| Miniproposals | ||||||||||
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| Operators | |
| Session leader(s): | Robert Granetz |
| Physics operator(s): | Robert Granetz |
| Engineering operator(s): | Unknown |
| Engineering Operator Run Comment |
| Bob Granetz,Plasma fusion run. |
| Session Leader Plans |
| Physics Operators Plans |
| Session Leader Summaries |
| Entered: Jul 7 2004 03:49:07:070PM |
| Author: To Be Determined |
| Run summary for 18 May 1993: ---------------------------------------------------------------------------- This run picked up where shot 930514018 (the 30 kA shot from the previous run) left off. During this past weekend, the EF2 power supplies were upgraded to enable significantly increased voltage and current maximums. We had plasma on the first 3 shots, but analysis of the magnetic fields using the flux data did not seem to show a null structure. It was subsequently discovered that one of the flux loops was not giving data, thus invalidating both the analysis, as well as the control of the machine. An hour shutdown allowed for the repair (a poor solder connection) and subsequent recool of the machine. Plasma operation began again on shot 005 and over the next couple of shots the increased capability of the EF2 supplies was utilized to help "tweak" away the gradient in Bz. EF3 was also tweaked to try and provide a rapidly growing Bz as the current took off. This resulted in a current of 34 kA on shot 007, at a pressure of 8e-5 torr. Most of the rest of the run consisted of a scan in fill pressure, without any changes in waveform programming. Gradually decreasing the pressure down to 4e-5 resulted in nearly 40 kA of plasma current on shot 009, and the first observation of x-ray emission. Further decreases in the pressure did not result in breakdown. The pressure was then gradually increased up to a maximum of 1.5e-4 torr, although the plasma current decreased somewhat. During this scan it was observed that the vertical field varied by +/- a few mT even though there were no programming changes. These drifts may have been enough to significantly influence the discharges. All of the shots exhibited outward-going instabilities, which perhaps indicated insufficient ramp-up of the vertical field. Returning to a pressure of 5e-5, several adjustments were made to EF3 and EF4 programming to try and improve the Bz ramp-up, without noticeable success. ********************* Power supply programming info ************************ Throughout most of the run, the EF3 supply was being controlled by feedback on Bz, in addition to its voltage preprogramming. All other supplies were feeding back on bus current demands, with the exception of the OH2's after t=0, which were then controlled by feedback on Br. Care was taken to ensure that all PLC current limits were set at least 3-5 kA above programmed demands. (The reliability of the power supplies was phenomenal!) ************ Suggested improvements/changes for next run ******************* Either find a way to increase the rate at which Bz ramps up, or decrease the rate of plasma current rise. The former possibility seems remote, since we were apparently driving EF3 as hard on as it could go, although shifting the voltage programming to slightly earlier times may help. The latter scenario (decreasing dIp/dt) could be accomplished by lowering some commutation resistors, thereby decreasing the loop voltage. |
| Physics Operator Summaries |
| Session Leader Comments | |||
| May 18 1993 08:40:08:630AM | Robert Granetz | Start by repeating 930514018 (the 30 kA shot from the last run on Friday).
The PCS tree from that shot was recalled and loaded into the hybrid. New (increased) limits for the EF2 max voltages and currents were then re-inserted into the hybrid. | |
| May 18 1993 09:57:54:710AM | Robert Granetz | Commutation resistors:
OH1 0.156 ohms OH2U&L 0.45 EF1U&L 0.153 Ballast resistor EF2U&L 0.045 PLC current limits: OH1 15 kA OH2U&L 18 kA EF1U&L 6 kA EF2U&L 3 kA EF3 10 kA EF4 3 kA | |
| May 18 1993 10:07:07:720AM | Robert Granetz | Looks like an N2 leak is back, judging from the RGA just before the start
of this run. | |
| May 18 1993 10:51:13:920AM | 930518001 | Robert Granetz | Got plasma on first pulse! TF crowbarred on way down.
OH2L had 2 kA more than programmed. Adjust voltage pre-programming on OH2L. Also, |Bz| rampup starts at 0.040 sec. If time permits, correct this as well, but perhaps not on the next shot. |
| May 18 1993 11:01:45:240AM | 930518001 | Robert Granetz | Turn on Bz feedback for next shot using EF3. Program Bz to rampup (actually
down) at about 10 msec. |
| May 18 1993 11:15:27:220AM | 930518002 | Robert Granetz | Pretty much the same as last shot, but even wimpier. OH2L is still 1.3 kA too
high, and Bz doesn't seem to have changed. Lower OH2L pre-programmed voltage again, from 20 to 12 volts. Look into Bz feedback. |
| May 18 1993 11:31:18:610AM | 930518002 | Robert Granetz | Slightly improved, but still pretty wimpy.
|
| May 18 1993 12:29:04:390PM | 930518002 | Robert Granetz | Slightly improved, but still pretty wimpy.
BROKEN FLUX LOOP!!! F23 is not giving any signal. This is screwing up the magnetic field calculations, resulting in no effective control of the machine. We are going to stop the LN2 cooling, let the oxygen levels rise in the cell, and go in and check it out. The loop was working yesterday morning for an EF2 test shot (930517001). After that, the magnetics racks were moved to allow John Rice to align his crystal spectrometers. |
| May 18 1993 12:30:56:550PM | 930518002 | Robert Granetz | A bad solder connection was found on one of the F23 pins in the Amphenol
connector at the input to the magnetics racks. It was resoldered and all 10 flux loops in that connector checked out okay. |
| May 18 1993 12:40:54:440PM | 930518003 | Robert Granetz | The previous two comments about the broken flux loop and its repair should
have been entered under shot 003, not shot 002. |
| May 18 1993 12:41:39:980PM | 930518003 | Robert Granetz | No programming changes were made between shots 003 and 004.
|
| May 18 1993 01:21:07:980PM | 930518004 | Robert Granetz | No PF power supplies. No magnetics data, no hybrid, lots of things did not
go. Probably a computer problem. |
| May 18 1993 01:52:33:980PM | 930518005 | Robert Granetz | Plasma. Ip=20 kA. Discharge lasted about 30 msec.
The radial field is acceptably small. Bz programming still doesn't seem right. The gradient is too negative. I will control this by making the current in EF2's drop faster during commutation. This requires more negative power supply voltage, which is now possible with the modifications made to the EF2 supply over the weekend. Set the pre-programmed voltage to drop to -900 volts at t=0. This will also make Bz more negative, which should help. |
| May 18 1993 02:07:21:850PM | 930518006 | Robert Granetz | Ip=22 kA. The gradient improved. Bz is still not turning on fast enough.
For the next shot, changed EF3 voltage pre-programming at t=.002 s from -2300 to -3000 volts. |
| May 18 1993 02:22:38:350PM | 930518007 | Robert Granetz | Ip=34 kA. New record. Bz has finally responded to our programming. We
could use even more negative Bz as the current grows. Raise the PLC limit for EF3 from 10 kA to 12 kA. Time for a gas pressure scan. This shot (and all previous shots today) were at a fill pressure of 8e-5 torr. The next shot will be at 6e-5. |
| May 18 1993 02:32:16:970PM | 930518008 | Robert Granetz | Got breakdown at 6e-5 torr, but just barely. Ip=25 kA.
Next shot at 4e-5 torr. |
| May 18 1993 02:40:36:410PM | 930518009 | Robert Granetz | Brokedown again. Ip=39 kA. New record. Lower pressure again from
4e-5 to 2-e5 for next shot. |
| May 18 1993 02:53:01:990PM | 930518010 | Robert Granetz | No breakdown. Increase pressure slightly from 2e-5 to 3e-5 for next shot.
|
| May 18 1993 02:56:43:110PM | 930518011 | Robert Granetz | No breakdown again. For the next shot set the pressure back at the "normal"
operating level of 8e-5 torr. |
| May 18 1993 03:15:46:480PM | 930518012 | Robert Granetz | Broke down at p=7.2e-5 torr. Ip=25 kA. Continue pressure scan and raise to
1.0e-4 on next shot. |
| May 18 1993 03:31:59:720PM | 930518014 | Robert Granetz | Ip=32 kA at p=1.0e-4. Raise to 1.2e-4 torr for next shot.
|
| May 18 1993 03:35:07:690PM | 930518014 | Robert Granetz | Correction: pressure raised to 1.5e-4 for this shot (after considerable
razzing from the monkey gallery. |
| May 18 1993 03:44:11:620PM | 930518014 | Robert Granetz | Broke down, but Ip=20 kA only. End of pressure scan.
|
| May 18 1993 03:58:47:450PM | 930518015 | Robert Granetz | No breakdown. p=5e-5 torr. On next shot, tweak vertical field upwards by
about 5 mT using a 90 amp increase in EF4 demand. |
| May 18 1993 04:08:23:560PM | 930518016 | Robert Granetz | Got it! Ip=27 kA. Vertical field got back up to zero at breakdown.
|
| May 18 1993 04:15:53:960PM | 930518017 | Robert Granetz | Increase EF3 demand voltage to the max (negative) at t=0.001 s
|
| May 18 1993 04:29:44:360PM | 930518017 | Robert Granetz | Ip=27 kA.
|
| May 18 1993 04:30:21:660PM | 930518018 | Robert Granetz | Change EF3 programming for this shot so that the maximum voltage demand stays
on for 20 msec. |
| May 18 1993 04:38:41:000PM | 930518018 | Robert Granetz | Ip=30 kA.
|
| May 18 1993 04:45:54:680PM | 930518019 | Robert Granetz | For this shot, the vertical field was decreased slightly by decreasing
the EF4 demand by 30 amps. No plasma! |
| May 18 1993 04:44:05:990PM | 930518020 | Robert Granetz | For this shot, the vertical field was decreased slightly by decreasing
the EF4 demand by 30 amps. |
| May 18 1993 04:50:03:180PM | 930518020 | Robert Granetz | For this shot, raise EF4 by 50 amps from the previous shot.
|
| May 18 1993 05:00:42:490PM | 930518020 | Robert Granetz | Ip=29 kA.
|
| May 18 1993 05:02:39:840PM | 930518021 | Robert Granetz | For this shot, take advantage of the rapid negative increase in Bz, which is
occurring a little too late. Change its programming earlier in time by 8 msec and simultaneously increase EF4 by another 30 amps to keep the field near zero at breakdown. |
| May 18 1993 05:03:46:700PM | 930518021 | Robert Granetz | No breakdown.
|
| May 18 1993 05:08:52:140PM | 930518021 | Robert Granetz | Bz started ramping negative way to early (-0.010 sec).
|
| Physics Operator Comments |
| Engineering Operator Comments | ||||
| Shot | Time | Type | Status | Comment |
| 1 | 10:32:16:750AM | Plasma | Ok | Plasma current TF power supply Fault |
| 2 | 11:05:43:150AM | Plasma | Ok | plasma current Alarm hung up pushed emergency stop . |
| 3 | 11:26:24:370AM | Plasma | Ok | Plasma Breakdown |
| 4 | 01:13:54:680PM | Plasma | Bad | Only tf fired Computer problem. |
| 5 | 01:33:10:320PM | Plasma | Ok | Plasma breakdown Power system OK |
| 6 | 01:52:09:850PM | Plasma | Ok | Plasma Breakdown Power supplies OK. |
| 7 | 02:07:47:410PM | Plasma | Ok | Plasma Breakdown OH1 Commutation fault Comm fault in Aux. cabin |
| 8 | 02:23:56:980PM | Plasma | Ok | Plasma breakdown power system OK. |
| 9 | 02:35:11:410PM | Plasma | Ok | Plasma Breakdown Power Systems OK. |
| 10 | 02:42:01:660PM | Plasma | Bad | No Breakdown Power System OK |
| 11 | 02:54:19:290PM | Plasma | Bad | No Breakdown Power System OK |
| 12 | 03:05:40:800PM | Plasma | Ok | Plasma Breakdown Power suplies OK. |
| 13 | 03:26:19:470PM | Plasma | Ok | Plasma breakdown power system OK |
| 14 | 03:35:30:960PM | Plasma | Ok | Plasma breakdown Power system OK |
| 15 | 03:48:50:910PM | Plasma | Bad | No breakdown Power System OK |
| 16 | 04:00:28:790PM | Plasma | Ok | Plasma breakdown Power systems OK |
| 17 | 04:16:33:250PM | Plasma | Ok | Plasma breakdown Power systems OK. |
| 18 | 04:31:19:880PM | Plasma | Ok | Plasma breakdown Power systems OK. |
| 19 | 04:43:02:650PM | Plasma | Ok | No plasma current Power Supplies OK |
| 20 | 04:52:18:300PM | Plasma | Ok | Plasma current Power systems OK. |
| 21 | 05:02:00:630PM | Test | Bad | |