| Miniproposals | ||||||||||
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| Operators | |
| Session leader(s): | Andrea Schmidt |
| Physics operator(s): | Bill Rowan |
| Engineering operator(s): | Bill Cochran,Andy Pfeiffer,Bill Byford |
| Engineering Operator Run Comment |
| Continuation of MP 468 (LH Modulation) |
| Session Leader Plans |
| Entered: Aug 30 2010 11:44:41:840AM |
| Author: Andrea Schmidt |
| Continuation of MP 468 (LH Modulation)
1) Try to establish good coupling for high-current condition (1000 kA, nl04=5e19, 146 deg phasing), at constant power. Start by calling up shot 1100825030 (reduce outer gap if possible). Launch 90 deg phasing, constant power for first shot. Attenuators will already be in on problem legs of LH system. Bring power and phasing up slowly, adjusting launcher position and outer gap as needed to obtain good coupling at 145 deg phasing. 2) Try modulated waveform into plasma using same scheme used on 8/25. Obtain 6 clean discharges at these conditions. |
| Physics Operators Plans |
| Entered: Aug 30 2010 01:32:45:120PM |
| Author: Bill Rowan |
|
Engineering setup and Physop plan for 1100831, Wednesday, August 31, 2010 MP 498, LH-driven fast electron diffusion time measurement. SL:Schmidt As time is available, continue with MP612, -Expanded exploration of LHCD Density Limit, SL: Wallace ----------------- Engineering Setup ----------------- Run begins at 09:00 and ends at 17:00 Power systems as on: 1100825030 Acoil: +Dtop -Dbot -Jtop +Jbot (standard) Hybrid Enabled Gas setup: Fill B-Top with 6 psi D2 Hybrid enabled (PG4) fill B-side lower with 1 psi Ar Hybrid DISABLED (PG1) leave B-side upper as is Hybrid DISABLED (PG2) fill B-main (C-side) with 40 psi D2 Hybrid enabled (PG3) fill NINJA with 10 psi D2 DISABLED Enable gate-valves and shutters: ECE, VUV, HiREX Sr, Xeus Leave z-bolo shutter as is (should be open) Torvac gatevalve toggle (yes/no): no Boronization(yes/no): no Overnight ECDC (yes/no): yes ICRF(yes/no): no LH(yes/no): yes Cryopump (yes/no): not for the first shot but for later in the day when we get to MP 612 DNB (yes/no): yes Vessel temperature: 35/35/35 ------------------------------ ECDC Parameters (if requested) ------------------------------ gas and pressure: D2 at 2e-4 Torr sweep: 44/45/103 cm scan: 20/120 s ------------------------------ Physop Plan ------------------------------ Start from the 1100825030 Optimize the LH coupling by varying the outer gap and possibly the x-point position following approximately the procedure used to develop the first successful condition on 1100825. Use LH probes as guides. SL requests Particular care in maintaining nl_04 flat Attempt to reduce the outer gap |
| Session Leader Summaries |
| Entered: Sep 1 2010 01:44:42:753PM |
| Author: Andrea Schmidt |
| Continuation of MP 468 (LH Modulation)
In the first half of the day, we successfully established good coupling to the high phasing desired. We had 3 discharges at the exact conditions desired, the first one of which we lost the HXR data due to a digitizer error. Starting on shot 15, we got a locked mode followed by a disruption on every single shot for the rest of the day. The locked mode appeared to be LH-induced (when LH was delayed, locked mode was delayed by the same amount). Even when the plasma did not disrupt during the LH pulse, the locked mode appeared to fundamentally change the plasma such that HXR data obtained after the start of the locked mode should be excluded from the analysis. For the second half of the day, we tried multiple methods to get rid of the locked mode: increasing the outer gap, raising the bulk density, lowering LH phasing, lowering LH power, and changing the A coil current (we also went back to shot 14, the last shot with no disruption, several times). None of these methods eliminated the locked mode. The end result is that we got 2 shots at the desired plasma conditions that ran all the way through and many more shots from which perhaps some hxr data can be used. The mechanism through which LH causes locked modes and the way to avoid them is unclear. |
| Physics Operator Summaries |
| Entered: Sep 1 2010 10:22:50:940AM |
| Author: Steve Scott |
| Executive summary: This was a frustrating run due to a large number of locked modes that led to disruptions during the current flattop. We were attempting 1.0 MA at low density (ideally NeL04=5.e19 m^-2). There is good evidence that injecting Lower Hybrid power is correlated with the onset of the locked modes. We tried a variety of measures to eliminate the locked modes including:
a. increase plasma density b. increase outer gap c. increase toroidal field d. adjust offset in A-coil e. change position of LH grill f. reduce LH power g. change LH phase h. moved lower X-point inward but nothing seemed to have a pronounced effect on the occurence of locked modes. For reasons that remain unclear, shots 12, 13 and 14 were free of locked modes during the Ip flattop and these were good shots for Andrea. We tried returning to the "physop conditions" of shot 14 later in the day, but these repeat-shots suffered from locked modes during the Ip flattop. Inner-wall tile problem: we did not see much light coming from the problematic inner-wall tile, and no disruptions were caused by it. In the table below, "none" under "locked" column means no locked mode before the start of the Ip rampdown at 1.4 sec. Shot locked disr ---LH--- comment pwr start 1 gas puff test 2 gas puff test 3 none none fuzzy load from 1100825030 with some changes 4 none none fuzzy decrease outer gap by 1.0 mm 5 ~1.52 none fuzzy no changes 6 0.85 1.49 200 0.80 decrease outer gap another 1.0 mm 7 0.83 0.94 150+ 0.80 LH ramps from 150 to 400 8 0.85 1.02 150+ 0.80 decrease outer gap another 1.0mm 9 1.67 none mod 0.80 increase outer gap 1mm; increase NeL start modulation of LH power 10 DUD - EF1 commutation problem decrease NeL demand to 5.25e19 11 1.075 1.46 mod 0.80 no changes from shot 10 12 none none mod 0.80 increase outer gap 1.0mm 13 none none mod 0.80 no changes from previous shot 14 1.275 none mod 0.80 no changes from previous shot 15 0.84 1.50 mod 0.80 no changes from previous shot 16 0.87? 0.90 mod 0.80 no changes from previous shot 17 0.83? 0.95 mod 0.80 increase NeL04 demand to 5.5e19 18 0.85? 0.99 mod 0.80 increase NeL04 demand to 6.0e19 19 0.84? 0.91 mod 0.80 increase outer gap by 1.0mm 20 0.94? 1.01 mod 0.80 decrease RXL by 1.0 cm 21 1.02 1.15 mod 1.00 reload shot 14 and delay start of LH Note that timing of locked mode seems to follow the change in start time of LH 22 ?? 1.02 mod 0.80 LH changed phasing 23 0.90 1.46 mod 0.80 increase outer gap by 5 mm 24 0.95 1.00 mod 0.80 reload shot 14, then increase BT to 5.8 Tesla 25 0.89 1.50 mod 0.80 BT to 6.1 T and decrease RCUR by 2.5mm 26 1.08 1.54 mod 0.80 re-position LH grill. "only a little LH" 27 0.83 0.94 mod 0.80 reload shot 14. 28 0.94 1.54 mod 0.80 *** OFFSET +0.0001 to B21_PROJ *** also, reduced LH power 29 1.01 1.49 mod 0.80 *** OFFSET +0.0002 to B21_PROJ *** 30 0.93 1.46 mod 0.80 *** OFFSET +0.0003 to B21_PROJ *** 31 0.84 1.50 mod 0.80 *** OFFSET +0.0002 to B21_PROJ *** Shot statistics Test shots 2 Duds 1 (EF1 commutation problem) Fizzles 0 Plasmas 28 |
| Session Leader Comments | |||
| Aug 31 2010 11:20:52:870AM | 1100831008 | Andrea Schmidt | Another disruption. It is unclear whether LH is playing a role in the disruptions. Next shot we will try modulation and bring phasing up to 145 deg. Hopefully the lower average power will help things. |
| Aug 31 2010 11:21:57:603AM | 1100831009 | Andrea Schmidt | Plasma ran clean, so did LH. Density and outer gap were increased for this shot. Will try to bring the density back down a little bit for next shot. |
| Aug 31 2010 11:20:17:340AM | 1100831010 | Andrea Schmidt | No plasma. Try again. |
| Aug 31 2010 12:29:18:437PM | 1100831011 | Andrea Schmidt | Plasma ran clean, LH ran clean. Lock mode showed up half way through LH. Increasing outer gap for next shot. |
| Aug 31 2010 12:30:03:647PM | 1100831012 | Andrea Schmidt | Excellent plasma, no LH trips. Unfortunately HXR digitizers hung and we were unable to recover the data. Try again. |
| Aug 31 2010 12:35:08:320PM | 1100831013 | Andrea Schmidt | Another excellent shot. Repeat. |
| Aug 31 2010 12:52:24:600PM | 1100831014 | Andrea Schmidt | Another excellent shot. Repeat. |
| Aug 31 2010 01:13:06:430PM | 1100831015 | Andrea Schmidt | LH trips continuously. Late disruption (after LH). Lock mode appears after 0.8 seconds. Try same plasma again. |
| Aug 31 2010 01:23:18:263PM | 1100831015 | Andrea Schmidt | LH ran until disruption at .9 s. Bringing density up slightly for next shot. |
| Aug 31 2010 01:51:59:130PM | 1100831016 | Andrea Schmidt | Another disruption at 0.9 s. |
| Aug 31 2010 01:50:12:923PM | 1100831017 | Andrea Schmidt | Another disruption. Bring the density up a litle more for next shot. |
| Aug 31 2010 01:50:46:883PM | 1100831018 | Andrea Schmidt | Another disruption. We will try to increase outer gap for next shot to see if that helps (it did earlier today). |
| Aug 31 2010 02:09:14:690PM | 1100831019 | Andrea Schmidt | Another disruption. We are going to move the lower x-point in by 1 cm for the next shot. |
| Aug 31 2010 02:42:48:170PM | 1100831020 | Andrea Schmidt | Another disruption. For the next shot we are going back to shot 14 parameters and moving LH later in the pulse to see if it is causing locked mode. |
| Aug 31 2010 02:43:44:053PM | 1100831021 | Andrea Schmidt | Locked mode followed LH turn on to later time. We will be lowering the phasing for the next shot to see if a different damping location helps. |
| Aug 31 2010 02:54:43:893PM | 1100831022 | Andrea Schmidt | At lower phasing, plasma still disrupted. We will increase out gap significantly (by 5 mm) and lower power because at lower phasing, reflections are much lower. |
| Aug 31 2010 03:06:13:000PM | 1100831023 | Andrea Schmidt | Bigger gap did not prevent locked mode. For next shot, we will go back to 145 degree phasing, shot 14 plasma conditions, but raise the field to 6 T. |
| Aug 31 2010 04:40:56:240PM | 1100831027 | Andrea Schmidt | Another lock mode/disruption. Lowering LH power and changing A coil current for next shot. |
| Aug 31 2010 04:42:30:747PM | 1100831028 | Andrea Schmidt | Another lock mode/disruption, seemed delayed by A coil current change. Changing A coil current more for next shot. |
| Aug 31 2010 04:42:47:277PM | 1100831029 | Andrea Schmidt | Another lock mode/disruption, seemed delayed by A coil current change again. Changing A coil current more for next shot. |
| Aug 31 2010 05:08:14:550PM | 1100831030 | Andrea Schmidt | Lock mode/disruption onset earlier. Going back to A coil configuration from shot 29 for next shot. |
| Aug 31 2010 05:08:42:190PM | 1100831031 | Andrea Schmidt | Lock mode/disruption at .86 s (very early). End of run. |
| Physics Operator Comments | |||
| Aug 31 2010 07:51:29:857AM | 1100831001 | Steve Scott | standard tue morning gas valve test. not particularly successful. so try again |
| Aug 31 2010 07:51:48:757AM | 1100831002 | Steve Scott | 2nd gas puff test. successful |
| Aug 31 2010 08:08:08:440AM | 1100831003 | Bill Rowan | loaded from shot 1100825030. then imported segment 1 from shot
1100827030 and reduced prefill to 23 ms (-0.523 --> -0.500). |
| Aug 31 2010 08:34:29:210AM | 1100831003 | Bill Rowan | NNIJA disabled on engineering screens but left ON on local control.
Plan calls for NINJA to be off so we turned it off prior to shot 3 |
| Aug 31 2010 09:08:02:330AM | 1100831003 | Bill Rowan | RESULT: good plasma at 1.0 MA. The density (Nl04=6.e19) is a little higher
than desired (5.e19) but we will assume that the density will drop a little on the next shot ... no adjustment of gas puff |
| Aug 31 2010 09:11:32:393AM | 1100831004 | Bill Rowan | CHANGE: increase RCUR by 0.5mm during flattop in order to decrease
outer gap by 1mm. |
| Aug 31 2010 09:35:29:797AM | 1100831004 | Bill Rowan | There was a small bounce at t=12 ms but we choose to make no adjustments |
| Aug 31 2010 09:39:27:387AM | 1100831005 | Bill Rowan | CHANGES: no physOp changes from previous shot |
| Aug 31 2010 09:50:22:980AM | 1100831005 | Bill Rowan | There seems to be a locked mode creeping back from the end of the discharge,
maybe starting at 1.52 sec. But we'll make no adjustment for the next shot |
| Aug 31 2010 10:10:24:613AM | 1100831006 | Bill Rowan | RESULT: small prad burst at 0.8 sec, at time of start of LH.
Got a locked mode at 0.85 sec that quickly led to a disruption |
| Aug 31 2010 10:15:45:173AM | 1100831006 | Bill Rowan | CHANGE: increase RCUR by 0.5mm in order to decrease outer gap by 1.0 mm. This change applied during time period 0.37 to circa 1.5 sec.
RESULT: outer gap varies from 2 to 3 mm. |
| Aug 31 2010 10:21:00:290AM | 1100831007 | Bill Rowan | CHANGES: no physOp changes. LH will change phasing. Will pray for elimination of the locked mode.
RESULT: disrupted at 0.935 second. There is a prad burst at 0.78 which precedes the start of LH. |
| Aug 31 2010 10:53:27:243AM | 1100831008 | Bill Rowan | CHANGES: decrease RCUR by 0.5 mm in order to increase outer gap by 1.0mm
RESULT: disrupted at 1.02 sec. looks like locked mode starting 0.85 sec. there is some light at the top of the divertor shelf. Maybe we need to think about moving the lower x-point in a little. Will remain at the present x-point location for the next shot. |
| Aug 31 2010 11:07:48:913AM | 1100831009 | Bill Rowan | CHANGES: increase Nel to 6.e19 and increase outer gap by 1 mm
RESULT: full length shot. locked mode not until 1.67 sec. Beware: there is an appearance of large sawteeth during LH, which I think is really just the effect of modulated LH on the electron temperature |
| Aug 31 2010 11:11:50:583AM | 1100831010 | Bill Rowan | CHANGES: Decrease flattop Nel demand to 5.25e19. Also, we have slightly decreased the early density ramp rate, hoping to decrease the size of the
early fluctuations in NeL. RESULT: EF1 early commutation problem. DUD. |
| Aug 31 2010 11:45:15:707AM | 1100831011 | Bill Rowan | No changes from the previous dud.
result: shot lasts into rampdown, but just a little. also, there is a locked mode starting at 1.07 sec, so although we didn't get quite the density that we asked for (asked for 5.25, got 5.6) we will make no density adjustments on the next shot. disrupted at 1.465 sec |
| Aug 31 2010 11:56:58:847AM | 1100831012 | Bill Rowan | CHANGES: decrease rcur by 0.5 mm in order to increase outer gap by 1.0 mm
RESULT: full length shot. However, I don't see much difference in the actual outer gap between shot 12 and the previous shot. Maybe operator error? |
| Aug 31 2010 11:58:07:407AM | 1100831013 | Bill Rowan | CHANGES: None. Andrea is happy with conditions that obtained on the previous shot. |
| Aug 31 2010 12:32:30:733PM | 1100831013 | Steve Scott | RESULT: after a delay to recover the LH-related data from shot 12 (ultimately unsuccessful) ... full length shot. No evidence of locked modes. NeL04 pretty
good at 5.35e19. |
| Aug 31 2010 12:50:58:447PM | 1100831014 | Steve Scott | CHANGES: none from previous shot.
RESULT: full length shot, very similar to shot 13. |
| Aug 31 2010 01:13:40:290PM | 1100831015 | Steve Scott | CHANGES: none. SL is happy.
RESULT: shot survived a little way into rampdown (1.5 sec). According to Steve Wolfe, this shot locked at 0.84. Although there was no difference in Nel programming, this shot got about 5.e18 less Nel than shot 14, which may have caused the locked mode. But in addition, the LH did not fire properly. So maybe we would have survived if the LH had fired properly. Decision: no changes for next shot. |
| Aug 31 2010 01:23:59:320PM | 1100831016 | Steve Scott | CHANGES: none.
RESULT: got about the same density at start of LH as previous shot. disrupted at 0.9 sec. So it looks like we just don't have enough density. Increase NeL demand for the next shot. |
| Aug 31 2010 01:24:23:947PM | 1100831017 | Steve Scott | CHANGES: increase NeL04 demand to 5.5e19 during flattop. |
| Aug 31 2010 01:51:40:923PM | 1100831018 | Steve Scott | CHANGE: increase NeL04 demand from 5.5e19 to 6.0e19 this shot (during flattop).
RESULT: disrupted at 1.0 sec. |
| Aug 31 2010 02:08:26:633PM | 1100831019 | Steve Scott | CHANGE: decreased RCUR by 0.5mm --> increase outer gap by 1.0 mm
Result: still disrupted early |
| Aug 31 2010 02:26:02:840PM | 1100831020 | Steve Scott | CHANGE: decrease RXL by 1.0 cm (radial position of lower X-point)
RESULT: (sigh). disrupted 1.01 seconds We did get the demanded change in R_XL i.e. it decreased about 1.0 cm relative to the previous shot |
| Aug 31 2010 02:35:02:340PM | 1100831021 | Steve Scott | CHANGE: we're so happy with recent progress that we're reloading shot 14. Also, LH changed its start time to 1.0 sec.
RESULT: disrupted 1.14. Wolfe: "The locked mode follows the LH like a faithful dog", i.e. locked mode moved from 0.84 to 1.02 sec. Tentative conclusion: LH is doing something to influence the current profile at a rational q-surface. Maybe we should change the LH phasing or its power |
| Aug 31 2010 02:45:44:543PM | 1100831022 | Steve Scott | CHANGES: no physOp changes. LH will change the phasing. We may also choose to sacrifice a goat. LH start time returned to 0.8 sec.
Result: disrupted at 1.01 seconds. |
| Aug 31 2010 03:00:31:607PM | 1100831023 | Steve Scott | CHANGE: make a more substantial change to RCUR (decrease by 2.5mm) which corresponds to a 5mm increase in the outer gap.
RESULT: some progress. disruption delayed until 1.46 sec, which is just after the start of the Ip rampdown. Locked mode started at t=0.9 seconds. |
| Aug 31 2010 03:37:00:737PM | 1100831024 | Steve Scott | CHANGES: reload shot 14 from today, but raise TF to 6.0 Tesla
RESULT: disrupted at 1.0 sec. Also, there seems to have been some operator error: got only 5.8 Tesla. raise TF next shot. Locked mode starts circa 0.95 sec. |
| Aug 31 2010 03:27:42:417PM | 1100831025 | Steve Scott | CHANGES: raise TF from 5.8 to 6.2 Tesla and decrease RCUR by 2.5mm |
| Aug 31 2010 03:49:09:500PM | 1100831026 | Steve Scott | CHANGES: no physop changes. LH may re-position the grill
RESULT: disrupted in rampdown, circa 1.54 seconds. Only a little LH. |
| Aug 31 2010 03:58:42:520PM | 1100831027 | Steve Scott | CHANGES: reload shot 14. No physop changes from shot 14. LH may choose to reduce its power. |
| Aug 31 2010 04:28:18:470PM | 1100831028 | Steve Scott | CHANGE: add offset of +0.0001 to B21_PROJ. Also, LH promises to reduce its power.
RESULT: disrupted 1.54 sec. locked mode at: 0.94 sec ... this is a little better than in previous shots. Discussion: is this due to the lower LH power or to the change in A-coil? We decided to investigate effect of acoil offset on next shot. |
| Aug 31 2010 04:37:11:320PM | 1100831029 | Steve Scott | CHANGE: increase B21_PROJ to 0.0002 Tesla (i.e. an increase of 0.0001 from value on previous shot)
RESULT: disrupted 1.49 and locked mode delayed until 1.01 |
| Aug 31 2010 04:51:45:567PM | 1100831030 | Steve Scott | CHANGE: increase offset on A-COIL (B21_PROJ) from 0.0002 to 0.0003 Tesla.
RESULT: disrupted at 1.46, locked mode at 0.93. so this seems to be a little worse than previous shot. So on next shot,return offset on Acoil back to 0.0002 |
| Aug 31 2010 05:06:04:750PM | 1100831031 | Steve Scott | CHANGES: set offset on Acoil (B21_PROJ) back to 0.0002.
RESULT: Locked mode moved earlier to circa 0.84, but disruption delayed until after 1.5 sec. ----- end of day -------------- |
| Engineering Operator Comments | ||||
| Shot | Time | Type | Status | Comment |
| 1 | 07:13:43:520AM | Test | Ok | Gas System Test |
| 2 | 07:21:19:673AM | Test | Ok | Gas System Test |
| 3 | 09:00:00:990AM | Plasma | Ok | |
| 4 | 09:23:17:683AM | Plasma | Ok | |
| 5 | 09:40:35:420AM | Plasma | Ok | |
| 6 | 09:58:47:480AM | Plasma | Ok | |
| 7 | 10:15:58:620AM | Plasma | Ok | |
| 8 | 10:30:59:890AM | Plasma | Ok | |
| 9 | 10:54:42:167AM | Plasma | Ok | |
| 10 | 11:08:50:710AM | Plasma | Ok | |
| 11 | 11:21:40:400AM | Plasma | Ok | |
| 12 | 11:50:46:097AM | Plasma | Ok | |
| 13 | 12:27:14:530PM | Plasma | Ok | |
| 14 | 12:46:29:413PM | Plasma | Ok | |
| 15 | 12:59:39:877PM | Plasma | Ok | |
| 16 | 01:17:10:123PM | Plasma | Ok | |
| 17 | 01:30:00:100PM | Plasma | Ok | |
| 18 | 01:43:05:593PM | Plasma | Ok | |
| 19 | 01:55:54:893PM | Plasma | Ok | |
| 20 | 02:10:23:850PM | Plasma | Ok | |
| 21 | 02:29:27:337PM | Plasma | Ok | |
| 22 | 02:42:23:840PM | Plasma | Ok | |
| 23 | 02:55:30:257PM | Plasma | Ok | |
| 24 | 03:13:47:070PM | Plasma | Ok | |
| 25 | 03:27:57:487PM | Plasma | Ok | |
| 26 | 03:46:07:767PM | Plasma | Ok | |
| 27 | 04:01:44:487PM | Plasma | Ok | |
| 28 | 04:16:21:853PM | Plasma | Ok | |
| 29 | 04:33:17:843PM | Plasma | Ok | |
| 30 | 04:47:05:530PM | Plasma | Ok | |
| 31 | 05:01:41:803PM | Plasma | Ok | |
| System Availability | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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