Miniproposals

Miniproposal: 049 Date Filed: 4/8/1994 Title: 2D Neutral Density Profile Measurements by Charge Exchange Recombination First Author: John Rice Session Leader: Francesca Bombarda (shots 1-24)

Engineering Operator Run Comment

049- 2-D Neutral Profile

Session Leader Plans

Physics Operators Plans

Session Leader Summaries

Entered: Jul 7 2004 03:49:11:180PM

Author: To Be Determined

The purpose of run 940614 was to try to measure 2D neutral density profiles by observations of argon and carbon lines populated by charge exchange recombination with intrinsic neutral deuterium. The key to the argon observations is the presence of hydrogen-like argon in a region with high neutral density. This requires fast transport from the core with a central electron temperature near 1800 eV. Since we were restricted to 5 T operation, this required running at low density, which is hard to control reproducibly. The first 11 shots of the run were devoted to limited discharges. By shot 007 a suitable set of conditions was reached and 5 similar shots were obtained. There was a slight indication of charge exchange at -18 cm and very little at +17 cm for shots 007 through 011. Beginning with shot 012, divertor operation was attempted. These plasmas were very difficult to control, from the point of view of constant density at nel = 5 x 10^19. By shot 018 an acceptable discharge was achieved, although the density was a bit high, and it terminated in disruption. Shots 018-024 were similar in this regard, but the argon level through most of the shots was very low. However, at around 700 ms, when the plasmas were diverted, the argon seemed to rise rapidly, along with the electron density, ending in disruption. In these diverted shots there was clear evidence of charge exchange in the bottom of the torus (-19.5 cm) which was not evident at the top (+17 cm). The number of shots was reduced by very slow cooling of the TF during the first half of the run. More reliable divertor operation would be desirable, including improved understanding of why the first 2 argon puffs were not penetrating, and why the third (smaller) puff at 700 ms seemed to be too large.

Physics Operator Summaries

Entered: Jul 7 2004 04:36:51:897PM

Author: To Be Determined

From: PHYSOP::SNIPES Date: 14-JUN-1994 18:57:07 Description: Physics Operator's Run Summary 940614 Overall, it was a reasonably good run. We started with Fairfax's Fiducial (FF) copy of shot 940603015. It fizzled. Then, we copied shot 940603019 and it went very well. I recommend that Fairfax change his fiducial to that shot. Then, we had 9 more very similar plasmas, changing only the D and Ar programming slightly. For shot 12, we copied shot 940610023 to try the same experiment in diverted discharges, but with the D and Ar programming from shot 940614011. It went o.k., but disrupted in the ramp down. We then extended the density for the longer discharges. The plasmas continued to disrupt during the flattop around 0.7 to 0.8 sec. Then, shot 16 fizzled. We then tried changing the EF4 current at breakdown both +/- 15 A (1 mT) with success both ways. So, it was not that sentitive to the EF4 level. Changes were also tried in the RXL gain and timing and in the gas. Disruptions continued. Finally, we turned down the Ar levels gradually and the plasmas began to last longer. The last discharge lasted until 1.1 sec, just after a Moly laser blowoff at 1 sec. Locked modes were observed preceding many of the high density disruptions, leading me to believe they were radiation dominated. Thus, it seems that the levels of Ar in the diverted discharges were too high for these plasmas to handle. The Ar was found to penetrate better to the plasma core in the limiter discharges, while even though the Ar levels were larger in the diverted discharges, the HIREX signals were not very large, indicating good screening of the Ar by the divertor. Scorecard: 2 fizzles "Fairfax' fiducial" shot 1 and shot 16 22 plasmas All systems performed well, though cooling was sometimes slow.

Session Leader Comments
Jun 14 1994 10:54:42:780AM	940614002	Francesca Bombarda	Nice shot, HIREX settings are: #1 -18, #2 -3.5, #3 -2., #4 2, #5 16.5 that is 1 and 5 are looking up and down at 82 cm, 2,3,4 are at the center. Nice signal on the central channels, no lines visible at the edge
Jun 14 1994 10:56:32:170AM	940614003	Francesca Bombarda	Again nice shot, but density still a bit high (~5e19)
Jun 14 1994 10:57:59:470AM	940614004	Francesca Bombarda	Flooded by hard X. Density obviously too low.
Jun 14 1994 10:58:46:440AM	940614005	Francesca Bombarda	SAme as 4
Jun 14 1994 11:00:50:220AM	940614006	Francesca Bombarda	Good shot, now density high again. Increase amount of argon
Jun 14 1994 11:07:21:640AM	940614007	Francesca Bombarda	Good shot, something is finally visible on 1 and 5, and the signals look symmetric! Start moving 4 outward, repeat for a couple of shots to get enough statistics.
Jun 14 1994 11:36:43:770AM	940614007	Francesca Bombarda	Finally some signal on 1 and 5.
Jun 14 1994 11:35:27:060AM	940614008	Francesca Bombarda	Similar to 7. #4 out to 7 cm
Jun 14 1994 01:09:48:600PM	940614008	Francesca Bombarda	Same
Jun 14 1994 01:11:15:040PM	940614009	Francesca Bombarda	Same
Jun 14 1994 01:13:47:880PM	940614010	Francesca Bombarda	Same
Jun 14 1994 01:14:24:770PM	940614011	Francesca Bombarda	Same
Jun 14 1994 01:33:55:480PM	940614012	Francesca Bombarda	First diverted plasma (late). Very long pulse. #1 and #5 not quite at the same radial position.
Jun 14 1994 01:36:49:460PM	940614013	Francesca Bombarda	Disrupt at 0.95. Low density. Less argon gets into the discharge.
Jun 14 1994 02:03:41:800PM	940614014	Francesca Bombarda	Disrupt at 0.8.
Jun 14 1994 02:05:01:730PM	940614015	Francesca Bombarda	Disrupt at 0.75, too much density.
Jun 14 1994 02:29:22:040PM	940614016	Francesca Bombarda	Fizzle
Jun 14 1994 02:44:47:510PM	940614017	Francesca Bombarda	Disrupt at 0.65.
Jun 14 1994 03:25:21:390PM	940614018	Francesca Bombarda	Disrupt at 0.75, but much better
Jun 14 1994 03:59:18:240PM	940614019	Francesca Bombarda	Disrupt again at 0.75.
Jun 14 1994 04:01:03:280PM	940614020	Francesca Bombarda	Disrupt again at 0.75.
Jun 14 1994 04:27:04:070PM	940614021	Francesca Bombarda	Same
Jun 14 1994 04:33:17:970PM	940614022	Francesca Bombarda	Same
Jun 14 1994 04:54:50:380PM	940614023	Francesca Bombarda	Disrupt at 0.85
Jun 14 1994 05:06:50:210PM	940614024	Francesca Bombarda	Disrupt at 1.1! Suppose we can call this a good shot!

Physics Operator Comments
Jun 14 1994 09:10:36:170AM	940614001	Joseph Snipes	Shot 1 Copied shot 940603015 as a fiducial. Fizzle!
Jun 14 1994 09:18:43:270AM	940614002	Joseph Snipes	Shot 2 Copied shot 940603019 for neutral density run. Decent shot.
Jun 14 1994 09:58:51:870AM	940614003	Joseph Snipes	Shot 3 Added third Ar puff for HIREX at 0.676 sec. for about 12 msec at 90 V. Good shot
Jun 14 1994 09:59:45:710AM	940614004	Joseph Snipes	Shot 4 Some hard x rays. Density during current rise dropping on its own as the machine cleans up.
Jun 14 1994 10:21:46:250AM	940614005	Joseph Snipes	Shot 5 Increased gas early to try to bring up the density. Also added a gas puff at 0.8 sec for Luke of 10 msec duration.
Jun 14 1994 10:42:52:020AM	940614006	Joseph Snipes	Shot 6 Increased gas early to try to bring up the density. Better shot. Very few hard x rays though density is a bit high.
Jun 14 1994 11:08:41:240AM	940614006	Joseph Snipes	Shot 7 Good shot. Early current rise problems around 58 ms as the position jumps apparently inward. May need to decrease EF4 to reduce the vertical field early.
Jun 14 1994 11:09:01:220AM	940614007	Joseph Snipes	Shot 7 Good shot. Early current rise problems around 58 ms as the position jumps apparently inward. May need to decrease EF4 to reduce the vertical field early.
Jun 14 1994 11:39:18:580AM	940614008	Joseph Snipes	Shot 8 Tweaked second D gas puff time point slightly higher to try to improve the current rise in the hope of preventing the hesitation in the current. Decent shot. Current rise improved around 60 msec, but there is still a glitch at 22 msec. Horne noticed that the EF2's actually start to ramp down before t=0 (starting around -5 ms) and he thinks that might be responsible for changes observed at breakdown.
Jun 14 1994 12:20:08:110PM	940614009	Joseph Snipes	Shot 9 Same. Good shot!
Jun 14 1994 12:20:52:760PM	940614010	Joseph Snipes	Shot 10 Same. Decent shot!
Jun 14 1994 12:44:04:200PM	940614011	Joseph Snipes	Shot 11 Same. Decent shot!
Jun 14 1994 01:00:17:510PM	940614011	Joseph Snipes	Shot 11 Moly laser blow-off injection at 0.9 sec.
Jun 14 1994 01:19:40:450PM	940614012	Joseph Snipes	Shot 12 Copied shot 940610023 to run in a diverted configuration. Not bad. Disrupted in ramp down.
Jun 14 1994 01:26:10:640PM	940614013	Joseph Snipes	Shot 13 Increased gas late for the longer plasmas. Added more Ar puffs and increased the duration of each puff by a couple of msec. Also increased fizzle detector time to 1.45 sec. Disrupted at 0.95 sec.
Jun 14 1994 01:39:16:560PM	940614013	Joseph Snipes	Shot 13 Moly laser blow-off at 0.9 sec probably led to the disruption.
Jun 14 1994 01:45:31:750PM	940614014	Joseph Snipes	Shot 14 Increased gas during flattop to flatten out the density. Also increased the duration of the Ar puffs by a couple of msec. Decreased pre-fill to 1.1 x 10**-5 Torr. O.K. but disrupted again at 0.82 sec.
Jun 14 1994 02:00:29:700PM	940614015	Joseph Snipes	Shot 15 Increased gas during flattop to flatten out the density. Also increased the duration of the Ar puffs by a couple of msec. Disrupted at 0.75 sec.
Jun 14 1994 02:09:44:570PM	940614015	Joseph Snipes	Shot 15 Increased gas during flattop to flatten out the density. Also increased the duration of the Ar puffs by a couple of msec. Disrupted at 0.75 sec. Locked mode at 0.738 sec.
Jun 14 1994 02:18:25:640PM	940614016	Joseph Snipes	Shot 16 Increased gas early and decreased it a little during the flattop to try to avoid a density limit disruption and avoid hard x rays early. Fizzle!
Jun 14 1994 02:49:18:220PM	940614017	Joseph Snipes	Shot 17 Increased EF4 current at breakdown by 15 A from 1030 to 1045 A to try to push the plasma in a little. It seemed to go out at about 20 msec on both the H alpha and ECE polychromator data. No, I got the sign wrong. Nonetheless, the plasma went. Disrupted at 0.65 s.
Jun 14 1994 03:27:46:080PM	940614018	Joseph Snipes	Shot 18 Decreased EF4 current at breakdown by 30 A from 1045 to 1015 A to try to push the plasma in a little. Reduced proportional gain after 0.6 sec by about 20% on RXL. Then, moved the staircase earlier by about 50 msec so that the maximum gain is reached at 0.6 sec. Also, changed ZCUR to be flat at -1 cm from 0.6 sec to 1.2 sec. Disrupted at 0.76 sec. Locked mode at 0.742 sec.
Jun 14 1994 03:41:48:200PM	940614019	Joseph Snipes	Shot 19 Again density ramping up until a locked mode and disruption. It seems that there may be too much Argon.
Jun 14 1994 04:00:18:630PM	940614020	Joseph Snipes	Shot 20 Disrupted again at 0.75 sec. No locked mode. No density ramp. Ar does not seem to be responsible.
Jun 14 1994 04:05:21:300PM	940614021	Joseph Snipes	Shot 21 Return to D gas programming from shot 19. Increased RXL gain back to 5 after 0.6 sec. Disrupted at 0.8 sec. with a locked mode at 0.78 sec.
Jun 14 1994 04:24:48:890PM	940614022	Joseph Snipes	Shot 22 Reduced D gas a bit after 0.6 sec. Disrupted again with a locked mode.
Jun 14 1994 04:44:06:630PM	940614023	Joseph Snipes	Shot 23 D pellet at 0.3 sec. Reduced later Ar puffs by a few msec. Locked mode at 0.82 sec, disrupted at 0.87 sec. Pellet did not make it as the gate valve did not open.
Jun 14 1994 05:23:28:900PM	940614024	Joseph Snipes	Shot 24 Reduced the Ar puffs slightly after 0.4 sec. Plasma lasted longer until about 1.1 sec. Either late Ar puff or Moly injection at 1.0 sec may have led to the disruption. Locked mode at 1.04 sec.

Engineering Operator Comments
Shot	Time	Type	Status	Comment
1	08:54:20:110AM	Plasma	Ok	No faults.
2	09:10:28:850AM	Plasma	Ok	No Faults
3	09:24:41:970AM	Plasma	Ok	No faults.
4	09:46:56:260AM	Plasma	Ok	no faults
5	10:11:25:040AM	Plasma	Ok	No faults.
6	10:31:22:130AM	Plasma	Ok	No faults
7	10:58:43:150AM	Plasma	Ok	No faults.
8	11:23:18:510AM	Plasma	Ok	No Faults.
9	11:53:23:640AM	Plasma	Ok	no faults
10	12:18:18:260PM	Plasma	Ok	no faults
11	12:39:59:010PM	Plasma	Ok	no faults
12	01:02:58:620PM	Plasma	Ok	no faults
13	01:23:10:200PM	Plasma	Ok	600 kA disruption
14	01:43:35:220PM	Plasma	Ok	Another 600 kA disruption; induced EF1L commutation fault
15	01:58:27:660PM	Plasma	Ok	Another 600 kA hit
16	02:13:27:860PM	Plasma	Ok	Fizzle!
17	02:29:03:330PM	Plasma	Ok	another 600 ka hit; TF supply crowbar after plasma ended.
18	03:04:19:890PM	Plasma	Ok	600 kA disruption induced EF1L commutation failure
19	03:28:19:290PM	Plasma	Ok	another 600 kA disruption; EF1L commutation failure
20	03:45:22:320PM	Plasma	Ok	disruption induced comm fails
21	04:02:26:280PM	Plasma	Ok	600 kA disruption; no faults
22	04:21:29:570PM	Plasma	Ok	another 600 kA hit; 3 power supplies knocked off-line
23	04:39:37:010PM	Plasma	Ok	yet another 600 kA disruption; fizzle detector has not been working sinc
24	05:02:19:700PM	Plasma	Ok	longer but still a 600 kA disruption