| Miniproposals | ||||||||||||
|
| Operators | |
| Session leader(s): | Robert Granetz,Steve Wolfe |
| Physics operator(s): | Earl Marmar |
| Engineering operator(s): | Joe Daigle |
| Engineering Operator Run Comment |
| closed loop, icrf tuning |
| Session Leader Plans |
| Physics Operators Plans |
| Session Leader Summaries |
| Entered: Jul 7 2004 03:49:10:007PM |
| Author: To Be Determined |
| Part II of Run Summary for 940519 (Bob Granetz will write up part I, containing most of the good news) SL: Wolfe PO: Marmar EO: Daigle Miniproposal 41 - Restart C-MOD Granetz turned over the run to me at around 13:30, after shot 8. Things had been going well, about six good shots in a row; somehow he managed to sabotage things before I even sat down. Shot 9, which had already been set up and differed from shot 8 only by changes after 0.6 sec, fizzled. Following this inauspicious beginning, we floundered for a few shots, some of which were actually duds, the first of theday. Shot 14 ran until 530msec, then was lost down. This shot, like earlier shots, was programmed to be at ZCUR=0.0, but in fact bothe xrays and EFIT claimed it was at -2cm. The Hybrid Aout claimed it was centered. Apparently, there was a problem with the ZCUR predictor. Ignoring the ZCUR problem for the moment, since we couldn't find any bad magnetics by inspection, we tried getting rid of some of the IC controllers which were fighting the shape controllers. Specifically, we turned off the gain on IC_EF1L and IC_EF2L after .2sec, when ZXL and RXL turned on. RXL was running inside and did not appear well-controlled. The next several shots were failures of one flavor or another. For shot 21 I decided to bite the bullet and work on the null. I made the EF1 currents 300 amps more positive to try to reverse the Bz gradient and provide a stable index during the current rise. Amazingly, this worked, and shot 21 ran through 700msec. The null was only there briefly, because we did not compensate for the Bz increase, but it broke down and the current rise was good. On shot 22, we attempted to compensate the Bz, but may have overdone it; the shot fizzled. Shot 23 was a reload of shot 21, and ran well until 530msec. Both shots 21 and 23 had the same ZCUR problem as shot 14, namely the hybrid thought they were centered when the xrays and EFIT thought they were low by at least 2cm. After the run, the problem with ZCUR predictor on the later shots was investigated. It turns out that BP17_DE went bad sometime between shots 8 and 14, possibly right at the end of shot 8. This failure is insidious, in that on shot 14 at least the signal comes back to zero at the end of the shot, but is wrong (relative to BP17_JK, aka the processed flux) by up to .15 Tesla during flattop. This was found by direct comparison of all of the BP inputs to the hybrid, with BTOR_PICKUP*\BTOR subtracted, to the corresponding JK loops. Since BP17_DE was installed last year as a replacement for BP17_BC, it will be necessary to replace it with the JK loop (or the GH, provided we reconnect it to CAMAC). Essentially no progress on the miniproposal was made during the second half of the run, although turning off the superfluous IC_EF1L and IC_EF2L controls is logically a good thing, and seemed to do no harm. The null with the EF1's more positive is a step in the direction of more stable breakdowns and current rises, I believe, but it needs some additional tweaking up. The Bz is presently too positive, and the index may actually be a bit too positive during the early rise phase. The plasma is still fat and riding the inner limiter until after 0.5 sec. CLEARIN does not seem to be working correctly when turned on early. RXL is too far inside and did not seem well controlled. ZXL is close to where it is being commanded, which is somewhat too high for good matching to the divertor. The elongations get quite high with the plasma centered if we allow the xpoint height to be correct. It may be that xpoint control will improve when BP17 is replaced with a working signal, but the RXL control didn't seem to be working earlier in the run either. |
| Entered: Jul 7 2004 03:49:10:180PM |
| Author: To Be Determined |
| Part I of Run Summary for 940519 SL: Granetz/Wolfe PO: Marmar EO: Daigle Miniproposal 41 - Restart C-MOD The first half of this run was more successful than prior runs this week. We had 8 shots, 6 of which had plasma currents of more than 0.8 MA. Most of these lasted to at least 0.7 s, with one actually getting part way down the current rampdown before disrupting. There sometimes is a position control problem early in the plasma formation (25-50 ms). It kills the proto-plasma on shots which have a relatively slower current rise. So far the only way around this is to have a clean enough machine so that dIp/dt is not slowed down. Obviously not very satisfactory. There was a problem with blown SCR's and a failed gate-driver board in EF2L, which was discovered after the first couple of shots, but which probably had been bad since April. The first two plasmas that we got both disrupted due to excessive elongation. This probably was caused by CLEARIN feedback on the OH2's, and is not understood. By delaying CLEARIN feedback until after 0.6 s, we managed to get longer shots. The best shots (6,7,8) were diverted after 0.5 s and were centered on the midplane, which is required for matching to the antennas. The programmed position of the x-point was pushed outward in major radius on successive shots, and this seems to be working, for the most part, although RXL is still not as far out as we'd like. During the second half of the run, it was discovered that 2 Bp coils became flaky. These both are connected at D-bottom port, which is the other flange that was re-installed during my absence last March. It is very likely that those connectors were also not properly screwed on, just like at B-bottom. |
| Physics Operator Summaries |
| Session Leader Comments | |||
| May 19 1994 06:26:39:980PM | Steve Wolfe | We have another bad bp-coil hooked to the hybrid, and this time it's a DE loop.
BP17_DE went bad sometime during the run today. Furthermore, you can't tell from looking at the reset; it is bad during the shot and comes back to zero. I found it by direct comparison with BP17_JK, after subtracting the BTOR_PICKUPs from each. On shot 14, which ended up 2cm low despite the fact that ZCUR said it was centered, the BP17_DE (corrected by BTOR_PICKUP) goes to -.6T during flattop, while BP17_JK (similarly corrected, identical to processed BP_16) goes to -.75, a discrepancy of 0.15 Tesla. On this shot both signals come back to zero, within 10mT. On shot 8, which actually was centered, the two signals overlay perfectly during the shot, both getting to about -.75T, but the DE loop has about a .1Tesla offset at the end of the shot. We (Bob) need to fix this before tomorrow's run. I suppose we'll have to use the JK loop, unless we want to reconnect the GH loop to CAMAC. Note that BP17_xx is on the outer shelf, right next to the crandulated flux loop. Maybe there's a connection, maybe not, but we clearly need this coil to help make up for the lack of F17. We are still losing magnetics at an alarming rate. This one is presumably on a different port, and may not be related to connector problems at all, but it could be. Perhaps Bob's thumbs should be re-lengthened. | |
| May 19 1994 09:28:33:180AM | 940519001 | Robert Granetz | Fizzle, but current started to rise. Ipmax=0.16 MA, duration=.056 s.
Lost vertical control, downward VDE. Rate of current rise was not as fast as yesterday's shot. I think that we do not have adequate feedback control of ZCUR early on. This is not a problem if we have adequate rate of current rise. Next shot, repeat. Also lower the pulse gas a little after 50 ms. Also change pre-fill from 1.2 to 1.1e-5. |
| May 19 1994 10:05:09:480AM | 940519002 | Robert Granetz | Plasma. Higher current. Ip=0.83 MA, duration=0.43 s. Downward VDE. No
halo signals. Elongation got to 1.6 at 0.4 s, so we don't have much chance of handling vertical position in this case. We have to reduce the maximum elongation. The x-point is 5 cm too far inside, and a couple of cm low. Voltage demand to EF2L is behaving properly, but the supply is not responding well. Next shot, raise programmed ZCUR to 0.0 cm (rather than -2 cm), RXL feedback gain is turned on earlier, and ZXL gain is enabled. |
| May 19 1994 10:37:36:340AM | 940519003 | Robert Granetz | Fizzle with some current. Same as shot 001. Lose plasma downward. dIp/dt
was slower than the previous good shot. Problem with EF2L fuses. Will take about an hour to fix. Meanwhile, during a cell access, I found that we had patched the halo signals into Joe Snipes's Aurora camac, rather than the TRAQ's. This has now been remedied for the next shot. |
| May 19 1994 12:09:07:560PM | 940519003 | Robert Granetz | For next shot, RXL and ZXL and CLEARIN gains now turn on at 0.2 s (which is
how it was on the shot from last October. |
| May 19 1994 12:23:32:310PM | 940519004 | Robert Granetz | Plasma, but not as long. Ipmax=0.73 MA, duration=0.32 s. Downward VDE.
Things start to decrapitate starting at 0.20 s, which is when we're turning on CLEARIN, RXL, and ZXL. The problem with EF2L is still there also. Consensus is that CLEARIN is screwing up the OH2's. |
| May 19 1994 12:32:21:070PM | 940519004 | Robert Granetz | Next shot, delay CLEARIN until 0.6 s. Engineers replaced bad gate driver
board in EF2L. |
| May 19 1994 12:54:05:060PM | 940519005 | Robert Granetz | Plasma. Ip=0.85 MA, duration=0.71. Plasma position control was good until
late, when kappa went above 1.6. Plasma was vertically centered, which is what the RF group needs. Clearance to inner and outer divertors was good after 0.5 s. Next shot, add offset to RXL to move it further out, move ZXL farther up by 5 mm, correct EF1U current programming to undo change we made yesterday, and increase pulse gas. |
| May 19 1994 01:11:07:870PM | 940519006 | Robert Granetz | Plasma. Ip=0.85 MA, duration=0.74 s. RXL moved out, but not enough.
Looks like plasma disrupted first, and then the remnants went down. Next shot, increase offset on RXL again, resulting in about another cm farther out. |
| May 19 1994 01:20:23:580PM | 940519007 | Robert Granetz | Plasma, getting better too. Ip=0.85 MA, duration=0.79 s. Current ramped
down to 0.6 MA before it disrupted. Density is dropping alot late in the shot. Next shot, more gas puffing. |
| May 19 1994 01:29:25:050PM | 940519008 | Robert Granetz | Plasma. Ip=0.84 MA, duration=0.75 s. I'm going to hand the reins over to
Steve Wolfe. |
| May 19 1994 01:49:35:760PM | 940519009 | Steve Wolfe | 940519009
---------- Wolfe replaces Granetz as SL Raised controller on Fast ZCUR by a factor of 2, starting at 0.6sec Result: fizzle. Thanks, Bob! |
| May 19 1994 01:58:58:180PM | 940519010 | Steve Wolfe | 940519010
---------- Lower P to 1.0e-5 No other changes Result: dud! |
| May 19 1994 02:09:37:720PM | 940519011 | Steve Wolfe | 940519011
---------- Change Br_0 from -3.0mT to -2.5mT Result: Another dud. Pressure was <1.0e-5 when the shot went |
| May 19 1994 02:28:40:430PM | 940519012 | Steve Wolfe | 940519012
---------- Reload shot 8, just in case something got changed inadvertantly. Result: ------- Early breakdown (5.5msec) Lost it at 65msec, screaming down. Looks like earlier today. |
| May 19 1994 02:46:20:190PM | 940519013 | Steve Wolfe | 940519013
---------- Lower the puff after 400msec, and try again. This worked before!! Result: ------- dud. What the hell is going on. |
| May 19 1994 03:02:45:990PM | 940519014 | Steve Wolfe | 940519014
---------- Raise fill to 1.3e-5 and try it again. Result: ------- Plasma. Lasted till 530msec |
| May 19 1994 03:18:50:910PM | 940519015 | Steve Wolfe | 940519015
---------- Turn IC_EF1L control to zero at .2sec Turn IC_EF2L control to zero at .2sec Result: ------- Fizzle |
| May 19 1994 03:22:40:770PM | 940519016 | Steve Wolfe | 940519016
---------- Lowered pressure to 1.2e-5 Result: ------- Screamer down. |
| May 19 1994 03:35:45:040PM | 940519017 | Steve Wolfe | 940519017
---------- Change Br0 offset from -3 to -2mT Result: ------- Screamer down Lasted till 65msec, 220ka. |
| May 19 1994 03:41:45:950PM | 940519017 | Steve Wolfe | 940519017
---------- Change Br0 offset from -3 to -2mT Result: ------- Screamer down Lasted till 65msec, 220ka. |
| May 19 1994 03:52:25:430PM | 940519018 | Steve Wolfe | 940519018
---------- Leave Br_0 control on until 59msec Result: ------- fizzle. Early breakdown (5.5msec) |
| May 19 1994 04:01:47:730PM | 940519018 | Steve Wolfe | 940519019
---------- lower p to 1.1e-5 Result: ------- fizzle - looks like the last one. |
| May 19 1994 04:01:57:500PM | 940519019 | Steve Wolfe | 940519019
---------- lower p to 1.1e-5 Result: ------- fizzle - looks like the last one. |
| May 19 1994 04:18:03:220PM | 940519020 | Steve Wolfe | 940519020
---------- Change IC_EF1L and IC_EF1U from -4800 to -4500 at commutation. This should give about 20mT/m more negative Bz'. Result: ------- No power supplies? \ENGINEERING::TOP.POWER_SYSTEM was turned off in the tree!!!!! |
| May 19 1994 04:34:23:410PM | 940519021 | Steve Wolfe | 940519021
---------- Change IC_EF1L and IC_EF1U from -4800 to -4500 at commutation. This should give about 30mT/m more negative Bz'. Result: ------- Plasma, lasts till 700msec Early vertical thrash looks (and feels) MUCH BETTER NOW... Breaks down at 6msec The index looks good. Now for the bad news- there is no null after 3msec. RXL is still way in. |
| May 19 1994 04:51:21:070PM | 940519022 | Steve Wolfe | 940519022
---------- Change EF4 from -1020 to -1050A Turn on Argon puff again Result: ------- fizzle- breaks down at 7msec. |
| May 19 1994 06:19:25:830PM | 940519023 | Steve Wolfe | 940519023
---------- Reload 21 Result: ------- PLasma lasts till 500msec. Dies down. |
| Physics Operator Comments |
| Engineering Operator Comments | ||||
| Shot | Time | Type | Status | Comment |
| 1 | 09:07:58:520AM | Plasma | Ok | oh2l + ef1 comm fault |
| 2 | 09:27:29:310AM | Plasma | Ok | no faults |
| 3 | 10:05:53:970AM | Plasma | Bad | ef2l two fuses blown |
| 4 | 12:06:32:340PM | Plasma | Bad | ef2l still has a problem |
| 5 | 12:34:32:890PM | Plasma | Ok | no faults |
| 6 | 12:53:57:140PM | Plasma | Ok | oh1 comm fault after plasma |
| 7 | 01:08:40:700PM | Plasma | Ok | no faults |
| 8 | 01:23:58:720PM | Plasma | Ok | .84 meg amp no faults |
| 9 | 01:39:42:170PM | Plasma | Bad | |
| 10 | 01:50:28:940PM | Plasma | Bad | DUD no faults |
| 11 | 02:03:33:100PM | Plasma | Bad | Dud no faults. |
| 12 | 02:21:14:590PM | Test | Ok | plasma dis oh2l comm fail |
| 13 | 02:34:28:200PM | Test | Bad | dud power sys. O K. |
| 14 | 02:49:44:430PM | Plasma | Ok | good shot no faults |
| 15 | 03:08:21:780PM | Plasma | Bad | DUD NO faults |
| 16 | 03:19:08:480PM | Plasma | Bad | dud No faults |
| 17 | 03:30:15:130PM | Plasma | Ok | comm fault oh2l & ef1U plasma disr. early |
| 18 | 03:43:38:720PM | Plasma | Bad | dud no faults |
| 19 | 03:56:37:830PM | Plasma | Ok | |
| 20 | 04:08:12:400PM | Plasma | Bad | NO shot P.S. off |
| 21 | 04:20:52:520PM | Plasma | Ok | good shot comm fault OH2 L |
| 22 | 04:45:14:620PM | Plasma | Bad | DUD NO faults. |
| 23 | 04:54:48:020PM | Plasma | Ok | Good shot NO faults. |