Alcator C-Mod Run 931014 Information

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Miniproposals
Miniproposal:
Date Filed:
Title:
First Author:
Session Leader:Bruce Lipschultz (shots 1-26)

Operators
Session leader(s):Bruce Lipschultz
Physics operator(s):John Goetz
Engineering operator(s):Frank Silva,David Gwinn

Engineering Operator Run Comment
gwinn/silva

Session Leader Plans

Physics Operators Plans

Session Leader Summaries

Physics Operator Summaries
Entered: Jul 7 2004 04:36:50:490PM
Author: To Be Determined
Physics operator summary for 931014

EO: Silva, Gwinn
PO: Goetz
SL: Lipschultz

Run 931014 was in support of Mini-Proposal #016 - Scrape-off Layer
Characterization. To this end SN discharges were run in deuterium and the
divertor gas puff system was used to put deuterium into the private flux
region. The divertor gas was puffed in at different times, for varying
durations and varying supply pressures. Pellets were also fired into these
discharges. Results from this run will be provided by the Session Leader.

The run started with a reload of shot 931012005 which was an 800 kAmp shot
that had the strike points and the x-points in somewhat the correct location.
Changes to this shot included lowering the plasma, moving the x-point in,
some tweaks to the feedback on ZCUR(2), and some tweaks to PULSE_GAS_3.

The run was much better in terms of startup. Only minor tweaks to the early
fuel gas were needed to slow the density rise. There were no MARFES early in
the discharges which led to rapid density rises. Fill gas was up to 1.5e-5
gauge for the last half of the run.

There were three duds today, two of which had RF assist on for breakdown. The
fill was raised after the second dud and twelve plasmas followed. It is
difficult to know when and if to raise the fill after disruptions. Should it
be changed when it was a moly injection induced disruption?, a pellet induced
disruption?, a shark fin?


Notes: ZCUR was programmed to be -.03m to get the x-points in the correct
location for these plasma currents
Changes to RCUR and IC_EF1L were done to try and keep the plasma off
of the inner nose and outer limiter (early) respectively.
The gains on the slow ZCUR wire were fiddled with before the run to get
back to Run 931008
Plasmas were obtained with the fill pressure as high as 1.5e-5 gauge.


Engineering today: One unexplained inversion of the OH1 power supply (shot
003, time = .4s) Otherwise reliable operation at 5.2T and 800+kA
plasma current. Two shots with commutation failures but no blown fuses.
Trouble with DAQ3 highway held up the run for 40 minutes. A crate
in the power room was glitched some time before the run (also took
out the RF until it was reset). Inspection of the DAQ3 crates is to
be added to the pre-run routine.

Scorecard: 26 shots = 23 plasmas + 3 duds

Shot summary for Run 931014

Reload of 931012005

Changes:
lowered PULSE_GAS_3 to 40V @ .8s
extended V_EF3 until 1.3s
S_IP = -780000 (rampdown from .9 to 1.3)
S_ZCUR ramps back to 0. @ 1s (was 1.4s)
S_ZCUR = -.025
P_ZCUR(2) = 1 @ .4 D_ZCUR(2) = 2 @ .5 I_ZCUR(2) = 2
S_RXL = -.01 @ .5
removed dropout from P_ZCUR(3) and D_ZCUR(3)

Shot change result
____ _____ ______
1 P_0=1.2e-5 plasma
2 lower PULSE_GAS_3 between .05 & .1s plasma
3 S_RCUR=.7 @ 0 & .68 @ .15s PG3 = 35V @ .8s plasma
4 no changes plasma
5 S_IP = 825000 @ .9s plasma
6 S_IP = 850000 @ .9s S_ICEF1U = 3000A @ .5s plasma
7 lower PG3 to 30V @ .4s lower PG3 before .1s D2 puff in
divertor @.35 pellet @ .65 RF @ .85 plasma
8 lower PG3 to 31.5V @ .075s S_R_IN = 0 for all time plasma
9 turn off PG3 @ .45s dud
10 RF assist for breakdown plasma
11 add PG3 after .9s raise div gas puff pressure plasma
12 raise div puff pressure turn off PG3 earlier two pellets
RF throughout shot plasma
13 div puff @ .15 PG3 off @ .3 raise S_IP to counteract Ne dud
14 P_0=1.3e-5 plasma
15 P_0=1.4e-5 div puff @ .25s plasma
16 pellet @ .75s up div puff presure S_ZCUR=-.03
lower P_ICEF1L after .5 plasma
17 small pellet @ .75s div puff now on inner wall PG3=33V@.075s
S_ZCUR=-.03@.7 S_ICEF1L = 0 @ 1.5 plasma
18 div puff to outer divertor S_ZCUR=-.03 after .4s plasma
19 no div gas puff large pellet @ .7s S_ZXL = -.01 @ .4s
S_ZCUR = -.03 @ .4s S_ICEF1L= 0 @ 1.s plasma
20 div gas puff in private flux large pellet @ .75s plasma
21 PG3 = 30V @ .9s no div gas puff plasma
22 Ar gas puff in div plasma
23 Ar puff from inner wall S_IP=-900000 @ .9s plasma
24 Ar puff in div S_IP=-950000 @ .9s PG3 = 38V @ .3s plasma
25 PG3 = 50V @ .15s IC_EF4=1500A @ 1. IC_EF1L=-3250A @ .15s plasma
26 PG3 = 54V @ .15s S_IP=1.1e6 dud

Session Leader Comments
Oct 14 1993 09:35:19:730AMBruce Lipschultzrun 931014

session leader: Bruce Lipschultz
physics operator: John Goetz
eng. operator: D. Gwinn, F. Silva

This run is based on mini-proposal 16 Scrapeoff Layer Characteristics I.
We will start the run by loading in shot number 931014005 an 800kA 8e19
nel shot. We will then try to lower the density to ~ 4e19. At that point
the D2 gas puffing in the divertor will be turned on and we will try
to control the central plasma density by puffing with the the three
available capillary tubes. We will try to asses the maximum density
achievable with the different tubes and thus the relative efficiency of the
different gas puff locations. The tubes in use today are numbers
7, 9 and 14 (on the feedthru). These deliver gas respectively to the
outer divertor, the private flux region and the inner wall (above the
inner divertor). For those tile aficianados, the specific tube locations
are B31-014G, B26-019G and B20-001G.
The piggyback experiment for this run are pellets. The current
plan is to locate the gas puff earlier in the shot (~300 - 400 ms) with
the pellet later (~600 ms). The FSP will be inserted before and after
the pellet to asses differences in the edge profiles.

Oct 14 1993 09:48:38:390AM931014001Bruce LipschultzShot # 1
This shot disrupted after ~ 200 ms. It looks like there may have been
too much density. Change things slightly and try again. We also tryed
puffing Ar on that shot (300 ms) and it did get in. However since
it was after the shot we couldn't see if it was the requisite amount for
J. Rice.

Oct 14 1993 10:08:53:200AM931014002Bruce LipschultzShot # 2

This shot disrupted after ~ 690 ms. The density control was better and
the density flattened out at 6e19 nel. The Ar puff actually was
triggered at 200 ms which means that it arrived at the
plasma after 300 ms. The pressure in the plenum was 1.6 psia and
the puff period was 200 ms. J. Rice saw what he thought was an appropriate amount
for his purposes in the plasma. For the next shot the Ar puff
will be delayed to 300 ms. and pilse length shortened to 100 ms.
We apparently have had Fe injections around 170 ms (McPherson) and
so we will try to move the plasma out to see if there is any effect
at this point in the shot.

Oct 14 1993 10:26:06:240AM931014003Bruce LipschultzShot # 3

This plasma disrupted because of a failure in EF1upper. Try again.

Oct 14 1993 10:53:13:950AM931014004Bruce LipschultzShot # 4

This plasma disrupted after 800 ms. We seem to be getting a shark fin which
ends the shot. To remedy this we will try to program the current with
positive di/dt. The Ar will go in this next shot as well.

Oct 14 1993 11:13:16:810AM931014005Bruce LipschultzShot # 5

This one also disrupts at ~ 800 ms. The changing di/dt did flatten out
the current but to no avail - still a shark fin and a disruption. The
Iron is coming in later this shot - 300 ms instead of 170. The movement
of the plasma out early in time may have had a positive effect. We will
program even more didt for the next shot and there will be a pellet at
700 ms. No Ar puff.

Oct 14 1993 11:32:04:780AM931014006Bruce LipschultzShot # 6

This one made it all the way to Ip rampdown. It disrupted at halfway
down to zero. The next shot we will turn on the divertor gas puff
with D2, pellet at 650 ms and rf @ 850 ms. We lowered the main gas fueling at ~ 450
ms and thereafter in anticipation of the divertor gas puff.

Oct 14 1993 11:50:33:060AM931014007Bruce LipschultzShot # 7

The current rise was better on that shot. We had lowered the first gas puff (~100 ms)
to try and lower the density rise that occurs then. Because of the drop
in regular gas puffing, the density is ~ 4.5e19 when the divertor gas puff
starts. The gas puff is for 200 ms (trigger at 350 ms arriving at the plasma at
~ 450 ms) and is through the private flux tube (#7 on the flange).
By the time the pellet goes in at 650 ms the density is 6 e19 from the gas
puff.

Oct 14 1993 12:06:52:120PM931014008Bruce LipschultzShot # 8

This shot disrupts at 524ms. There seems to be large injection of unknown
Z at 509 ms. We intend to reduce the main plasma gas injection to zero
after the divertor gas injection is turned on (trigger 350 ms - enter plasma
at 450 ms). The divertor gas puff has been extended to 500 ms. Otherwise
there will be no other changes for the next shot.

Oct 14 1993 12:20:15:990PM931014009Bruce LipschultzShot # 9

This shot was a dud. There does not seem to be a particular problem
other than the disruption on the previous shot.

Oct 14 1993 12:39:26:480PM931014010Bruce LipschultzShot # 10

This shot was fine. The divertor gas puff (12 psi) was only able to hold the density
constant at 4.e19. The pellet injected on this shot was large 1.8e20 peak
with the density dropping to 8e19 afterwards. The next shot will be the same except
for an increase in the gas puff from the divertor to 18 psia.

Oct 14 1993 01:01:35:850PM931014011Bruce LipschultzShot # 11

This shot was fine. The divertor gas puff (18 psi) was only able to increase the
density to 7.e19. The pellet injected on this shot was large 1.8e20 peak
with the density dropping to 9e19 afterwards. At 800 ms a divertor
MARFE occurs and the density screams up until current inversion. At that
point we get a detached plasma and the plasma disrupts. The maximum density after
the pellet is1.4 e20.
For the next shot we will increase the divertor gas puff rate
once again (plenum pressure to 22 PSIA) and move it 100 ms earlier.
The pulse length for the divertor puff will stay the same (500 ms).
There will be two pellets (650 and 700 ms) and the rf will be on the
entire shot at a low level (5kW).

Oct 14 1993 01:22:50:990PM931014012Bruce LipschultzShot # 12

This shot disrupted on the second pellet. The density at that time
was over 3.e20. The divertor gas puff (22 psi) was able to increase the
density to 1.e20 before the pellet (from 4.e19). There appears to
be a divertor MARFE before the pellet which causes the density to increase.
For the next shot we will keep the divertor gas puff rate
the same (plenum pressure to 22 PSIA) and move it another 100 ms earlier.
to 150 ms (trigger).
The pulse length for the divertor puff will stay the same (500 ms).
There will be two pellets (650 and 700 ms) and the rf will be on the
entire shot at a low level (5kW).

Oct 14 1993 01:38:41:250PM931014013Bruce LipschultzShot # 13

This shot was a dud. Try again.

Oct 14 1993 01:56:52:860PM931014014Bruce LipschultzShot # 14

This shot went but we disrupted again at the second pellet. In addition,
the ion saturation currents on the outer divertor probes reached a
peak value of 1.5 A. These same probes were reading .2 A several shots ago
before the gas puff was increased (shot 10).
Because we are not able to see the density reach an equilibrium
value during the divertor gas puff and before the pellet we will turn
the pellets off the next shot.

Oct 14 1993 02:35:20:880PM931014015Bruce LipschultzShot # 15

This shot went. The divertor gas puff raised the density to 1.e20 (750 ms)after
which a divertor MARFE took over and raised the density to 1.5e20. For the
next shot we will increase the gas puff plenum pressure to 25psia to
increase the gas flow and see whether the density can be raised further.
The pellets will go again with a single pellet at 850 ms.

Oct 14 1993 02:39:55:790PM931014016Bruce LipschultzShot # 16

This shot went. The divertor gas puff ( 25.2 psia-100tl/sec)
raised the density to 1.2e20 (750 ms)after
which a divertor MARFE took over and raised the density to 1.4e20. The
pellet that went in at 750 ms disrupted the plasma. For the
next shot we will change the gas puff location to the inner wall. This
is tube number 14 which puts the gas just above the inner divertor.
The gas flow rate will stay the same at 100 tl/sec.

Oct 14 1993 02:55:10:740PM931014017Bruce LipschultzShot # 17

This shot survived the pellet. The gas puff was at the inner
limiter. The effect seems to be similar to the private flux region.
For the next shot we will switch the gas puff to the outer divertor.
However, the location of the tube in the divertor plate is suvh that
the gas will probably come in below the strike point (private flux
region).

Oct 14 1993 03:15:55:180PM931014018Bruce LipschultzShot # 18

Similar results were obtained with puffing through the outer divertor
location. For the next shot the divertor gas puffing will not be on at
all. The main gas puffing will be discontinued at its usual time - 350 ms.
This will allow us to identify what the background density would be
without the divertor puff. There will be a large pellet at 700 ms.

Oct 14 1993 03:30:39:910PM931014019Bruce LipschultzShot # 19

Without the gas puff the density dropped to 2e19. The pellet raised the
density to 1.2e20 and disrupted the plasma. For the next shot we will
return to the original puff location in the private flux region and
lower the plenum pressure to 15 psia. The pellet injection time will
be changed to 750 ms.

Oct 14 1993 03:53:51:910PM931014019Bruce LipschultzShot # 19

Without the gas puff the density dropped to 2e19. The pellet raised the
density to 1.2e20 and disrupted the plasma. For the next shot we will
return to the original puff location in the private flux region and
lower the plenum pressure to 15 psia. The pellet injection time will
be changed to 750 ms.

Oct 14 1993 04:03:49:470PM931014020Bruce LipschultzShot # 20

The plasma survived the pellet at 750 ms. The divertor gas puff raised
the density to 9e19 before the pellet. For the next shot we will switch
the fueling back to A-side for all of the shot. There will be 2 pellets; one
at 600 and the next at 650 ms.

Oct 14 1993 04:09:14:010PM931014021Bruce LipschultzShot # 21

This shot had alot of problems. It appears that the probe may have
been inserted too far because we get a series of injections at the
time of its maximum insertion. The first pellet after the probe insertion
disrupts the plasma. There was no Ar puff during that shot. There was no
capillary tube during that shot to get a baseline.

For the next shot the Ar puff will be done through the divertor capillary
tube in the private flux region. The fill pressure of that plenum
is 1.3 psia. Again we will try for two pellets.

Oct 14 1993 04:27:01:190PM931014022Bruce LipschultzShot # 22

This shot had an Ar puff at 200 ms, arrives in the plasma ~ 400ms with
pulse length of 100 ms. There was a pellet at 600 ms from which the
plasma did not survive. The Ar level in the plasma (HIREX) started
rising slightly after 400 ms and came to a constant value shortly after
500 ms. The next shot will be the same except the Ar will be injected through
the limiter capillary tube (just above the inner divertor).

Oct 14 1993 04:36:26:990PM931014023Bruce LipschultzShot # 23

We repeated the Ar puff, but this time with the limiter capillary tube.
The level of Ar in the plasma (HIREX) appears to be approximately the
same as with puffing in the private flux region. A small pellet was injected
at 600 ms followed by a large one at 700 ms from which the plasma does
not recover.

For the next shot the Ar puff will be switched back to the private
flux region and the density raised in the plasma. We are trying to determine
if the divertor does a better job of trapping the Ar as the density
is raised.

Oct 14 1993 04:59:04:050PM931014024Bruce LipschultzShot # 24

We repeated the Ar puff, this time with the private flux capillary tube.
The density was increased to 6e19 and the Zeff dropped accordingly (2->1.4).
The plasma almost survived the second pellet. For the next shot we will
try and increase the density to close to 1.e20. The Ar signal in the
plasma is reduced but we don't know how much of that reduction is due
to a plasma temperature change.

Oct 14 1993 05:14:30:200PM931014025Bruce LipschultzShot # 25

We repeated the Ar puff, and increased the density was increased to 8e19.
However the plasma was dirty and did not survive until the pellets.
For the next shot we will push on to 1 MA, without pellets and with
the Ar puff delayed by 100 ms (coming in around 500 ms).

Oct 14 1993 05:20:22:640PM931014026Bruce LipschultzShot # 26

This was a dud. Good night.

Physics Operator Comments
Oct 14 1993 08:53:13:700AMJohn GoetzRun 931014 - Mini-proposal #016 Scrape-off layer characterization

1) Set-up high current SN disharges
2) Puff into divertor
3) Fire pellets


Start from shot 931012005

Changes:
S_IP = -780000 from .3 to .9s
S_ZCUR = -.025 & ramps to 0. starting @ .9s
PULSE_GAS_3 lowered to 40V @ .8s
S_RXL = -.01 @ .5s
P_ZCUR(2) = 1 @ .4s D_ZCUR(2) = 2 @.5s I_ZCUR(2) = 2.
remove dropout from P_ZCUR(3) and D_ZCUR(3) @ .75

Oct 14 1993 09:47:07:510AM931014001John GoetzShot 001: P_0 = 1.2e-5
Disruptive - short shot

For 002: lower PULSE_GAS_3 between .05 & .1s

Oct 14 1993 10:07:10:260AM931014002John GoetzShot 002:
Disruption @ .688


For 003: divertor argon puff @ .3s for .1s
lower PULSE_GAS_3 to 35V @ .8s
S_RCUR = .7 @ 0s & .68 @ .15

Oct 14 1993 10:27:08:520AM931014003John GoetzShot 003:
OH1 - EF1U power supply problem @ .4


For 004: no changes

Oct 14 1993 10:59:06:970AM931014004John GoetzShot 004:
disruption


For 005:
S_IP = 825000 @ .9s

Oct 14 1993 11:10:58:680AM931014005John GoetzShot 005:
disruption @ .825


For 005:
S_IP = 850000 @ .9s
S_ICEF1U = 3000A @ .5 (was .4)

Oct 14 1993 11:31:39:850AM931014006John GoetzShot 006:
good shot disruption @ 1.16s


For 007:
lower PG3 to 30V @ .4s
lower PG3 @ .1s

Oct 14 1993 11:48:43:510AM931014007John GoetzShot 007:
good shot disruption @ 1.15s


For 008:
lower PG3 to 31.5V @ .075s
change S_R_IN to 0 for all time

Oct 14 1993 12:05:12:880PM931014008John GoetzShot 008:
disruption @ .524s - big injection of ???? @ .509


For 009:
turn off PG3 @ .45s

Oct 14 1993 12:18:12:080PM931014009John GoetzShot 009:
dud - fields o.k.


For 010:
RF assist for breakdown

Oct 14 1993 12:38:07:800PM931014010John GoetzShot 010:
plasma disruption @ .968


For 011:
add PG3 after .9s
raise divertor gas puff pressure

Oct 14 1993 12:59:21:090PM931014011John GoetzShot 011:
plasma disruption @ 1.06


For 012:
raise divertor gas puff pressure and move earlier
turn off PG3 earlier
pellets at .65s and .7s
RF on throughout whole shot

Oct 14 1993 01:22:17:120PM931014012John GoetzShot 012:
plasma disruption @ .717


For 013:
move div gas puff earlier to .15s
turn off PG3 @ .3s
pellets at .65s and .7s

Oct 14 1993 01:34:45:570PM931014013John GoetzShot 013:
dud - fields o.k.


For 014:
P_0 = 1.3e-5

Oct 14 1993 01:54:27:810PM931014014John GoetzShot 014:
plasma - disruption @ .724


For 015:
P_0 = 1.4e-5
div puff to .25s

Oct 14 1993 02:14:07:960PM931014015John GoetzShot 015:
plasma - disruption @ 1.09


For 016:
pellet @ .75s
up div puff pressure

Oct 14 1993 02:32:14:970PM931014016John GoetzShot 016:
plasma - disruption @ .76


For 017:
PG3 = 33V @ .075s
S_ZCUR = -.03 @ .7s
S_ICEF1L = 0 @ 1.5
P_0 = 1.5e-5
small pellet @ .75s
change to div puff tube (inner wall)

Oct 14 1993 02:51:59:440PM931014017John GoetzShot 017:
plasma - disruption @ .915s


For 018:
div puff to outer divertor
S_ZCUR = -.03 after .4s

Oct 14 1993 03:12:45:870PM931014018John GoetzShot 018:
plasma - disruption @ .95s


For 019:
no div gas puff
large pellet @ .7s
S_ZXL = -.01 @ .4s
S_ZCUR = -.03 after .4s
S_ICEF1L = 0 @ 1.

Oct 14 1993 03:27:39:040PM931014019John GoetzShot 019:
plasma - disruption @ .71s


For 020:
div gas puff back to private flux - lower pressure
large pellet @ .75s

Oct 14 1993 03:51:03:390PM931014020John GoetzShot 019:
plasma - disruption @ .92s


For 020:
PG3 = 30V @ .9s

Oct 14 1993 04:05:02:760PM931014021John GoetzShot 020:
plasma - disruption @ .627s
moly injection from FSP

For 021:
argon puff in private flux

Oct 14 1993 04:23:06:220PM931014022John GoetzShot 022:
plasma - disruption @ .753s

For 023:
argon puff from inner wall

Oct 14 1993 04:37:45:280PM931014023John GoetzShot 023:
plasma - disruption @ .857s

For 024:
argon puff from private flux
S_IP = -950000 @ .9s
PG3 = 38V @ .3s

Oct 14 1993 04:55:26:580PM931014024John GoetzShot 024:
plasma - disruption @ .746s

For 025:
PG3 = 50V @ .15s
IC_EF4 = 1500A @ 1.
IC_EF1L = -3250A @ .15

Oct 14 1993 05:12:46:080PM931014025John GoetzShot 025:
plasma - disruption @ .71s

For 026:
PG3 = 54V @ .15s
S_IP = 1.1e6

Oct 14 1993 05:21:23:710PM931014026John GoetzShot 026:
DUD!!!!!!!!!!!!!!!!!!!!!!!!

Engineering Operator Comments
ShotTimeTypeStatusComment
109:00:29:920AMPlasmaOk30 min delay daq3 down, ps,s ok plasma
209:48:34:950AMPlasmaOk890ka
310:06:17:170AMPlasmaBadcomm fail, plasma
410:36:05:110AMPlasmaOk870ka
510:54:13:550AMPlasmaOk800 ka
611:12:02:420AMPlasmaOkok
711:30:35:060AMPlasmaOk
811:49:50:960AMPlasmaOk
912:07:02:300PMTestOkps,s ok dud
1012:22:48:510PMPlasmaOkps,s ok plasma
1112:40:38:080PMPlasmaOkps,s ok p-lasma
1201:03:28:590PMPlasmaOkps,s ok plasma
1301:23:46:190PMPlasmaOk
1401:38:39:850PMPlasmaOk900 ka
1501:55:59:940PMPlasmaOk1.1 sec 850 ka
1602:16:57:470PMPlasmaOk920ka
1702:36:09:800PMPlasmaOkps,s ok plasma
1802:54:05:520PMPlasmaOkcomm fail plasma
1903:14:11:480PMPlasmaOkps,s ok plasma
2003:30:51:230PMPlasmaOkps,s ok plasma
2103:52:11:370PMPlasmaOkps,s ok plasma
2204:08:32:990PMPlasmaOkps,sok plasma
2304:25:11:630PMPlasmaOkps,s ok plasma
2404:41:40:390PMPlasmaOkps,s ok plasma
2504:57:57:790PMPlasmaOkps,s ok plasma
2605:14:06:440PMPlasmaOkps,s ok dud