Alcator C-Mod Run 990223 Information

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Miniproposals
Miniproposal:217a
Date Filed: 1/13/1999
Title:Toroidal Rotation during Ohmic H-Modes
First Author:John Rice
Session Leader:John Rice (shots 1-21)
Miniproposal:220a
Date Filed: 1/14/1999
Title:Ohmic H Mode Pedestals
First Author:T. Sunn Pederson
Session Leader:T. Sunn Pederson (shots 1-21)

Operators
Session leader(s):John Rice,T. Sunn Pederson
Physics operator(s):Robert Granetz
Engineering operator(s):Frank Silva

Engineering Operator Run Comment
MP217A,220A/Granetz/Silva

Session Leader Plans

Physics Operators Plans

Session Leader Summaries
Entered: Jul 7 2004 03:49:19:337PM
Author: To Be Determined
Run summary for 990223, MP217A, Toroidal Rotation during Ohmic H-modes

There were 7 plasmas with Ohmic H-modes, most of about 80 ms duration with
stored energy increases of nearly 20 kJ. The toroidal rotation velocities,
measured from the doppler shifts of argon lyman alpha, were typically
-20000 m/s (counter current) during the Ohmic L-mode portion of the discharges.
During the Ohmic H-modes, the rotation switched to the co-current direction,
with changes in velocity of 20-30,000 m/s. These stored energy and corresponding
velocity increases are very similar to the values during some ICRF heated
discharges, suggesting that the rotation is associated with stored energy,
regardless of the mechanism. Similar rotation for these discharges has
been inferred from magnetics measurements.

Due to the limited number of discharges, most observations for 990223
were at 1.0 MA in a limited density range, and further study is desirable.

Entered: Jul 7 2004 03:49:19:540PM
Author: To Be Determined
Session leader run summary for MP220A "Ohmic H-mode pedestals":
The object of MP220A was to see if there are any measurable differences between
ohmic H-modes, and H-modes obtained with RF heating, and check
for a possible pedestal width scaling with plasma current. The results for
MP217A "Rotation in Ohmic H-modes" are in RUN_SUMMARY_990223A.TXT

We were able to obtain ELM-free H-modes of a duration of up to 100 msec,
all but one at 3.5 T toroidal B-field and 1 MA plasma current. The soft x-ray
pedestals in these ohmic H-modes are just like less-than-impressive
ELM-free H-modes with RF heating. That is, they are very narrow (2 mm width
mapped to the midplane on both arrays), and located within a few mm of
the separatrix at the top of the machine (array 2) and about 10 mm inside
the separatrix at the outboard midplane (array 4).

Thus, at 1 MA current, there are no measurable differences between RF-
heated ELM-free H-modes and ohmic (ELM-free) H-modes. This answers the
MP's main physics question.

The run got cut short by a delay in the morning and an alternator power glitch
in the afternoon, so we were lucky to get two H-modes at 0.8 MA on our
last plasma attempt (shot 21).
The width at 0.8 MA seems to be around 3 mm for the outboard midplane array, ie.
more than for the 1MA shots. However, the soft x-ray emissivity on
the outboard array was low (about 5kW/m^3 vs 15 or more for good
ohmic H-modes at 1 MA) so the signal/noise ratio was poor, and the pedestal
does not seem broader to the naked eye. There was no
discernible difference in the pedestal width at
the top of the machine (array 2) for the lower current (still 2 mm).
More ohmic H-modes at 0.8 MA (or lower), with longer durations and/or
neon injections are needed in order to determine a pedestal width scaling for
ohmic H-modes.

Physics Operator Summaries
Entered: Jul 7 2004 04:37:00:270PM
Author: To Be Determined
Physics operator summary for run 990223.

MP 217A -- Toroidal Rotation in Ohmic H-modes
MP 220A -- Ohmic H-mode Pedestals

SL: J. Rice/T. Sunn Pedersen
PO: R. Granetz (J. Irby assisting)

The goals for today:

(1) Measure plasma rotation in ohmic H-modes to determine whether or
not the plasma rotation is due to RF specifically.
(2) Measure pedestal characteristics in ohmic H-modes to determine if
there are any differences due to RF fields in the edge region.

Summary: Today's run had many delays, but still managed to get enough ohmic
H-modes at 1.0 MA and 0.8 MA to begin answering some of the important
physics questions. Ohmic H-mode plasmas rotate even without the RF,
and the x-ray pedestals look very similar to RF H-modes. See the
session leaders' reports for more details.

The first plasma shot was delayed until just before 11 am by a faulty
door switch in the power room, which prevented the enabling of the
access system. The run was nearly terminated at 15:15 due to a
power glitch in the alternator building which tripped out the
alternator and left time for only two more shots. Also there were
several delays due to data acquisition problems and network hangups.

Every plasma disrupted near the end of flattop or early in the
rampdown. q95 was 2.5-2.6. Halo currents up to 200 kA were seen.
An alternating pattern of disruptions and fizzles was the norm today.

Scorecard: 11 plasmas
8 fizzles
0 duds (0 due to power supply faults)
2 tests
----------
21 total

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

Engineering Setup for Tuesday, 990223:

Load from 990219030

NO OVERNIGHT ECDC.

TF under hybrid control

Gas setup - fill B-top with 6 psi of D2 Hybrid enabled
fill B-side lower with 1 psi of Ar Hybrid DISABLED
fill B-side upper with 2 psi of Ne Hybrid DISABLED(yes, neon)
fill C-side with 30 psi of D2 Hybrid enabled
fill J-bottom with 2 psi of Kr Hybrid DISABLED

The following gate valves should be enabled, assuming no vacuum problems:

ECE, VUV

-------------------------------------------------------------------------------
Run Plan for 990223:

Start with shot 990219030 (1 MA, 5.4 T). After the first good plasma, program
Bt to ramp down from 5.4 T at t=0.1 s to 3.5 T at t=0.7 s, and then remain at
3.5 tesla. This should give q95=2.4-2.6 . Also lower the target density to
nl04=0.8e20 m-2, and turn on the argon puff. If we get ohmic H-modes at higher
fields, adjust the Bt flattop to the higher level (to ease cutoff problems with
the ECE during H-mode). If we do not get ohmic H-modes, then raise the plasma
current to 1.1 MA. Once we get good H-modes and good data, we may try to run
lower plasma currents. Throughout the day we will be watching out for low-q
disruptions.

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

Note: no ECDC was done prior to the run, nor over the weekend.

Hybrid coldstart done; no errors found
($set default cmod$models:[hybrid.tcl]
$@hybinit_dispatch
$@show_bitbus_log
Use editor search to verify no occurrences of "error" nor
"not respond")
Reload 990219030, remove Bt tweak.
Confirm that RF feedback on RCUR is turned off (RF_LOAD_E = 0.0)

There was a long delay to begin the run, due to some problem with a "master
relay", which is part of the access system.

During the delay, the TCI CO2 laser was being monitored and was found to have
very large power oscillations. Jim Irby has recommended that we switch to
the visible bremsstrahlung for density feedback. I have done this by loading
wire from the last shot (I think) that used NL_ZMETER, which was 990205004,
segment 2. That shot had a line density of 1.0e20 m-2, which is just what we
want for the first shot.


Shot 01 -- OH test (at 10:40). All OK.

Next shot: go for plasma. 1 MA, 5.4 T, 1.0e20 m-2.

Shot 02 -- Fizzle. Br is 0.002 T higher than last Friday. It may be due to
a new bolo input signal to the hybrid, which is saturated before
t=0.

Next shot: John Goetz has disconnected the bolo input to the hybrid.
Also decrease Br by 0.001 T

Shot 03 -- Fizzle. Almost went. Bz was a touch low, but I'm not going to
change it. Pre-fill pressure looks good. Br looks good.

Next shot: try again, no changes

Shot 04 -- Fizzle. Same as previous shot.

Next shot: raise Bz by +15 amps and increase pre-fill pulse from 18
to 20 ms.

Shot 05 -- Plasma. Good shot. 1 MA, 5.4 T, 1.0e20 m-2. There was RF on
this shot.

Next shot: ramp Bt down to 3.5 T (from t=0.1 to 0.7 s), switch
back to TCI for density control, reduce density to nl_04=0.8e20 m-2,
turn off ICRF. Turn on argon valve.

Shot 06 -- Fizzle. Null looks fair.

Next shot: reduce Br another 1.5 mT (now offset=0.0015 T)

Shot 07 -- Plasma. Two ohmic H-modes, ELMfree. Bt flattopped at 3.6 T. NL_04
was about 0.95e20 m-2. John Rice sees rotation in the normal
direction even though there definitely was no RF. Chord_24 in edge
array_2 went bad again. Outboard xray pedestal is very similar to
H-modes with RF. q95 was 2.5-2.6, as expected. I think the
disruption was caused by a several molybdenum injections.

Next shot: reduce gas maintenance a little and reduce nl_04 to
0.7e20 m-2.

There was a network hangup between shots 7 and 8. The node SHAPE crashed, and
this required a recycling of the shot cycle. I also did a coldstart on the
hybrid.

Shot 08 -- Test. Actually this was a no-power shot to reset the shot cycle.

Shot 09 -- Plasma. No H-modes, even though the density was 0.8e20 m-2.
q95 got down to 2.5.

Next shot: start Ip rampdown at 1.1 s instead of 1.2 s. Reduce
argon pulse width from 32 to 27 ms.

Shot 10 -- Plasma. An ohmic H-mode started just before Ip rampdown, and then
there was a disruption at t=1.13 s. Lower halo current=200 kA.

Next shot: reload segment 2 from shot 7. This should bring the
density back up to nl04=1.0e20 m-2 and restore the argon pulse to
32 ms.

Shot 11 -- Fizzle. Null looks the same as preceding shots.

Next shot: no changes

Shot 12 -- Plasma. One ohmic ELMfree H-mode. Rotating. Normal pedestals.
Prad surpasses 1 MW. Disrupted at t=1.04 s.

Next shot: no changes

Shot 13 -- Plasma. One short ohmic ELMfree H-mode. Disrupted at 0.994 s.

Next shot: no changes

Shot 14 -- Plasma. One short ohmic ELMfree H-mode. Disrupted at 0.992 s.

Next shot: raise nl04 from 0.8 to 1.0e20 m-2.

Shot 15 -- Fizzle.

Next shot: raise Br offset by 0.5 mT (to 0.002 T)

Shot 16 -- Plasma. One ohmic H-mode. nl04=1.07e20 m-2.

Next shot: reduce Ip to 0.8 MA.

Shot 17 -- Fizzle. Null was OK.

Next shot: reduce prefill puff from 20 to 18 ms.

Shot 18 -- Plasma. Ip=0.8 MA. No H-modes. Disrupted at t=1.24 s.
NL04=0.2e20 m-2.

Next shot: lower the density to nl04=0.7e20 m-2, AND turn on the
ICRF between t=0.35 to 0.50 s (not related to today's runs).

Shot 19 -- Fizzle. Null is OK.

There was a power glitch in the alternator building after this shot which
caused the alternator to drop down to speed 1 (800 rpm). This is causing
another delay in the run.

Next shot: since we may only have time for one more shot, the
session leaders have requested a repeat of shot 07. I have loaded
segment 2 from that shot. (1 MA, 3.6 T, 0.8e20 m-2)

Shot 20 -- Plasma. One ohmic ELMfree H-mode. 1 MA, 3.6 T, 0.9e20 m-2.
Disrupted at 1.01 s.

Next shot: reduce Ip to 0.8 MA, reduce Bt to 2.9 T, and add -15 amps
to EF4 because the plasma current rise is a little slower than
earlier today (Earl's suggestion).

Shot 21 -- Plasma. Two ohmic ELMfree H-modes. 0.8 MA, 3.0 T, 0.8e20 m-2.
Disrupted at 1.12 s.

End of run.

Session Leader Comments
Feb 24 1999 09:20:22:513AM990223001Steve Wukitch001 plasma multiple H-modes
faults on #2

next shot: reduce power so both run cleanly
Feb 24 1999 09:31:26:293AM990223001Steve Wukitchnext shot: retune both D and E - port
last shot: E-port faults were due to mismatch
Feb 24 1999 10:12:20:640AM990223002Steve Wukitch002 plasma - H-mode
screen overcurrent on #1
#2 fault
Feb 23 1999 12:15:24:763PM990223007T. Sunn PedersonTwo H-modes, ELM-free, duration 60 msec and 100 msec appr.
Array 4 (the outboard array) has a pedestal position and width
similar to ELM-free H-modes WITH RF.
Array 2 needs to be recalculated because channel 24 was bad
and it wasn't turned off in the tree.
Feb 23 1999 12:41:11:187PM990223007T. Sunn PedersonArray 2 has now been inverted. The pedestal is right at the separatrix,
and narrow.
Array 4 has a pedestal width appr. 2 mm. Array 2 has a pedestal width
of 2 mm as well. This is consistent with RF-induced ELM-free H-modes.
The Emissivity only goes to about 10 kW/m^3, so these are weak H-modes,
as expected.
These two H-modes look exactly like two weak, RF-induced ELM-free H-modes.
Feb 23 1999 12:52:31:280PM990223009T. Sunn PedersonI will increase the spatial resolution in the inversions from shot 9
to 1.0 mm for the top array and 1.3 mm for the outboard midplane
array. Although the signal levels aren't great, we're looking at very
narrow pedestals, so the extra spatial resolution will be helpful,
if it doesn't increase the noise too much.
Feb 23 1999 01:17:55:950PM990223009T. Sunn PedersonThis shot did not go into H-mode but there was high emission on both arrays
and the top array sees a mini-pedestal, and there's a hint of one on the outboard
array. The sawteeth are VERY visible on the x-rays, in some cases increasing the
emission a factor of 2
The density was lower on this shot, and it seems to be a bad thing.

Feb 23 1999 01:25:46:187PM990223010T. Sunn PedersonOne shortlived H-mode from 1.07 s to 1.098 s
I am changing the spatial resolutions back to 1.2 mm and 1.5 mm after this shot,
the profiles looked a little too noisy.
Feb 23 1999 02:10:07:857PM990223013T. Sunn PedersonAnother H-mode, 90 msec duration, similar to last shot

Feb 23 1999 05:42:11:780PM990223021T. Sunn PedersonThis shot had two ELM-free H-modes at 800kA, so is particularly interesting for the
scaling of the pedestal width with current. We did see the pedestal width increase
to about 3 mm for the outboard midplane array but the emissivity was very low so
there is some uncertainty there. The outboard midplane emissivity reached only
about 5kW/m^3 so the signal/noise ratio was bad. A neon injection would have been nice.

Physics Operator Comments
Feb 23 1999 08:17:16:250AMRobert GranetzMP 217A -- Toroidal Rotation in Ohmic H-modes
MP 220A -- Ohmic H-mode Pedestals

SL: J. Rice/T. Sunn Pedersen
PO: R. Granetz (J. Irby assisting)

The goals for today:

(1) Measure plasma rotation in ohmic H-modes to determine whether or
not the plasma rotation is due to RF specifically.
(2) Measure pedestal characteristics in ohmic H-modes to determine if
there are any differences due to RF fields in the edge region.
Feb 23 1999 08:17:56:607AMRobert GranetzEngineering Setup for Tuesday, 990223:

Load from 990219030

NO OVERNIGHT ECDC.

TF under hybrid control

Gas setup - fill B-top with 6 psi of D2 Hybrid enabled
fill B-side lower with 1 psi of Ar Hybrid DISABLED
fill B-side upper with 2 psi of Ne Hybrid DISABLED(yes, neon)
fill C-side with 30 psi of D2 Hybrid enabled
fill J-bottom with 2 psi of Kr Hybrid DISABLED

The following gate valves should be enabled, assuming no vacuum problems:

ECE, VUV
Feb 23 1999 08:18:25:590AMRobert GranetzRun Plan for 990223:

Start with shot 990219030 (1 MA, 5.4 T). After the first good plasma, program
Bt to ramp down from 5.4 T at t=0.1 s to 3.5 T at t=0.7 s, and then remain at
3.5 tesla. This should give q95=2.4-2.6 . Also lower the target density to
nl04=0.8e20 m-2, and turn on the argon puff. If we get ohmic H-modes at higher
fields, adjust the Bt flattop to the higher level (to ease cutoff problems with
the ECE during H-mode). If we do not get ohmic H-modes, then raise the plasma
current to 1.1 MA. Once we get good H-modes and good data, we may try to run
lower plasma currents. Throughout the day we will be watching out for low-q
disruptions.
Feb 23 1999 08:18:43:200AMRobert Granetz Note: no ECDC was done prior to the run, nor over the weekend.

Hybrid coldstart done; no errors found
($set default cmod$models:[hybrid.tcl]
$@hybinit_dispatch
$@show_bitbus_log
Use editor search to verify no occurrences of "error" nor
"not respond")
Reload 990219030, remove Bt tweak.
Confirm that RF feedback on RCUR is turned off (RF_LOAD_E = 0.0)
Feb 23 1999 10:12:43:607AMRobert GranetzThere was a long delay to begin the run, due to some problem with a "master
relay", which is part of the access system.
Feb 23 1999 10:12:56:030AMRobert GranetzDuring the delay, the TCI CO2 laser was being monitored and was found to have
very large power oscillations. Jim Irby has recommended that we switch to
the visible bremsstrahlung for density feedback. I have done this by loading
wire from the last shot (I think) that used NL_ZMETER, which was 990205004,
segment 2. That shot had a line density of 1.0e20 m-2, which is just what we
want for the first shot.
Feb 23 1999 10:39:59:170AM990223001Robert GranetzShot 01 -- OH test (at 10:40). All OK.

Next shot: go for plasma. 1 MA, 5.4 T, 1.0e20 m-2.
Feb 23 1999 11:02:22:607AM990223002Robert GranetzShot 02 -- Fizzle. Br is 0.002 T higher than last Friday. It may be due to
a new bolo input signal to the hybrid, which is saturated before
t=0.

Next shot: John Goetz has disconnected the bolo input to the hybrid.
Also decrease Br by 0.001 T
Feb 23 1999 11:10:56:450AM990223003Robert GranetzShot 03 -- Fizzle. Almost went. Bz was a touch low, but I'm not going to
change it. Pre-fill pressure looks good. Br looks good.

Next shot: try again, no changes
Feb 23 1999 11:28:25:967AM990223004Robert GranetzShot 04 -- Fizzle. Same as previous shot.

Next shot: raise Bz by +15 amps and increase pre-fill pulse from 18
to 20 ms.
Feb 23 1999 11:51:45:187AM990223005Robert GranetzShot 05 -- Plasma. Good shot. 1 MA, 5.4 T, 1.0e20 m-2. There was RF on
this shot.

Next shot: ramp Bt down to 3.5 T (from t=0.1 to 0.7 s), switch
back to TCI for density control, reduce density to nl_04=0.8e20 m-2,
turn off ICRF. Turn on argon valve.
Feb 23 1999 11:52:36:750AM990223006Robert GranetzShot 06 -- Fizzle. Null looks fair.

Next shot: reduce Br another 1.5 mT (now offset=0.0015 T)
Feb 23 1999 12:31:01:140PM990223007Robert GranetzShot 07 -- Plasma. Two ohmic H-modes, ELMfree. Bt flattopped at 3.6 T. NL_04
was about 0.95e20 m-2. John Rice sees rotation in the normal
direction even though there definitely was no RF. Chord_24 in edge
array_2 went bad again. Outboard xray pedestal is very similar to
H-modes with RF. q95 was 2.5-2.6, as expected. I think the
disruption was caused by a several molybdenum injections.

Next shot: reduce gas maintenance a little and reduce nl_04 to
0.7e20 m-2.
Feb 23 1999 12:46:03:450PM990223008Robert GranetzThere was a network hangup between shots 7 and 8. The node SHAPE crashed, and
this required a recycling of the shot cycle. I also did a coldstart on the
hybrid.
Feb 23 1999 12:48:04:310PM990223008Robert GranetzShot 08 -- Test. Actually this was a no-power shot to reset the shot cycle.
Feb 23 1999 01:09:44:420PM990223009Robert GranetzShot 09 -- Plasma. No H-modes, even though the density was 0.8e20 m-2.
q95 got down to 2.5.

Next shot: start Ip rampdown at 1.1 s instead of 1.2 s. Reduce
argon pulse width from 32 to 27 ms.
Feb 23 1999 01:21:52:810PM990223010Robert GranetzShot 10 -- Plasma. An ohmic H-mode started just before Ip rampdown, and then
there was a disruption at t=1.13 s. Lower halo current=200 kA.

Next shot: reload segment 2 from shot 7. This should bring the
density back up to nl04=1.0e20 m-2 and restore the argon pulse to
32 ms.
Feb 23 1999 01:32:49:653PM990223011Robert GranetzShot 11 -- Fizzle. Null looks the same as preceding shots.

Next shot: no changes
Feb 23 1999 01:50:26:513PM990223012Robert GranetzShot 12 -- Plasma. One ohmic ELMfree H-mode. Rotating. Normal pedestals.
Prad surpasses 1 MW. Disrupted at t=1.04 s.

Next shot: no changes
Feb 23 1999 02:19:01:310PM990223014Robert GranetzShot 14 -- Plasma. One short ohmic ELMfree H-mode. Disrupted at 0.992 s.

Next shot: raise nl04 from 0.8 to 1.0e20 m-2.
Feb 23 1999 02:28:14:090PM990223015Robert GranetzShot 15 -- Fizzle.

Next shot: raise Br offset by 0.5 mT (to 0.002 T)
Feb 23 1999 02:44:58:060PM990223016Robert GranetzShot 16 -- Plasma. One ohmic H-mode. nl04=1.07e20 m-2.

Next shot: reduce Ip to 0.8 MA.
Feb 23 1999 02:58:29:077PM990223017Robert GranetzShot 17 -- Fizzle. Null was OK.

Next shot: reduce prefill puff from 20 to 18 ms.
Feb 23 1999 03:18:21:310PM990223018Robert GranetzShot 18 -- Plasma. Ip=0.8 MA. No H-modes. Disrupted at t=1.24 s.
NL04=0.2e20 m-2.

Next shot: lower the density to nl04=0.7e20 m-2, AND turn on the
ICRF between t=0.35 to 0.50 s (not related to today's runs).
Feb 23 1999 03:51:17:013PM990223019Robert GranetzThere was a power glitch in the alternator building after this shot which
caused the alternator to drop down to speed 1 (800 rpm). This is causing
another delay in the run.
Feb 23 1999 04:19:48:250PM990223019Robert GranetzShot 19 -- Fizzle. Null is OK.

There was a power glitch in the alternator building after this shot which
caused the alternator to drop down to speed 1 (800 rpm). This is causing
another delay in the run.

Next shot: since we may only have time for one more shot, the
session leaders have requested a repeat of shot 07. I have loaded
segment 2 from that shot. (1 MA, 3.6 T, 0.8e20 m-2)
Mar 5 1999 09:30:27:217AM990223020Robert GranetzShot 20 -- Plasma. One ohmic ELMfree H-mode. 1 MA, 3.6 T, 0.9e20 m-2.
Disrupted at 1.01 s.

Next shot: reduce Ip to 0.8 MA, reduce Bt to 2.9 T, and add -15 amps
to EF4 because the plasma current rise is a little slower than
earlier today (Earl's suggestion).
Feb 23 1999 05:08:21:670PM990223021Robert GranetzShot 21 -- Plasma. Two ohmic ELMfree H-modes. 0.8 MA, 3.0 T, 0.8e20 m-2.
Disrupted at 1.12 s.

End of run.

Engineering Operator Comments
ShotTimeTypeStatusComment
110:36:19:670AMTestOkOhtest ok
210:45:27:700AMTestOkno faults/fizzel
311:03:10:030AMTestOkno faults/fizzel
411:17:27:750AMTestOkno faults/fizzel
511:30:19:090AMTestOkno faults/plasma
611:43:31:717AMTestOkno faults/fizzel
712:00:56:483PMTestOkno faults/plasma
812:36:53:437PMTestBadno power cycle/ computer down
912:56:10:810PMPlasmaOkno faults/plasma
1001:11:04:717PMPlasmaOkno faults/plasma
1101:24:44:327PMPlasmaOkNo Faults
1201:38:52:513PMPlasmaOkNo Faults
1301:53:35:543PMPlasmaOkNo Faults / Plasma
1402:06:58:030PMPlasmaOkNo Faults / Plasma
1502:22:19:903PMPlasmaOkNo Faults
1602:35:23:903PMPlasmaBadFault on OH2L
1702:51:38:263PMPlasmaOkNo Faults
1803:04:25:107PMPlasmaOkNo Faults / Plasma
1903:20:44:950PMPlasmaOkNo Faults
2004:39:30:170PMPlasmaOkNo Faults / Plasma
2104:56:38:153PMPlasmaOkNo Faults / Plasma