| Miniproposals | ||||||||||
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| Operators | |
| Session leader(s): | John Goetz |
| Physics operator(s): | Steve Wolfe |
| Engineering operator(s): | Joe Daigle,Frank Silva |
| Engineering Operator Run Comment |
| mp163/goetz/wolfe/silva/daigle |
| Session Leader Plans |
| Physics Operators Plans |
| Session Leader Summaries |
| Physics Operator Summaries |
| Entered: Jul 7 2004 04:36:56:770PM |
| Author: To Be Determined |
| Physics Operator Report for 960906 SL: Goetz PO: Wolfe EO: Silva MP #163 High q_parallel Dissipative Divertor This proposal is an attempt to simultaneously achieve a good confinement H-mode with low Zeff and a detached divertor. The goal is to determine the threshold amount of impurity gas necessary to detach the divertor. Also, operation just above and just below the detachment threshold will be investigated. The plan was to start with a shot with seg 1 from a good recent shot and seg2 from 960227019 (1MA, 5.3T). Try to get acceptable H-mode (preferably enhanced D-alpha). Then begin puffing N2 into the h-mode phase to try to detach. Start with 100msec puff from B-side lower, beginning 100msec after the RF. If successful in detaching with high q||, then try setting up feedback on the b-side lower valve using the divertor bolo signals. As a contingency, if the h-modes don't work out, get probe data for Brian. Before any of this could be considered, however, we needed to convince ourselves that the OH2U coax situation was safe to run, after yesterday's events. Briefly, yesterday we terminated the run because on shot 3 the OH2U coax resistance was reported by Irby's automatic routine to have exceeded the mandatory stoppage level of 3uohm, and on subsequent testing it rose to 3.9 then 4.4 and ultimately 6uohm. This resistance was confirmed by putting 100A DC through the coil and measuring the voltage with a microvoltmeter. We then warmed the oh coils by passing current (1kA) from the PEI through them, and observed a steady decrease in the resistance from 3uohm (to which it had changed while we spent an hour or so deciding what to do) to 0.6uohm with the OH1 coax thermocouple reading -10C. The warmup was terminated at 6PM, and the cryo system was left on the vaporizer overnight. When Frank came in this morning, the coax had cooled down to -30C and the resistance was reading 0.8uohm. Cooling down to LN2 temperature resulted in a further reduction in the resistance to 0.4uohm, which is near the lowest values seen for this joint. Encouraged but puzzled by this behavior we began tests to determine if the high resistance problem had somehow fixed itself. This is not entirely wishful thinking, as we had a similar occurrence on 951102 and 951103, when the resistance of the oh2u coax had gone above 2uohm, come down a little during the runs but remained above 1uohm, but then, after a week of downtime during APS, had returned to its earlier levels and not bothered us again for most of the last campaign. Shots 960906001 and 2 were oh only tests at 5 and 10kA, and showed constant resistance at 0.4uohm. Shot 3 was a 5kA test with 5.4T TF pulse. This shot seemed to show a ramping resistance from 0.14 to 0.44uohm, but this was shown on shot 4, a tf-only pulse, to be due to a change in the pickup of dItf/dt pickup. This pickup appeared to be of the same magnitude but opposite sign from the value built into Irby's scope. Applying a reversed sign coefficient, shot 3 was found to have essentially constant resistance at 0.4uohm. Everything looked good until shot 5, which was a 10ka ohtest with 5.4T TF. The resistance on this pulse ramped up during the pulse from 0.4 to 1.1uohm, with an increasing slope until TF flattop. This result caused us to terminate the testing and cancel the plasma run until we can assess the situation better. The rationale for not continuing testing is based on uncertainty whether, in view of the large excursion observed on shot 9 yesterday, and on shot 5 today, a single test pulse could result in an increase that would result in damage to the coax joint. Most of the remainder of the day was spent considering possible explanations for the observed behavior and reviewing prior experience and old test data on the feltmetal joint properties. We were unable to convince ourselves that further testing could be done without undue risk, although this decision is not necessarily final. In view of the possibility that an in situ inspection might be required, several TF only pulses, without TF cooling, were taken to prepare the machine in case we decide to do a partial disassembly. Such an inspection had already been proposed by Gwinn to take place before the spring 97 campaign. |
| Session Leader Comments |
| Physics Operator Comments | |||
| Sep 6 1996 07:31:52:910AM | Steve Wolfe | Setting up for run of 960906 (I hope)
OH2U Coax resistance is still down, now reading 0.45uohm. Last night it ended up at 0.62 or 0.68. We will begin with a series of resistance test shots. Coil is at -182 (resistance reading before putting the 100A). D2 ECDC is about to begin (07:30). We will only get about an hour's worth. | |
| Sep 6 1996 07:32:54:520AM | Steve Wolfe | Run Plan for Friday 960905
MP#163 High q_parallel dissipative divertor SL: Goetz PO: wolfe EO: Silva/Daigle ECDC in D2 for 2hours before operation if possible. Engineering setup as for 960904038 Gas setup: 20psi D2 in A-side 5psi D2 in B-top 10psi N2 in B-side lower Enable B-top and A-side for first shot. Check coax resistance with DC supply before cooling down and again during and after cooldown. If resistance is within acceptable limits, then do a 5KA oh resistance test, followed by a 10kA oh resistance test. If these are also acceptable, then proceed with the run. | |
| Sep 6 1996 07:37:51:300AM | Steve Wolfe | Run Plan for Friday 960905
Start with a shot with seg 1 from a good recent shot and seg2 from 960227019 (1MA, 5.3T). Try to get acceptable H-mode (preferably enhanced D-alpha). Then begin puffing N2 into the h-mode phase to try to detach. Start with 100msec puff from B-side lower, beginning 100msec after the RF. If successful in detaching with high q||, then try setting up feedback on the b-side lower valve using the divertor bolo signals. Contingency (if the h-modes don't work out)- Get probe data for Brian | |
| Sep 6 1996 08:05:28:400AM | Steve Wolfe | coldstart:6-SEP-1996 07:56:16.82
All ok. Note that the log file contains a string of %RMS-E-FNF, file not found errors from the CAMAC test shot. This is now normal. | |
| Sep 6 1996 08:20:10:180AM | Steve Wolfe | Additional information on coax resistance: before start of
cooling, with temp of oh1 coax down to -39 (from -10 last night), oh2u coax resistance read .8uohm. This came down to .54uohm quickly after cooling started. | |
| Sep 6 1996 08:35:59:090AM | 960906001 | Steve Wolfe | 960906001: oh test shot, 5ka plc.
oh1: 0.1842 uohm oh2u: 0.4348 uohm oh2l: 0.2644 uohm So far so good. Traces look good; no glitches. |
| Sep 6 1996 08:48:03:900AM | 960906002 | Steve Wolfe | 960906002: oh test shot, "10ka" plc (tuesday test levels).
shot: 960906002 oh1: 0.2151 uohm oh2u: 0.4125 uohm oh2l: 0.3163 uohm Still ok. Note that sign of oh2l voltage is now correct, which means the scope is reading negative resistance. |
| Sep 6 1996 09:07:53:560AM | 960906003 | Steve Wolfe | 960906003: oh test shot, 5kA, with TF at 156ka
shot: 960906003 oh1: 0.1886 uohm oh2u: 0.4400 uohm oh2l: 0.3649 uohm Trace is ramping, from .14 to .44, with a glitch up at -.12. This may be ditf/dt effect as per JHI. |
| Sep 6 1996 09:25:15:970AM | 960906004 | Steve Wolfe | 960906004: TF-only test at 156ka to check whether pickup has changed
Looks like the sign of the TF pickup has reversed. Now using a coeff of +2.1e-9*_ditfdt, gives residual error of +/-0.0002 V . Applying this to shot 3 gives aresistance that ramps from 0.35 to 0.47uohm |
| Sep 6 1996 10:42:25:640AM | 960906005 | Steve Wolfe | 960906005: One more test: Tuesday "10kA" with 156kA TF.
shot: 960906005 oh1: 0.3884 uohm oh2u: 1.1144 uohm oh2l: 0.4866 uohm Resistance climbs throughout the pulse. Check it with DC 100A. It gives 1.25uohm. The change is real. |
| Sep 6 1996 03:41:15:030PM | 960906006 | Steve Wolfe | 960906006: TF only pulse, no TF cooling afterward.
Preparing in case we decide to dismantle. With 100A in the OH2U, the resistance after the shot reads 1.4uohm. |
| Sep 6 1996 03:57:37:740PM | 960906007 | Steve Wolfe | 960906007: TF only pulse, no TF cooling afterward.
Preparing in case we decide to dismantle. No pulse. |
| Sep 6 1996 04:05:05:480PM | 960906008 | Steve Wolfe | 960906008: TF only pulse, no TF cooling afterward.
Preparing in case we decide to dismantle. Snipes noted that the apparent TF pickup is different from the one obtained on shot 4 by a factor of at least 2. This could be due to the changed circuitry: They now have 100A in the coil and are reading out the amplifier output on the volt-meter, in parallel with the camac. On this one and on 6, it reads +/- .001V, as opposed to .0002 before. |
| Sep 6 1996 04:21:09:240PM | 960906009 | Steve Wolfe | 960906009: TF only pulse, no TF cooling afterward.
Preparing in case we decide to dismantle. Remove the 100A source and the meter from the oh2u coax measurement. See if it is really different. Still +/-.001. They turned off the fix. det. so the flattop is longer. |
| Engineering Operator Comments | ||||
| Shot | Time | Type | Status | Comment |
| 1 | 08:30:28:440AM | Test | Ok | oh test |
| 2 | 08:39:27:980AM | Test | Ok | oh 10ka test |
| 3 | 08:50:35:920AM | Test | Ok | oh test 5ka with 156ka tf |
| 4 | 09:14:29:370AM | Test | Ok | tf test only 156ka |
| 5 | 09:33:27:650AM | Test | Ok | 10ka oh test with 156ka tf |
| 6 | 03:36:12:040PM | Test | Ok | tf warm up shot |
| 7 | 03:50:00:400PM | Test | Ok | breakers open tf test no go |
| 8 | 03:56:27:430PM | Test | Ok | tf warm up |
| 9 | 04:11:51:700PM | Test | Ok | tf warm up no fizzel |
| 10 | 04:27:22:230PM | Test | Bad | |