium gas pressure had dropped to about 13 pounds. It will be raised to 17 pounds for this shot. Increased Ip to 1.1 MA. Disrupted at 1.1 sec with just over 1 MA of Ip.
Feb 9 1995 11:00:47:360AM	950209010	Joseph Snipes	Shot 10 Try again. Shot 9 hit the OH1 current limit at 20 kA. We will raise it for this shot to 26 kA. Also adjusted the EF4U programming to extend out to 1 sec. It had been ramping down at 0.944 sec. Reduced RCUR to 0.6645 m to increase outer gap. Ramped CLEARIN to zero at 0.257 sec rather than 0.37 sec. Also increased EF3 current limit to 17 kA. Disrupted at about 0.5 sec.
Feb 9 1995 11:24:15:120AM	950209011	Joseph Snipes	Shot 11 Reversed change made on shot 10 to CLEARIN so that it reached zero at 0.45 sec. Also increased EF4U current to 2 kA throughout the flattop to try to remove the demand on EF3 and EF2. Disrupted violently at 0.6 sec. It appears that the OH1 voltage is railed at 400 V, so we need a slower ramp rate.
Feb 9 1995 11:35:22:730AM	950209012	Joseph Snipes	Shot 12 Reloaded segment 2 from shot 8 to backtrack to 1 MA. Changed RCUR from 0.67 to 0.6655 m to take some heat off of the RF limiter. Fizzle!
Feb 9 1995 11:53:26:780AM	950209013	Joseph Snipes	Shot 13 Try again. Disrupted at 0.4 sec. Looks like a slow current rise. We may have impurity problems or too high a prefill.
Feb 9 1995 11:59:19:410AM	950209014	Joseph Snipes	Shot 14 Try reducing the prefill to 1.6 x 10^-5 Torr. Fizzle.
Feb 9 1995 12:05:39:070PM	950209015	Joseph Snipes	Shot 15 Try increasing the prefill to 1.8 x 10^-5 Torr. Fizzle!
Feb 9 1995 12:29:14:580PM	950209016	Joseph Snipes	Shot 16 Increased EF4 current early to -1050 A from -1035 A. Changed the wrong segment, segment 2. However, the startup looked a bit better anyway. Wolfe suggests a fix Ian made for low field startup by increasing the RCUR gain early from 0.01 to 0.04 sec from 4 to 9.5.
Feb 9 1995 12:38:02:990PM	950209017	Joseph Snipes	Shot 17 Wolfe suggests a fix Ian made for low field startup by increasing the RCUR gain early from 0.01 to 0.04 sec from 4 to 9.5. Disrupts violently at 0.46 sec at about 0.85 MA.
Feb 9 1995 12:52:11:660PM	950209018	Joseph Snipes	Shot 18 Reloading shot 2. Good shot.
Feb 9 1995 01:09:29:900PM	950209019	Joseph Snipes	Shot 19 Raising Ip to 0.9 MA with a slow ramp to 0.915 at 1 sec. Reduced rate of rise of Ip by a bit for the final 50 kA. Also increased RCUR to 0.662 m from 0.66 m. Good shot.
Feb 9 1995 01:19:16:450PM	950209020	Joseph Snipes	Shot 20 Reduced early gas puff in segment 1 by a small amount between 30 and 70 msec to try to improve the current rise. Good shot.
Feb 9 1995 01:34:31:340PM	950209021	Joseph Snipes	Shot 21 Increased Ip to 1 MA with a slow rate of rise so that it reaches 1 MA at 0.552 sec and ramps to 1.015 MA by 1 sec. Good shot.
Feb 9 1995 01:56:15:630PM	950209022	Joseph Snipes	Shot 22 Increased Ip to 1.1 MA with a slow rate of rise so that it reaches 1.1 MA at 0.65 sec and ramps to 1.115 MA by 1 sec. Good shot, but disrupted at 1 sec due to a fault in OH1.
Feb 9 1995 02:09:55:230PM	950209023	Joseph Snipes	Shot 23 Try again. Reduced the initial gas puff a bit between 0.03 and 0.1 sec to try to improve the current rise. Good shot at 1.12 MA!
Feb 9 1995 02:10:58:410PM	950209023	Joseph Snipes	Shot 23 Try again. Reduced the initial gas puff a bit between 0.03 and 0.1 sec to try to improve the current rise. Good shot at 1.12 MA! Dithering on H alpha. Near the H-mode threshold.
Feb 9 1995 02:21:51:840PM	950209024	Joseph Snipes	Shot 24 One more time . . . Violent disruption at 1.12 sec. EF3 fault at 0.93 sec.
Feb 9 1995 02:33:22:810PM	950209025	Joseph Snipes	Shot 25 Try again. Another violent disruption. OH1 fault at 0.98 sec. Disrupted at 1.005 sec.
Feb 9 1995 02:46:10:660PM	950209026	Joseph Snipes	Shot 26 One more once. Good shot at 1.12 MA!
Feb 9 1995 03:05:35:500PM	950209026	Joseph Snipes	Shot 27 Raised Ip to 1.2 MA from 0.75 s to 1.0 s. Also decreased the rate of decay of Ip after 1 sec. Disrupted violently at 0.5 sec.
Feb 9 1995 03:06:31:430PM	950209028	Joseph Snipes	Shot 28 Fizzle!
Feb 9 1995 03:22:31:470PM	950209029	Joseph Snipes	Shot 29 Got 1.2 MA, but EF3 failed at 0.92 sec and led to a disruption against the RF antenna at 0.98 sec with nearly 1 MA of plasma current. 200 kA halo current on lower halo rogowski.
Feb 9 1995 03:44:58:680PM	950209030	Joseph Snipes	Shot 30 Try 1.2 MA one more time. Changed EF4 current from 1943 A to 2500 A during the current flattop. Fizzle! EFC failed. Short delay to look into the problem.
Feb 9 1995 04:07:11:670PM	950209031	Joseph Snipes	Shot 31 EF3 and EFC test shot. EFC worked, but EF3 inverted again on its own. More time needed to try to fix the problem.
Feb 9 1995 04:18:11:190PM	950209032	Joseph Snipes	Shot 32 Another EF3 test shot. EF3 inverted again at only 6 kA. There are real problems with EF3. Wolfe's idea is to bring EF4 up in proportion to Ip so that it should be up to 3 kA during the flattop. So, I loaded that into model in case we do get another shot.
Feb 9 1995 04:21:33:010PM	950209032	Joseph Snipes	Run ending now to allow the engineers to fix the EF3 supply.
Feb 9 1995 04:38:00:940PM	950209032	Joseph Snipes	Overall, the run was not very successful due to the power supplies not being able to handle being pushed to their limits. There were failures in OH1 and EF3 that cost us a large number of shots and the failure of EF3 finally ended the run early around 4:00 pm. Nonetheless, some progress was made at developing high current discharges. Two shots were achieved above 1.1 MA without disruptions (shots 23 and 26). We also reached 1.2 MA on shot 29 which disrupted late due to power supply problems. There were a total of 32 shots, 22 plasmas, 8 fizzles, and two power supply test shots.

Engineering Operator Comments
Shot	Time	Type	Status	Comment
1	08:29:19:620AM	Plasma	Ok	no faults, plasma
2	08:43:37:910AM	Plasma	Ok	no faults, plasma
3	08:57:30:580AM	Plasma	Ok	no faults
4	09:06:17:290AM	Plasma	Ok	comm fail ef1L, plasma
5	09:25:34:050AM	Plasma	Bad	ef1l comm fault
6	09:43:15:160AM	Plasma	Ok	no faults
7	09:56:18:100AM	Plasma	Ok	no faults
8	10:07:25:610AM	Plasma	Ok	no faults
9	10:24:55:650AM	Plasma	Ok	comm fail oh2L plasma
10	10:56:45:930AM	Plasma	Ok	no faults
11	11:13:24:120AM	Plasma	Ok	disruption induced comm faults
12	11:33:06:770AM	Plasma	Ok	no faults
13	11:43:24:470AM	Plasma	Ok	no faults
14	11:54:18:090AM	Plasma	Ok	no faults
15	12:03:55:690PM	Plasma	Ok	no faults
16	12:14:04:980PM	Plasma	Ok	no faults
17	12:28:13:820PM	Plasma	Ok	no faults
18	12:38:48:160PM	Plasma	Ok	no faults
19	12:56:33:390PM	Plasma	Ok	no faults
20	01:10:51:180PM	Plasma	Ok	no faults
21	01:22:28:580PM	Plasma	Ok	no faults
22	01:36:13:560PM	Plasma	Ok	oh1 cond fault after disruption
23	01:58:38:750PM	Plasma	Ok	no faults
24	02:10:39:700PM	Plasma	Ok	no faults
25	02:23:07:480PM	Plasma	Bad	conduction fail oh1
26	02:37:38:520PM	Plasma	Ok	no faults
27	02:51:58:980PM	Plasma	Ok	no faults
28	03:03:36:190PM	Plasma	Ok	no faults
29	03:12:56:130PM	Plasma	Bad	ef3 inverts early
30	03:29:48:540PM	Plasma	Bad	no efc
31	03:59:41:760PM	Test	Bad	ef3 dig sys fault at 10ka
32	04:12:33:900PM	Test	Bad	ef3 fault