Alcator C-Mod Run 1060726 Information

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Miniproposals
Miniproposal:428
Date Filed: 7/8/2005
Title:Separating ITB formation from the initial transient phase of EDA H-modes
First Author:David Mikkelsen
Session Leader:David Mikkelsen (shots 1-33)
Session Leader:Martin Greenwald (shots 21-33)

Operators
Session leader(s):David Mikkelsen,Martin Greenwald
Physics operator(s):Joseph Snipes
Engineering operator(s):Bill Byford,Bill Parkin

Engineering Operator Run Comment
MP 428 Separation of ITB from EDA SL: D. Mikkelsen/M. Greenwald PO: J. S

Session Leader Plans
Entered: Jul 25 2006 03:41:19:353PM
Author: David Mikkelsen
The goal of MP 428 is to delay the beginning of the ITB phase until after steady H-modes have been established, and look for small changes in the Te profile that are needed to form ITBs. The delay is accomplished by heating the central region for the first 150-250 msec of the RF heating pulse; central and off-axis heating are both used in this period. Removing central heating while continuing with off-axis heating is expected to slightly broaden the temperature profile shape, leading to less transport in the central region of the plasma.

We will begin with the 'large ELM' shape used in 1060719025, but use higher Btor=5.5 T so the FRC-ECE system can be used to monitor the Te profile. Target density at 0.5 sec should be NL04 = 0.8E20.

If the above scenario is unsatisfactory, the first alternate plasma conditions are those in 1021011004 (800 kA, 5.5 T, 70 MHz off-axis heating).

If the J power is insufficient for sustaining H-modes, we will have to use D&E for off-axis heating and switch to 4.5 T. On this branch we will repeat 1060719025 very closely, but will perhaps have higher target density since this MP does not particularly require low density.

1) get H-modes with combined 80 and 70 MHz ICRH starting at 0.5 sec and running until 1.0 sec at first. For ECE cross calibrations, a programmed Btor ramp down of 0.1 T (3 kA in TF current?) should occur between 1.2 and 1.4 sec, final ramp down begins at 1.5 sec. We will actually see a smaller change in Btor, but this gave what we needed last week.

2) Once the ECE calibration phase looks good (steady temperature profiles between 1.2 and 1.5 sec), shift the start of ICRH to 0.7 sec and stop at 1.4 sec (to compare with the ITB shots with long duration heating). Adjust the target density as needed, aiming for prompt H-modes. The J power needed later will be ~1 MW, so push for that; we'll need only 1-2 MW from D&E combined, so focus on steady power from those.

3) Once long H-mode phases have been established and we have a clean no-ITB shot with reasonably steady RF for 0.7 sec, try to make ITBs by ramping down the central RF (D&E if we are at 5.5 T) beginning about 50 msec after the time that the H-mode density rise has saturated; estimated to be about 150 - 200 msec after the RF start time. Ramp down central power over 50 msec to zero, but continue heating off-axis with J; look for rising central density. Adjust Btor to search for ITB location.

If ITBs do not materialize after varying Btor, shorten the initial central heating period to 150, 100, 75, 50 msec. ITBs have been produced with short initial periods of central heating (Fiore 200x).

4) Document ITB transitions; this requires steady RF through the transition. Adjust the duration of initial central heating phase (and possibly adjust the duration of the central ramp down) in order to average over a number of sawteeth. Search for a clear difference - before and after central ramp down - in the ratios of Te in neighboring FRC-ECE channels. The ratios should be steady before the central power starts to ramp down, and if the ratios are still rapidly changing when the density rise begins we will try a slower central ramp down.

5) Study fluctuations in the central density peak (attempt MP 403) with the 132 GHz reflectometer. If the density has been too high for this above, reduce the peripheral density below 2.E20 by lowering the target density and Ip as needed. Turn central heating back on after an ITB is well established to look for fluctuation changes in the central density peak. Monitor changes in Te ratios when central heating is turned back on. Use enough central power to arrest the central density growth, but don't kill off the ITB.

Physics Operators Plans
Entered: Jul 25 2006 11:55:55:980AM
Author: Joseph Snipes
Physop plan and engineering setup for Wednesday, 26-July-2006

MP 428 Separation of ITB from EDA
SL: D. Mikkelsen/M. Greenwald
PO: J. Snipes

Overnight boronization.
Boronization Recipe:

10% B2D6 / 90% He 6L bottle.
vessel temperature at 60/60/60.
120 psi to be deposited.
PEI setting to 44/70/80 (Rmin/Rres/Rmax) with no pulser.
20 s/60 s sweep time
Gas Pressures: TC3/TC6/TC9/TC6Request = [4 to 7]/150/95/150

Helium ECDC at 5e-5 Torr to be started after the boronization.
Run until 7am.
Multipactor conditioning is needed before the run for the ICRF.

Engineering setup:
-------------------
Power system setup as on 1060719025
Gas Setup:
fill B-Top with 6 psi D2 Hybrid enabled (PG4)
fill B-side lower with 1 psi Ar Hybrid DISABLED (PG1)
leave B-side upper as is DO NOT TOUCH
fill B-main (C-side) with 40 psi D2 Hybrid enabled (PG3)
NINJA not needed (Disable)

Enable the following gate valves and shutters: ECE, VUV, Z-bolo shutters.

RF setup:
FMIT#1,2, 3 and 4 in Run-on by 8:30AM

Diagnostic needs:
Need density and temperature profiles for transport analysis.

Run plan: Start with shot 1060719025 but at 5.5 T with target nebar ~ 0.5 x 10^20
and with steady PRF ~ 1 MW from J-port at 70 MHz and ~ 2 MW from D + E at 80 MHz.
Looking to produce H-modes with ITBs. Need steady RF initially for 0.5 s
duration starting at 0.7 s into the shot. Once steady H-modes are obtained,
the RF power will be extended to 0.7 s duration to attempt to extend the
ITBs. Looking for small changes in the Te profile so steady RF is
essential.

Session Leader Summaries
Entered: Jul 26 2006 06:09:23:010PM
Author: Martin Greenwald
MP 428 - Separate L-H transition from ITB formation

We achieved the basic goal of the MP. Running at 5.6 T, 0.9 MA and target nebar of 1.5e20, we created steady H-mode shots which transitioned from 100% on-axis (D+E at 80 MHz) to 100% off-axis (J at 70 MHz) heating at constant power (1-1.5 MW). The shots reached a quasi-steady state with the on-axis heating, before the frequency switchover began, about 5 tau_E times after the start of the RF. ITBs were clearly observed. ITB formation occurred at about the point where the RF power was 100% off-axis. Density peaking reached ne(0)/ne(a) = 2-3, with peak densities approaching 6e20.

Good Te profiles were obtained with the HECE system. A quick analysis showed that the gradients did relax as the power moved off-axis. Pulling numbers off some plots, and evaluating at the radii near the eventual ITB foot (R = 0.77 to 0.81 m) we find R/L_T ~ 7.8 with all on-axis heating (t = 0.85) dropping to R/L_T ~ 6.4 at t=1.0 sec, with only off-axis heating.

Shots of particular interest included:
10607026021   J-port only, good ITB
         22   D+E overlapped with J, good ITB
         25   constant power, good ITB
         26   constant power, good ITB
         27   constant power, good ITB
         31   constant power, good ITB

The last two are the best shots

Physics Operator Summaries
Entered: Jul 26 2006 05:04:00:000PM
Author: Joseph Snipes
The machine ran very well and there was only one delay early in the run to repair the TCI that cost us about
half an hour. There were only a few small changes to the startup and there were no fizzles or duds. There
were a number of disruptions due to impurity injections but most plasmas went well into the rampdown. Some
disrupted in rampdown due to Li pellets. A number of nice long EDA H-modes were obtained with ITBs with strong
density peaking. The session leader left for Princeton just before the best results but he should be able to
analyze the data and give a good report on the physics of the run as well. There were 33 shots and 33 plasmas
with nearly one minute of plasma overall today.

Setting date to that of current shot. Change if necessary.
Shot,Duration(s),Ipmax(MA),Result Shot,Duration(s),Ipmax,Result
| 01 1.958 0.747 Plasma | 02 1.955 0.759 Plasma |
| 03 1.961 0.760 Plasma | 04 1.957 0.734 Plasma |
| 05 1.960 0.921 Plasma | 06 1.627 0.942 Plasma |
| 07 1.630 0.951 Plasma | 08 1.966 0.928 Plasma |
| 09 1.964 0.928 Plasma | 10 1.959 0.928 Plasma |
| 11 0.990 0.954 Plasma | 12 1.013 0.943 Plasma |
| 13 0.699 0.981 Plasma | 14 1.966 0.927 Plasma |
| 15 1.958 0.924 Plasma | 16 1.951 0.920 Plasma |
| 17 1.949 0.920 Plasma | 18 1.950 0.916 Plasma |
| 19 1.638 0.915 Plasma | 20 1.959 0.916 Plasma |
| 21 2.010 0.917 Plasma | 22 2.010 0.918 Plasma |
| 23 2.010 0.919 Plasma | 24 2.010 0.918 Plasma |
| 25 2.010 0.918 Plasma | 26 2.010 0.917 Plasma |
| 27 1.797 0.920 Plasma | 28 1.769 0.919 Plasma |
| 29 1.863 0.920 Plasma | 30 1.771 0.920 Plasma |
| 31 1.770 0.920 Plasma | 32 0.840 0.921 Plasma |
| 33 2.010 0.918 Plasma
Date 1060726: 33 shots. 33 plasmas. 0 fizzles. 0 duds. 0 System Error.
(Plasma = Ip gt 50.0 kA Dud = H_alpha lt 0.40 V)
Total plasma duration: 58.89 s (exceeding -74 kA)

Session Leader Comments
Jul 26 2006 09:32:35:860AM1060726001David Mikkelsendensity profile has H-mode shape immediately with ICRH
ohmic H-mode after RF, too?
no Te pedestal, though
calibration Btor ramp started later than desired
fixed that in '003
Jul 26 2006 09:35:44:187AM1060726002David Mikkelsen quick H-mode density shape, but big early Prad burst causes H->L
ohmic H-mode after RF, too?
no Te pedestal again, though
calibration Btor ramp started later than desired
fixed that in '003
Jul 26 2006 09:47:16:097AM1060726003David Mikkelsendensity staying higher than 1060719; high post-boronization gas influx
quick H-mode density shape, Prad stays moderate this time
ohmic H-mode after RF, too?
no Te pedestal again, though

Jul 26 2006 10:17:10:360AM1060726004David Mikkelsendensity staying higher than 1060719; high post-boronization gas influx
TS not on for '004
quick H-mode density shape,
big Prad spike around 0.930; see H->L in NL04?
1070719004 has higher central density than today
Next: reduce Btor to 5.4, raise Ip to 900 kA to match last week
Jul 26 2006 11:06:50:550AM1060726006David Mikkelsensteady D&E RF power; also higher ne(0), but NL04 is quite high
target density staying higher than 1060719; high post-boronization gas influx?
Next: raise Btor to 5.5, keep Ip = 900 kA
Jul 26 2006 11:19:06:647AM1060726007David Mikkelsensteady D&E RF power; also higher ne(0), but NL04 is quite high
so density profile is rather flat
target density staying higher than 1060719; high post-boronization gas influx?
Prad large 0.75-0.90 sec
Next: later, longer RF; on from 0.7 to 1.4 sec
Jul 26 2006 11:38:00:937AM1060726008David Mikkelsentarget density is lower now
Next: reduce ELMs with lower triangularity and higher elongation
Jul 26 2006 11:57:20:833AM1060726010David Mikkelsentarget density is higher again; very flat density profiles
large Prad causes H->L at 0.85 and 1.00 ?
wait for steady J in this shape
Jul 26 2006 12:30:31:487PM1060726011David Mikkelsenlarge Prad causes H->L at 0.84 and disruption at 0.99
steady J for 0.5 sec
Jul 26 2006 12:31:25:927PM1060726011David Mikkelsenlarge Prad causes H->L at 0.81 and disruption at 1.0
steady J for 0.3 sec
Jul 26 2006 12:32:14:583PM1060726011David Mikkelsenlarge Prad causes disruption at 0.69

Jul 26 2006 12:41:38:273PM1060726013David Mikkelsenlarge Prad causes disruption at 0.69

Jul 26 2006 12:54:30:120PM1060726014David Mikkelsensteadily increasing Prad until H->L transitions
J is steady at 1 MW
Next: try for ITB next by cutting off D&E RF at 0.95 sec
Jul 26 2006 01:01:45:970PM1060726015David Mikkelsenincreasing Prad saturates at 1.5 MW - at 0.81 sec when J goes to zero
J faults early

Jul 26 2006 01:19:27:727PM1060726016David Mikkelsenincreasing Prad saturates below 4 MW - when D faults to zero
J is enough for H-mode after 1 sec !
Next: bring D&E down slowly to avoid H->L transition
Jul 26 2006 01:31:51:370PM1060726017David Mikkelsenincreasing Prad saturates below 8 MW then J faults to zero and recovers
J is again enough for H-mode after 1 sec
Next: no D&E at all
Jul 26 2006 01:41:59:890PM1060726018David Mikkelsenincreasing Prad saturates below 1.5 MW then J faults to zero and recovers
lower total RF power led to lower Prad
ne(0) rises steadily until first H->L transition
J is again enough to make H-mode
Again: no D&E at all; need steady J for longer
Jul 26 2006 02:02:35:477PM1060726019David MikkelsenPrad saturates below 1 MW then J faults to zero and recovers
lower total RF power led to lower Prad
ne(0) rises steadily until first H->L transition
J is again enough to make H-mode
Again: no D&E at all; need steady J for longer
Jul 26 2006 02:26:23:267PM1060726021Martin GreenwaldGood shot
just steady off-axis power ~ 1
clear peaking late, rising stored energy
Jul 26 2006 02:41:23:850PM1060726022Martin GreenwaldAdded on-axis power to previous shot
1 MW of D+E for 0.15 sec, then ramp down over the next 0.15 sec
no sign of ITB until after D and E are off
moderate peaking afterwards, becoming very strong by end of shot

Jul 26 2006 03:04:07:453PM1060726024Martin GreenwaldRamp up J-port late, so that total power remains constant over pulse
We lost the h-mode before D+E went to 0
Jul 26 2006 03:25:55:697PM1060726025Martin GreenwaldGood shot
as previous shot, constant total power with 80 MHz trading off with 70
steady h-mode
peaking late
Jul 26 2006 03:27:47:447PM1060726026Martin GreenwaldGood shot, ITB forms after central power off
flattop extended to 1.6 seconds
peaking remains
power constant at 1.2 MW

Jul 26 2006 03:43:57:577PM1060726027Martin GreenwaldPushed up power to 1.5 MW
still constant power
ITB forms at about 1 second
Jul 26 2006 03:52:11:627PM1060726028Martin GreenwaldUsed a faster ramp on the 80-70 MHz switchover
lost the h-mode shortly afterwards

Jul 26 2006 04:06:42:273PM1060726029Martin GreenwaldSimilar to last shot, lost h-mode early
Jul 26 2006 04:18:23:683PM1060726030Martin GreenwaldLost the H-mode early again
Jul 26 2006 04:42:43:850PM1060726031Martin GreenwaldWent back to slow ramp
shot similar to 27
Good ITB, steady power
Jul 26 2006 04:43:13:833PM1060726032Martin Greenwalddisrupts early

Jul 26 2006 04:58:08:170PM1060726033Martin GreenwaldH-mode ends early

Physics Operator Comments
Jul 26 2006 09:26:20:373AM1060726001Joseph SnipesShot 1: Loaded shot 1060719025. Then loaded segment 2 from 1021011004 into segment 3. However, the predictors
using FLUXIHH could not be recalculated because they refer to an equilibrium from shot 930817004 which is
missing because of problems with the RAID disk. So, we are at present unable to recalculate predictors from
any old shot until 930817004 can be recalled from tape.
Jul 26 2006 09:26:33:687AM1060726001Joseph SnipesShot 1: Loaded shot 1060719025. Changed TF current to 153 kA until 1.2 s then a slow ramp to 150 kA at 1.4 s
then constant until 1.5 s to begin rampdown. Runaways in the startup but otherwise a decent shot.
Jul 26 2006 09:26:40:547AM1060726002Joseph SnipesShot 2: Increased prepuff by 2 ms to 22 ms duration and reduced |EF4 current| by 15 A to -1330 A. Good shot.
Jul 26 2006 09:53:36:193AM1060726004Joseph SnipesShot 4: Repeat. Good shot. Finally got some 300 kW each out of J3 and J4.
Jul 26 2006 10:33:53:177AM1060726005Joseph SnipesShot 5: Cell access before shot 5 to repair the TCI, change the fibers for the active MHD, setup the
reflectomter, etc. TF current dropped by 3 kA to 150 kA with a ramp to 147 kA at the end. Ip raised to
0.9 MA. Li pellet at 1.6 s. Enabled Ar gas puff from 0.35 s for 40 ms duration. Good shot.
Jul 26 2006 10:52:14:170AM1060726006Joseph SnipesShot 6: Enabled DNB gate valve. RF needed to tune up to the new plasma current value. Got Li pellet
at 1.6 s and the plasma disrupted at 1.62 s. Good shot with nearly 3 MW of ICRF, though J-port does not
stay on.
Jul 26 2006 11:07:22:627AM1060726007Joseph SnipesShot 7: Increased TF current by 3 kA to 153 kA with a slow ramp at the end to 150 kA. Reduced nl04 to
5.0 x 10^19 m^-2 from 5.5. Good shot. J-port is still not very constant.
Jul 26 2006 11:19:18:837AM1060726008Joseph SnipesShot 8: Shifted ICRF timing by 0.2 s to start at 0.7 s and end at 1.4 s. Alex report 140 km/s rotation as
high as ever seen! Good shot.
Jul 26 2006 11:43:56:720AM1060726009Joseph SnipesShot 9: NINJA D2 puff for gas puff imaging diagnostic starting at 0.8 Changed RCUR, ZCUR, CLEARIN, RXL, ZXL,
RXU, and ZXU to a standard shape by copying waveforms from shot 1060720010. Good shot with standard shape.
Jul 26 2006 11:59:33:257AM1060726010Joseph SnipesShot 10: Repeat. Good shot but J-port tripped. A large injection at 0.83 s.
Jul 26 2006 12:11:08:213PM1060726011Joseph SnipesShot 11: Repeat. Disrupted at 0.986 s. Large injections again.
Jul 26 2006 12:15:21:780PM1060726012Joseph SnipesShot 12: Dropped ZXL by 1.3 cm to -2.3 cm and moved RXL in by 5 mm to 0. Increased nl04 to 6 x 10^19 m^-2.
Disrupted again at 1 s.
Jul 26 2006 12:27:59:877PM1060726013Joseph SnipesShot 13: Reloaded shot 11 and increased nl04 to 9 x 10^19 m-2. Disrupted at 0.695 s.
Jul 26 2006 01:10:15:440PM1060726015Joseph SnipesShot 14: Increased nl04 to 1 x 10^20 m^-2. Try again. Good shot.
Jul 26 2006 01:10:24:003PM1060726015Joseph SnipesShot 15: Repeat. Good shot but J-port did not stay on.
Jul 26 2006 01:11:47:783PM1060726016Joseph SnipesShot 16: Repeat. Good shot but did not stay in H-mode after D-port switched off.
Jul 26 2006 01:32:30:620PM1060726017Joseph SnipesShot 17: Repeat. Good shot but there were several impurity injections from 0.88 to 0.92 s.
Jul 26 2006 01:38:48:373PM1060726018Joseph SnipesShot 18: Repeat. Good shot with J-port only but J-port trips a few times so the plasma does not stay in
H-mode.
Jul 26 2006 01:59:41:913PM1060726019Joseph SnipesShot 19: Repeat. Great shot! Long steady EDA H-mode but still no clear ITB.
Jul 26 2006 02:08:06:323PM1060726020Joseph SnipesShot 20: Increase TF current to 155.5 kA to get 5.6 T looking for the ITB. Removed slow ramp in TF current
so that it remains constant at 155.5 kA to 1.5 s. Good shot but there was an impurity injection at 0.8 s.
Still no ITB.
Jul 26 2006 02:22:30:267PM1060726021Joseph SnipesShot 21: Mikkelsen went home. Try again. Good shot with a long EDA but not very strong density peaking.
Jul 26 2006 02:41:36:523PM1060726022Joseph SnipesShot 22: Try again with D&E&J together to begin with. Good shot. Got density peaking late in the H-mode.
Jul 26 2006 02:49:15:087PM1060726023Joseph SnipesShot 23: Repeat. Good shot. Impurity injection at 1.26 s knocked it out of H-mode.
Jul 26 2006 02:58:46:107PM1060726024Joseph SnipesShot 24: Repeat. Decent shot with several H-modes. Breakdown is a bit shaky.
Jul 26 2006 03:19:38:647PM1060726025Joseph SnipesShot 25: Increased prepuff by 2 ms to 24 ms duration. Decreased Br0 by 0.4 mT to -1.4 mT. Good shot with
a long EDA H-mode with and ITB. There is an impurity injection at 1.34 s followed by strong peaking.
Jul 26 2006 03:29:44:447PM1060726026Joseph SnipesShot 26: Extended the flattop out to 1.6 s on Ip, Bt, and all shape parameters as well as the density. Good
shot. Nice long EDA H-mode with an ITB out to the end of the flattop.
Jul 26 2006 03:39:01:373PM1060726027Joseph SnipesShot 27: Repeat. Good shot. Disrupted in rampdown at 1.79 s after a Li pellet at 1.71 s. Got a nice long EDA
H-mode with an ITB peaking the density up.
Jul 26 2006 03:52:03:470PM1060726028Joseph SnipesShot 28: Repeat. Decent shot but now there are several H-modes. Disrupted at 1.76 s after a Li pellet at
1.71 s. There is an m=1 snake between 1.74 and 1.76 s visible on the TCI and on the magnetics and core ECE.
Jul 26 2006 04:12:18:743PM1060726029Joseph SnipesShot 29: Repeat. Good shot. Two H-modes. The last one peaks up.
Jul 26 2006 04:17:44:247PM1060726030Joseph SnipesShot 30: Repeat. Good shot with several H-modes. Not so strong density peaking.
Jul 26 2006 04:33:49:533PM1060726031Joseph SnipesShot 31: Repeat. Good shot with a nice long EDA with an ITB with strong density peaking.
Jul 26 2006 04:43:57:943PM1060726032Joseph SnipesShot 32: Repeat. Disrupted at 0.83 s following impurity injections.
Jul 26 2006 04:57:44:073PM1060726033Joseph SnipesShot 33: Reduced Br0 by 0.3 mT to -1.7 mT. Good shot. Several H-modes with impurity injections.

Engineering Operator Comments
ShotTimeTypeStatusComment
109:07:05:910AMPlasmaOk
209:20:56:960AMPlasmaOk
309:34:14:640AMPlasmaOk
409:47:59:783AMPlasmaOk
510:32:20:020AMPlasmaOk
610:46:59:447AMPlasmaOk
711:01:48:877AMPlasmaOk
811:15:11:473AMPlasmaOk
911:34:43:997AMPlasmaOk
1011:47:12:923AMPlasmaOk
1111:59:44:773AMPlasmaOk
1212:12:12:357PMPlasmaOk
1312:24:48:720PMPlasmaOk
1412:41:16:977PMPlasmaOk
1512:53:51:560PMPlasmaOk
1601:06:31:627PMPlasmaOk
1701:19:36:960PMPlasmaOk
1801:32:17:670PMPlasmaOk
1901:46:12:313PMPlasmaOk
2002:00:29:820PMPlasmaOk
2102:15:12:527PMPlasmaOk
2202:28:41:157PMPlasmaOk
2302:42:39:867PMPlasmaOk
2402:55:16:107PMPlasmaOk
2503:08:03:610PMPlasmaOk
2603:20:44:320PMPlasmaOk
2703:34:18:997PMPlasmaOk
2803:46:49:767PMPlasmaOk
2904:01:13:727PMPlasmaOk
3004:15:25:213PMPlasmaOk
3104:28:07:940PMPlasmaOk
3204:40:42:490PMPlasmaOk
3304:53:31:463PMPlasmaOk