Miniproposals

Miniproposal: Date Filed: Title: First Author: Session Leader: Jim Terry (shots 1-27) Session Leader: Bruce Lipschultz (shots 1-27)

Engineering Operator Run Comment

x-point study

Session Leader Plans

Physics Operators Plans

Session Leader Summaries

Entered: Jul 7 2004 03:49:12:727PM

Author: To Be Determined

run 950317 Engineering operator: V. Bertolino Physics operator Y. Takase Session leader J. Terry Run coordinator B. Lipschultz The purpose of this experiment was to investigate the plasma characteristics in the region around the X-point in a number of Alcator C-Mod plasma regimes (sheath-limited, high-recycling, and detached). The investigation included measurement of the visible, VUV, and x-ray spectra along chords viewing the X-point region, the standard bolometer and Reticon array data and spectra from the cx analyzer. Using these diagnostics we explored the makeup of the large volumetric emission near the x-point measured by the divertor bolometer array. In particular the relative contributions of impurities and neutrals are of interest. We will also address the opacity of the plasma to the emission in the Lyman series of hydrogen. The major results are: (1) The radiation (defined by the peak in emissivity from the divertor bolometer array) is normally between the inner nose and the x-point when the x-point is in its standard position (e.g. R=55, z=-39.0 for shot 4). When the x-point was shifted up and out to R=56.2, z=-37.3. the emissivity peak moved to the x-point. Thus, because the radiation was already at the xpoint, we did not observe any obvious movement of the radiation peak at detachment. When the x-point was shifted back down in 1 cm steps (shots 25 & 27) the emissivity pattern returned to a more standard pattern. These bolometry observations are consistent with those of the Reticon arrays. (2) The 'death ray' which has been observed previously for outer strike point positions near probe 2 appeared as well when we operated the strike point near probe 7. It is important to note that the 'death ray' appeared at the same nl04=1.1e20 as when the strike point was located lower on the divertor surface. (3) Both HIREX and the CX analyzer were able to measure Ti in the region at or slightly above the x-point for nl04=0.5e20. HIREX Ti was about 150 eV while that determined from the cx spectrum was closer to 300 eV. (4) Ar spectra from HIREX were measured simultaneously at the top and bottom of the machine from the same flux surface. The data indicate that the chord near the x-point integrates emission from plasma with significantly lower Te than at the same flux surface at the top of the machine. (5) VUV spectra show very little Mo emission from the x-point region. Also emission from H-like and He-like carbon was absent. Lower charge states of C, O and Ar (ground state transitions) were observed and will be used to quantify the contributions of these impurities to the x-point radiation emissivity. Shots 4 and 27 were discharges when the x-point was in a fairly standard location. Shot 27 was detached at 0.73 seconds. Shots 9-15 were cases with the x-point up and out and the density was varied shot to shot. Shots 17-24 were discharges that again had the shifted x-point but the density was ramped during the shot from a level of nl04=0.5e20 to a value of approximately 1.3e20 m^-2. Most of these shots started to detach when nl04 increased past a value of 1.1e20. The detailed shot list follows: shot 1: alternator delay (2 hours) followed by power supply test shot 2: fizzle shot 3: This shot went. hard x-rays early on followed by a strong MARFE and then a moly injection. After that (600 ms) things settle down. shot 4: Very nice baseline shot. No problems with MARFEs. A few small moly injections. Strike point on probe 3. Next shot switch to sweeping of the x-point up and down. shot 5: disrupted after the x-point sweep brought the x-point to its peak height and EF2 turned off. shot 6: disrupted earlier. try again. shot 7: another disruption. We will cut the sweep and try to keep the x-point position constant and have the shot run completely through. shot 8: fizzle shot 9: sweep discarded, x-point at R=56.3, z= -38.2. Shot was fine with the strike point slightly above probe 7 and dropping. shot 10: fine shot z= -37.7, R= 56 - 56.4. nl04=0.9e20. ReJean has a view slightly above the x-point and measures a 350 eV Ti. OMA is looking at the Balmer series for Stark broadening. McPherson looking at OVI, Lyman Beta and CIII. shot 11: same as shot 10 with slightly more Ar. nl04=0.9e20. Next shot with lower density. shot 12: low density, nl04=0.5e20. No probe scan. Repeat again for FSP and HIREX. shot 13: This shot slightly better than 12. nl04=0.5 but no problems with the plasma sawtoothing. John R has scanned HIREX even further down towards the x-point. We also got a probe scan. shot 14: nl04=1.1e20. Shot went well with probe scan. HIREX losing signal with the higher density. There was a 'death ray' in pressure at both the inner and outer divertor this shot around 0.48 seconds. shot 15: nl05=1.5e20 eventually with disruption at 1.0 seconds. 'Death ray' evident on probe 7 this shot. We did get a probe scan. shot 16: fizzle shot 17: density step - nl04=0.5e20 until 0.7 seconds followed by a step up to 1.2e20. Not sure about detachment shot 18: very sick shot from the very beginning. Try again with higher fill pressure. shot 19: step up in density from nl04=0.5e20 to 1.3e20 starts at 0.65 seconds. probe scan ok. We will continue to hold this shot with the only change being to start the density increase earlier in the shot. shot 20: fine shot - same as before. We will be staying with this shot while wavelength scans are done. shot 21: same,no change shot 22: same,held the strike point position a little better. 'Death ray' on probe 7. shot 23: same, no change. shot 24: same, no change. Next shot shift the x-point down by 1 cm. Big Mo injection at .65 seconds. 'Death ray' comes back during RF pulse at end of shot. shot 25: x-point dropped by 1 cm (R=56, Z= -38.6). The strike point dropped to probe 6. shot 26: fizzle shot 27: x-point dropped again (R=56, z= -39.6). Final density of nl04=1.5e20. Usual 'death ray' which disappears during the density rise and reappears during the RF pulse.

Physics Operator Summaries

Entered: Jul 7 2004 04:36:53:567PM

Author: To Be Determined

Run 950317 Physics Operator's Summary X-pt run SL: BLip/Terry PO: Takase EO: Bertolino/Daigle The run started late due to an alternator problem. After obtaining a shot with STRIKEPSI control (shots 3-4) we switched to X-pt control. The ZXL ramp that was requested for this mini-proposal turned out to be tricky, with I_EF2L going to 0 (opposite of the more familiar "railing"), resulting in hard disruptions (shots 5-7, 1 strike and 1 warning). We tried to alleviate this problem by changing I_EF4, which had a favorable effect but not enough to solve the problem (I_EF4 needs to be less positive to get I_EF2 to be more negative). It was decided to run steady ZXL shots with ZXL moved up (shots 9-10). After a density scan (shots 10-15), a density step was programmed (nel_04=0.5 to 1.5e20, shots 17-24). Finally, the X-point was moved down shot-to-shot (shots 25-27). Shot Run start delayed due to alternator problem. 01 Test DAQ test 02 Fiz Start from 950315034, nel_04=0.9e20, fill=2.3e-5, no Ar cap bank charging supplies weren't turned on, backed out of sequence 03 Pla lower fill to 2.0e-5, hards, marfes, ramp-down disruption 04 Pla slowed density rise, good shot 05 Pla X-pt control (trying to get RXL=0.57, ZXL sweep -0.3875 to -0.36) Ar on 0.4-0.425 sec, disrupted @ 0.93 (I_EF2L went to 0 @ 0.7s) 06 Pla shifted ZXL sweep up by .01, increased I_EF4, disrupted (strike 1) 07 Pla lowered I_EF4 to 1500A, disrupted (warning) 08 Fiz get rid of ZXL ramp (and RXL ramp) 09 Pla good shot 10 Pla ZXL up by 5mm (-37.6cm), ZCUR up by 1cm (to -0.01) 11 Pla extend Ar puff to .43 sec 12 Pla extend Ar puff to .435 sec, lower density to nel_04=0.5e20 13 Pla slowed initial density rise 14 Pla raise density to nel_04=1.1e20 15 Pla raise density to nel_04=1.5e20, disrupt @ 1 sec 16 Dud density step, nel_04=0.5 to 1.4e20 @ 0.7 sec, no EF3 17 Pla good shot, density didn't get to programmed value 18 Pla raise plenum pressure (18 to 20), put in 50kA Ip ramp (0.6 to 1 sec) move density step to 0.6 sec, nel_04=0.5 to 1.3e20, runaway shot 19 Pla raise fill to 2.2e-5, good shot 20 Pla move density step to 0.55 sec, Ip ramp (0.55 to 0.85 sec) 21 Pla small ramp on RXL (3mm inward) 22 Pla repeat 23 Pla repeat 24 Pla repeat, extended Ip flattop to 1.05 sec 25 Pla lower ZXL by 1cm, 4mm inward RXL ramp, nel_04=0.5 to 1.5e20 TORVAC problem, cell access 26 Fiz lower ZXL another 1cm 27 Pla lower fill to 2.0e-5 Test 1 PS Dud 1 Fizzle 3 Plasma 22 ----------- Total 27

Session Leader Comments
Mar 17 1995 08:37:55:830AM		Bruce Lipschultz	un 950317 Engineering operator: V. Bertolino Physics operator Y. Takase Session leader BLip The purpose of this experiment is to investigate the plasma characteristics in the region around the X-point in a number of Alcator C-Mod plasma regimes (sheath-limited, high-recycling, and detached). The investigation includes measurement of 1) the visible, UV, VUV, and x-ray spectra along chords viewing the X-point region, the standard Reticon array data and the spectrum from the cx analyzer. Using these diagnostics we plan to explore the makeup of the large volumetric emission measured by the divertor bolometer array in this region. In particular, what are the relative contributions of impurities and neutrals. Another topic of interest which we hope to address is the opacity of the plasma there to Lyman series of hydrogen emission. The first step will be to set ip a several shots at different densities where the x-point is scanned up and down. Using these plasmas each diagnostic will be utilized to determine the 'best' x-point position for observation. After choosing an x-point position we will take complete UV and x-ray emission spectra for several fixed desities.
Mar 17 1995 10:22:52:130AM	950317001	Bruce Lipschultz	shot 1: alternator delay followed by power supply test
Mar 17 1995 10:42:49:280AM	950317002	Bruce Lipschultz	shot 2: fizzle
Mar 17 1995 10:55:34:660AM	950317003	Bruce Lipschultz	shot 3: This shot went. hard x-rays early on followed by a strong MARFE and then a moly injection. After that (600 ms) things settle down.
Mar 17 1995 11:13:56:650AM	950317004	Bruce Lipschultz	shot 4: Very nice baseline shot. No problems with MARFEs. A few small moly injections. Strike point on probe 3. Next shot switch to sweeping of the x-point up and down.
Mar 17 1995 11:59:43:860AM	950317005	Bruce Lipschultz	shot 5: sweep started from 0.5 to 0.7 sec. However, this causes EF2 to turn off and the plasma disrupts. Try again with some changes.
Mar 17 1995 12:00:38:760PM	950317006	Bruce Lipschultz	shot 6: disrupted earlier. try again.
Mar 17 1995 12:18:30:880PM	950317007	Bruce Lipschultz	shot 7: another disruption. We will cut the sweep and try to keep the x-point position constant and have the shot run completely through.
Mar 17 1995 12:22:03:360PM	950317008	Bruce Lipschultz	shot 8: fizzle
Mar 17 1995 12:44:51:090PM	950317009	Bruce Lipschultz	shot 9: sweep discarded, x-point at R=56.3, z= -38.2. Shot was fine with the strike point slightly above probe 7 and dropping.
Mar 17 1995 01:09:37:900PM	950317010	Bruce Lipschultz	shot 10: fine shot z= -37.7, R= 56 - 56.4. ReJean has a view slightly above the x-point and measures a 350 eV Ti. OMA is looking at the Balmer series for Stark broadening. McPherson looking at OVI, Lyman Beta and CIII.
Mar 17 1995 01:10:33:210PM	950317011	Bruce Lipschultz	shot 11: same as shot 10 with slightly more Ar. nl04=0.9e20. Next shot with lower density.
Mar 17 1995 01:21:28:030PM	950317012	Bruce Lipschultz	shot 12: low density, nl04=0.5e20. No probe scan. Repeat again for FSP and HIREX.
Mar 17 1995 01:34:44:530PM	950317013	Bruce Lipschultz	shot 13: This shot slightly better than 12. nl04=0.5 but no problems with the plasma sawtoothing. John R has scanned HIREX even further down towards the x-point. We also got a probe scan.
Mar 17 1995 01:49:41:010PM	950317014	Bruce Lipschultz	shot 14: nl04=1.1e20. Shot went well with probe scan. HIREX losing signal with the higher density.
Mar 17 1995 02:18:36:410PM	950317015	Bruce Lipschultz	shot 15: nl05=1.5e20 eventually with disruption at 1.0 seconds. 'Death ray' evident on probe 7 this shot.
Mar 17 1995 02:19:18:650PM	950317015	Bruce Lipschultz	shot 15: nl05=1.5e20 eventually with disruption at 1.0 seconds. 'Death ray' evident on probe 7 this shot. We did get a probe scan.
Mar 17 1995 02:28:15:800PM	950317016	Bruce Lipschultz	shot 16: fizzle
Mar 17 1995 02:33:30:240PM	950317017	Bruce Lipschultz	shot 17: density step - nl04=0.5e20 until 0.7 seconds followed by a step up to 1.2e20. Not sure about detachment
Mar 17 1995 02:47:23:170PM	950317018	Bruce Lipschultz	shot 18: very sick shot from the very beginning. Try again with higher fill pressure.
Mar 17 1995 03:09:58:700PM	950317019	Bruce Lipschultz	shot 19: step up in density from nl04=0.5e20 to 1.3e20 starts at 0.65 seconds. probe scan ok. We will continue to hold this shot with the only change being to raise the density earlier in the shot.
Mar 17 1995 03:37:11:480PM	950317020	Bruce Lipschultz	shot 20: fine shot - same as before. We will be staying with this shot while wavelength scans are done.
Mar 17 1995 04:05:57:460PM	950317021	Bruce Lipschultz	shot 21: same,no change
Mar 17 1995 04:07:50:350PM	950317022	Bruce Lipschultz	shot 22: same,held the strike point position a little better. 'Death ray' on probe 7.
Mar 17 1995 04:08:19:310PM	950317023	Bruce Lipschultz	shot 23: same, no change.
Mar 17 1995 04:08:52:110PM	950317024	Bruce Lipschultz	shot 24: same, no change. Next shot shift the x-point down by 1 cm.
Mar 17 1995 04:56:55:140PM	950317025	Bruce Lipschultz	shot 25: x-point dropped by 1 cm. The strike point is dropped as well.
Mar 17 1995 04:57:29:350PM	950317026	Bruce Lipschultz	shot 26: fizzle
Mar 17 1995 05:03:48:590PM	950317026	Bruce Lipschultz	shot 27: x-point dropped again (R=56, z= -39.6). Final density of nl04=1.5e20. Usual 'death ray' which dissapears during the density rise and reappears during the RF pulse.

Physics Operator Comments
Mar 17 1995 10:18:10:770AM	950317001	Yuichi Takase	X-pt Run SL: BLip PO: Takase EO: Bertolino 2 hrs of ECDC in D2 Run start delayed due to alternator problem. shot 01: Start from 950315034, nel_04=0.9e20, fill=2.3e-5 Shot 01 is a DAQ test.
Mar 17 1995 10:45:55:250AM	950317002	Yuichi Takase	shot 02: Fiz Start from 950315034, nel_04=0.9e20, fill=2.3e-5, no Ar
Mar 17 1995 11:03:38:750AM	950317003	Yuichi Takase	shot 03: Pla Lowered fill to 2.0e-5, no Ar got hards, then marfe on density rise
Mar 17 1995 11:14:57:960AM	950317004	Yuichi Takase	shot 04: Pla slowed density rise, good shot
Mar 17 1995 11:46:46:410AM	950317005	Yuichi Takase	shot 05: Pla X-pt control (trying to get RXL=0.57, ZXL sweep -0.3875 to -0.36) Ar on 0.4-0.425 sec, disrupted @ 0.93 (I_EF2L went to 0 @ 0.7s)
Mar 17 1995 12:17:58:820PM	950317006	Yuichi Takase	shot 06: Pla shifted ZXL sweep up by .01, increased I_EF4, disrupted (strike 1)
Mar 17 1995 12:18:42:290PM	950317007	Yuichi Takase	shot 07: Pla lowered I_EF4 to 1500A, disrupted (warning)
Mar 17 1995 12:44:01:130PM	950317008	Yuichi Takase	shot 08: Fiz get rid of ZXL ramp (and RXL ramp)
Mar 17 1995 12:45:16:920PM	950317009	Yuichi Takase	shot 09: Pla no ZXL ramp @ -38.2cm, good shot
Mar 17 1995 01:05:27:790PM	950317010	Yuichi Takase	shot 10: Pla ZXL up by 5mm (-37.6cm), ZCUR up by 1cm (to -0.01)
Mar 17 1995 01:05:56:670PM	950317011	Yuichi Takase	shot 11: Pla extend Ar puff to .43 sec, good shot
Mar 17 1995 01:23:29:340PM	950317012	Yuichi Takase	shot 12: Pla extend Ar puff to .435 sec, lower density to nel_04=0.5e20
Mar 17 1995 01:50:37:220PM	950317013	Yuichi Takase	shot 13: Pla slowed initial density rise, good shot
Mar 17 1995 01:51:09:430PM	950317014	Yuichi Takase	shot 14: Pla raise density to nel_04=1.1e20, good shot
Mar 17 1995 02:09:07:800PM	950317015	Yuichi Takase	shot 15: Pla raise density to nel_04=1.5e20, disrupt @ 1 sec
Mar 17 1995 02:31:06:380PM	950317016	Yuichi Takase	shot 16: PS dud no EF3
Mar 17 1995 02:31:47:490PM	950317017	Yuichi Takase	shot 17: Pla density step, nel_04=0.5 to 1.4e20 @ 0.7 sec good shot, but density didn't get to programmed value
Mar 17 1995 02:43:23:660PM	950317018	Yuichi Takase	shot 18: Pla raise plenum pressure (18 to 20), put in 50kA Ip ramp (0.6 to 1 sec) move density step to 0.6 sec, nel_04=0.5 to 1.3e20 runaway shot, disrupted early
Mar 17 1995 03:09:25:370PM	950317019	Yuichi Takase	shot 19: Pla raise fill to 2.2e-5, good shot
Mar 17 1995 03:57:35:170PM	950317020	Yuichi Takase	shot 20: Pla move density step to 0.55 sec, Ip ramp (0.55 to 0.85 sec)
Mar 17 1995 03:57:57:540PM	950317021	Yuichi Takase	shot 21: Pla small ramp on RXL (3mm inward)
Mar 17 1995 03:58:10:200PM	950317022	Yuichi Takase	shot 22: Pla repeat
Mar 17 1995 03:58:23:520PM	950317023	Yuichi Takase	shot 23: Pla repeat
Mar 17 1995 04:58:19:810PM	950317024	Yuichi Takase	shot 24: Pla repeat, extended Ip flattop to 1.05 sec
Mar 17 1995 04:59:14:890PM	950317025	Yuichi Takase	shot 25: Pla lower ZXL by 1cm, 4mm inward RXL ramp, nel_04=0.5 to 1.5e20 TORVAC problem, cell access to cycle power
Mar 17 1995 04:59:43:470PM	950317026	Yuichi Takase	shot 26: Fiz lower ZXL another 1cm
Mar 17 1995 05:02:06:520PM	950317027	Yuichi Takase	shot 27: Pla lower fill to 2.0e-5 ZXL=-39.6cm

Engineering Operator Comments
Shot	Time	Type	Status	Comment
1	10:14:01:280AM	Test	Ok	data system only
2	10:23:44:540AM	Plasma	Ok	no faults
3	10:43:44:260AM	Plasma	Ok	disruption induced comm faults
4	11:03:38:710AM	Plasma	Ok	no faults
5	11:19:51:080AM	Plasma	Ok	no faults
6	11:45:57:590AM	Plasma	Ok	no faults
7	12:03:37:490PM	Plasma	Ok	no faults
8	12:18:15:910PM	Plasma	Ok	no faults
9	12:27:37:420PM	Plasma	Ok	disruption induced comm fault oh1
10	12:44:06:720PM	Plasma	Ok	no faults
11	12:54:01:940PM	Plasma	Ok	no faults
12	01:10:58:210PM	Plasma	Ok	no faults
13	01:26:29:020PM	Plasma	Ok	no faults
14	01:39:12:820PM	Plasma	Ok	no faults
15	01:53:03:480PM	Plasma	Ok	no faults
16	02:08:57:760PM	Plasma	Bad	no ef3
17	02:17:38:840PM	Plasma	Ok	no faults
18	02:30:58:700PM	Plasma	Ok	No Faults.
19	02:50:27:650PM	Plasma	Ok	No Faults.
20	03:07:20:230PM	Plasma	Ok	no faults
21	03:18:55:530PM	Plasma	Ok	No Faults.
22	03:34:31:000PM	Plasma	Ok	No Faults.
23	03:46:46:010PM	Plasma	Ok
24	04:01:26:640PM	Plasma	Ok	No Faults.
25	04:14:38:640PM	Plasma	Ok	No Faults.
26	04:38:00:670PM	Plasma	Ok	No Faults
27	04:47:24:100PM	Plasma	Ok	No Faults.