Alcator C-Mod Run 930803 Information

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Miniproposals
Miniproposal:013
Date Filed: 7/16/1993
Title:Discharge development
First Author:Steve Wolfe
Session Leader:John Goetz (shots 1-15)

Operators
Session leader(s):John Goetz
Physics operator(s):Earl Marmar
Engineering operator(s):Frank Silva

Engineering Operator Run Comment
silva/vinnie oh test start

Session Leader Plans

Physics Operators Plans

Session Leader Summaries

Physics Operator Summaries
Entered: Jul 7 2004 04:36:50:270PM
Author: To Be Determined
Summary of 930803
Physics Op: Marmar
Assistant: Goetz
Engineer: Silva

This was a classic Tuesday run.

Goals of the run:

1) set up a good discharge for the fast probe experiments: elongated, fat
(R ~ 69 cm), moved down (z ~ -2 cm).

2) Piggy-back pellets, laser ablation impurity injection, RF conditioning,
I_p feedback.

3) test the effects of ECDC over the weekend, with no ECDC in the morning
before the run.

There were 8 attempts to make plasma. Of these 2 were good (shots 3 and 7),
2 were fizzles and 4 were duds. All but one of the duds were due to power
supply / CAMAC problems.

The 2 shots we got had current feedback enabled, and there were some
apparent effects, although the control was not evident.

On shot 3, the feedback tried to reduce the current late in the shot,
possibly contributing to the disruption. On shot 7, we reprogrammed the
demand to look more like what we got on shot 3. Shot 7 was a good long
shot, although the R and z positions were not in good agreement with what
we had asked for. The z_cur controller gain was rather low, which might
have been part of the problem, although the I_p feedback may also have been
interfering. Had we gotten another shot, the I_p feedback would have been
turned off.

Problems:

The EFC lower coil was not cooling, so we could not use the chopper.

EF1U had a ripple problem throughout the day.

For most of the run, there were spurious noise spikes on the magnetics and
soft x-ray signals from the TRAQ digitizers. They were not present on the
hybrid digitized signals. This was traced to a software problem with crate
controller software.

On shot 2, the EF breakers tripped before commutation, leading to a dud.

Shots 4 and 5 were duds for no apparent reason. Shot 6 was a fizzle, with
relatively high fill pressure (1.4e-5)

After shot 7, the data aquisition did not complete in a timely fashion.
During the first attempt to init for shot 8, there was a computer problem.
After going back to recool and then init again, the cycle went through but
there were many errors. In particular, failure to initialize decoders led
to the the result that the bus Rogowski integrators appeared to be
resetting throughout the shot. This in turn caused to the hybrid to force
extra current out of the EF's, but apparently not up to the PLC-set current
limits. The init problems also meant that most of the data from the shot
were lost. During the shot, several GFI electrical outlets in the cell
tripped, causing a loss of power to 2 TV cameras, and an inner seal pump.
These were reset after the shot; the cause was not discovered. At this time
ground faults were also discovered. There was a fault with about 20 mA of
current flowing from the E section of the support stand to ground. This was
traced to ventilation hose, a piece of which was touching the stand under D
port. The vessel was also showing a 3 ohm resistance to ground. The cause
of this was not determined; it was speculated that it is due to ice at one
of the legs.

In light of the data aquisition problems, we ran a data aquisition only
test shot (9) which was successful. Shot 10 was a power supply test shot
with the PLC current limits all set to low values. This showed ripple
problems on EF1, OH1 and OH2.

Shot 11 was a PLC control test of EF1. The ripple persisted, and it was
decided to terminate the physics run to work on the power supply problems.
Shot 11 was also used to test the pellet injector, firing 3 small pellets
into the chamber. This caused an overpressure alarm on TORVAC, with the
vessel pressure rising to approximately 100 millitorr just after the shot.
The torus gate valves and pumps did not shut down, and the torus pressure
was back to normal after about 1 minute (<1e-6). The RGA showed that approximately
1% of the gas was deuterium, and the rest hydrogen (the pellets are
deuterium, the pusher gas is hydrogen).


Session Leader Comments
Aug 3 1993 09:09:53:180AMJohn GoetzRUN 930803

PO: Marmar
Asst: Goetz
Eng: Silva

Today's run is a discharge development run. It is following MP013 in support
of MP014 and MP016. Some hoped for accomplishments today are:
debug OH1 ripple (engineering)
achieve reliable startup
make fat low plasmas to match the limiter and the FSP
plasma current control (secondary)
impurity injection (piggyback)
argon puffing (piggyback)
pellet injection (piggyback)


Aug 3 1993 09:18:02:180AMJohn GoetzRUN 930803

PO: Marmar
Asst: Goetz
Eng: Silva

Start from shot 930729019
Changes:
-load the ZCUR controller from shot 930728025 (has -2 cm movement)
change the PID start time from 30 to 50 msec and allow the
request for the -3cm program to last from 150msec til the end.
-change RCUR controller from 0.64 to 0.66 m
-lowered the argon puff
-raised PULSE_GAS_2 (the main fueling) and removed the second puff
from PULSE_GAS_3
-ZCUR (chopper) PID's zeroed because no EFC coil cooling today
-loaded EF2 waveform from 930730014 to compensate for no EFC
-loaded IP controller from 930630028 which consists of OH1, EF1L,
EF1U, and EF3. PID turns on in steps of 2 from 150 to 260msec.
Drawn value of 400kA.

Aug 3 1993 09:20:33:250AMJohn GoetzShot 930803001

Fizzle
1mT radial field at breakdown

For shot 002:
Change S_Br from +8.5mT to +7.5mT

Aug 3 1993 09:37:44:690AM930803002John GoetzShot 930803002

Dud
EF1 troubles - PF breaker pulled out - commutation failure

For shot 003:
none for breakdown
less ambitious on the IP controller PID values

Aug 3 1993 10:09:35:840AM930803003John GoetzShot 930803003

Plasma
450 kAmps - disruptive
bad x-ray channel and trouble with the flux loops
FFIT says the plasma moves in around 180msec

For shot 004:
load in plasma waveform from shot 003 for IP and remove the disruption
increased PULSE_GAS_2 (main fueling)

Aug 3 1993 10:25:03:030AM930803004John GoetzShot 930803004

Dud
noise troubles with the flux loops

For shot 005:
fill pressure to 1.2e-5 from 1.1e-5

Aug 3 1993 11:06:39:100AM930803005John GoetzShot 930803005

Dud
things look o.k., should have gone
noise troubles with the flux loops - Granetz through the wall to investigate
no problems found

For shot 006:
fill pressure to 1.4e-5 from 1.2e-5

Aug 3 1993 11:32:28:600AM930803006John GoetzShot 930803006

Fizzle
still noise on magnetics and x-ray signals. No extra noise on the probes and
bolometry signals.

For shot 007:
fill pressure to 1.0e-5 from 1.4e-5

Aug 3 1993 11:59:50:960AM930803006John GoetzShot 930803007

Plasma - 450kA - 520msec duration
couldn't hold the plasma out and couldn't hold it down
pellet injector gate valve opened during check - brought the pressure down
to 7e-6 - will change to open during INIT

For shot 008:
no changes

Aug 3 1993 02:07:55:270PM930803008John GoetzShot 930803008

Dud
many errors in decoder INITs and stores
an INIT trouble with the bus rogowski decoder caused a bad integrator reset
which in turn put garbage in - garbage out on the hybrid
some TV cameras have turned off - heater power GFI's tripped at E,F, & J-port
exhaust tube causing ground fault remedied

For shot 009:
data shot only - no power supplies

Aug 3 1993 02:26:48:230PM930803009John GoetzShot 930803009

No data init and store problems
Noise is back on the magnetics

For shot 010:
low current power supply test

Aug 3 1993 02:47:51:540PM930803010John GoetzShot 930803010

EF1 commutation failure.
Much noise on OH1, OH2's, and EF1's
Still some noise on the magnetics

For shot 011:
EF1 only under PLC control

Aug 3 1993 03:27:52:400PM930803011John GoetzShot 930803011

EF1 supply didn't work
Pellet fired into vessel - pressure to tens of mTorr

For shot 012:
Rest of run dedicated to engineering tests of coil systems

Physics Operator Comments

Engineering Operator Comments
ShotTimeTypeStatusComment
109:06:53:560AMPlasmaOk09:11 first shot
209:22:22:300AMPlasmaBadcommm fail ef1
309:39:31:450AMPlasmaOk450ka
410:08:47:910AMPlasmaOkno faults
510:25:17:010AMPlasmaOk
611:17:56:530AMPlasmaOk
711:41:50:020AMPlasmaOkgood shot
812:12:26:480PMTestBadquestion
902:13:09:290PMTestOktest ok
1002:31:43:930PMTestBadef1 comm. fail. all supplies current liomi
1103:02:02:700PMTestBadef1 still much ripple
1203:34:53:240PMTestOkdata system test
1303:54:27:760PMTestOkSeems ok
1404:12:32:330PMTestOkef1 u+l much better now with V + I currents lowered by .5
1504:36:32:640PMTestBad