Alcator C-Mod Run 1060721 Information

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Miniproposals
Miniproposal:454
Date Filed: 5/24/2006
Title:High Bootstrap Current Fraction Plasmas
First Author:Chuck Kessel
Session Leader:Chuck Kessel (shots 1-27)

Operators
Session leader(s):Chuck Kessel
Physics operator(s):Robert Granetz
Engineering operator(s):Andy Pfeiffer,Bill Byford,Bill Parkin

Engineering Operator Run Comment
MP# 454: High bootstrap current fraction plasmas Session leaders: C. Kes

Session Leader Plans
Entered: Jul 20 2006 04:14:51:717PM
Author: Amanda Hubbard
Session Leader plan for 1060721: MP 454: High Bootstsrap Current Fraction Plasmas

Session Leader: Chuck Kessel
Physics Operator: Bob Granetz

Aim: To establish the feasibility of obtaining high bootstrap fraction plasmas using controlled ITBs at low current, via off and on-axis heating. We will use 4.5 T scenario with off-axis heating at 80 MHz, on-axis at 70 MHz.
If successful scenarios are developed, and LH is available, may try LHCD to drive additional non-inductive current. This would be dependent on being able to run both LH and ICRH systems together.

Overnight boronization followed by ECDC is desired; see phsyop plan for details. May also necessitate ICRF conditioning before the run.

1) Establish 'standard' ITB at 4.5 T, 800 kA, target nel 9e19 m-2. Suggest starting from 1060707031 (4.7 T, 700 kA) and adjusting waveforms as needed.
Apply 80 MHz only 2-3 MW, starting early in I/Bt flat top (~ 0.6-1.4 s) no on-axis power, produce H-mode and ITB
Repeat until steady H-modes, ITB achieved. (3-4 shots). May apply J-port late in flat top to condition. LHCD may wish to test at low power late in RF pulse.

2) add 70 MHz on-axis power to successful case above, 0.5 & 1.0 MW , timing depending on ne and Prad ramp. (3 shots)

3) following same Ip ramp as 800 kA, flattop at 600 kA, move on-time of 80 MHz earlier, no on-axis power, produce H-mode and ITB. Extend flat top length if volt-seconds permit, to allow more time for ITB development.

4) add 70 MHz on-axis power to successful case above, 0.5 & 1.0 MW

5, 6) Assuming success, repeat above ITB production and stabilization at 450 kA, 300 kA. Determine lower limit for getting decent confinement.

7) If steady, reasonable low ne ITBs have been achieved, return to most promising condition and try applying LHCD during flat top. Probably 90 degree phasing, maximum power from 1060720. This should maximize the non-inductive fraction and give useful info for future AT scenarios.
Entered: Jul 21 2006 08:37:46:857AM
Author: Chuck Kessel
Aim: To establish the feasibility of obtaining high bootstrap fraction
plasmas using controlled ITBs at low current, via off and on-axis
heating. We will use 4.5 T scenario with off-axis heating at 80 MHz,
on-axis at 70 MHz.
If successful scenarios are developed, may try LHCD to drive additional
non-inductive current.

Overnight boronization followed by ECDC is desired; see phsyop plan for
details. May also necessitate ICRF conditioning before the run.

1) Establish 'standard' ITB at 4.5 T, 800 kA, target nel 9e19 m-2.
Suggest starting from 1060707031 (4.7 T, 700 kA) and adjusting
waveforms as needed.
Apply 80 MHz only 2-3 MW, starting early in I/Bt flat top (~
0.6-1.4 s) no on-axis power, produce H-mode and ITB
Repeat until steady H-modes, ITB achieved. (3-4 shots). May
apply J-port late in flat top to condition.

2) add 70 MHz on-axis power to successful case above, 0.5 & 1.0 MW ,
timing depending on ne and Prad ramp. (3 shots)

3) following same Ip ramp as 800 kA, flattop at 600 kA, move on-time of
80 MHz earlier, no on-axis power, produce H-mode and ITB

4) add 70 MHz on-axis power to successful case above, 0.5 & 1.0 MW

5, 6) Assuming success, repeat above ITB production and stabilization
at 450 kA, 300 kA. Determine lower limit for getting decent
confinement.

7) If steady, reasonable low ne ITBs have been achieved, return to
most promising condition and try applying LHCD during flat top.
Probably 90 degree phasing, maximum power from 1060720. This should
maximize the non-inductive fraction and give useful info for future AT
scenarios.

Physics Operators Plans
Entered: Jul 21 2006 08:13:08:750AM
Author: Robert Granetz
Engineering setup for Friday 21 July 2006

MP# 454: High bootstrap current fraction plasmas

Session leaders: C. Kessel/A. Hubbard
Physics operator: R. Granetz

Overnight boronization, followed by the usual ECDC in helium (~4 hours),
and finally by an hour or two of ECDC in deuterium.  Bake at 60 C.

The run will start at 09:00 and end at 17:00.

Power systems as on 1060707031 (except tweak Bt to 4.5 T and Ip to 0.8 MA).

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     as is           Hybrid DISABLED (PG2)   
   fill B-main (C-side)  with 40 psi D2  Hybrid enabled  (PG3)
  leave NINJA            as is           disabled

Enable the following gate valves and shutters, assuming no vacuum problems:
  ECE, VUV, Z-bolo shutters
 
Torvac setup: Gate valves open

Key diagnostics: ECE, VB, TCI, TS essential.  Reflectometry, PCI, MSE high
desirable.

-------------------------------------------------------------------------------
ICRF Setup: all transmitters (70 and 80 MHz) in run-on by 08:30.  We will
need 0.5-1.5 MW at 70 MHz, and 2-3 MW at 80 Mhz.

-------------------------------------------------------------------------------
Run plan: Start with 4.5 T and 0.8 MA.  We will basically be decreasing Ip
shot-to-shot, while varying the application of RF frequencies and timing.
See the session leaders' plan for more information.


Session Leader Summaries
Entered: Jul 24 2006 09:19:54:563AM
Author: Chuck Kessel
H-mode + ITB plasmas were established at plasma currents of 800, 600 and 450 kA. The toroidal field was fixed at 4.5 T, with the (1-2.8 MW) 80 MHz launcher giving off-axis heating (HFS, turned on at 600 ms) and the (0.5-1.0 MW) 70 MHz launcher giving on-axis heating. At 800 kA, H-modes with mild ITBs were generated, however, some impurity influx was consistently causing radiative collapses which resulted in H-to-L transitions. Density profile peakings of 1.25 were observed. The source of impurity was not found, but the X-pt position was moved and plasma current lowered to 600 kA. At 600 kA, the 70 MHz was effective at slowing the density rise (010, 012, 014), with 014 clearly the best stabilized H-mode+ITB discharge of the day. Soon after 014 the 70 MHz launcher was no longer working, and we had to run off-axis heating only discharges. The plasma current was lowered to 450 kA, and a power scan of the 80 MHz heating was done. Due to the lack of the on-axis heating the density rises were not controlled, and resulted in back transitions to the L-mode. Fast density rises resulted from ITB formation, giving short lived peaked density phases, although the ITB's were still clearly visible in the density profile data prior to the H-to-L transitions. The power scan (at 450 kA) showed that 1.0 MW was insufficient to get into the H-mode, 1.5 MW appeared to slowly enter H-mode, 1.75-2.8 MW had H-modes and appear to have ITB's as well before the H-to-L transition. Finally a power ramp was tried to try to slow the density rise, and appears to have worked, but there was no time left to examine it further.

Overall, it appears that H-mode + ITB's can be created at lower currents, as low as 450 kA. There was no apparent limitation to lowering the plasma current even further. The density and stored energies dropped with lower plasma current, although the peak electron temperatures consistently reached 1.25-1.5 keV regardless of current. From a cursory examination, the loop voltage did not drop over the plasma current variation, but the transient nature of the H-mode + ITB's in these discharges make this difficult to interpret. Whether higher bootstrap current would have resulted if the transport regime was sustained will be examined.

Several questions arose out of the experiments:
1) how important was the timing of the on-axis power versus its magnitude in setting the final density in H-mode+ITB shots?
2) are there power trajectories that can make the formation of these plasmas more reliable (more directly, slow the density rise down), such as a power ramp versus full on?
3) as the plasma current is lowered, the pulse length can be extended (desirable for future experiments to establish long steady configurations), what are the limitations to doing this (TF coil, ICRF, PFC heating??)
4) are the features of these H-mode+ITB plasmas changing as the current is lowered?

Physics Operator Summaries
Entered: Jul 21 2006 05:02:18:643PM
Author: Robert Granetz
Run summary for Friday 21 July 2006:

MP# 454: High bootstrap current fraction plasmas

Session leaders: C. Kessel/A. Hubbard
Physics operator: R. Granetz

The tokamak ran quite reliably today in terms of plasma operation.  D and E
antenna systems regularly gave 2+ MW for long, fault-free times.  J-antenna
(70 MHz) was also operated at the 0.5-0.75 MW level until transmitter #3
developed a problem after shot 16.  Good core peaking was observed on many
shots, and there were some ITBs, but there were problems keeping the core
temperature high.  See the session leaders' summaries for detailed physics
results.

Note: the DNB was fired into every plasma, starting with shot 3.

Scorecard: 27 plasmas
            0 duds
            0 fizzles
            0 gas system tests
            0 TF scanner tests
            0 power supply tests (EF3-only)
            0 no power MDS shot cycles
           --------------
    Total: 27 shot cycles

Session Leader Comments
Jul 21 2006 09:38:49:723AM1060721001Chuck Kessel
good test shot
Jul 21 2006 09:56:11:417AM1060721002Chuck Kesselinteresting shot, H-mode and density rise, then a little RF power < 1 MW and another density rise
Jul 21 2006 10:18:08:690AM1060721003Amanda HubbardNice shot . 2 MW D and E, clean, gives nice long H-mode. And apparently an ITB, judging from bremstrahlung. Te starts to drop around 1.3 secs, will try to add some J-port.
Jul 21 2006 10:22:29:910AM1060721003Chuck Kesselgood RF pulse at 2 MW, density rise follows RF on time, Te flat at 1.25 keV in spite of density rise, probably a smaller ITB
Jul 21 2006 10:41:57:107AM1060721004Chuck KesselRF power was up, disruption
Jul 21 2006 10:59:03:960AM1060721005Chuck Kesselanother disruption, something getting into plasma and radiating
Jul 21 2006 11:13:43:400AM1060721006Chuck Kesselpulse much better, more stuff into plasma and strong radiation blips, plasma recovers, but drops out of H-mode, RF power good and 70 MHz fired
Jul 21 2006 11:25:56:920AM1060721007Chuck KesselRF power dropped to 1.8 MW, radiation bursts occur earlier in discharge, plasma in H-mode and struggling to stay in H-mode, Te contuning to recover thru shot, radiative collapse
Jul 21 2006 11:33:17:377AM1060721007Amanda HubbardThis shot did have an ITB after the injections. But, presumably because of them, Prad increased in core and caused an early end.
Jul 21 2006 11:46:45:380AM1060721007Chuck KesselIp = 600 kA, shorter pulse, RF power at 1.8 MW, another radiation collapse
Jul 21 2006 11:55:11:120AM1060721009Chuck Kessellonger 600 kA pulse, RF pulse good at 1.8 MW, but 70 MHz barely on before end of discharge, density profile peaking
Jul 21 2006 12:14:43:860PM1060721009Amanda Hubbard
This one definitely had an ITB, with max peaking at 1.0 secs. However, Te starts decreasing ~ 0.87 secs, getting to a few 100 eV by end of H-mode (~1.3 s). H-factor declines accordingly, from 1 to ~ 0.2!

Next shot, add some central heating earlier, 0.85 s in hoes of avoiding this.
Jul 21 2006 12:15:35:860PM1060721010Amanda HubbardAdding J-port earlier did help - Te collapse delayed to 1 second. Peaking transiently arrested, but still continues. Raise power on all RF next shot.
Jul 21 2006 12:42:37:653PM1060721012Chuck Kesselnice long pulse, density peaking stronger, RF pulse good except drop out of on axis power which causes drop out of H-mode
Jul 21 2006 12:45:33:310PM1060721012Amanda Hubbard
Cleat ITB. The increased central heating (0.7 MW) does work; Te0 increases and Prad, ne0 stop rising. But, following a J-port trip at 0.93, get strong cooling from which ITB doesn't recover even after J returns.
61 kJ, beta_p =0.6, H=1.1 (at 0.92 s).

Jul 21 2006 01:06:30:710PM1060721014Chuck Kesselgood long pulse, RF power perfect, ITB forming and RF clamping density rise maybe too hard or too early
Jul 21 2006 01:20:59:637PM1060721015Chuck Kesselmoved on axis RF from 0.85 to 0.95 s,dropped out of H-mode, density rose too fast before we could get on-axis power on
Jul 21 2006 01:28:34:687PM1060721016Chuck Kesselsimilar to 15, drop out in temperature before on-axis RF power
Jul 21 2006 01:28:47:187PM1060721016Amanda HubbardOn this shot the Te collapse came a little earlier (0.85 s), I think due to a small injection at 0.81 secs. nepeaking to 1.36, decays after J-port on.

Next shot, move J to 0.9 secs, and try to increase 80 MHz power
Jul 21 2006 02:46:25:637PM1060721017Amanda HubbardChange of run plan due to problem with J-port. We will have to use 80 MHz only for the remainder. Have decided to explore the impact of power variation on rate of rise/duration of ITBs, along with continuing to lower current.

Start with 2.2 MW. Without the central heating, get Te collapse at 0.85 secs. Amazingly, Te0 stays steady at 300 eV for the rest of the RF pulse (and what looks like multiple H-modes).
Jul 21 2006 03:14:04:257PM1060721017Chuck Kesselno on-axis power, so have strong density rise makeing plasma exit H-mode, RF power at 2.3 MW, Ip = 600 kA
Jul 21 2006 03:15:04:883PM1060721018Chuck Kesselsame as 17 but RF at 1.5 MW, slower density rise (more linear?)
Jul 21 2006 03:40:27:643PM1060721019Chuck KesselIp = 450 kA, P = 1.0 MW, not enough power to get in H-mode
Jul 21 2006 03:49:47:927PM1060721020Chuck KesselIp = 450 kA, P = 2.0 MW, density rise with RF power but no Thomson
Jul 21 2006 03:50:51:100PM1060721021Chuck Kesselsame as 20, got Thomson, get fast density rise and drop out of H-mode, transient ITB
Jul 21 2006 03:52:21:833PM1060721021Amanda Hubbard
This shot was a repeat. Got YAG and confirmed a clear, if brief, ITB. ne0 to 3e20 m-3 at 0.84 s, peaking factor to 1.6, foot around 79 cm.
Te collapse at 0.79 secs, ITB collapse at 0.84

Next shot, reduce RF power.
Jul 21 2006 04:09:14:717PM1060721021Amanda HubbardAt 1.5 MW, got a later H-mode (L-H 0.96 s).

Very brief but definite ITB at 1.1 secs - ne0 2.67e20, peaking factor 1.7.
But Te0 drops from 1.04 s, is 0.6 by 1.1 s. We really need the central heating!

Jul 21 2006 04:43:23:730PM1060721024Amanda HubbardHigher power, 2.8 MW. Again, clear ITB on ne.2e0 2.8e20 m-3.
Te0 drop is only slightly earlier, at 0.78 secs; ne is pretty peaked at this point, would be a good case to try central heating if we had it.

Physics Operator Comments
Jul 20 2006 11:16:59:553PMRobert GranetzUse segments 1,3, and 4 from yesterday's run, and load segment 2 from
1060707031 segment 2. (I confirmed that segment 2 was the one in use
back on that shot.)

Changed Ip to 0.8 MA.
Changed Bt to 4.5 T (125 kA)
Changed nl_04 to 0.9e20 m-2

Saved in /home/granetz/pcs_scratch as shot 1060721000.
Jul 21 2006 09:24:13:843AMRobert GranetzA small air leak opened up around 08:45 (N2, Ar), but it mysteriously went
away after a few minutes.
Jul 21 2006 09:42:00:910AM1060721001Robert GranetzJust noticed that A-coil current is programmed with a ramp, which is an unnecessary
holdover from the shot I copied from. I will set it at a constant 2 kA, starting with
the next shot.
Jul 21 2006 10:29:18:570AM1060721001Robert GranetzShot 01 -- Plasma. Good shot. 0.8 MA, 4.6 T, 1.0e20 m-2.

Next shot: tweak Bt down to 4.5 T (123 kA) and a slightly flattop earlier time.
Also take 1 ms off of pre-fill, and program A-coils with a flat 2 kA,
rather than the ramp that's there now.
Jul 21 2006 10:28:58:837AM1060721002Robert GranetzShot 02 -- Plasma. Good shot. 0.8 MA, 4.5 T. H-mode and pretty high density. Got a little
power from D and E, but lots of faulting.

Next shot: repeat with more RF.
Jul 21 2006 10:11:18:783AM1060721003Robert GranetzShot 03 -- Plasma. Good shot. Prf=2.0 MW, long pulse (D+E, 80 MHz). Long H-mode.

Next shot: no PCS changes. Get J-port on (70 MHz).
Jul 21 2006 10:41:40:183AM1060721004Robert GranetzShot 04 -- Plasma. Disrupted at t=0.85. It looks like there was an impurity injection
at t=0.81 s.

Next shot: repeat, no DPCS changes.
Jul 21 2006 10:52:59:353AM1060721005Robert GranetzShot 05 -- Plasma. Disrupted at t=0.97 s due to another injection at t=0.86 s. The
video cameras do not show anything obvious. Prf=2.25 MW from D and E.

Next shot: try again.
Jul 21 2006 11:04:04:543AM1060721006Robert GranetzShot 06 -- Plasma. Good shot, no disruption. There were still some injections around
t=0.8-0.9 s. Prf(D+E)=2.2 MW, P(70 Mhz)=0.5 MW at t=1.3 s.

Next shot: repeat, no DPCS changes.
Jul 21 2006 11:23:04:323AM1060721007Robert GranetzShot 08 -- Plasma. Good shot. ITB? Still got some injections. D+E=1.8 MW, J=0.5 MW.

Next shot: reduce Ip to 0.6 MA but with the same initial rampup.
Jul 21 2006 11:42:04:940AM1060721008Robert GranetzShot 08 -- Plasma. Disrupted at t=0.87 s. Ip=0.6 MA.

Next shot: move RXL in by 1 cm.
Jul 21 2006 12:02:22:247PM1060721010Robert GranetzShot 09 -- Plasma. Disrupted at t=1.38 s. RXL moved in 1.1-1.2 cm, as requested. Got an ITB.

Next shot: no DPCS changes.
Jul 21 2006 12:12:20:157PM1060721011Robert GranetzShot 10 -- Plasma. Disrupted at 1.38 s. J-port is now coming on at t=0.85 s.
Core peaking was not as good as the previous shot.

Next shot: load A-coil feedback into wire 9 (was just preprogrammed).
Jul 21 2006 12:21:20:190PM1060721011Robert GranetzShot 11 -- Plasma, but very short, ugly, and disruptive.
(Forgot to remove A-coil preprogramming, but it didn't get a chance
to turn on anyway.)

Next shot: Remove A-coil pre-programming; move integrator start time to 0.3 s (from 0.5)
Jul 21 2006 12:37:02:730PM1060721012Robert GranetzShot 12 -- Plasma. Good shot. Full length. Got 2.0 MW from D+E, 0.5 MW from J.
Got some good core peaking.

Next shot: repeat, no DPCS changes.
Jul 21 2006 12:47:04:780PM1060721013Robert GranetzShot 13 -- Plasma, but very short. Impurity injection at 0.27 s killed it.

Next shot: repeat, no DPCS changes
Jul 21 2006 01:04:19:270PM1060721014Robert GranetzShot 14 -- Plasma. Good shot, full length. 2.0 MW from D+E, 0.75 MW from J, both 70 and
80 MHz for long, fault-free pulse...beautiful. Almost no core peaking though.

Next shot: no DPCS changes.
Jul 21 2006 01:15:15:663PM1060721015Robert GranetzShot 15 -- Plasma. Disrupted at t=1.4 s. 2.0 MW (D+E), 0.6 MW (J). Core peaking
increases until J-port turns on.

Next shot: no DPCS changes.
Jul 21 2006 01:31:36:577PM1060721016Robert GranetzShot 16 -- Plasma. Good shot, full length.

Next shot: no DPCS changes. RF timing will be changed.
Jul 21 2006 02:34:22:600PM1060721016Robert GranetzTransmitter #3 had a problem after this shot which required extended power room
access. After considerable time, it was decided that the problem could not be
fixed in a reasonable time. Therefore the run will carry on without J-port (70 MHz).
Jul 21 2006 02:46:06:433PM1060721017Robert GranetzShot 17 -- Plasma. Good shot, full length. Lots of short H-modes. 2.2 MW from D+E. J-port
is no longer working today.

Next shot: no DPCS changes. Decrease 80 MHz RF power.
Jul 21 2006 03:18:17:650PM1060721019Robert GranetzShot 18 -- Plasma. Good shot, full length. 1.5 MW from D+E.

Next shot: reduce Ip to 0.45 MA and nl_04 to 0.65e20 m-2.
Jul 21 2006 03:19:41:430PM1060721019Robert GranetzShot 19 -- Plasma. Good shot, full length. 0.45 MA, 4.5 T. Prf=1.0 MW, which was not
enough to get an H-mode.

Next shot: repeat, no DPCS changes. Increase RF power.
Jul 21 2006 03:39:40:703PM1060721020Robert GranetzShot 20 -- Plasma. Good shot, full length. 0.45 MA. Not sure we even had an H-mode.
(Amanda thinks there was an H-mode.)

Next shot: Enable an Ar/Ne puff (B-side-lower) from t=1.300 to 1.350 s for A. Graf.
Also change RF timing.
Jul 21 2006 03:56:09:273PM1060721022Robert GranetzShot 21 -- Plasma. Good shot, full length. 0.45 MA. Prf=2.0 MW.

Next shot: no DPCS changes
Jul 21 2006 04:06:42:213PM1060721022Robert GranetzShot 22 -- Plasma. Good shot, full length.

Next shot: no DPCS changes.
Jul 21 2006 04:17:41:330PM1060721023Robert GranetzShot 23 -- Plasma. Good shot, full length. 0.45 MA. Prf=1.75 MW.

Next shot: no DPCS changes. More RF power.
Jul 21 2006 04:32:10:413PM1060721024Robert GranetzShot 24 -- Plasma. Good shot, full length. 0.45 MA. Prf=2.9 --> 1.6 MW

Next shot: reduce nl_04 to 0.5e20 m-2.
Jul 21 2006 04:45:58:543PM1060721025Robert GranetzShot 25 -- Plasma. Good shot, full length. Prf=2.8 MW.

Next shot: no DPCS changes.
Jul 21 2006 04:53:03:093PM1060721026Robert GranetzShot 26 -- Plasma, but very short. May have been an impurity injection, but not obvious.

Next shot: no changes. (last shot)
Jul 21 2006 05:02:58:800PM1060721027Robert GranetzShot 27 -- Plasma. Good shot, full length. RF power was linearly ramped to 2.6 MW.

End of run

Engineering Operator Comments
ShotTimeTypeStatusComment
109:24:46:500AMPlasmaOk
209:42:22:320AMPlasmaOk
310:03:35:263AMPlasmaOk
410:30:27:383AMPlasmaOk
510:43:49:153AMPlasmaOk
610:57:33:983AMPlasmaOk
711:12:36:087AMPlasmaOk
811:25:55:107AMPlasmaOk
911:43:40:677AMPlasmaOk
1011:58:47:527AMPlasmaOk
1112:11:57:110PMPlasmaOk
1212:24:37:943PMPlasmaOk
1312:38:19:057PMPlasmaOk
1412:52:13:470PMPlasmaOk
1501:05:17:800PMPlasmaOk
1601:17:54:480PMPlasmaOk
1702:36:53:883PMPlasmaOk
1803:00:30:347PMPlasmaOk
1903:14:08:023PMPlasmaOk
2003:26:37:043PMPlasmaOk
2103:40:41:440PMPlasmaOk
2203:54:46:930PMPlasmaOk
2304:08:32:200PMPlasmaOk
2404:21:04:627PMPlasmaOk
2504:34:00:117PMPlasmaOk
2604:46:36:683PMPlasmaOk
2704:59:31:813PMPlasmaOk