Alcator C-Mod Run 1060622 Information

Miniproposals

Miniproposal: 450

Date Filed: 4/14/2006

Title: Disruption mitigation using high pressure gas-mixture injection

First Author: Mohammad Bakhtiari

Session Leader: Robert Granetz (shots 1-13)

Operators
Session leader(s):	Robert Granetz
Physics operator(s):	Jim Irby
Engineering operator(s):	Andy Pfeiffer,Sam Pierson,Bill Parkin

Engineering Operator Run Comment
MP #450 -- Disruption mitigation w/mixed gas jet Session leaders: M. Bah

Session Leader Plans

Entered: Jun 21 2006 04:20:37:400PM

Author: Robert Granetz

MP #450 -- Disruption mitigation w/mixed gas jet Session leaders: M. Bahktiari, R. Granetz Physics operator: J. Irby ECDC overnight and bake at 60 C. Power systems as on 1060414009 (1.0 MA, 5.4 T, LSN fiducial) A-coil configuration: normal [+Dtop -Dbot -Jtop +Jbot] and enabled. Gas Setup: fill B-Top with 6 psi D2 Hybrid enabled (PG4) fill B-side lower with 1 psi Ar + 2 psi Ne Hybrid DISABLED (PG1) leave B-side upper with whatever Hybrid disabled fill B-main (C-side) with 40 psi D2 Hybrid enabled (PG3) No NINJA for this run. Gas jet plenum has been filled with pure helium at 70 bar. THE SUPPLY TANK IS A 50/50 MIX OF HELIUM AND ARGON. Torvac setup: unnecessary diagnostic gate valves (ECE) should be kept closed on all shots. Enable the following, assuming no vacuum problems: Z-bolo shutters, VUV (yes, enable the VUV gate valve) Necessary diagnostics: IR divertor camera Fast PSI camera on B-horizontal, if possible, starting at t=0.800 s, Ar+0 filter Thomson scattering, with timing set so that one profile is obtained at t=0.800 s and the other varies shot-to-shot from 0.804 to 0.810 s (subject to change) Bolometry Two pi bolometers Halo current Rogowskis SX arrays with fast sampling window (t=0.795 to 0.820 s) Mirnov Bp fluctuations ------------------------------------------------------------------------------- ICRF Setup: We'll need 2-3 MW shortly after we begin this MP. ------------------------------------------------------------------------------- Run plan: Start with 1060414009, except do not turn off the ZCUR feedback (i.e. P and D gains should not be zeroed). If this choice is too cumbersome (because of the F11 updating issue), it is probably okay to use shot 20 from yesterday (1060621020), except with Btor set to 5.4 T and nl_04 to 1.0e20 m-2. Starting on either shot 1 or 2 we will fire the gas jet at t=0.800 s with pure helium for two shots. Observe timing of Te and SX decrease, as well as other typical disruption-relevant signals (halos, Erad/Etot, etc). Then do an in-situ top-off refill of the plenum using the 50/50 He/Ar mix. Continue doing two disruption shots with each plenum mix, then a top-off refill. This will gradually increase the argon fraction of the plenum, allowing us to do a scan of argon fraction throughout the day, without needing any cell accesses, in principle. The number of shots will be greatly reduced compared to most run days because it will take a long time to pump out the fill lines after each top-off fill.

Physics Operators Plans

Entered: Jun 21 2006 04:47:47:437PM

Author: Jim Irby

MP #450 -- Disruption mitigation w/mixed gas jet

Session leaders: M. Bahktiari, R. Granetz
Physics operator: J. Irby

ECDC overnight and bake at 60 C.

Power systems as on 1060414009 (1.0 MA, 5.4 T, LSN fiducial)
but DPCS loaded from 1060621020

A-coil configuration: normal [+Dtop -Dbot -Jtop +Jbot] and enabled.

Gas Setup:
fill B-Top with 6 psi D2 Hybrid enabled (PG4)
fill B-side lower with 1 psi Ar + 2 psi Ne Hybrid DISABLED (PG1)
leave B-side upper with whatever Hybrid disabled
fill B-main (C-side) with 40 psi D2 Hybrid enabled (PG3)
No NINJA for this run.

Gas jet plenum has been filled with pure helium at 70 bar. THE SUPPLY
TANK IS A 50/50 MIX OF HELIUM AND ARGON.

Torvac setup: unnecessary diagnostic gate valves (ECE) should be kept
closed on all shots.

Session Leader Summaries

Entered: Jun 22 2006 06:02:01:660PM

Author: Mohammad Bakhtiari

Disruption mitigation experiments were carried out using pure helium and mixtures of helium (>50%) and argon (<50%). Every thing worked well thanks to Robert Granetz and co-workers in C-Mod. A brief summary of the observations is as follows:

1. For all mixture cases the halo current was less than 120 kA while for those with pure helium injection we got I_halo=138 and 157 kA.

2. The current quench time with mixtures was about 1 ms while it was more than 2.5 ms with pure helium.

3. When the fraction of argon is small the mixture approaches the plasma almost as fast as a pure helium gas, while as we mentioned above the current quench is faster and halo current is lower with mixtures.

4. The density increment with mixtures, when the fraction of argon is small, was comparable with that in pure helium cases. This is one of the advantages of this method to avoid runaway generation.

Entered: Jun 22 2006 06:19:30:730PM

Author: Robert Granetz

Run summary for Thursday 22 June 2006: MP#450 Disruption mitigation with mixed gas jet Session leader: M. Bahktiari, R. Granetz Physics operator: J. Irby We got through the run pretty much as planned. We were able to scan the He/Ar ratio successfully, although perhaps we might want smaller increments. At each condition we obtained data on halo currents, radiated energy, Te profiles, soft x-rays, density, etc. There were clear differences as we varied the mixture ratio. I haven't had a chance to assemble all the information and get a clear picture yet, but Val Izzo, Mohammed Bahktiari, and Matt Reinke are also looking at the data. After the first few shots we got the RGA to give us post-shot information on the He/Ar ratio, which seems to correlate fairly well with the volume/pressure estimates I was making. The gas jet hardware worked well, particularly considering that it was not designed to do gas mixture studies. Because of all the required pumpouts of the machine and the gas jet system, we only got 13 shots (which is one more than I was hoping for). Plasma operation went well, and again there were no fizzles or duds all day.

Physics Operator Summaries

Entered: Jun 22 2006 05:11:29:327PM

Author: Jim Irby

The machine ran extremely well today (twelve plasmas/twelve attempts).
Th only adjustments made were small, probably unnecessary, adjustments
to the prepuff gas. Time between shots was very long since the
machine was going up to at least 300 mTorr from the massive gas puffs
(we need to write down the recovery procedure).

We had trouble adjusting SV4 properly to produce a good range in
pressure for the RGA. In addition, its position was not reproducible.
The same setting of 140 clicks could result a factor of 100 variation
in the pumpstack pressure.

Session Leader Comments

Jun 21 2006 05:58:24:243PM Robert Granetz The night before the run, the plenum contains 70+ bar of pure helium. I
evacuated the fill lines, hooked up the bottle of 50/50 He/Ar mix (2400 psi), and
set the regulator at 1000+ psi (70+ bar). But I've left the fill lines evacuated.

The gas jet system is ready to go. The firing signal currently goes through
the interface box, so in principle it may not fire during a fizzle, although
I'm not sure.

Jun 22 2006 08:53:52:360AM Robert Granetz Fast gas trigger is enabled in camac. 50 kHz sampling window is enabled for
the SX arrays from t=0.795 to 0.820 s.

Jun 22 2006 08:57:53:800AM Robert Granetz We will have to supply the mixed gas directly from its bottle, rather than from
just the intrinsic volume of the gas fill lines, because this intrinsic volume
is way too small. This will reduce the accuracy with which we know the plenum
mixture, but we will have the RGA sampling the torus gas after each shot, so that
should help.

Jun 22 2006 09:22:50:693AM 1060622001 Robert Granetz This was too much gas. I had the fast valve set for 2.0 ms, which is the setting
for argon. I will reduce this to 1.3 ms for the next shot (still pure helium).

Jun 22 2006 09:36:59:517AM 1060622001 Robert Granetz I was going to do a repeat shot with pure helium, but I calculate that if
I do a top-off fill with the 50/50 mix now, I will end up with 90% He/ 10% Ar.
If I did a repeat shot, I will have even more of a changeover, which is more
than I want. So I will not do a repeat shot with pure helium, but rather
do the top-off fill now.

Jun 22 2006 11:20:42:133AM 1060622001 Robert Granetz
Shot 01 -- Good shot. Gas jet fired at t=0.800 s. Current quench spike is at t=0.805 s. Current quench duration is about 3 ms. I_halo=138 kA Prf=2.0 MW Wth=125 kJ. Plenum gas: pure helium Pulse length (ms): 2.0 Plenum pre -pulse pressure (bar): 72 Plenum post-pulse pressure (bar): 56 Plenum change in pressure (bar): 16

Jun 22 2006 10:04:01:953AM 1060622002 Robert Granetz Pulse length was still 2.0 ms. My mistake, I guess I didn't "OK" the change.
But I definitely have loaded it now...it will be 1.3 ms on the next shot.

This should have been a 90/10 He/Ar mix. The current quench is much faster than
with pure helium (1 ms compared to 3 ms), and the halo current is 77 kA, compared
to 138 kA. I wish we could do smaller mixture increments. If I had used a shorter
pulse, we could have had an intermediate point.

I'm planning now on doing one shot at each mixture, then around mid-day I will
go into the cell and reinstall the pure helium bottle and start another series
of shots. Hopefully we will also get the RGA to work then too.

Jun 22 2006 10:05:47:203AM 1060622002 Robert Granetz For the next shot I will do another top-off fill, which should bring the
mixture to about 83/17 He/Ar.

Jun 22 2006 11:20:25:697AM 1060622002 Robert Granetz
Shot 02 -- Good shot. Gas jet fired at t=0.800 s. Current quench spike is at t=0.805 s. Current quench duration is about 1 ms. I_halo=77 kA Prf=2.0 MW Wth=113 kJ. Plenum gas: 90% He / 10% Ar (calculated) Pulse length (ms): 2.0 Plenum pre -pulse pressure (bar): 70.5 Plenum post-pulse pressure (bar): 57 Plenum change in pressure (bar): 13-14

Jun 22 2006 10:28:14:397AM 1060622003 Robert Granetz Got the desired valve pulse length this time, and correspondingly less
gas injected. Next shot, repeat with this 83/17 mixture. Plenum is
at 63 bar.

Jun 22 2006 11:20:04:930AM 1060622003 Robert Granetz
Shot 03 -- Good shot. Gas jet fired at t=0.800 s. Current quench spike is at t=0.8047 s. Current quench duration is about 1 ms. I_halo=100 kA Prf=2.0 MW Wth=125 kJ. Plenum gas: 83% He/ 17% Ar Pulse length (ms): 1.3 Plenum pre -pulse pressure (bar): 70.5 Plenum post-pulse pressure (bar): 63 Plenum change in pressure (bar): 7-8

Jun 22 2006 11:19:46:320AM 1060622004 Robert Granetz
Shot 04 -- Good shot. Gas jet fired at t=0.800 s. Current quench spike is at t=0.805 s. Current quench duration is about 1 ms. I_halo=78 kA Prf=2.0 MW Wth=122 kJ. Plenum gas: 83% He/ 17% Ar Pulse length (ms): 1.3 Plenum pre -pulse pressure (bar): 63 Plenum post-pulse pressure (bar): 56.5 Plenum change in pressure (bar): 6-7

Jun 22 2006 11:21:30:367AM 1060622004 Robert Granetz I will do another top-off fill for the next shot. This will bring the fractions
to 77% He / 23% Ar (calculated).

Also, the butterfly/bypass valve on the RGA system is now fixed. Starting
with the next shot we should get argon measurements. When we reset to helium
at mid-day and do another scan, we should have the RGA for all those shots.

Jun 22 2006 02:26:05:600PM 1060622004 Mohammad Bakhtiari Sx-ray signals at edge start to drop at ~0.8033 s

Maximum electron density before current quench nl04~4e20 m-2.

Maximum Halo current during current quench is ~80 kA.

Jun 22 2006 11:48:17:143AM 1060622005 Robert Granetz
Shot 05 -- Good shot. Gas jet fired at t=0.800 s. Current quench spike is at t=0.805 s. Current quench duration is about 1 ms. I_halo=90 kA Prf=2.0 MW Wth=121 kJ. Plenum gas: 77% He/ 23% Ar (calculated) Pulse length (ms): 1.3 Plenum pre -pulse pressure (bar): 70.5 Plenum post-pulse pressure (bar): 64.5 Plenum change in pressure (bar): 6

Jun 22 2006 12:03:04:550PM 1060622005 Robert Granetz The RGA is dominated by the He and Ar peaks. The raw RGA amplitudes are 1.6e-6 and
1.5e-6. The RGA sensitivity of Ar wrt N2 is 1.29, and for He wrt N2 is 0.18. The
the relative sensitivity of Ar to He is 7.17. Therefore the raw amplitude ratio
of He/Ar needs to be multiplied by 7.17. So I think the RGA is telling us the
ratio is 88% He / 12% Ar. My plenum mixing calculations give 77% He/ 23% Ar.

We can sort of do an in-vessel calibration of the RGA using the 50/50 mix. We'll
do this on shot 7.

The next shot (06) will be a repeat (77/23 He/Ar)

Jun 22 2006 02:05:03:200PM 1060622005 Robert Granetz In order to make the RGA-measured ratio on shot 08 come out to 50% He/ 50% Ar, I
have to assume a relative correction factor of 2.766 (i.e. the helium peak has
to be multiplied by 2.766 relative to the argon peak).

Applying this relative correction factor to the RGA data on shot 05 gives
75% He/ 25% Ar, which compares very well to my mixing calculations of 77% He/ 23% Ar.

Jun 22 2006 02:25:30:850PM 1060622005 Mohammad Bakhtiari Sx-ray signals at edge start to drop at ~0.8034 s

Maximum electron density before current quench nel4~4e20 m-2.

Maximum Halo current during current quench is ~90 kA.

Jun 22 2006 12:23:22:587PM 1060622006 Robert Granetz After this shot I pumped out the plenum and supply lines and filled the
plenum with the 50/50 He/Ar mix. We will use this on the next shot, both
to get a 50/50 data point, and also to calibrate the RGA.

Jun 22 2006 12:26:13:353PM 1060622006 Robert Granetz The raw data from the RGA on this shot is 2.1e-6 He and 2.0e-6 Ar. Using the
correction factor of 7.17 (see previous entry), this gives 88% He/ 12% Ar again
(not yet calibrated with the 50/50 mix).

Jun 22 2006 02:26:52:303PM 1060622006 Mohammad Bakhtiari Sx-ray signals at edge start to drop at ~0.8035 s

Maximum electron density before current quench nl04~4e20 m-2.

Maximum Halo current during current quench is ~105 kA.

Jun 22 2006 02:56:19:410PM 1060622006 Robert Granetz
Shot 06 -- Good shot. Gas jet fired at t=0.800 s. Current quench spike is at t=0.805 s. Current quench duration is about 1.5 ms. I_halo=105 kA Prf=2.0 MW Wth=116 kJ. Plenum gas: 77% He/ 23% Ar Pulse length (ms): 1.3 Plenum pre -pulse pressure (bar): 64.5 Plenum post-pulse pressure (bar): 58.5 Plenum change in pressure (bar): 6

Jun 22 2006 12:51:35:020PM 1060622007 Robert Granetz Strange result. Much less gas went into the machine, but we still got a gas
jet disruption. The valve worked properly. It seems that this is a result of
increasing the argon fraction to 50%. We'll have to study this a bit.

For the next shot, increase the valve pulse length to 2.0 ms.

Jun 22 2006 12:57:24:753PM 1060622007 Robert Granetz
Shot 07 -- Good shot. Gas jet fired at t=0.800 s. Current quench spike is at t=0.806 s. Current quench duration is about 1.5 ms. I_halo=94 kA Prf=2.0 MW Wth=123 kJ. Plenum gas: 50% He/ 50% Ar (straight from the bottle) Pulse length (ms): 1.3 Plenum pre -pulse pressure (bar): 70.5 Plenum post-pulse pressure (bar): 70 Plenum change in pressure (bar): 0.5

Jun 22 2006 01:03:25:560PM 1060622007 Robert Granetz RGA readings were 2.25e-7 for He and 5.0e-7 for Ar. Using a correction factor
of 7.17 gives a mix ratio of 76% He / 24% Ar. So either the RGA correction factor
needs to be changed (which is why we did this calibration shot), or the delivery
of argon was reduced because of the 1.3 ms pulse length. We'll find out on the
next shot when we use a 2.0 ms pulse length for the fast valve.

Jun 22 2006 02:27:46:600PM 1060622007 Mohammad Bakhtiari Sx-ray signals at edge start to drop at ~0.8043 s

Maximum electron density before current quench nl04~4e20 m-2.

Maximum Halo current during current quench is ~95 kA.

Jun 22 2006 01:12:27:043PM 1060622008 Robert Granetz
Shot 08 -- Good shot. Gas jet fired at t=0.800 s. Current quench spike is at t=0.8057 s. Current quench duration is about 1 ms. I_halo= kA Prf=2.0 MW Wth=123 kJ. Plenum gas: 50% He / 50% Ar (straight from the mix bottle) Pulse length (ms): 2.0 Plenum pre -pulse pressure (bar): 70 Plenum post-pulse pressure (bar): 62 Plenum change in pressure (bar): 8

Jun 22 2006 01:13:28:873PM 1060622008 Robert Granetz The RGA raw data is 1.11e-6 for He, 3.07e-6 for Ar. Using a correction factor
of 7.17 gives a mixture of 72% He/ 28% Ar. So it's clear that the factor of
7.17 needs to be changed.

Jun 22 2006 01:14:26:780PM 1060622008 Robert Granetz For the next shot, I will purge the plenum and gas lines and refill with pure
helium. I will need a cell access to switch the gas bottles.

Also, the fast valve pulse width will be reduced back to 1.3 ms.

Jun 22 2006 01:53:40:250PM 1060622008 Mohammad Bakhtiari Sx-ray signals at edge start to drop at ~0.8033 s and current quench starts at 0.8057. It seems it has taken a longer time, compare to other cases, to start current quench.

Jun 22 2006 02:04:49:560PM 1060622008 Robert Granetz In order to make the RGA-measured ratio on shot 08 come out to 50% He/ 50% Ar, I
have to assume a relative correction factor of 2.766 (i.e. the helium peak has
to be multiplied by 2.766 relative to the argon peak).

Applying this relative correction factor to the RGA data on shot 05 gives
75% He/ 25% Ar, which compares very well to my mixing calculations of 77% He/ 23% Ar.

Jun 22 2006 02:58:42:110PM 1060622009 Robert Granetz
Shot 09 -- Good shot. Gas jet fired at t=0.800 s. Current quench spike is at t=0.8054 s. Current quench duration is about 2.5 ms. I_halo=157 kA Prf=2.0 MW Wth=123 kJ. Plenum gas: pure helium Pulse length (ms): 1.3 Plenum pre -pulse pressure (bar): 70.5 Plenum post-pulse pressure (bar): 60 Plenum change in pressure (bar): 10.5

Jun 22 2006 03:09:12:470PM 1060622009 Robert Granetz RGA shows pure helium, as expected.

For the next shot I've topped off the plenum with the 50/50 mix. This
should result in a mixture ratio of 92% He/ 8% Ar. Can't really do
much smaller increments with the bottle we have.

Jun 22 2006 03:11:04:750PM 1060622009 Mohammad Bakhtiari Sx-ray at edge start to decrease at ~0.8028 s.
Halo current ~155 kA. Maximum nl04~6e20 m-2 before current quench.
Current quench at ~0.8055 ms.
Comparing to the first shot with 2 ms gas injection, it seems the gas pulse length
is important in disruption mitigation.

Jun 22 2006 03:27:15:197PM 1060622010 Robert Granetz
Shot 10 -- Good shot. Gas jet fired at t=0.800 s. Current quench spike is at t=0.8047 s. Current quench duration is about 1 ms. I_halo=107 kA Prf=2.0 MW Wth=118 kJ. Plenum gas: 92% He/ 8% Ar Pulse length (ms): 1.3 Plenum pre -pulse pressure (bar): 70.5 Plenum post-pulse pressure (bar): 62.5 Plenum change in pressure (bar): 8

Jun 22 2006 03:31:31:040PM 1060622010 Robert Granetz For the next shot, do another top-off fill at Mohammed's request. This should
bring the mix ratio to 86% He / 14% Ar.

Jun 22 2006 03:32:53:353PM 1060622010 Mohammad Bakhtiari Sx-ray at edge start to decrease at ~0.8028 s (almost same time
as a pure helium in previous shot)
With less Halo current ~105 kA (compare to pure helium). Maximum nl04~7e20 before current quench.
Current quench at ~0.805 ms (faster than that in pure helium).

Jun 22 2006 03:35:32:210PM 1060622010 Robert Granetz The RGA measurements for this shot, using the new calibration number of 2.766, gives
a mixture ratio of 87% He / 13% Ar. My mixing calculation gives 92% He / 8% Ar.

Jun 22 2006 04:04:17:453PM 1060622011 Robert Granetz
Shot 11 -- Good shot. Gas jet fired at t=0.800 s. Current quench spike is at t=0.8047 s. Current quench duration is about 1 ms. I_halo=120 kA Prf=2.0 MW Wth=118 kJ. Plenum gas: 87% He / 13% Ar Pulse length (ms): 1.3 Plenum pre -pulse pressure (bar): 70.5 Plenum post-pulse pressure (bar): 63.5 Plenum change in pressure (bar): 7

Jun 22 2006 04:08:43:843PM 1060622011 Robert Granetz The RGA looks like it screwed up on this shot. It might not have recorded a post-shot
mass spectrum.

Jun 22 2006 04:16:32:530PM 1060622011 Robert Granetz For the next (and probably final) shot, we want to do a repeat at this mixture in
order to get the RGA data.

Jun 22 2006 04:35:46:060PM 1060622012 Robert Granetz
Shot 12 -- Good shot. Gas jet fired at t=0.800 s. Current quench spike is at t=0.8048 s. Current quench duration is about 1 ms. I_halo=114 kA Prf=2.0 MW Wth=121 kJ. Plenum gas: 87% He / 13% Ar Pulse length (ms): 1.3 Plenum pre -pulse pressure (bar): 63.5 Plenum post-pulse pressure (bar): 56 Plenum change in pressure (bar): 7.5

Jun 22 2006 04:38:13:653PM 1060622012 Robert Granetz We'll have one more shot. I've done a final top-off, which should bring the
mixture to 79% He / 21% Ar.

Jun 22 2006 04:47:01:940PM 1060622012 Mohammad Bakhtiari Sx-ray at edge start to decrease at ~0.8032 s.
Halo current ~114 kA.
Maximum nl04~3e20 cm-2 before current quench.
Current quench at ~0.805 ms.

Jun 22 2006 04:50:33:910PM 1060622012 Robert Granetz The bypass valve on the RGA didn't work properly on this shot, so the
post-shot spectrum is very low amplitude (10^-8 scale). But by playing
around manually with the valve, Jim was able to get a later spectrum
in the 10^-6 range, which I read off the screen with the cursor:

He 5.3e-6
Ar 2.8e-6

With the calibration number of 2.766, this gives a ratio of 84% He / 16% Ar.

Jun 22 2006 05:07:20:453PM 1060622013 Robert Granetz
Shot 13 -- Good shot. Gas jet fired at t=0.800 s. Current quench spike is at t=0.805 s. Current quench duration is about 1 ms. I_halo=107 kA Prf=2.0 MW Wth=119 kJ. Plenum gas: 79% He / 21% Ar Pulse length (ms): 1.3 Plenum pre -pulse pressure (bar): 70.5 Plenum post-pulse pressure (bar): 64.5 Plenum change in pressure (bar): 6

Jun 22 2006 05:07:48:577PM 1060622013 Robert Granetz End of run. I will close the bottle and pump everything out.

Jun 22 2006 05:11:01:343PM 1060622013 Robert Granetz RGA gives 80% He / 20% Ar

Jun 22 2006 05:18:36:273PM 1060622013 Mohammad Bakhtiari Sx-ray at edge start to decrease at ~0.8032 s.
Halo current ~110 kA.
Maximum nl04~5e20 m-2 before current quench.
Current quench at ~0.8047 ms.

Physics Operator Comments

Jun 22 2006 09:40:51:237AM 1060622001 Jim Irby loaded from 1060621020

bt to 5.4 T (150kA)
nl04 request at 1.0e29/m^2 at 0.6 s --- increased density rate of rise before 0.6 to get to the target.

loaded/clean

plasma --- got rf too

gatevalves toggled closed before the shot for 5 minutes with bypass at 270 clicks.
But 270 was too large --- RGA tripped

TMP2 shutdown --- water flow?

target density reached by h-mode time --- rf raises density a little

Jun 22 2006 10:17:57:510AM 1060622002 Jim Irby 30 minute delay before shot to get pumping system going again and for Bob to make changes to the big puff.

bypass to 180 clicks --- still too large

plasma

Jun 22 2006 10:55:22:767AM 1060622003 Jim Irby no DPCS changes

plasma

bypass at 150 clicks still too much -- now bypass appears to be broken.

Bob Childs goes into cell to check bypass

Jun 22 2006 11:17:28:773AM 1060622004 Jim Irby bypass fixed --- set at 130 clicks

ready for shot after about 41 minutes

prepuff from 20 to 21 ms.

plasma

Jun 22 2006 12:05:15:440PM 1060622005 Jim Irby bypass 140

raised early pg3 gas puff to help with neuts/hards from 60 to about 80V

gatevalves toggled closed for 10 minutes as of last shot

plasma

RGA provides good data at last

Jun 22 2006 12:17:33:760PM 1060622006 Jim Irby no DPCS changes

plasma

rga data looks good and making into MDS

Jun 22 2006 12:51:08:357PM 1060622007 Jim Irby No control system changes

cell entry before this shot as Bob makes changes to the gas mix.

ready for shot at 26 minutes

plasma --- pressure in machine only 30 mTorr with current He/Ar 50/50 mix

Jun 22 2006 02:14:35:853PM 1060622008 Jim Irby repeat DPCS

plasma

Jun 22 2006 02:59:15:190PM 1060622009 Jim Irby long break to enter cell and make changes to gas puff system --- 1:48

plasma

Jun 22 2006 03:36:21:413PM 1060622010 Jim Irby prepuff to 21 ms from 20 ms

plasma

ratiomatic turned on for this shot 8.1e-5 Torr at t=0 --- will drop prepuff or next shot

Jun 22 2006 04:20:39:440PM 1060622011 Jim Irby prepuff from 21 to 18 ms

start cycle at 35 minutes

plasma

no RGA data...

Jun 22 2006 04:45:14:190PM 1060622012 Jim Irby no DPCS changes

RGA is working

cycle start time: 31 minutes

plasma

RGA produced data, but the bypass valve at 140 clicks is not the same as it was. Basepressure in pumpstack 1 is on the 1e-8 Torr range vs 1e-6 range earlier today.

Engineering Operator Comments

Shot Time Type Status Comment

1 09:07:56:263AM Plasma Ok

2 09:45:33:940AM Plasma Ok

3 10:18:28:700AM Plasma Ok

4 11:02:31:373AM Plasma Ok

5 11:34:52:787AM Plasma Ok

6 12:04:02:283PM Plasma Ok

7 12:33:32:183PM Plasma Ok

8 01:01:12:950PM Plasma Ok

9 02:53:33:423PM Plasma Ok

10 03:22:31:633PM Plasma Ok

11 03:58:44:220PM Plasma Ok

12 04:28:51:950PM Plasma Ok

13 05:01:48:467PM Plasma Ok

Session Leader Comments
Jun 21 2006 05:58:24:243PM		Robert Granetz	The night before the run, the plenum contains 70+ bar of pure helium. I evacuated the fill lines, hooked up the bottle of 50/50 He/Ar mix (2400 psi), and set the regulator at 1000+ psi (70+ bar). But I've left the fill lines evacuated. The gas jet system is ready to go. The firing signal currently goes through the interface box, so in principle it may not fire during a fizzle, although I'm not sure.
Jun 22 2006 08:53:52:360AM		Robert Granetz	Fast gas trigger is enabled in camac. 50 kHz sampling window is enabled for the SX arrays from t=0.795 to 0.820 s.
Jun 22 2006 08:57:53:800AM		Robert Granetz	We will have to supply the mixed gas directly from its bottle, rather than from just the intrinsic volume of the gas fill lines, because this intrinsic volume is way too small. This will reduce the accuracy with which we know the plenum mixture, but we will have the RGA sampling the torus gas after each shot, so that should help.
Jun 22 2006 09:22:50:693AM	1060622001	Robert Granetz	This was too much gas. I had the fast valve set for 2.0 ms, which is the setting for argon. I will reduce this to 1.3 ms for the next shot (still pure helium).
Jun 22 2006 09:36:59:517AM	1060622001	Robert Granetz	I was going to do a repeat shot with pure helium, but I calculate that if I do a top-off fill with the 50/50 mix now, I will end up with 90% He/ 10% Ar. If I did a repeat shot, I will have even more of a changeover, which is more than I want. So I will not do a repeat shot with pure helium, but rather do the top-off fill now.
Jun 22 2006 11:20:42:133AM	1060622001	Robert Granetz	Shot 01 -- Good shot. Gas jet fired at t=0.800 s. Current quench spike is at t=0.805 s. Current quench duration is about 3 ms. I_halo=138 kA Prf=2.0 MW Wth=125 kJ. Plenum gas: pure helium Pulse length (ms): 2.0 Plenum pre -pulse pressure (bar): 72 Plenum post-pulse pressure (bar): 56 Plenum change in pressure (bar): 16
Jun 22 2006 10:04:01:953AM	1060622002	Robert Granetz	Pulse length was still 2.0 ms. My mistake, I guess I didn't "OK" the change. But I definitely have loaded it now...it will be 1.3 ms on the next shot. This should have been a 90/10 He/Ar mix. The current quench is much faster than with pure helium (1 ms compared to 3 ms), and the halo current is 77 kA, compared to 138 kA. I wish we could do smaller mixture increments. If I had used a shorter pulse, we could have had an intermediate point. I'm planning now on doing one shot at each mixture, then around mid-day I will go into the cell and reinstall the pure helium bottle and start another series of shots. Hopefully we will also get the RGA to work then too.
Jun 22 2006 10:05:47:203AM	1060622002	Robert Granetz	For the next shot I will do another top-off fill, which should bring the mixture to about 83/17 He/Ar.
Jun 22 2006 11:20:25:697AM	1060622002	Robert Granetz	Shot 02 -- Good shot. Gas jet fired at t=0.800 s. Current quench spike is at t=0.805 s. Current quench duration is about 1 ms. I_halo=77 kA Prf=2.0 MW Wth=113 kJ. Plenum gas: 90% He / 10% Ar (calculated) Pulse length (ms): 2.0 Plenum pre -pulse pressure (bar): 70.5 Plenum post-pulse pressure (bar): 57 Plenum change in pressure (bar): 13-14
Jun 22 2006 10:28:14:397AM	1060622003	Robert Granetz	Got the desired valve pulse length this time, and correspondingly less gas injected. Next shot, repeat with this 83/17 mixture. Plenum is at 63 bar.
Jun 22 2006 11:20:04:930AM	1060622003	Robert Granetz	Shot 03 -- Good shot. Gas jet fired at t=0.800 s. Current quench spike is at t=0.8047 s. Current quench duration is about 1 ms. I_halo=100 kA Prf=2.0 MW Wth=125 kJ. Plenum gas: 83% He/ 17% Ar Pulse length (ms): 1.3 Plenum pre -pulse pressure (bar): 70.5 Plenum post-pulse pressure (bar): 63 Plenum change in pressure (bar): 7-8
Jun 22 2006 11:19:46:320AM	1060622004	Robert Granetz	Shot 04 -- Good shot. Gas jet fired at t=0.800 s. Current quench spike is at t=0.805 s. Current quench duration is about 1 ms. I_halo=78 kA Prf=2.0 MW Wth=122 kJ. Plenum gas: 83% He/ 17% Ar Pulse length (ms): 1.3 Plenum pre -pulse pressure (bar): 63 Plenum post-pulse pressure (bar): 56.5 Plenum change in pressure (bar): 6-7
Jun 22 2006 11:21:30:367AM	1060622004	Robert Granetz	I will do another top-off fill for the next shot. This will bring the fractions to 77% He / 23% Ar (calculated). Also, the butterfly/bypass valve on the RGA system is now fixed. Starting with the next shot we should get argon measurements. When we reset to helium at mid-day and do another scan, we should have the RGA for all those shots.
Jun 22 2006 02:26:05:600PM	1060622004	Mohammad Bakhtiari	Sx-ray signals at edge start to drop at ~0.8033 s Maximum electron density before current quench nl04~4e20 m-2. Maximum Halo current during current quench is ~80 kA.
Jun 22 2006 11:48:17:143AM	1060622005	Robert Granetz	Shot 05 -- Good shot. Gas jet fired at t=0.800 s. Current quench spike is at t=0.805 s. Current quench duration is about 1 ms. I_halo=90 kA Prf=2.0 MW Wth=121 kJ. Plenum gas: 77% He/ 23% Ar (calculated) Pulse length (ms): 1.3 Plenum pre -pulse pressure (bar): 70.5 Plenum post-pulse pressure (bar): 64.5 Plenum change in pressure (bar): 6
Jun 22 2006 12:03:04:550PM	1060622005	Robert Granetz	The RGA is dominated by the He and Ar peaks. The raw RGA amplitudes are 1.6e-6 and 1.5e-6. The RGA sensitivity of Ar wrt N2 is 1.29, and for He wrt N2 is 0.18. The the relative sensitivity of Ar to He is 7.17. Therefore the raw amplitude ratio of He/Ar needs to be multiplied by 7.17. So I think the RGA is telling us the ratio is 88% He / 12% Ar. My plenum mixing calculations give 77% He/ 23% Ar. We can sort of do an in-vessel calibration of the RGA using the 50/50 mix. We'll do this on shot 7. The next shot (06) will be a repeat (77/23 He/Ar)
Jun 22 2006 02:05:03:200PM	1060622005	Robert Granetz	In order to make the RGA-measured ratio on shot 08 come out to 50% He/ 50% Ar, I have to assume a relative correction factor of 2.766 (i.e. the helium peak has to be multiplied by 2.766 relative to the argon peak). Applying this relative correction factor to the RGA data on shot 05 gives 75% He/ 25% Ar, which compares very well to my mixing calculations of 77% He/ 23% Ar.
Jun 22 2006 02:25:30:850PM	1060622005	Mohammad Bakhtiari	Sx-ray signals at edge start to drop at ~0.8034 s Maximum electron density before current quench nel4~4e20 m-2. Maximum Halo current during current quench is ~90 kA.
Jun 22 2006 12:23:22:587PM	1060622006	Robert Granetz	After this shot I pumped out the plenum and supply lines and filled the plenum with the 50/50 He/Ar mix. We will use this on the next shot, both to get a 50/50 data point, and also to calibrate the RGA.
Jun 22 2006 12:26:13:353PM	1060622006	Robert Granetz	The raw data from the RGA on this shot is 2.1e-6 He and 2.0e-6 Ar. Using the correction factor of 7.17 (see previous entry), this gives 88% He/ 12% Ar again (not yet calibrated with the 50/50 mix).
Jun 22 2006 02:26:52:303PM	1060622006	Mohammad Bakhtiari	Sx-ray signals at edge start to drop at ~0.8035 s Maximum electron density before current quench nl04~4e20 m-2. Maximum Halo current during current quench is ~105 kA.
Jun 22 2006 02:56:19:410PM	1060622006	Robert Granetz	Shot 06 -- Good shot. Gas jet fired at t=0.800 s. Current quench spike is at t=0.805 s. Current quench duration is about 1.5 ms. I_halo=105 kA Prf=2.0 MW Wth=116 kJ. Plenum gas: 77% He/ 23% Ar Pulse length (ms): 1.3 Plenum pre -pulse pressure (bar): 64.5 Plenum post-pulse pressure (bar): 58.5 Plenum change in pressure (bar): 6
Jun 22 2006 12:51:35:020PM	1060622007	Robert Granetz	Strange result. Much less gas went into the machine, but we still got a gas jet disruption. The valve worked properly. It seems that this is a result of increasing the argon fraction to 50%. We'll have to study this a bit. For the next shot, increase the valve pulse length to 2.0 ms.
Jun 22 2006 12:57:24:753PM	1060622007	Robert Granetz	Shot 07 -- Good shot. Gas jet fired at t=0.800 s. Current quench spike is at t=0.806 s. Current quench duration is about 1.5 ms. I_halo=94 kA Prf=2.0 MW Wth=123 kJ. Plenum gas: 50% He/ 50% Ar (straight from the bottle) Pulse length (ms): 1.3 Plenum pre -pulse pressure (bar): 70.5 Plenum post-pulse pressure (bar): 70 Plenum change in pressure (bar): 0.5
Jun 22 2006 01:03:25:560PM	1060622007	Robert Granetz	RGA readings were 2.25e-7 for He and 5.0e-7 for Ar. Using a correction factor of 7.17 gives a mix ratio of 76% He / 24% Ar. So either the RGA correction factor needs to be changed (which is why we did this calibration shot), or the delivery of argon was reduced because of the 1.3 ms pulse length. We'll find out on the next shot when we use a 2.0 ms pulse length for the fast valve.
Jun 22 2006 02:27:46:600PM	1060622007	Mohammad Bakhtiari	Sx-ray signals at edge start to drop at ~0.8043 s Maximum electron density before current quench nl04~4e20 m-2. Maximum Halo current during current quench is ~95 kA.
Jun 22 2006 01:12:27:043PM	1060622008	Robert Granetz	Shot 08 -- Good shot. Gas jet fired at t=0.800 s. Current quench spike is at t=0.8057 s. Current quench duration is about 1 ms. I_halo= kA Prf=2.0 MW Wth=123 kJ. Plenum gas: 50% He / 50% Ar (straight from the mix bottle) Pulse length (ms): 2.0 Plenum pre -pulse pressure (bar): 70 Plenum post-pulse pressure (bar): 62 Plenum change in pressure (bar): 8
Jun 22 2006 01:13:28:873PM	1060622008	Robert Granetz	The RGA raw data is 1.11e-6 for He, 3.07e-6 for Ar. Using a correction factor of 7.17 gives a mixture of 72% He/ 28% Ar. So it's clear that the factor of 7.17 needs to be changed.
Jun 22 2006 01:14:26:780PM	1060622008	Robert Granetz	For the next shot, I will purge the plenum and gas lines and refill with pure helium. I will need a cell access to switch the gas bottles. Also, the fast valve pulse width will be reduced back to 1.3 ms.
Jun 22 2006 01:53:40:250PM	1060622008	Mohammad Bakhtiari	Sx-ray signals at edge start to drop at ~0.8033 s and current quench starts at 0.8057. It seems it has taken a longer time, compare to other cases, to start current quench.
Jun 22 2006 02:04:49:560PM	1060622008	Robert Granetz	In order to make the RGA-measured ratio on shot 08 come out to 50% He/ 50% Ar, I have to assume a relative correction factor of 2.766 (i.e. the helium peak has to be multiplied by 2.766 relative to the argon peak). Applying this relative correction factor to the RGA data on shot 05 gives 75% He/ 25% Ar, which compares very well to my mixing calculations of 77% He/ 23% Ar.
Jun 22 2006 02:58:42:110PM	1060622009	Robert Granetz	Shot 09 -- Good shot. Gas jet fired at t=0.800 s. Current quench spike is at t=0.8054 s. Current quench duration is about 2.5 ms. I_halo=157 kA Prf=2.0 MW Wth=123 kJ. Plenum gas: pure helium Pulse length (ms): 1.3 Plenum pre -pulse pressure (bar): 70.5 Plenum post-pulse pressure (bar): 60 Plenum change in pressure (bar): 10.5
Jun 22 2006 03:09:12:470PM	1060622009	Robert Granetz	RGA shows pure helium, as expected. For the next shot I've topped off the plenum with the 50/50 mix. This should result in a mixture ratio of 92% He/ 8% Ar. Can't really do much smaller increments with the bottle we have.
Jun 22 2006 03:11:04:750PM	1060622009	Mohammad Bakhtiari	Sx-ray at edge start to decrease at ~0.8028 s. Halo current ~155 kA. Maximum nl04~6e20 m-2 before current quench. Current quench at ~0.8055 ms. Comparing to the first shot with 2 ms gas injection, it seems the gas pulse length is important in disruption mitigation.
Jun 22 2006 03:27:15:197PM	1060622010	Robert Granetz	Shot 10 -- Good shot. Gas jet fired at t=0.800 s. Current quench spike is at t=0.8047 s. Current quench duration is about 1 ms. I_halo=107 kA Prf=2.0 MW Wth=118 kJ. Plenum gas: 92% He/ 8% Ar Pulse length (ms): 1.3 Plenum pre -pulse pressure (bar): 70.5 Plenum post-pulse pressure (bar): 62.5 Plenum change in pressure (bar): 8
Jun 22 2006 03:31:31:040PM	1060622010	Robert Granetz	For the next shot, do another top-off fill at Mohammed's request. This should bring the mix ratio to 86% He / 14% Ar.
Jun 22 2006 03:32:53:353PM	1060622010	Mohammad Bakhtiari	Sx-ray at edge start to decrease at ~0.8028 s (almost same time as a pure helium in previous shot) With less Halo current ~105 kA (compare to pure helium). Maximum nl04~7e20 before current quench. Current quench at ~0.805 ms (faster than that in pure helium).
Jun 22 2006 03:35:32:210PM	1060622010	Robert Granetz	The RGA measurements for this shot, using the new calibration number of 2.766, gives a mixture ratio of 87% He / 13% Ar. My mixing calculation gives 92% He / 8% Ar.
Jun 22 2006 04:04:17:453PM	1060622011	Robert Granetz	Shot 11 -- Good shot. Gas jet fired at t=0.800 s. Current quench spike is at t=0.8047 s. Current quench duration is about 1 ms. I_halo=120 kA Prf=2.0 MW Wth=118 kJ. Plenum gas: 87% He / 13% Ar Pulse length (ms): 1.3 Plenum pre -pulse pressure (bar): 70.5 Plenum post-pulse pressure (bar): 63.5 Plenum change in pressure (bar): 7
Jun 22 2006 04:08:43:843PM	1060622011	Robert Granetz	The RGA looks like it screwed up on this shot. It might not have recorded a post-shot mass spectrum.
Jun 22 2006 04:16:32:530PM	1060622011	Robert Granetz	For the next (and probably final) shot, we want to do a repeat at this mixture in order to get the RGA data.
Jun 22 2006 04:35:46:060PM	1060622012	Robert Granetz	Shot 12 -- Good shot. Gas jet fired at t=0.800 s. Current quench spike is at t=0.8048 s. Current quench duration is about 1 ms. I_halo=114 kA Prf=2.0 MW Wth=121 kJ. Plenum gas: 87% He / 13% Ar Pulse length (ms): 1.3 Plenum pre -pulse pressure (bar): 63.5 Plenum post-pulse pressure (bar): 56 Plenum change in pressure (bar): 7.5
Jun 22 2006 04:38:13:653PM	1060622012	Robert Granetz	We'll have one more shot. I've done a final top-off, which should bring the mixture to 79% He / 21% Ar.
Jun 22 2006 04:47:01:940PM	1060622012	Mohammad Bakhtiari	Sx-ray at edge start to decrease at ~0.8032 s. Halo current ~114 kA. Maximum nl04~3e20 cm-2 before current quench. Current quench at ~0.805 ms.
Jun 22 2006 04:50:33:910PM	1060622012	Robert Granetz	The bypass valve on the RGA didn't work properly on this shot, so the post-shot spectrum is very low amplitude (10^-8 scale). But by playing around manually with the valve, Jim was able to get a later spectrum in the 10^-6 range, which I read off the screen with the cursor: He 5.3e-6 Ar 2.8e-6 With the calibration number of 2.766, this gives a ratio of 84% He / 16% Ar.
Jun 22 2006 05:07:20:453PM	1060622013	Robert Granetz	Shot 13 -- Good shot. Gas jet fired at t=0.800 s. Current quench spike is at t=0.805 s. Current quench duration is about 1 ms. I_halo=107 kA Prf=2.0 MW Wth=119 kJ. Plenum gas: 79% He / 21% Ar Pulse length (ms): 1.3 Plenum pre -pulse pressure (bar): 70.5 Plenum post-pulse pressure (bar): 64.5 Plenum change in pressure (bar): 6
Jun 22 2006 05:07:48:577PM	1060622013	Robert Granetz	End of run. I will close the bottle and pump everything out.
Jun 22 2006 05:11:01:343PM	1060622013	Robert Granetz	RGA gives 80% He / 20% Ar
Jun 22 2006 05:18:36:273PM	1060622013	Mohammad Bakhtiari	Sx-ray at edge start to decrease at ~0.8032 s. Halo current ~110 kA. Maximum nl04~5e20 m-2 before current quench. Current quench at ~0.8047 ms.

Physics Operator Comments
Jun 22 2006 09:40:51:237AM	1060622001	Jim Irby	loaded from 1060621020 bt to 5.4 T (150kA) nl04 request at 1.0e29/m^2 at 0.6 s --- increased density rate of rise before 0.6 to get to the target. loaded/clean plasma --- got rf too gatevalves toggled closed before the shot for 5 minutes with bypass at 270 clicks. But 270 was too large --- RGA tripped TMP2 shutdown --- water flow? target density reached by h-mode time --- rf raises density a little
Jun 22 2006 10:17:57:510AM	1060622002	Jim Irby	30 minute delay before shot to get pumping system going again and for Bob to make changes to the big puff. bypass to 180 clicks --- still too large plasma
Jun 22 2006 10:55:22:767AM	1060622003	Jim Irby	no DPCS changes plasma bypass at 150 clicks still too much -- now bypass appears to be broken. Bob Childs goes into cell to check bypass
Jun 22 2006 11:17:28:773AM	1060622004	Jim Irby	bypass fixed --- set at 130 clicks ready for shot after about 41 minutes prepuff from 20 to 21 ms. plasma
Jun 22 2006 12:05:15:440PM	1060622005	Jim Irby	bypass 140 raised early pg3 gas puff to help with neuts/hards from 60 to about 80V gatevalves toggled closed for 10 minutes as of last shot plasma RGA provides good data at last
Jun 22 2006 12:17:33:760PM	1060622006	Jim Irby	no DPCS changes plasma rga data looks good and making into MDS
Jun 22 2006 12:51:08:357PM	1060622007	Jim Irby	No control system changes cell entry before this shot as Bob makes changes to the gas mix. ready for shot at 26 minutes plasma --- pressure in machine only 30 mTorr with current He/Ar 50/50 mix
Jun 22 2006 02:14:35:853PM	1060622008	Jim Irby	repeat DPCS plasma
Jun 22 2006 02:59:15:190PM	1060622009	Jim Irby	long break to enter cell and make changes to gas puff system --- 1:48 plasma
Jun 22 2006 03:36:21:413PM	1060622010	Jim Irby	prepuff to 21 ms from 20 ms plasma ratiomatic turned on for this shot 8.1e-5 Torr at t=0 --- will drop prepuff or next shot
Jun 22 2006 04:20:39:440PM	1060622011	Jim Irby	prepuff from 21 to 18 ms start cycle at 35 minutes plasma no RGA data...
Jun 22 2006 04:45:14:190PM	1060622012	Jim Irby	no DPCS changes RGA is working cycle start time: 31 minutes plasma RGA produced data, but the bypass valve at 140 clicks is not the same as it was. Basepressure in pumpstack 1 is on the 1e-8 Torr range vs 1e-6 range earlier today.

Engineering Operator Comments
Shot	Time	Type	Status	Comment
1	09:07:56:263AM	Plasma	Ok
2	09:45:33:940AM	Plasma	Ok
3	10:18:28:700AM	Plasma	Ok
4	11:02:31:373AM	Plasma	Ok
5	11:34:52:787AM	Plasma	Ok
6	12:04:02:283PM	Plasma	Ok
7	12:33:32:183PM	Plasma	Ok
8	01:01:12:950PM	Plasma	Ok
9	02:53:33:423PM	Plasma	Ok
10	03:22:31:633PM	Plasma	Ok
11	03:58:44:220PM	Plasma	Ok
12	04:28:51:950PM	Plasma	Ok
13	05:01:48:467PM	Plasma	Ok