| Miniproposals | ||||||||||
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| Operators | |
| Session leader(s): | Earl Marmar |
| Physics operator(s): | Steve Wolfe |
| Engineering operator(s): | Steve Fairfax |
| Engineering Operator Run Comment |
| Try to raise plasma current to 100 kA. Wolfe on Physics, Fairfax at Eng |
| Session Leader Plans |
| Physics Operators Plans |
| Session Leader Summaries |
| Entered: Jul 7 2004 03:49:06:867PM |
| Author: To Be Determined |
| Run Summary for 5/13/93 Physics Operator/Session Leader: wolfe Assistant: marmar Engineering Operator: fairfax The object of today's run was to get the plasma current to take off by tweaking yesterday's final result in two ways: 1)improving the null so that breakdown could be reliably obtained at lower pressure (increasing chances for burn-through) and 2) improving the field evolution after breakdown so the current channel could evolve stably. These objectives were not met. Out of 25 shots today, 18 had plasma; shots#3-5 were EF1 tests under PLC control. The maximum current achieved was around 25kA. Some seemed to be relatively stable, as judged by the Xray/UV tomographic arrays, while others exhibhited "wild instability". Breakdowns were quick, typically around +7msec. Most showed a sharp initial H-alpha spike which dropped in 3msec to about half the peak value, but did not continue to burn out. Carbon was observed to be the dominant impurity, with CII being brighter than H-beta. All the successful breakdowns were run with fill pressure 8e-5 Torr (gage). Two attempts with 6e-5 failed (the second had a very weak light flash at 45 msec, but no current). Radial field error was successfully controlled by a combination of Br feedback applied to the OH2 coils, and adjustment of the OH2 voltage pre-programming. The gain on Br after commutation was raised to about half the maximum available value, corresponding to 20msec nominal time constant, but this was insufficient to control the error field without pre-adjustment of the OH2 voltages. A 3mT offset was programmed into the Br S-waveform to compensate for offsets in the hybrid. It was found to be advantageous to turn off current feedback control after commutation. This eliminated oscillations and some commutation failures in the EF1 and OH2 supplies. Programming of the voltage and current waveforms for OH1 and OH2 were adjusted for early times to flatten the OH1 current trace and eliminate the big bite out of OH2 current when the OH1 ramps up. The radial plasma position of the plasma, as seen by the Granetz arrays, was shown to respond to changes in the EF3 voltage programming (ie the vertical field) as expected (shots#17-19). A change of about 7mT gave of order 3cm shift in the apparent centroid position. Note that these discharges actially had two "filaments". The IP_RCUR predictor of the hybrid also appeared to track the plasma position, at least qualitatively; the changes were at the 100 A-m level for apparent position changes of .01m and 10-20kA of plasma current. The offset and spurious signal on this predictor is of order 1000 A-m. Troubles: The first plasma shot was not obtained until almost 13:30, due to a number of problems in the morning. The run was delayed by one hour at the start by a hybrid problem. The bitbus communications were bad due to a 12V power supply on the optical transceiver which had dropped to 6V. Alternator and access control problems resulted in an additional hour delay. IN the course of trying to diagnose the bitbus problem SHAPE was power cycled and rebooted. This apparently caused other problems for the Loader, which led to bitbus errors in the INIT cycle and garbage in the matrices. This was eventually remedied, and the loads executed successfully the rest of the day. EF1 and OH2 power supply modifications performed overnight were only partially successful. The mod to the voltage regulator to eliminate spurious delays worked well. The supplies seemed to be responding correctly to demands from the hybrid all day. The attempt to increase voltage on EF1 led to power supply faults. Fairfax undid this mod, and increased the phase margin setting instead. This seemed to provide adequate voltage, about 300V from the supply. A similar adjustment was made to OH1 supply to provide more inversion voltage. There seems to be a calibration problem with the OH1 supply voltage; it reads 100V when the voltage is in fact 300V. Care must be taken not to PASTE this trace into the PCS V waveform until it is fixed. The approach of tweaking parameters from a basis of the 930512 run was not successful in making substantial improvements in the null quality, as judged by plasma performance. While longer duration plasmas at marginally higher currents were obtained today, there was no indication that the current was close to taking off, or that a complete burn-through was being approached. A new starting point, or more radical changes, seem to be called for. Tony Taylor has prepared a scenario employing EF2, and substantially reduced OH1, EF1, EF3, and EF4 currents, which might be a good place to re-start the effort. |
| Physics Operator Summaries |
| Session Leader Comments | |||
| May 13 1993 08:45:41:350AM | Earl Marmar | There is a problem on the bitbus discovered this morning by Steve Horne. As an attempt
to fix, we are going to reboot shape now. | |
| May 13 1993 10:06:17:730AM | Earl Marmar | The bitbus problem has been fixed. A 12 V power brick used for the fiber optic
transmitter on the bitbus had failed (output = 6 V). | |
| May 13 1993 11:25:09:130AM | 930513001 | Earl Marmar | Same settings as last shot yesterday, except EF1 inversion moved
so both are at commutation. Commutation resistors: OH2 46 mOhm EF1 250 mOhm OH1 156 mOhm Fill: 8e-5 on IGT Results: 1'st try: No shot. Alternator never ramped up. Bad relay contact. 2'nd try: No plasma. No poloidal fields. TF only, 5T. Apparently problems initializing the hybrid. |
| May 13 1993 12:24:41:050PM | 930513002 | Earl Marmar | Try again after TWF checked out hybrid initializiation.
Result: No plasma. Power supply faults. Hybrid bitbus apparently also had problems. |
| May 13 1993 12:29:07:360PM | 930513003 | Earl Marmar | EF1 test under PLC control. Partially successful, but still problem with
voltage apparently related to last night's fix to supplies. That fix will be undone for shot 4. A cold start was done before shot 3, but not completed before init. As a result, the A matrix was OK, but the wavegen and M matrix were not. |
| May 13 1993 12:45:28:150PM | 930513003 | Earl Marmar | EF1 closed circuit PLC control test.
Result: EF1 ok Hybrid functioned ok. There was a problem with the P waveforms for EF2 and EF3, which did not return to 0; this was due to a drawing error in the model, corrected for the next shot. |
| May 13 1993 12:53:14:760PM | 930513005 | Earl Marmar | Another EF1 closed circuit test under PLC control.
Result: EF1's ok. Voltage was increased. EF1U gave lower maximum voltage than EF1L. Hybrid functioned ok. |
| May 13 1993 01:21:55:150PM | 930513006 | Earl Marmar | Attempt for plasma.
Result: Weak flash. Too much radial field. OH2's were driven close to turn-off by OH1 turn-on. |
| May 13 1993 01:39:53:640PM | 930513007 | Earl Marmar | Try again.
Changes for this shot: OH1 & OH2 V programming and OH1 current programming adjusted for first part of shot. +3mT offset put into B_radial waveform to compendate for offset in the predictor waveform. Result: Similar I_p (~10 kA) as on shot 6. Radial field at commutation was -1 mT, but then goes +ve to +4mT after comm.e |
| May 13 1993 01:52:30:830PM | 930513008 | Earl Marmar | Changes for this shot: Raised programming voltage on OH2U&L to try to get
closer to the requested currents. Result: About 18 kA plasma current. 2Pi bolo peak = 30 kW. |
| May 13 1993 02:13:28:530PM | 930513009 | Earl Marmar | Changes for this shot: Raised gain on OH2U&L from 1 to 2 (PID) to get
closer to the requested currents. Lowered post commutation voltage demand on OH2L from 100 to 90V, to try to affect the radial field. Result: About 24 kA plasma current. 2Pi bolo peak = 40 kW. Broke down at 7 mS; still badly evolving radial field; gradient slightly -ve at breakdown, but going +ve at about the right rate. |
| May 13 1993 02:29:48:130PM | 930513010 | Earl Marmar | Changes for this shot: EF1U&L current feedback turned off at -4mS.
Result: Got 20 kA; cured oscillation and fault problems on EF1. |
| May 13 1993 02:48:17:260PM | 930513011 | Earl Marmar | Changes for this shot: Turned up gain (PID) on radial field at +2 mS from 1 to 5
Gain turned off at 62 mS. Result: Very similar to shot 10; 20 kA plasma current; 2PI = 40 kW peak. Radial field error similar to shot 10; radial field gain trying but not big enough. |
| May 13 1993 02:57:23:730PM | 930513012 | Earl Marmar | Changes for this shot: Turned off current gains (PID) on OH2's at -2mS;
reduced voltage demand on OH2L by -100V after commutation. Change fill pressure to 6e-5. Result: No breakdown. Null was ok. |
| May 13 1993 03:10:47:120PM | 930513013 | Earl Marmar | Changes for this shot:
Fill pressure back to 8e-5. Result: ok. Radial field still good. Granetz says "wildly unstable". Fill Pressure: 8e-5 B_toroidal: 5.0 T Peak current: 21 kA 2Pi bolo peak: 80 kW Breakdown time: 7.4 mS |
| May 13 1993 03:26:15:170PM | 930513014 | Earl Marmar | Changes for this shot:
OH1 inversion voltage set to -400v (after commutation until crowbar). Result: Got more V_loop, but OH1 did not give complete response (got 100V instead of 400V) Fill Pressure: 8e-5 B_toroidal: 5.0 T Peak current: 22 kA 2Pi bolo peak: 40 kW Breakdown time: 6.3 mS |
| May 13 1993 03:42:34:020PM | 930513015 | Earl Marmar | Changes for this shot:
Fairfax has made a change to improve the OH1 voltage response; Reduced voltage on OH2's between commutation and crowbar by 100V each. Result: Got a little more voltage. Fill Pressure: 8e-5 B_toroidal: 5.0 T Peak current: 24 kA 2Pi bolo peak: 50 kW Breakdown time: 7.2 mS |
| May 13 1993 04:01:14:720PM | 930513016 | Earl Marmar | Changes for this shot:
Fairfax has made another change to improve further the OH1 voltage response; Result: Got a little more voltage, but OH1 power supply commutation failure occured. Fill Pressure: 8e-5 B_toroidal: 5.0 T Peak current: 23 kA 2Pi bolo peak: 55 kW Breakdown time: 7.2 mS |
| May 13 1993 04:15:09:730PM | 930513017 | Earl Marmar | Changes for this shot:
Extended EF3 voltage after commutation to 40 mS; raised OH2 voltages back up by 100V after commutation Result: Fill Pressure: 8e-5 B_toroidal: 5.0 T Peak current: 22 kA 2Pi bolo peak: 40 kW Breakdown time: 8.6 mS |
| May 13 1993 04:27:40:430PM | 930513018 | Earl Marmar | Changes for this shot:
Dropped EF3 voltage by 100 V Result: Fill Pressure: 8e-5 B_toroidal: 5.0 T Peak current: 20 kA 2Pi bolo peak: 30 kW Breakdown time: 6.3 mS |
| May 13 1993 04:40:41:880PM | 930513019 | Earl Marmar | Changes for this shot:
Dropped EF3 voltage another 100V, after breakdown time Result: Appeared to be a little farther outside, consistent with change in EF3. Fill Pressure: 8e-5 B_toroidal: 5.0 T Peak current: 17 kA 2Pi bolo peak: 30 kW Breakdown time: 5.8 mS |
| May 13 1993 04:54:22:260PM | 930513020 | Earl Marmar | Changes for this shot:
Dropped OH2U voltage by ~100V Result: Radial field looks good. Granetz sees plasma 1 cm farther in. Fill Pressure: 8e-5 B_toroidal: 5.0 T Peak current: 19 kA 2Pi bolo peak: 30 kW Breakdown time: 6.3 mS |
| May 13 1993 05:03:28:630PM | 930513021 | Earl Marmar | Changes for this shot:
Dropping fill pressure to 6.e-5 Result: No plasma current -- magnetic signals same as previous. Tiny flash very late. Fill Pressure: 5.5e-5 B_toroidal: 5.0 T Peak current: 0 kA 2Pi bolo peak: 0 kW Breakdown time: 43.3 mS |
| May 13 1993 05:08:45:710PM | 930513021 | Earl Marmar | Changes for this shot:
Dropping fill pressure to 6.e-5 Result: No plasma current -- magnetic signals same as previous. Tiny flash very late. Fill Pressure: 5.5e-5 B_toroidal: 5.0 T Peak current: 0 kA 2Pi bolo peak: 0 kW Breakdown time: 43.3 mS |
| May 13 1993 05:22:25:730PM | 930513022 | Earl Marmar | Changes for this shot:
More -ve voltage on OH2's after commutation (~150 V) Increase fill back to 8e-5 Result: Reversed the direction of the dB_z/dR gradient with more or less the correct slope in time; got worse radial field because of OH2 imbalance; OH2L has oscillations after 15 mS. Fill Pressure: 8e-5 B_toroidal: 5.0 T Peak current: 20 kA 2Pi bolo peak: 30 kW Breakdown time: 7.3 mS |
| Physics Operator Comments |
| Engineering Operator Comments | ||||
| Shot | Time | Type | Status | Comment |
| 1 | 10:19:19:760AM | Plasma | Bad | Long delay; hybrid 1hour, access 20 minutes, alt 35 min. Then no PF due |
| 2 | 11:26:28:090AM | Plasma | Bad | EF1L supply autocrowbar at -1.45 seconds from 600 V positive spikes. |
| 3 | 12:07:18:270PM | Test | Ok | EF1 closed circuit test OK; still positive spikes on EF1U |
| 4 | 12:30:11:010PM | Test | Ok | EF1 closed circuit test withj forward limits eneabled OK |
| 5 | 12:43:59:960PM | Test | Ok | EF1 closed circuit test |
| 6 | 12:59:49:140PM | Plasma | Ok | flash is back |
| 7 | 01:23:06:380PM | Plasma | Ok | flash; EF1 shows commutation failures after blip |
| 8 | 01:41:08:490PM | Plasma | Ok | Flash but same faults on EF1 and OH1 |
| 9 | 01:53:27:010PM | Plasma | Ok | looks like EF1 comm faults may be induced by hybrid |
| 10 | 02:14:43:680PM | Plasma | Ok | turning off current feedback in EF1 after commutation stopped comm fault |
| 11 | 02:29:45:290PM | Plasma | Ok | OK. |
| 12 | 02:47:53:700PM | Plasma | Ok | 1 scr out oh1; not real |
| 13 | 02:59:28:380PM | Plasma | Ok | no faults |
| 14 | 03:10:06:350PM | Plasma | Ok | flash; no faults; set oh1 inversion end-stop from 55 to 35 degrees |
| 15 | 03:26:15:180PM | Plasma | Ok | ok |
| 16 | 03:42:45:600PM | Plasma | Ok | OH1 commutation failure; set margin angle back to 30 from 20; should be |
| 17 | 04:02:27:950PM | Plasma | Ok | EF1 and OH1 commutation failures after blip. |
| 18 | 04:16:23:850PM | Plasma | Ok | no faults; good flash; still no Ip>30 kA |
| 19 | 04:29:55:970PM | Plasma | Ok | Plasma-- no faults with power systems |
| 20 | 04:44:50:320PM | Plasma | Ok | Plasma -- no power system faults |
| 21 | 04:55:50:320PM | Plasma | Ok | very late, tiny flash. No plasma current |
| 22 | 05:13:20:080PM | Plasma | Ok | EF1 and OH1 Commutation failures indicated but not visible on traces. F |