| Miniproposals | ||||||||||
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| Operators | |
| Session leader(s): | Robert Granetz |
| Physics operator(s): | Steve Golovato |
| Engineering operator(s): | Vinny Bertolino |
| Engineering Operator Run Comment |
| Plasma shots all day |
| Session Leader Plans |
| Physics Operators Plans |
| Session Leader Summaries |
| Entered: Jul 7 2004 03:49:07:290PM |
| Author: To Be Determined |
| Summary of Run 930520 Session Leader/Physics Operator: Granetz Assistant Physics Operator: Golovato Engineering Operator: Bertolini ------------------------------------------------------------------------------- Overview: The main goal of this week's operation is to establish a quiescent, steady state plasma, with a flattop current of 0.20-0.25 MA lasting for at least 0.10 sec. Such conditions are desirable in order to study feedback control of the plasma current and shape in the coming weeks. Today's run made some progress towards this goal, with flattops of 0.03 s at Ip=0.24 MA (shot #014) and disruption-free periods of >0.11 s, before running into plasma position control problems. ------------------------------------------------------------------------------- Prior to run: ECDC was run for several hours yesterday. Changes have been made to the hybrid computer and the PCS model file which affect the scaling of signals, as well as the residual offsets. The bad SCR and fuse in the TF supply has been fixed. ------------------------------------------------------------------------------- Detailed summary: The power supply programming for the start of the run was copied from shot 930520031 from last week. The first 5 shots had problems due to a very large ripple on OH2L, which was eventually found to be due to a bad solder connection on a gate control board. Shot #006 was the first shot on which all supplies worked properly, and #007 reached 0.22 MA with a disruption at 0.075 s. This is about where we left off from last week. The following four shots all fizzled, with two of them at slightly higher fill pressure (8e-5 rather than 6e-5 torr). No programming changes were made. It was subsequently noticed that the radial field, Br, was being driven to -5 mT by the hybrid feedback. This appeared to be due to a baseline offset in the hybrid, and was overcome by demanding +5 mT more for Br (prior to shot #012). That did the trick, and all but two of the following 15 shots surpassed 0.2 MA. Shots #012, 013, & 014 had increasingly extended quiescent periods before the occurrence of a disruption (up to t=0.113 s), at currents of 0.24 MA and flattops of up to 0.03 s. The disruptions did not have any obvious causes. X-ray imaging clearly showed slow, continual outward and downward movement of the plasmas. At times, the motion as determined by magnetics may not have agreed with the x-rays. The plasma motion was not responding to changes made in the hybrid demand for R_CUR, possibly due to internal overflow errors. On shot #016, the hybrid scaling for R_CUR and Z_CUR feedback was changed, which reduced the outward motion, but didn't entirely eliminate it. It was noticed that EF3 (which was being used to control R_CUR) was approaching the PLC current limit, so this was raised for shot #017 from 12 kA to 15 kA. From this point on, the plasma position control was quite poor, with inward and very large downward motion (up to 20 cm). Plasma current continued to ramp up instead of flattopping, with shot #022 reaching 0.36 MA. Changing gains for R_CUR and Z_CUR feedback did not help. It is possible that the imbalance in the decay of the OH1 and OH2 currents was causing the plasma to be pulled toward OH2L (i.e. the vertical instability). Attempts to better match the relative decays in those supplies did not help either, although by the last shot (#026) the disruption-free period had again reached 0.112 s, even though the plasma was moving in and very far downward. It was also sawtoothing the entire time. ------------------------------------------------------------------------------- Shot statistics: Total shots: 26 No breakdowns: 2 (both due to failure of multiple power supplies) Fizzles (i.e. < 0.2 MA): 10 (4 due to power supply faults, 6 to bad program- ming) Plasmas (i.e. > 0.2 MA): 14 (max Ip=0.36 MA, max disruption-free period=0.113s) ------------------------------------------------------------------------------- Suggestions/comments for next run: Work on problems of position control. One might be tempted to re-start with shot #014, but that would require reducing the EF3 PLC current limit, which is an unsatisfactory way to operate. The $64 question: What causes the disruption at 0.110-0.115 sec? |
| Physics Operator Summaries |
| Session Leader Comments | |||
| May 25 1993 12:58:33:480PM | Robert Granetz | Note: ECDC was done for 4 or 5 hours yesterday
| |
| May 25 1993 09:37:35:430AM | 930525001 | Robert Granetz | Commutation resistors:
OH1 0.100 ohms (0.050 each) OH2U&L 0.025 ohms EF1U&L 0.180 ohms Crowbar closure times: OH1 0.040 s OH2U&L 0.050 s EF1U&L 0.050 s Power supply invert times: All PF supplies invert at 0.250 s. |
| May 25 1993 09:45:16:590AM | 930525001 | Robert Granetz | This run will begin by trying to repeat shot 930520031 from last Thursday.
It was a very long (>0.15 s), stable (no disruptions until 0.15 s), sawtoothing discharge. Once we establish it, the goal is to get a flattop for >0.1 s at Ip=0.2-0.25 MA. If successful, we can begin feedback operation on Ip (plasma L/R time is of order 0.1 s). |
| May 25 1993 09:45:48:780AM | 930525001 | Robert Granetz | Fizzle. OH2L has a very large oscillation on it (1500 amps @ 55 Hz). It
must be fixed or we will waste the day trying to get repeatable operation. |
| May 25 1993 10:57:22:700AM | 930525002 | Robert Granetz | Fizzle. OH2L still has oscillation problem. OH1 faulted during commutation.
|
| May 25 1993 10:59:56:400AM | 930525003 | Robert Granetz | Fizzle (short pulse reached 100 kA). OH2 still has oscillation problem.
Pause run for 15 minutes to investigate probably gate pulse problem. |
| May 25 1993 11:00:55:560AM | 930525003 | Robert Granetz | Cold solder joint on gate pulse control board of OH2L !
|
| May 25 1993 11:03:01:030AM | 930525004 | Robert Granetz | No breakdown. No OH2's
|
| May 25 1993 11:14:40:660AM | 930525005 | Robert Granetz | No breakdown. Multiple PF power supplies faulted early.
|
| May 25 1993 11:35:21:030AM | 930525006 | Robert Granetz | Before shot #006, lowered the early voltage pre-programming on the OH2's in
order to avoid the brief railing of the supplies against the PLC limits at about t=-1.5 s. |
| May 25 1993 12:09:15:110PM | 930525006 | Robert Granetz | Fizzle. All supplies worked. OH2L's ripple has been fixed.
|
| May 25 1993 12:35:18:550PM | 930525007 | Robert Granetz | Good shot. Ip=0.22 MA Shot lasted until t=0.155 s, but disruptions started
at 0.075 s. Plasma position was about z=-1 cm, as requested. |
| May 25 1993 12:37:26:740PM | 930525008 | Robert Granetz | Gas prefill raised from 6e-5 to 8e-5 torr for this shot.
Fizzle. Try a repeat |
| May 25 1993 12:43:10:290PM | 930525009 | Robert Granetz | Fizzle.
|
| May 25 1993 12:56:40:850PM | 930525010 | Robert Granetz | Fizzle again. Gas pre-fill was lowered for this shot from 8e-5 back to
the nominal 6e-5 torr. |
| May 25 1993 01:25:39:500PM | 930525011 | Robert Granetz | Fizzle. There might be an offset problem with the hybrid's control of Br.
|
| May 25 1993 01:30:13:540PM | 930525012 | Robert Granetz | Offset the Br demand by +0.005 Tesla from the previous shots.
Good shot. Maybe what we did had something to with the good plasma, maybe it didn't. |
| May 25 1993 01:41:35:080PM | 930525012 | Robert Granetz | There is no indication that the plasma hit any material surface to cause
the disruption. Try a repeat. |
| May 25 1993 01:46:26:180PM | 930525013 | Robert Granetz | Another good one. Disruption at 0.095 s.
|
| May 25 1993 01:56:25:000PM | 930525013 | Robert Granetz | Change hybrid programming of R_CUR from 0.665 to 0.650 m. The PID gain is
turned on at 0.040 s. (for the next shot) |
| May 25 1993 02:15:48:280PM | 930525014 | Robert Granetz | Better. Ip=0.24 MA. First disruption occurs at 0.113 s. Plasma is still
moving outward throughout the shot. The magnetics reconstructions do not show the plasma moving outward. That's why the feedback doesn't seem to be working correctly? X-rays definitely show plasma moving outward at about 7 to 10 mm per 10 msec. For the next shot, change programmed R_CUR from 0.650 to 0.640 m. |
| May 25 1993 02:20:47:950PM | 930525015 | Robert Granetz | Almost identical to the previous shot
|
| May 25 1993 02:41:33:850PM | 930525015 | Robert Granetz | Hybrid may have an internal saturation. Change scale bit for R_CUR. Change
it for Z_CUR also, just to be on the safe side. |
| May 25 1993 02:46:23:980PM | 930525016 | Robert Granetz | Similar to previous 2 shots. Plasma outward motion is definitely reduced
compared to the preceding shots. Next shot: raise EF3 PLC current limit. |
| May 25 1993 03:04:52:860PM | 930525017 | Robert Granetz | Ip=0.32 MA. Plasma went in and very far down. We don't know why it went down.
Apparently changing the EF3 PLC current limit caused this change. For the next shot, change R_CUR programming back to 0.665 m. |
| May 25 1993 03:21:06:970PM | 930525018 | Robert Granetz | Ip=0.30 MA, but OH1 faulted during commutation. Plasma was not very good...
no sawteeth. Repeat for next shot. |
| May 25 1993 03:29:26:110PM | 930525019 | Robert Granetz | Okay shot. Ip=.35 MA Disrupts at 0.110 s
|
| May 25 1993 03:37:14:620PM | 930525019 | Robert Granetz | Okay shot. Ip=.35 MA Disrupts at 0.110 s. Plasma shifts inward by 4-5 cm
at t=0.045, and dives downward after 0.085 s |
| May 25 1993 03:38:20:230PM | 930525019 | Robert Granetz | For next shot, increase PID gain on R_CUR by factor of 2. This will max out
the feedback for radial plasma position. |
| May 25 1993 03:43:30:320PM | 930525020 | Robert Granetz | Fizzle
|
| May 25 1993 04:10:19:020PM | 930525021 | Robert Granetz | Fizzle. OH1 faulted
|
| May 25 1993 04:11:53:090PM | 930525022 | Robert Granetz | Ip=0.36 MA. Better shot. Radial position okay, R(x-rays)=0.61 m
Plasma is still falling downward after about 0.080 s. |
| May 25 1993 04:17:13:320PM | 930525022 | Robert Granetz | Hybrid demands for Z_CUR feedback look proper, so let's just double the
PID gain on Z_CUR feedback for the next shot |
| May 25 1993 04:44:25:830PM | 930525023 | Robert Granetz | Ip=0.30 MA. Disrupted at 0.095 sec. May be being sucked into the lower
x-point. Try to adjust OH1/OH2 ratio to remain constant. Do this by playing with OH1. Adjust the voltage preprogramming for the next shot. |
| May 25 1993 04:47:13:010PM | 930525023 | Robert Granetz | Oops, I think I programmed the voltage on OH1 in the wrong direction. Oh well,
it wasn't a large change anyway. Too late to change it now. |
| May 25 1993 04:48:04:830PM | 930525024 | Robert Granetz | Nearly identical to the previous shot. For the next shot, adjust OH1 voltage
upward by +250 volts after t=0.050 sec. |
| May 25 1993 05:04:56:960PM | 930525025 | Robert Granetz | Bad shot. Ip=0.2 MA. Plasma disrupted and ended at 0.060 s. It was quite
low. |
| May 25 1993 05:05:50:720PM | 930525025 | Robert Granetz | For the next shot back off on the OH1 voltage change after 0.040 s
|
| May 25 1993 05:10:09:120PM | 930525026 | Robert Granetz | Ip=0.3 MA Sawtoothing. Disrupted at 0.112 s.
|
| Physics Operator Comments |
| Engineering Operator Comments | ||||
| Shot | Time | Type | Status | Comment |
| 1 | 09:32:36:960AM | Plasma | Ok | oh2l current ripple of 2ka, 20ka plasma |
| 2 | 10:08:50:280AM | Plasma | Ok | oh2l gate missing probable nothing found, will try another shot then che |
| 3 | 10:32:33:820AM | Plasma | Ok | Bad Gate OH2 L, fixed |
| 4 | 11:00:03:960AM | Plasma | Ok | oh2l not synchronized with state pc, resync'ed |
| 5 | 11:09:45:580AM | Plasma | Ok | oh2l comm fault |
| 6 | 11:59:25:440AM | Plasma | Ok | 60ka plasma, oh1 |
| 7 | 12:10:09:990PM | Plasma | Ok | 220ka-good plasma again!! |
| 8 | 12:32:39:810PM | Plasma | Ok | 20KA |
| 9 | 12:40:06:510PM | Plasma | Ok | 30KA PLASMA |
| 10 | 12:52:49:800PM | Plasma | Ok | 90KA |
| 11 | 01:10:36:370PM | Plasma | Ok | 110KA PLASMA |
| 12 | 01:27:14:870PM | Plasma | Ok | 240KA PLASMA |
| 13 | 01:42:16:830PM | Plasma | Ok | 230KA PLASMA |
| 14 | 01:59:27:500PM | Plasma | Ok | 240KA |
| 15 | 02:17:10:230PM | Plasma | Ok | 240KA PLASMA |
| 16 | 02:35:48:170PM | Plasma | Ok | 280KA PLASMA |
| 17 | 02:52:57:030PM | Plasma | Ok | 320KA PLASMA |
| 18 | 03:07:47:230PM | Plasma | Ok | 300KA PLASMA-- FAULTS IN EF1,OH1 |
| 19 | 03:20:47:210PM | Plasma | Ok | 350KA PLASMA |
| 20 | 03:39:06:760PM | Plasma | Ok | 80KA PLASMA |
| 21 | 03:48:53:930PM | Plasma | Ok | 70KA OH1 COMM FAULT |
| 22 | 04:03:20:620PM | Plasma | Ok | 360KA PLASMA |
| 23 | 04:18:09:960PM | Plasma | Ok | 300KA PLASMA |
| 24 | 04:41:17:840PM | Plasma | Ok | 320KA PLASMA |
| 25 | 04:50:42:240PM | Plasma | Ok | 220KA PLASMA |
| 26 | 05:05:17:330PM | Plasma | Ok | 310KA PLASMA |