Alcator C-Mod Run 930615 Information

Miniproposals

Miniproposal:

Date Filed:

Title:

First Author:

Session Leader: John Goetz (shots 1-25)

Operators
Session leader(s):	John Goetz
Physics operator(s):	Unknown
Engineering operator(s):	Unknown

Engineering Operator Run Comment
Plasma position and shape control; test of OH2 will use some shots but n

Session Leader Plans

Physics Operators Plans

Session Leader Summaries

Entered: Jul 7 2004 03:49:07:900PM

Author: To Be Determined

A leak opened up in the vacuum around 8:30 am when the cooling was
turned on again to prepare for the run. The leak showed up as almost
all nitrogen, although that may be an air leak. It may have been
related to the freezing of the G-bottom, which arose because a heater
had been left disconnected. This must not happen. Whoever was
responsible, don't do it again.

The leak did not disappear but remained in the low 10^-7 range partial
pressure of nitrogen even after unfreezing the port. Therefore
no attempts at plasma were undertaken. Instead, various power tests
were done. Also ECDC between shots, under manual control, was
successfully tested.

It was established by deliberately inducing a commutation failure that
at the present voltages, OH2 is able to protect itself against
overcurrent via the PLC-set current limits. The test showed OH2
limitation at 18kA, the set limit.

Danger still exists if OH2 were to fail to invert to protect itself.
OH2 inversion does not seem to be fully reliable, as the persistent
imbalance in OH2s has shown. Tests under PLC control (8-11)
demonstrate OH2 PLC regulation at about 25kA but the inversion is
very clearly imbalanced.

OH1 under PLC control shows much the same syndrome as OH2U. It does
not immediately give its full inversion voltage. Instead, when
inverted from about 25kA it gives about -200V gradually increasing to
-500V as the current ramps down.

It is believed that the problem has been isolated and it will be
worked on tonight.

This is important not only because of the OH2 imbalance but also
because the safest way to avoid OH2 overcurrents in the event of
commutation failure is NOT to commutate OH1. That way, even if the OH2
power-supply were to autocrowbar (the worst scenario for the
overcurrent problem), provided that all OH supplies autocrowbar
together (which I am told is the case) there would be automatic
removal of the dangerous induced voltage. OH1 voltage would be zeroed
as well as OH2 so the current would not be driven up in OH2. This is
in contrast to the situation where OH1 is commutated into the resistor.
The resistor will continue to apply voltage regardless of the OH1
supply being autocrowbarred. If we can get the full specified
inversion voltage out of OH1 then we can probably dispense with the
need to commutate it.

The last half hour was devoted to single coil current tests for the
purposes of verifying the structure electromagnetic response.

Physics Operator Summaries

Session Leader Comments

Jun 15 1993 10:45:21:200AM John Goetz Outline for today's run:
1) Test OH1 and OH2 to see if higher precharge on OH1 is acceptable
if OH2 fails to commutate.
2) Understand hard x-ray bursts.
3) Use EF3 for divertor work.

Jun 15 1993 10:43:20:600AM 930615002 John Goetz TF & OH only for engineering test. EF1 by mistake.

Jun 15 1993 10:38:48:910AM 930615003 John Goetz This shot is OH only to get a baseline.

Jun 15 1993 11:19:11:170AM 930615005 John Goetz Commutation failure induced in OH2L on purpose.
Current in OH2L rises to 18kA (PLC limit)

Jun 15 1993 11:19:23:680AM 930615005 John Goetz Commutation failure induced in OH2L on purpose.
Current in OH2L rises to 18kA (PLC limit)

Jun 15 1993 11:20:14:370AM 930615006 John Goetz Commutation failure induced in OH2U on purpose.
Current in OH2L rises to 19.5kA (PLC limit = 18kA)

Jun 15 1993 11:26:53:650AM 930615007 John Goetz TF and OH's on this time.
Commutation failure induced in OH2U on purpose.
Current in OH2U rises to 19.5kA (PLC limit = 18kA)
TF does not seem to change the OH2U waveform between shots 006 and 007.

Note: OH2L in notes for shot 006 should be OH2U.

Jun 15 1993 12:32:22:380PM 930615007 John Goetz The previous shots were to show that the OH2's could protect themselves at
the present current level. The PLC limit was obeyed and the OH2's protected
the coils.

Next, the OH supplies will be run at the higher current levels,
put into inversion, and then checked for commutation failures.

Attempting to do ECDC between shots.

OH2U and OH2L at 25kA.
OH2L current limits at 24.6kA and OH2U current limits at 26.2kA
No commutation faults.
OH2L makes it to full inversion (-200V) but OH2U does not (-100V)

Jun 15 1993 12:32:34:350PM 930615008 John Goetz The previous shots were to show that the OH2's could protect themselves at
the present current level. The PLC limit was obeyed and the OH2's protected
the coils.

Next, the OH supplies will be run at the higher current levels,
put into inversion, and then checked for commutation failures.

Attempting to do ECDC between shots.

OH2U and OH2L at 25kA.
OH2L current limits at 24.6kA and OH2U current limits at 26.2kA
No commutation faults.
OH2L makes it to full inversion (-200V) but OH2U does not (-100V)

Jun 15 1993 12:50:33:960PM 930615009 John Goetz Repeat of shot 008. Try to fix the inversion discrepancy.

No changes in inversion voltages.
No commutation faults.

Jun 15 1993 02:15:44:060PM 930615010 John Goetz Engineers think they know where the OH2 inversion discrepancy lies. Needs to
be fixed offline.

Error in inversion traced to loose connection. Unsure whether or not problem
was fixed as it disappeared during investigation.

Shot 010 stopped due to PLC hangup.

Jun 15 1993 02:49:35:540PM 930615011 John Goetz OH2U only. Still only -80V during full inversion.

Jun 15 1993 03:06:52:380PM 930615012 John Goetz OH1 only. 25kA under PLC control. No commutation.

25kA from -1.5 to -1.2 sec then ramp down to 1200A. Causes unknown.

Jun 15 1993 03:49:47:160PM 930615013 John Goetz Repeat of shot 012.

Errors of shot 012 appear to be due to the fact that the power supply was not
under PLC control but under hybrid control.

Pulse was indeed at 24.4kA but at inversion the supply did not go directly
to full inversion (-500V). It only went to -200V. Power supply did invert
correctly on shot 012.

Next shot will be with a narrow pulse to see if the inversion problem
is pulse width related.

Jun 15 1993 04:07:34:780PM 930615015 John Goetz OH1 only under PLC control at 25kA.

Pulse narrower than 013. Inversion is only to -200V instead of -500V.

Jun 15 1993 04:29:40:870PM 930615016 John Goetz OH1 only at 12kA under PLC control to check inversion behavior with no
commutation.

Inversion voltage is now about -350V.

Jun 15 1993 04:42:02:310PM 930615017 John Goetz EF1U only for Horne-Tinios tests.

Jun 15 1993 04:50:21:380PM 930615018 John Goetz EF2U only for Horne-Tinios tests.

Jun 15 1993 05:00:04:390PM 930615019 John Goetz EF2L only for Horne-Tinios tests.

Physics Operator Comments

Engineering Operator Comments

Shot Time Type Status Comment

1 08:09:22:830AM Test Ok Static test of OH2 OK

2 09:53:17:150AM Test Ok TF and OH test; all OK but OH2L still shows spurious commutation fault

3 10:22:00:300AM Test Ok OH test w/o TF; all OK

4 10:39:23:120AM Test Bad data system did not arm the CAMAC - data from last shot

5 10:53:14:850AM Test Ok Deliberate commutation failure in OH2 SCR switch. OK; current does not e

6 11:06:17:810AM Test Ok OH2U deliberate SCR switch comm failure. Power supplies responded OK

7 11:21:17:740AM Test Ok Test OH2 with TF; OK

8 12:22:14:530PM Test Ok 25 kA commutation test of OH2U and OH2L OK; some difference in inversion

9 12:38:42:630PM Test Ok OH2 commutation test 25 kA OK but still inversion imbalance

10 02:10:38:670PM Test Ok OH2 still unbalanced in inversion; no other problems

11 02:41:44:600PM Test Ok OH2U ONLY, still not inverting hard enough

12 02:54:41:720PM Test Bad OH1 test did not follow PLC program; instead followed hybrid program!

13 03:36:13:910PM Test Ok OH1 pul;se OK but inversion the same as problem OH2 supply

14 03:51:04:910PM Test Bad OH1 commutation was inadvertently enabled; disable during CHECK caused f

15 04:02:30:390PM Test Ok OH1 short pulse ok

16 04:25:10:450PM Test Ok OH1 12 ka test shows that current gain in inversion endstop calc is too

17 04:39:15:000PM Test Ok EF1 U test OK

18 04:48:34:810PM Test Ok EF2U test OK

19 04:56:52:690PM Test Ok EF2L test OK

20 05:41:48:780PM Test Ok josh testing data system

21 06:58:26:190PM Test Ok steve's camac problems ....

22 07:07:43:050PM Test Ok turned off 10 and 9 and 11 got fixed

23 07:15:05:500PM Test Ok still testing worked again

24 07:20:58:060PM Test Bad a missing cadf breaks the next cadf !!!!

25 07:29:01:010PM Test Ok turned off cadf_10 and it all worked again

Session Leader Comments
Jun 15 1993 10:45:21:200AM		John Goetz	Outline for today's run: 1) Test OH1 and OH2 to see if higher precharge on OH1 is acceptable if OH2 fails to commutate. 2) Understand hard x-ray bursts. 3) Use EF3 for divertor work.
Jun 15 1993 10:43:20:600AM	930615002	John Goetz	TF & OH only for engineering test. EF1 by mistake.
Jun 15 1993 10:38:48:910AM	930615003	John Goetz	This shot is OH only to get a baseline.
Jun 15 1993 11:19:11:170AM	930615005	John Goetz	Commutation failure induced in OH2L on purpose. Current in OH2L rises to 18kA (PLC limit)
Jun 15 1993 11:19:23:680AM	930615005	John Goetz	Commutation failure induced in OH2L on purpose. Current in OH2L rises to 18kA (PLC limit)
Jun 15 1993 11:20:14:370AM	930615006	John Goetz	Commutation failure induced in OH2U on purpose. Current in OH2L rises to 19.5kA (PLC limit = 18kA)
Jun 15 1993 11:26:53:650AM	930615007	John Goetz	TF and OH's on this time. Commutation failure induced in OH2U on purpose. Current in OH2U rises to 19.5kA (PLC limit = 18kA) TF does not seem to change the OH2U waveform between shots 006 and 007. Note: OH2L in notes for shot 006 should be OH2U.
Jun 15 1993 12:32:22:380PM	930615007	John Goetz	The previous shots were to show that the OH2's could protect themselves at the present current level. The PLC limit was obeyed and the OH2's protected the coils. Next, the OH supplies will be run at the higher current levels, put into inversion, and then checked for commutation failures. Attempting to do ECDC between shots. OH2U and OH2L at 25kA. OH2L current limits at 24.6kA and OH2U current limits at 26.2kA No commutation faults. OH2L makes it to full inversion (-200V) but OH2U does not (-100V)
Jun 15 1993 12:32:34:350PM	930615008	John Goetz	The previous shots were to show that the OH2's could protect themselves at the present current level. The PLC limit was obeyed and the OH2's protected the coils. Next, the OH supplies will be run at the higher current levels, put into inversion, and then checked for commutation failures. Attempting to do ECDC between shots. OH2U and OH2L at 25kA. OH2L current limits at 24.6kA and OH2U current limits at 26.2kA No commutation faults. OH2L makes it to full inversion (-200V) but OH2U does not (-100V)
Jun 15 1993 12:50:33:960PM	930615009	John Goetz	Repeat of shot 008. Try to fix the inversion discrepancy. No changes in inversion voltages. No commutation faults.
Jun 15 1993 02:15:44:060PM	930615010	John Goetz	Engineers think they know where the OH2 inversion discrepancy lies. Needs to be fixed offline. Error in inversion traced to loose connection. Unsure whether or not problem was fixed as it disappeared during investigation. Shot 010 stopped due to PLC hangup.
Jun 15 1993 02:49:35:540PM	930615011	John Goetz	OH2U only. Still only -80V during full inversion.
Jun 15 1993 03:06:52:380PM	930615012	John Goetz	OH1 only. 25kA under PLC control. No commutation. 25kA from -1.5 to -1.2 sec then ramp down to 1200A. Causes unknown.
Jun 15 1993 03:49:47:160PM	930615013	John Goetz	Repeat of shot 012. Errors of shot 012 appear to be due to the fact that the power supply was not under PLC control but under hybrid control. Pulse was indeed at 24.4kA but at inversion the supply did not go directly to full inversion (-500V). It only went to -200V. Power supply did invert correctly on shot 012. Next shot will be with a narrow pulse to see if the inversion problem is pulse width related.
Jun 15 1993 04:07:34:780PM	930615015	John Goetz	OH1 only under PLC control at 25kA. Pulse narrower than 013. Inversion is only to -200V instead of -500V.
Jun 15 1993 04:29:40:870PM	930615016	John Goetz	OH1 only at 12kA under PLC control to check inversion behavior with no commutation. Inversion voltage is now about -350V.
Jun 15 1993 04:42:02:310PM	930615017	John Goetz	EF1U only for Horne-Tinios tests.
Jun 15 1993 04:50:21:380PM	930615018	John Goetz	EF2U only for Horne-Tinios tests.
Jun 15 1993 05:00:04:390PM	930615019	John Goetz	EF2L only for Horne-Tinios tests.

Engineering Operator Comments
Shot	Time	Type	Status	Comment
1	08:09:22:830AM	Test	Ok	Static test of OH2 OK
2	09:53:17:150AM	Test	Ok	TF and OH test; all OK but OH2L still shows spurious commutation fault
3	10:22:00:300AM	Test	Ok	OH test w/o TF; all OK
4	10:39:23:120AM	Test	Bad	data system did not arm the CAMAC - data from last shot
5	10:53:14:850AM	Test	Ok	Deliberate commutation failure in OH2 SCR switch. OK; current does not e
6	11:06:17:810AM	Test	Ok	OH2U deliberate SCR switch comm failure. Power supplies responded OK
7	11:21:17:740AM	Test	Ok	Test OH2 with TF; OK
8	12:22:14:530PM	Test	Ok	25 kA commutation test of OH2U and OH2L OK; some difference in inversion
9	12:38:42:630PM	Test	Ok	OH2 commutation test 25 kA OK but still inversion imbalance
10	02:10:38:670PM	Test	Ok	OH2 still unbalanced in inversion; no other problems
11	02:41:44:600PM	Test	Ok	OH2U ONLY, still not inverting hard enough
12	02:54:41:720PM	Test	Bad	OH1 test did not follow PLC program; instead followed hybrid program!
13	03:36:13:910PM	Test	Ok	OH1 pul;se OK but inversion the same as problem OH2 supply
14	03:51:04:910PM	Test	Bad	OH1 commutation was inadvertently enabled; disable during CHECK caused f
15	04:02:30:390PM	Test	Ok	OH1 short pulse ok
16	04:25:10:450PM	Test	Ok	OH1 12 ka test shows that current gain in inversion endstop calc is too
17	04:39:15:000PM	Test	Ok	EF1 U test OK
18	04:48:34:810PM	Test	Ok	EF2U test OK
19	04:56:52:690PM	Test	Ok	EF2L test OK
20	05:41:48:780PM	Test	Ok	josh testing data system
21	06:58:26:190PM	Test	Ok	steve's camac problems ....
22	07:07:43:050PM	Test	Ok	turned off 10 and 9 and 11 got fixed
23	07:15:05:500PM	Test	Ok	still testing worked again
24	07:20:58:060PM	Test	Bad	a missing cadf breaks the next cadf !!!!
25	07:29:01:010PM	Test	Ok	turned off cadf_10 and it all worked again