Miniproposals

Miniproposal: 444 Date Filed: 11/23/2005 Title: Alfvén cascade studies during current ramp-up with ICRF Heating First Author: Eric Edlund Session Leader: Eric Edlund (shots 1-12) Session Leader: Joseph Snipes (shots 13-18)

Engineering Operator Run Comment

MP444: Alfven cascade studies during current ramp with ICRF heating.

Session Leader Plans

Entered: May 24 2006 05:35:15:383PM

Author: Eric Edlund

SL: Eric Edlund PO: Ron Parker MP #444a Alfvén cascade studies during the current ramp-up with ICRF Heating The purpose of these experiments is to expand the database of Alfven cascades, specifically looking at the dependence of the initial frequency on temperature. Excitation of the cascade modes is induced by resonant interaction with the RF generated ion tail. Previous thresholds for activity were about 2.5 MW. It is expected that stong activity will be seen at 3 and 4 MW. A scan of RF power at 1 MW steps will be used to vary the bulk temperature. Furthermore, a change to off-axis heating at 5.9 T will be used to look for variations in cascade characteristics due to modification of the pressure profile. Concluding the plan is a change to lower density, 0.5 10^19 in nl_04 to look for density dependence. Setup: RF, all 4 transmitters run-on by 8:30 am diagnostics, PCI and magnetics are the principal diagnostics. ECE and Thomson are required for temperature and density profile measurements. The CNPA, Hirex, and neutrons are requested to help monitor ion temperatures. Run Plan: Use a target plasma similar to 1050429015. Begin at 5.4 T, Ip = 800 kA, nl_04 = 0.7 10^19 in flattop. RF on at 3MW total power beginning at 0.09 sec, full power by 0.10 sec. Establish Alfven cascade activity and then proceed with power scan from 2MW to 5MW (if possible) in 1MW steps. Shots will be repeated to improve the RF matching, if necessary. Change to off-axis heating at 5.9 T. Repeat the power scan. Perform a power scan in lower density, nl_04 = 0.5 10^19, at 5.4T.

Physics Operators Plans

Entered: May 24 2006 06:36:03:723PM

Author: Ron Parker

Physop plan and engineering setup for Thursday, May 25, 2006 MP444: Alfven cascade studies during current ramp with ICRF heating. SL: Eric Edlund PO: Ron Parker Overnight ECDC Engineering setup: ------------------- Power system setup as on 1060524014 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 15psi He3 as is. Hybrid disabled (PG2) fill B-main with 40 psi D2 Hybrid enabled (PG3) leave NINJA as is. Hybrid disabled. Enable the following gate valves and shutters, assuming no vacuum problems: ECE, VUV, Z-bolo shutters FMIT#1,2,3,4 in Run-on by 8:30AM; turn on earlier if requested by RF (ICRF (D,E and J ports) ready for first shot at 9:00 AM) Run Plan: --------------------- Start with 1060524014 with RF beginning at 0.09 sec. Full power by 0.10 sec. Tune discharge for rapid current rise and density ne_l(04) ~ 0.7e20 cm-2 Establish Alfven cascade and do power scan from 2 MW up in 1 MW steps. Change to off-axis heating at 5.9 T. Repeat power scan. Reduce density to ne_l(04) ~ 0.5e20 cm-2 at 5.4T, repeat power scan.

Session Leader Summaries

Entered: May 25 2006 05:16:33:360PM

Author: Joseph Snipes

The run got off to a slow start because of alternator problems. The RF behaved reasonably well, but as always, it is difficult to maintain good coupling during the current rise. So, there were a number of trips of the RF that made it difficult to get good cascades before the current profile evolved into positive shear. Still, we managed to get 14 plasmas, most of which had AE activity in the current rise. There were a number of shots with Alfven cascades including shots 4, 5, 7, 14, and 15. There may have been very weak cascades on the PCI for a couple of other shots. Still, with the goal of the MP to try to determine a scaling for the starting frequency of the Alfven cascades, it will be quite difficult because the cascades were not all that clear at the low frequency end. So, while there are a number of shots with cascade data, it is unlikely that the data will provide a clear scaling for the minimum frequency as desired by the MP. An interesting set of what look like tornado modes were seen on the magnetics and PCI from 0.175 to 0.188 s and from 520 to 600 kHz on shot 1060525015. It is possible that they appear just before the first very small sawtooth, but the ECE data is not clear that it is indeed a sawtooth at that time.

Physics Operator Summaries

Entered: May 25 2006 04:57:45:173PM

Author: Ron Parker

The run was delayed by 4 hours due to alternator problem in the drive motor circuitry. When underway at 1:00, the run was devoted to producing Alfven cascades by ramping the current rapidly and simultaneously coupling strong ICRF heating during the early current ramp phase. This combination resulted in disruptions at ~ 0.4 s for most of the shots. However, since the cascades terminated when sawteeth appeared, typically at 0.22 s, the early disruption did not interfere with the cascade studies. Up to 4 MW of ICRF was applied, both on and off axis, and cascade modes were produced on most shots. Scorecard: 16 plasma attempts, 2 fizzles, 2 full length plasmas and the rest early disruptions.

Session Leader Comments
May 25 2006 01:33:19:690PM	1060525003	Eric Edlund	1 MW RF from D&E, density range looks good try for 2MW
May 25 2006 01:47:57:343PM	1060525004	Eric Edlund	cascades detected near 0.175 seconds, initial frequency not measurable with PCI try for higher power
May 25 2006 02:06:11:237PM	1060525005	Eric Edlund	P_RF (tot) ~ 2-3 MW stronger cascade activity, still no initial frequencies visible try again with J ramp from 0.10 to 0.15 seconds
May 25 2006 02:19:30:953PM	1060525006	Eric Edlund	fizzle
May 25 2006 02:27:14:080PM	1060525007	Eric Edlund	P_RF(tot) ~ 3MW using J port power ramp from 0.10 to 0.15 seconds good cascade data, interesting mode (possibly n=2 or 3) mode coming in much later than usual, possibly q=1 mode???
May 25 2006 02:44:27:033PM	1060525008	Eric Edlund	P_RF(tot) ~ 3.6MW no cascade activity, puzzling
May 25 2006 02:55:52:580PM	1060525009	Eric Edlund	P_RF(tot) ~ 3+ MW again, no chirping modes, densities look similar to shot 7 with strong activity try for 4 MW
May 25 2006 03:25:25:343PM	1060525010	Eric Edlund	P_RF(tot) ~ 3MW one early up-chirping mode followed by a down-chirping mode no other significant cascade activity Sawtooth modes seen near 0.35 seconds
May 25 2006 03:26:21:970PM	1060525011	Eric Edlund	change to 5.9 T P_RF(tot) ~ 2.5MW no cascade activity, a few TAE's
May 25 2006 03:35:00:330PM	1060525012	Eric Edlund	P_RF(tot) ~ 3.0 MW no cascades, some TAE's small sawteeth
May 25 2006 03:56:25:733PM	1060525013	Joseph Snipes	Snipes taking over for Edlund as Session Leader. Shot 13 is OK, but no Alfven Cascades were observed. There were some TAEs between 0.11 and 0.16 s in the range from 350 to 500 kHz.
May 25 2006 04:07:42:047PM	1060525014	Joseph Snipes	Shot 14: Finally got the Alfven cascades back. It appears that slightly higher density is important to get the cascades. We also got 4 MW of RF.
May 25 2006 04:24:51:093PM	1060525015	Joseph Snipes	Shot 15: Got 4 MW again and Alfven cascades, though the RF trips at 0.15 s and so do the AEs. No AEs after about 0.2 s.
May 25 2006 04:35:06:860PM	1060525016	Joseph Snipes	Shot 16: Fizzle.
May 25 2006 04:53:08:580PM	1060525017	Joseph Snipes	Shot 17: RF tripped. Got about 2.5 MW early which eventually reached 4 MW after 0.22 s, but by then the AEs are gone. No cascades. Try raising the density early between 0.05 and 0.1 s as well as after 0.1 s in segment 2 for the next and last shot.
May 25 2006 05:13:33:877PM	1060525018	Joseph Snipes	Shot 18: Very similar modes to shot 17. No cascades. RF trips keep the power around 2.5 MW until after 0.22 s when it reaches 4 MW.

Physics Operator Comments
May 25 2006 08:42:27:847AM	1060525002	Ron Parker	There will be a delay this morning due to an alternator problem. Stay tuned for more details. Delay looks like at least an hour.
May 25 2006 09:07:17:753AM	1060525002	Ron Parker	Latest word is that the delay will be at least 2 hours.
May 25 2006 11:44:57:847AM	1060525002	Ron Parker	For those of you waiting, here is my uunderstanding: The alternator problem has to do with the switching out of an autotransformer in the drive motor excitation. This should happen at around 1200 RPM, but it chattered when this speed was passed earlier, causing a drop out. At the moment the alternator crew is awaitng some instrumentation to monitor the problem. They will then try to pass the transfer speed again. If successful, there will be a run; if not, it will likely be scrubbed. In any event, the earliest that we could have plasma shots would be 12:00.
May 25 2006 12:15:28:533PM	1060525002	Ron Parker	The alternator is coming up to speed, about 1030 RPM as this is written. It should be passing the critical speed soon and we'll know then if there will be a run. The earliest start time now looks to be about 1:00 or shortly thereafter.
May 25 2006 12:38:18:463PM	1060525002	Ron Parker	Good news. The alternator went through the critical speed with no problem (although we may see this problem again on another day!) and we'll have a run, although abbrieviated (we need a spell check for the logbook!). First shot should be at ~1:15.
May 25 2006 01:28:50:690PM	1060525003	Ron Parker	First shot (3) went off well. RF ~ 1 MW. Next: Increase RF to 2MW
May 25 2006 02:10:19:220PM	1060525004	Ron Parker	Shot 4 was OK, but disrupted at 0.6 s
May 25 2006 02:10:42:093PM	1060525005	Ron Parker	Shot 5 was OK, but disrupted at 0.4 s.
May 25 2006 02:11:01:767PM	1060525006	Ron Parker	Shot 6 fizzled.
May 25 2006 02:40:01:033PM	1060525007	Ron Parker	Shot started up OK, disrupted at 0.5 s.
May 25 2006 02:41:02:280PM	1060525008	Ron Parker	Shot disrupted at 0.27 s
May 25 2006 02:51:31:563PM	1060525009	Ron Parker	Shot 9 disrupted at 0.25 s
May 25 2006 03:09:58:610PM	1060525010	Ron Parker	Shot 10 disrupted at 0.42 s. Next: Increase field to 5.9 T
May 25 2006 03:35:15:797PM	1060525011	Ron Parker	Shot 11 disrupted at ~ 0.41 s
May 25 2006 03:38:50:860PM	1060525012	Ron Parker	Shot 12 disrupted at ~ 0.39 s.
May 25 2006 03:57:50:610PM	1060525013	Ron Parker	A full length shot.
May 25 2006 03:58:33:470PM	1060525014	Ron Parker	Back to disruptions at 0.44 s
May 25 2006 04:22:11:813PM	1060525015	Ron Parker	Shot 15 disrupted at 0.38 s
May 25 2006 04:31:30:377PM	1060525016	Ron Parker	Fizzle
May 25 2006 04:46:25:797PM	1060525017	Ron Parker	Shot disrupted at 0.37 s.
May 25 2006 05:00:02:140PM	1060525018	Ron Parker	Shot 18 was the last shot. It disrupted at ~0.4 s.

Engineering Operator Comments
Shot	Time	Type	Status	Comment
1	08:18:16:470AM	Test	Ok	ok
2	08:32:50:360AM	Test	Ok
3	01:18:52:610PM	Plasma	Ok
4	01:34:53:830PM	Plasma	Ok
5	01:51:14:360PM	Plasma	Ok
6	02:06:47:797PM	Plasma	Ok
7	02:19:21:297PM	Plasma	Ok
8	02:33:24:407PM	Plasma	Ok
9	02:46:00:110PM	Plasma	Ok
10	03:00:02:220PM	Plasma	Ok	PF breaker opened after disruption
11	03:17:28:127PM	Plasma	Ok	PF breaker opened after disruption
12	03:30:01:703PM	Plasma	Ok	PF breaker opened after diruption
13	03:42:43:127PM	Plasma	Ok
14	03:55:21:533PM	Plasma	Ok	PF breaker opened after disruption
15	04:17:03:017PM	Plasma	Ok
16	04:30:00:580PM	Plasma	Ok
17	04:42:25:313PM	Plasma	Ok
18	04:55:30:703PM	Plasma	Ok