| Miniproposals | ||||||||||
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| Operators | |
| Session leader(s): | Amanda Hubbard |
| Physics operator(s): | Earl Marmar |
| Engineering operator(s): | Unknown |
| Engineering Operator Run Comment |
| MP#381 JFT2-M shape devel (1/2d) & MP#357 Low freq AMHD; SL:Hubbard/Snip |
| Session Leader Plans |
| Physics Operators Plans |
| Session Leader Summaries |
| Entered: Jul 7 2004 03:49:02:477PM |
| Author: Amanda Hubbard |
Run Summary for 1040128: MP 381 Shape development for joint EDA experiments with JFT2M. Session Leader: Amanda Hubbard Physics Operator: Earl Marmar Purpose: To start the process of shape development for future matching experiments with JFT2M. Goal is to match triangularity and elongation. It is possible that we will be able to start increasing the aspect ratio, though this is likely to require more shots. This will be an ohmic run, since RF is being reconfigured this week. Plan: Starting point: Load waveforms from 1031212011 (ITB delta scan). This shot had delta_u=0.3, and delta_l=0.7, not too far from where we want to go. For first shot, raise Bt to 5.0 T, and Ip to 1.0 MA. For subsequent shots we will want to: - reduce kappa to (or towards) 1.5 (from 1.67) - increase delta_l to 0.87 - reduce delta_u to 0.2 - adjust Ip to give q95=3.2 A shape sent by JFT2M will be used for shot-to-shot comparison (see saveset in /home/wolfe/efit/test/jft2m_97156_00700.sav ) If things go really well and we achieve this, go further and attempt to increase aspect ratio (ie make a very big inner gap) as per MP. Results: The run, which was deliberately started late, made good progress towards the goals. We succeeded in getting quite a good match to the JFT2M shape at our normal aspect ratio. Shot 1040128009 is perhaps the best example, though 10 and 11 were similar. Interestingly, these 5 T, 1 MA plasmas almost all had ohmic H-mode giving quite a low power threshold (P/nBS ~ 0.02). Subsequent discharges attempted to match the significantly higher aspect ratio of JFT2M, which requires a very large inner gap. The controllers did work quite well in this regime. Shot 1040128019 was the best, non disruptive, example with close to the right central position and vertical extent. However, the elongation was too low (1.3 vs 1.55). Attempts to reduce the minor radius (shots 20-22) resulted in early disruptions. It is not clear whether this is a fundamental limitation in the C-Mod control capability, though it is clear that such discharges are not easy to make! |
| Physics Operator Summaries |
| Entered: Jul 7 2004 04:36:48:880PM |
| Author: Earl Marmar |
| MP 381 Shape development for joint EDA experiments with JFT2-M SL: Hubbard PO: Marmar Start from 1031212011, Ip to 1 MA, Bt to 5.0 T Tweak from there to get JFT-2M poloidal shape at C-Mod normal aspect ratio Then go to JFT2-M aspect ratio Note that there was an air leak into the machine yesterday (up to .2 Torr for a while) ECDC and bake yesterday afternoon and overnight, stopping at about 11:00 am. The run started at noon, and ended at 5:00 pm. Results: The machine ran well today. Cleanliness was not a problem.in spite of the air leak yesterday, H/D was low throughout the day. The shots were ohmic only, with no ICRF. We made significant progress on the MP. This was a real wire-head run, calling for unusual shapes, especially for the second half of the MP. We came pretty close to the JFT2-M poloidal shape at the C-Mod aspect ratio (see shot 11), not as close at the JFT2-M aspect ratio (shot 19 was probably the best). The former had ohmic H-modes (5 Tesla, 1 MA), even at quite high density. The latter were very touchy, mostly disrupting early, and tended toward outboard limited. Getting a large enough inner gap seems to be the biggest challenge, although x-point control is also difficult. EF2-lower went to 0 on a number of shots, leading to loss of vertical control in some cases. Many PCS factors had to be changed, along with time constants, to keep within limits for a number of wires (RCUR, CLEARIN, RXL, ZXL, EF2 by EF4). There were 5 fizzles, at least some because BR0 drifted a bit positive. Scorecard: 17 plasmas 5 fizzles 22 data cycles. |
| Session Leader Comments | |||
| Jan 28 2004 12:57:35:153PM | Amanda Hubbard | Run Plan for 1040128: MP 381 Shape development for joint EDA experiments with JFT2M. Purpose: To start the process of shape development for future matching experiments with JFT2M. Goal is to match triangularity and elongation. It is possible that we will be able to start increasing the aspect ratio, though this is likely to require more shots. This will be an ohmic run, since RF is being reconfigured this week. Starting point: Load waveforms from 1031212011 (ITB delta scan). This shot had delta_u=0.3, and delta_l=0.7, not too far from where we want to go. For first shot, raise Bt to 5.0 T, and Ip to 1.0 MA. For subsequent shots we will want to: - reduce kappa to (or towards) 1.5 (from 1.67) - increase delta_l to 0.87 - reduce delta_u to 0.2 - adjust Ip to give q95=3.2 A shape sent by JFT2M will be used for shot-to-shot comparison (see saveset in /home/wolfe/efit/test/jft2m_97156_00700.sav ) If things go really well and we achieve this, go further and attempt to increase aspect ratio (ie make a very big inner gap) as per MP. | |
| Jan 28 2004 12:56:35:197PM | 1040128004 | Amanda Hubbard | Shape getting pretty close, top half matches JFT2M well. Bottom needs x-pt up and in. Still ohmic H-modes. |
| Jan 28 2004 02:16:19:077PM | 1040128009 | Amanda Hubbard | This shot has fairly good match to JFT2M shape, except for the squareness in lower outside quadrant. Still H-modes, even though we raised nel. |
| Jan 28 2004 02:33:26:740PM | 1040128011 | Amanda Hubbard | Similar shape, stayed in L-mode at high nel (~ 1.5e20). This is probably the best shape match we can get. q95=3.05; would reduce Ip to 950 kA to get q=3.2 Next, try to increase aspect ratio.... |
| Jan 28 2004 03:21:33:527PM | 1040128014 | Amanda Hubbard | Got small plasma, went limited on outside. Good first step. |
| Jan 28 2004 04:32:29:063PM | 1040128019 | Amanda Hubbard | This is the best plasma so far. Stays diverted to ~ 1 sec, about right R0, height. amin still too large; kappa 1.35, 340 kA. |
| Physics Operator Comments | |||
| Jan 28 2004 11:58:08:613AM | Earl Marmar | MP 381 Shape development for joint EDA experiments with JFT2-M SL: Hubbard Start from 1031212011, Ip to 1 MA, Bt to 5.0 T Tweak from there to get JFT-2M poloidal shape at C-Mod normal aspect ratio Then go to JFT2-M aspect ratio Note that there was an air leak into the machine yesterday (up to .2 Torr for a while) ECDC and bake yesterday afternoon and overnight | |
| Jan 28 2004 12:12:51:337PM | 1040128001 | Earl Marmar | load from 1031212011 load segment 1 from 1040127002 increase Ip to 1 MA increase nl_04 demand to 9e19 increase flattop TF to -136 kA (5 T) Base pressure 2.3e-7 before the shot Plasma, full length |
| Jan 28 2004 12:23:55:067PM | 1040128002 | Earl Marmar | lower ZCUR to -2.5 cm during flattop tweak early Ip ramp to get rid of current lurch plasma kappa=1.6 |
| Jan 28 2004 12:39:12:693PM | 1040128003 | Earl Marmar | tweak the shape: Increase ZXL Decrease RXL Increase ZXU Increase RXU fizzle |
| Jan 28 2004 01:00:27:360PM | 1040128004 | Earl Marmar | lower prefill by 2 msec to 13 msec plasma |
| Jan 28 2004 01:09:14:977PM | 1040128005 | Earl Marmar | RXL decrease 2.5 cm ZXL increase 2.5 cm plasma early disrupt (0.51 s) EF2 lower goes to 0, lose vertical control |
| Jan 28 2004 01:25:31:717PM | 1040128006 | Earl Marmar | slow down the RXL, ZXL ramps EF2 by EF4 to -2500 (from -2000) plasma disrupt at .753 s EF2L going to 0 around 0.5 seconds |
| Jan 28 2004 01:28:12:750PM | 1040128007 | Earl Marmar | ease off on RXL and ZXL extremes (by 1 cm each) EF2 by EF4 to -4000 fizzle |
| Jan 28 2004 01:53:57:433PM | 1040128008 | Earl Marmar | reduce BR0 offset to .0005 to .0002 plasma made it to 1.25 seconds, shape not too bad not sure why we're losing it, EF1L is getting close to 0, but not there there is a strong radiated power increase around 1.2 seconds |
| Jan 28 2004 02:09:33:837PM | 1040128009 | Earl Marmar | raise nl_04 program to 1.1e20 (try to stay out of H-Mode) plasma made it to 1.5 seconds still getting H-modes EF2L is riding very close to 0 after .65 s |
| Jan 28 2004 02:13:04:073PM | 1040128010 | Earl Marmar | increase nl_04 target to 1.25e20 start Ip rampdown at 1.2 seconds fizzle |
| Jan 28 2004 02:22:21:490PM | 1040128011 | Earl Marmar | reduce prefill puff by 1 msec to 12 msec |
| Jan 28 2004 02:41:24:857PM | 1040128012 | Earl Marmar | no segment 1 changes fizzle |
| Jan 28 2004 02:56:05:467PM | 1040128013 | Earl Marmar | BR0 offset increase by .5 mT to .0007T segment 2: RCUR to 0.72 clearin to .1 various x-pt changes Ip to 0.5 MA nl_04 target to 8.3e19 fizzle |
| Jan 28 2004 03:26:17:330PM | 1040128014 | Earl Marmar | BR0 offset to 0.0000 limited on outside disrupt at ~0.6 seconds, very high density |
| Jan 28 2004 03:38:20:577PM | 1040128015 | Earl Marmar | increase clearin another 4 cm decrease nl_04 target to 0.6e20 plasma disrupt at 0.43 seconds too elongated, n/ncrit=1.2 |
| Jan 28 2004 03:52:59:703PM | 1040128016 | Earl Marmar | increase zxl by 12 cm (ramping until .7 seconds) plasma to .66 seconds outboard limited |
| Jan 28 2004 04:00:59:650PM | 1040128017 | Earl Marmar | EF2 by EF4 to -5000 plasma looks pretty similar to 16; EF2_L still going to 0 |
| Jan 28 2004 04:18:34:873PM | 1040128018 | Earl Marmar | Ramp RCUR out more gradually, not so far plasma made it through this time R is just about right (maybe 1 cm too small) still outboard limited |
| Jan 28 2004 04:30:49:153PM | 1040128019 | Earl Marmar | increase clearin reduce Ip to 0.4 MA plasma getting close, still kissing the outboard limiter and inner gap still a bit small |
| Jan 28 2004 04:40:30:070PM | 1040128020 | Earl Marmar | Eliminate small RCUR ramp between .7 and 1.2 seconds increase clearin disrupt at 0.7, not obvious why shape doesn't look bad |
| Jan 28 2004 04:58:27:140PM | 1040128021 | Earl Marmar | tweak clearin Ip prog to .45 MA plasma earlier disruption (0.57 s) OH1 near crossover |
| Jan 28 2004 05:04:23:960PM | 1040128022 | Earl Marmar | lower Ip program at segment switch plasma disrupt at .584 s, still near OH1 crossover, but not obvious this is the problem |
| Engineering Operator Comments | ||||
| Shot | Time | Type | Status | Comment |
| 1 | 12:04:30:903PM | Plasma | Ok | |
| 2 | 12:18:04:043PM | Plasma | Ok | |
| 3 | 12:32:41:950PM | Plasma | Ok | |
| 4 | 12:45:07:060PM | Plasma | Ok | |
| 5 | 12:58:02:933PM | Plasma | Ok | |
| 6 | 01:12:00:357PM | Plasma | Ok | |
| 7 | 01:24:42:480PM | Plasma | Ok | |
| 8 | 01:37:16:963PM | Plasma | Ok | |
| 9 | 01:53:24:730PM | Plasma | Ok | |
| 10 | 02:09:46:053PM | Plasma | Ok | |
| 11 | 02:22:17:130PM | Plasma | Ok | |
| 12 | 02:38:46:290PM | Plasma | Ok | |
| 13 | 02:51:33:480PM | Plasma | Ok | |
| 14 | 03:06:25:353PM | Plasma | Ok | |
| 15 | 03:25:34:190PM | Plasma | Ok | |
| 16 | 03:39:06:047PM | Plasma | Ok | PF breaker opened to disruption |
| 17 | 03:53:29:800PM | Plasma | Ok | |
| 18 | 04:06:22:110PM | Plasma | Ok | |
| 19 | 04:19:13:797PM | Plasma | Ok | |
| 20 | 04:32:25:110PM | Plasma | Ok | |
| 21 | 04:45:46:797PM | Plasma | Ok | |
| 22 | 04:58:42:080PM | Plasma | Ok | |