| Miniproposals | ||||||||||||
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| Operators | |
| Session leader(s): | Chris Rost,John Reardon,Miklos Porkolab |
| Physics operator(s): | Robert Granetz,Steve Wolfe |
| Engineering operator(s): | Vinny Bertolino,Joe Daigle |
| Engineering Operator Run Comment |
| plasma run |
| Session Leader Plans |
| Physics Operators Plans |
| Session Leader Summaries |
| Entered: Jul 7 2004 03:49:15:523PM |
| Author: To Be Determined |
SL Summary for Run 960223 Topic: ERS/ PEP Mode Experiment: MP SL: M. Porkolab PO: S. Wolfe EO: J. Daigle The run went very well, in that there was only one fizzle, the last shot. All other shots were executed with substantial RF power being coupled into the plasma early into the discharge, typically 2 MW, with highly variable plasma conditions as the current was being ramped. Typical plasma conditions were nel=0.5-1.5, Ip=0.8 MA, Bt=5.3T. RF power was coupled in at times 0.08-0.14 s, at power levels 1-2 MW, quite successfully, initially without feedback, and during later shots with feedback. Occasionally RF was also injected at 0.8 sec to form PEP modes. Typical electron temperatures were 4 keV at 1 MW, and 5 kev (+) with 2 MW RF pulse during the ramp phase as long as the density was low enough (i.e., no pellet injection). Ion temperatures were of the order of 3 keV (needs to be confirmed). Zeff = 2-3 in the initial low density phase, and this may be lower than the previous ERS run w/o boronization (need to be confirmed!). So, in principle we should have had a better chance to get into the ERS mode than before boronization. This was the idea behind this run. Pellets were injected at two differrent times, early into the discharge (0.18 sec) and late into the discharge (0.8 sec). Evidence of PEP mode was apparent. H-modes were obtained with H-factors of the order of 2, but were transient in nature. Typical stored energies were of the order of 100 kJ, with the best approaching 120 kJ at 2 MW of RF power. An attempt was made to measure the q profile during the ERS mode, as well to peak the density profile, using Li pellet injection. However, owing to the high temperatures (5 keV), pellet penetration was poor even for the medium sized pellets (Rmin = 78 cm). The latter half of the shots had lithium pellets injected for PEP mode studies. A few important observations were made. First, the early collapse of the mode often seen with D pellet PEP modes and post-boronized Li PEP modes was eliminated by reducing the RF input power to 1 MW. Ni was injected with the laser blowoff diagnostic and was seen to exist in the plasma as long as the PEP mode existed, indicating an extremely long particle confinement time. In summary, it is not clear whether the ERS mode was obtained. Initially the electron temperatures were hollow during the ramp, but quickly peaked up to 4-5 keV during RF injection by 02sec. According to Yuichi, these temperatures are consistent with L-Mode confinement at these low densities without any ERS mode. It should be noted that at these low densities we do not expect much coupling of RF power to ions, and the minority tail should heat mostly electrons. Therefore, a detailed TRANSP analysis may be required to determine whether there is any evidence of ERS mode confinement. Recommendation for future experiments: (1)The RF pulse shape could be altered, in particular inject at maximum power ( 2 MW ) initially as now, but once the electron temperature increased to its maximum value, cut the power into half (1 MW), to see if the high electron temperatures would hold up at reduced power -this would indicate that the plasma may be in the ERS mode. The timing of the RF power drop should be varied to optimize the results. The tail slowing down must be assessed for this experiment, to be sure it does not dominate the temporal evolution of the discharge. (2) Another variation on this experiment might include a minor Bt field scan (10%) to attempt slight off-axis heating ( r/a=0.3-0.4); this might aid in increasing the off-axis electron heating and current, thus lowering q(r) off axis, thus creating a reversed shear equilibria while still maintaining good core heating. |
| Entered: Jul 7 2004 03:49:15:540PM |
| Author: To Be Determined |
| 960223(a) Session Leader Summary The purpose of today's run is to study the thresholds and saturation levels of edge ion heating and RF decay waves during Parametric Decay Instabilities in ICRH plasmas, and impurity generation by these effects. The plan is to have 3-4 good shots at each of 2.75T, 3.4T, 3.0T toroidal fields, to perform scans in the PCX and RF probes. The RF will fire in pulses of increasing height, with the maximum at less than .5MW. Then we will return to the magnetic field of greatest interest to do 1-2 shot scans in density and outer gap, and switch to D port antenna. Next, we'll try to achieve a 2.35T plasma for more scans. Most of the goals were attacked to some degree, though definitive scans eluded us. We got a good number of shots at 3.4T and 2.81T, which had resonances in the edge, and at 2.75T which did not. The PCX got measures of energetic neutral flux during edge heating versus RF power for three pitch angles at the different fields. As expected, the apparent tail temperature decreased at pitch angles away from perpendicular, and was hotter for higher RF power. The tail was larger in D at 2.81T, and large in H at 3.4T, and small at 2.75T. Quantitative analysis to follow. The RF probes took spectra on all shots, and additionally the new scanning probe was used to measure radial profiles of the pump and decay waves. At 3.4T, a shot-to-shot radial scan of the RF probe showed that the 80 MHz power level dropped off slowly behind the limiter. The RF probe unexpectedly did not detect any power at the local Deuterium fundamental (19 MHz or thereabouts). After the change to Bt of 2.75T, weak decay waves at about 20 and 45 MHz were observed. We moved to 2.8 T for shot 28 and found what appeared to be two types of PDI, one into the outer edge Deuterium fundamental and the other into the outer edge hydrogen fundamental. The highest level of PDI recorded during the day appeared on shot 32, but wasn't accompanied by a moly outburst. The RF probe was scanned in radius again for shots 32, 34, and 36 and found that a. the PDI level decreased quickly with radius and b. the frequency of the detected PDI fundamental varied with radius, as if the PDI were being generated at the same radius as the probe. One goal of the run was to generate large PDI levels and large amounts of energetic edge particles in the absence of large RF powers and look for a correlation with impurity levels. Examining data from the moly monitor, 2pi bolometer, and the calculated main plasma power from the bolo array, we see that there is no measurable increase in impurity level due to PDI or energetic edge particles on Alcator C-Mod. The run was plagued by fizzles and disruptions: on 36 attempts we had 16 full plasmas, 10 disruptions before 550ms, 7 fizzles, and 3 duds. Also, the PCX lost several shots because the gate valve closed early (this is part of a system to prevent excess gas pressure from damaging detectors). In the 2.8 T range, there was apparently a very weak ohmic h-mode throughout the flattop on almost every shot, with some stronger elm-free periods during RF. The density crept up during the dithering, and rose sharply during the elm-free h-mode periods. The disruptions were unfortunately quite repeatable. In the 3.4T low-field startup part of the run, the plasmas that disrupted did so at 220ms, with concurrent moly injections. The plasma would then limp along at 200kA until around 450ms. These plasmas had a dip in q95 at 220ms, but only down to 3.2 in some cases. The plasmas that went all the way also had q95 down to 3.1 at the same period, but without a problem. The second half of the run, with the high-field startup, had disruptions characterized by a density droop down to nl04=.34e20 at 500ms. All the settings were identical to those of shots that went. Wild speculation is that this might be related to wall fueling. These are the full length shots: 03 Plasma remains outboard limited, only 1 7kW RF pulse, Bt=3.47T, nl04~=.6 06 .5cm outer gap, 4 RF pulses in flattop, up to 80kW 11 1cm outer gap, PCX at 20cm (sightline ~40° from perpendicular at LCFS) 13 similar, PCX at 10cm 16 sim., added a 500kW RF pulse, PCX at perpendicular Install breaker, go to 5T startup and 2.75T flattop 20 long dithering h-mode, with elm-free periods, density slowly rising throughout, flux to PCX much lower than expected (erroneously believing this to be due to h-mode, we tried to get rid of h-mode and left analyzer at perpendicular) 21 sim. 22 sim., JT injecting stuff at ~600ms (and for many shots after) 24 sim., PCX gate valve closed 25 sim., 26 sim., put 20kW RF in TF ramp, see that PCX flux is more sensitive to field today than past measurements indicate, so slightly modify TF. These shots give good info on how sensitive threshold is to exact edge Bt. 28 good plasma at 2.82T, early PCX GV, mistrigger RF SpecAn. Outer gap ~1cm 29 sim., but got data! 32 sim., early PCX GV, PCX at 20cm 34 sim., but lost an RF pulse. Mike F. is looking for it..... 36 sim., but rearranged RF pulse heights PCX at 10cm |
| Physics Operator Summaries |
| Entered: Jul 7 2004 04:36:56:223PM |
| Author: To Be Determined |
| Physop Summary for 960223 (second part) MP125A ERS/PEP SL Porkolab PO wolfe EO Daigle We began the run at 5PM after the conclusion of the MP141 run. The breaker had been repaired during the afternoon, allowing us to operate at 5.3T again. The EF1 problem has not recurred since the PF breaker was pulled yesterday, and seems to in fact have been a consequence of the breaker problem. Started from shot 960221035, the successful shot from the first try at this run. A-side, which had had a D2/H2 mix for the first part of the run, was purged and filled with D2. The H concentration was therefore dropping through the run, starting from about 10%. In view of the fact that we only had four hours, it was decided to try combining the PEP mode and ERS studies in the same shots, with a pellet injected at .8sec. Proposed run plan for ERS/PEP run on 960223, same as on 960221. . Part I. Negative central shear ------------------------------ Start from a standard fast 800kA startup, like a fiducial, but bring RF on as early as possible. Things to try: reduce early density move position out earlier to match antenna (maybe use loading feedback?) Try small pellet during current rise, before RF. Monitor sawtooth onset, neutron rate. Note that automatic EFIT stored energies will be meaningless for inverted pressure profiles, but we may be able to get something from w_diamagnetic. If we seem to be getting anything reproducible, try popping some Li pellets to get a cigar measurement of Bz(R). Part II. PEP modes ------------------- If feasible, this part can be started during the late flattop of shots from the first part of the run. Set up standard 800MA plasma. Vary pellet timing relative to RF turn-on to optimize neutron rate. Document it to death, including Sc injections for tau_p. May want to try a pre-pellet Sc injection as well. Results: -------- All of the technical objectives were achieved, except that moving the RCUR programming to better match the antenna was not tried. We did turn on the RF loading feedback at the beginning of Seg 1, at low gain (-1000.). RF turned on as early as 70msec, with 2MW by 100msec. Yuichi is to be congratulated for accomplishing the tuning necessary to couple to this moving target. The peak electron temperatures reached before sawtoothing were over 5keV. H-modes were obtained on all shots, with lots of dropouts; good but not great H-factors (transiently above 2). The first H-mode seemed to start at about the time of sawtooth onset, possibly triggered by the first sawtooth. The late PEP modes were similar to others since boronization, not well sustained and neutron rates around 2e13. Ni injection before the second pellet showed essentially infinite impurity confinement in the PEP phase, before the H-mode set in. On shot 42 the density programming was lowered to .5e20, which increased the Te and may have helped delay sawtoothing some. Sawtoothing was not delayed further than 230msec, compared to 180msec without early RF. There was no evidence of ERS mode improved confinement. Darren got some cigar data from the early pellets, although the data is limited because he had a problem with his tracker and because the penetration was low even for the big pellets. The density perturbation was surprisingly small. There seemed to be little effect on the sawtooth onset, and the neutron rate seemed to be suppressed if affected at all. The current rise disruptions (before 100msec) were partly suppressed by the early RF. Shot 44 has a good example of MHD on the ECE during the current rise. On shot 45 Joe moved the fast magnetics to .080-.210sec to look at activity around the disruption at 90msec and the pellet at 180. The disruption was found to be associated with an m=4 locked mode. Reducing the OH voltage between 50 and 100msec on shot 49 seemed to get rid of the last vestiges of the locked mode. The last shot (50) was an attempt to get better pellet penetration by shooting two big pellets, but the shot fizzled. The plasma was surprisingly robust, disrupting only on two shots (39,, after the second pellet when there was no RF following it. There was a problem with the cell air to the Li pellet injector caused by a freeze up in the air hose due to ice from the bus tunnel building up as far as Kport. This was corrected between shots 42 and 43. This could have caused a serious problem, and should be dealt with on a more permanent basis. Scorecard --------- Shots 14 (37-50) Plasmas 13 Fizzles 1 |
| Entered: Jul 7 2004 04:36:56:240PM |
| Author: To Be Determined |
| Physics operator's summary for run 960223A: MP #141, RF edge physics. SL: Rost/Reardon PO: Granetz EO: V. Bertolino Today's run will study the parametric decay of RF waves at the edge of the plasma. This is most easily studied at low fields in L-mode. About four shots at each of three fields (2.75, 3.40, and 3.00 T) will be required. The plasma current will be 0.55 MA. The plasma composition will be 7.5% H and 92.5% D. RF power will be varied in steps from 0.1 to 0.8 MW. Summary: The first half of the run was spent trying to get breakdown at 3.4 tesla. This was partially successful, with about 1 out of every 3 shots providing good RF probe data. Shortly after noontime, the faulty breaker was fixed and installed, allowing for more typical (and reliable) plasma initiation at 4.8 tesla, ramping down to 2.75 tesla (2.82 tesla late in the day). The plasmas we obtained here were very good, with Ip=450-550 kA, nl_04=0.5-0.7e20 m-2, and flattops lasting to 1.5 s. Lots of RF probe data were obtained. There were, however, ohmic H-modes on every shot, although they were really wimpy. There were no power supply problems today. Scorecard: 26 plasmas (but 10 disrupted before RF turnon) 7 fizzles 0 tests 3 duds (none due to power supplies) ---------- 36 total Run plan: Load from yesterday's low-field (3.4 T breakdown) shot #960222027, except decrease early Ip programming demand to try and avoid reaching q=3. This particular shot lasted less than 0.2 s, but it's the only recent shot with low-field breakdown and current rise. The low-field breakdown is necessary because of a problem with 2 breakers, which has temporarily left only 2 of 4 TF cabinets operational. This is also why we cannot begin the run with a fiducial plasma shot. If we are successful at getting good 3.4 tesla plasmas, we will switch to hybrid control of the TF so that we can run shots at 3.0 and 2.75 tesla. Engineering setup for Tuesday 23 Feb 1996: Discharge clean in helium for a couple of hours before the run. A-side (actually K-side) plenum: 1.5 psi of H2 and 18.5 psi of D2 B-top plenum: 5 psi of deuterium. B-side-lower plenum: 4 psi of argon. NINJA plenum: make sure this is pumped out. Enable hybrid control of A-side, B-top, and B-side-lower valves for start of run. Enable the ECE, VUV, Moly monitor, PCX, and TCX valves, assuming status of each is okay. Use engineering settings from shot 960222027 (low-field breakdown shot from yesterday). After (if?) we establish a 3.4 tesla shot, we will ask for hybrid control of the TF so that we can go to 3.0 and 2.75 tesla. Detailed shot log: Shot 01 -- Plasma, but it looks like it got hit by a brick at 0.2 s, leading to a termination at 0.44 s. q95 stayed above 3.1, and the plasma was well away from the outboard limiter at the brick injection time. Next shot: repeat with no changes. Shot 02 -- Fizzle. Null looks reasonable. Pre-fill pulse duration is 19 ms, but this is what Joe found was necessary yesterday, so I'll keep it that long for now. Next shot: repeat with no changes. Shot 03 -- Plasma. Good shot, except that the plasma was limited on the outboard limiter for nearly the entire duration. Ip=0.56 MA, Bt=3.4 T, nl_04=0.68e20 m-2. q95=4 during flattop, but briefly touches 3.0 early in the shot. No ohmic H-modes. Next shot: reduce RCUR by 5 mm in order to generate an outer gap of about 1 cm Shot 04 -- Plasma, but a series of moly injections starting at 0.2 s finally terminates the plasma at 0.46 s. Very similar to shot 001. The injections begin at about the same time that q95 briefly drops to 3.0, so perhaps there's a connection. Next shot: reduce early Ip programming demand to try and keep q95 above 3 at all times. Shot 05 -- Fizzle. No surprise, given the 001/002 shot sequence. Next shot: repeat with no changes. Shot 06 -- Plasma, good shot. Bt=3.4 T, nl_04=7.3e20 m-2. Density is higher than previous good shot, even though no changes have been made. Outer gap was only a couple of mm at best. q95 briefly went down to 3.1, but plasma managed to survive this time. RF pulses look very good. Next shot: decrease RCUR by another 4 mm, and decrease early Ip programming again. Shot 07 -- Plasma, but a series of moly injections starting at 0.2 s finally terminates the plasma at 0.46 s. Very similar to shot 001 and 003, even though q95 is no longer flirting with 3.0. Next shot: if I do nothing, I bet there'll be a fizzle, so I'll do something: shorten pre-pulse puff duration from 19 to 17 ms. Shot 08 -- Plasma, but a series of moly injections starting at 0.2 s finally terminates the plasma at 0.35 s. q95 doesn't go below 3.2. At least it didn't fizzle! Unfortunately, there's no fast infrared camera, so we can't see where these moly injections are coming from. Next shot: no changes. Shot 09 -- Dud. It turns out that for the last several shots we've been having a small RF pulse at t=0. For this shot, it was turned off. Looks like it might have been doing something after all. Next shot: repeat, except have the RF turned on at t=0. Shot 10 -- Fizzle. Next shot: increase pre-pulse gas puff durations from 17 to 19 ms. Shot 11 -- Plasma. Good shot. Outer gap is about 1 cm. Good RF performance. Nice RF probe data. It's showing different stuff than on shot 006, which had a much smaller outer gap. Next shot: repeat with no changes. Shot 12 -- Dud. How's that for reproducibility! Next shot: increase Br by 0.5 mT (from 4.5 to 5.0 mT). Shot 13 -- Plasma. Good shot. Good RF. Good data. Next shot: no changes. Jim Reardon is changing his RF probe position. Shot 14 -- Fizzle. %*$#&#@^!! Next shot: repeat with no changes. Shot 15 -- Fizzle again. Next shot: on Steve W's suggestion, I'll raise Bz by increasing I_EF4 from -1200 to -1185 amps. Shot 16 -- Plasma. It turned out to be an okay shot, only because it just barely survived two huge moly injections at 0.2 s. The plasma current trace looks truly bizarre. But the data are good, and there was an additional RF pulse late in the flattop which reached 0.5 MW. Next shot: repeat with no changes. Shot 17 -- Plasma. Disrupted at 0.36 s, accompanied by a large Mo injection. At this point in the run, the breaker has been repaired, and we are having a short pause to install it. All four TF cabinets will now be available. Next shot: repeat with no changes. Keep the PLC limit at 100 kA (3.4 T startup) Shot 18 -- Plasma. Disrupted at 0.35 s, just like the last shot. The plasma is hitting the outboard limiter around this time. Next shot: since we now have all four TF cabinets, we will abandon low-field startups and recall a shot which started at 4.8 tesla and ramped down to 2.6 tesla (960118032). However, changes will be made to ramp the field down to 2.75 tesla (under hybrid control), AND THE FLATTOP WILL BE EXTENDED TO 1.5 s! Shot 19 -- Dud. Not surprising, since the startup from 960118032 needed to be adjusted last Tuesday as well. Next shot: reduce Br from 6.6 to 5.5 mT. Shot 20 -- Plasma. Good shot, except there were H-modes at the higher RF powers and lower fields. Bt=2.75 T, flattop lasted until the plasma disrupted at t=1.54 s. Outer gap is small. Don't quite know what to do to prevent H-modes. Next shot: tweak RXL at the request of Brian L. Shot 21 -- Plasma. Good shot. Very similar to previous shot. H-modes even in ohmic phase. Next shot: reduce Ip demand from 580 to 550 kA, and reduce density a bit as well. Shot 22 -- Plasma. Good shot. A little less H-modey than the previous shots, at least until the higher RF powers. Next shot: slightly lower density. Also bring CLEARIN down faster after t=1.5 s. Shot 23 -- Plasma, but disrupted at t=0.48 s. I don't think this one was caused by any moly injections. Not sure what caused it. Next shot: tweak up the density around 0.4 s. Shot 24 -- Plasma. Good shot, but there are still some H-modes. Next shot: lower Ip and nl some more. Shot 25 -- Plasma. Good shot. Ip is now down to 0.50 MA. There are still H-modes. Next shot: no changes Shot 26 -- Plasma. Good shot. Still have H-modes. Next shot: reduce Ip to 450 kA. Also increase Bt from 2.75 to 2.82 tesla. Shot 27 -- Plasma, but disrupted at 0.48 s for unknown reasons. Next shot: repeat with no changes. Shot 28 -- Plasma. Good shot. Ip is now 450 kA. Bt=2.82 T. Next shot: no changes Shot 29 -- Plasma. Good shot. Same as previous one. Next shot: no changes Shot 30 -- Fizzle. Null looks okay. Next shot: repeat Shot 31 -- Plasma, but disrupted at 0.53 s. On the shots that disrupt early, the density is noticeably lower than on shots which don't disrupt. Next shot: tweak the density up around 0.4 s. Shot 32 -- Plasma. Good shot. Same as 028 and 029. Next shot: no changes Shot 33 -- Fizzle. Null is okay. Next shot: repeat with no changes Shot 34 -- Plasma. Good shot. Same as 028, 029, and 032. Next shot: repeat with no changes Shot 35 -- Plasma, but disrupted at 0.54 s. Next shot: repeat Shot 36 -- Plasma. Good shot. Same as 028, 029, 032, and 034. End of this portion of the run (i.e. MP #141) Following this, Steve Wolfe and Miklos Porkolab will take over for the extended portion of today's run, which is devoted to the ERS/PEP MP. |
| Session Leader Comments | |||
| Feb 23 1996 05:46:51:480PM | 960223037 | Miklos Porkolab | Experimental Plan:
To continue ERS run from 960221 starting at 5:00 pm; Machine operating at 5.3 Tesla; SL: M. Porkolab PO: S. Wolfe EO: J. Daigle Shot was successfull, operate at 800 kA, RF power about 600 kA. No pellets yet. |
| Feb 23 1996 05:56:29:750PM | 960223038 | Miklos Porkolab | Good shot, Early RF first about 1 MW and then step up with
second transmitter to 2 MW. No pellet. |
| Feb 23 1996 06:03:41:560PM | 960223039 | Miklos Porkolab | Good shot, first pellet injected around 0.8 second, RF power between
1-2 MW in a ragged form. Plasma decays away rather quickly after pellet injection. Stored energy around 100 kJ. Not a good pellet shot performance - wise. |
| Feb 23 1996 07:00:50:390PM | 960223040 | Miklos Porkolab | Good shot,but Rf power only about 1 MW.
|
| Feb 23 1996 07:03:01:910PM | 960223041 | Miklos Porkolab | Good shot, RF power about 2 MW, early into the shot. But no evidence
of ERS mode ? |
| Feb 23 1996 07:34:46:890PM | 960223042 | Miklos Porkolab | Good shot, Rf power about 1.9 MW, max. stored energy about
120kJ, early on. Electron temperature above 4.2 keV. No pellet. |
| Feb 23 1996 07:42:00:700PM | 960223043 | Miklos Porkolab | Initial power only 1 MW, electron temperature 4 keV,
pellet at 0.8 sec, but no RF during pellet. |
| Feb 23 1996 07:53:07:840PM | 960223044 | Miklos Porkolab | Initial power only 1 MW, quickly rising to 2 mW around 120 ms.
Electron temperature up to 5 keV due to low initial density. Pellet injected at 0.8 sec, and there was 1 MW of RF power on top of it. PEP mode ?? |
| Feb 23 1996 08:25:07:770PM | 960223046 | Miklos Porkolab | Initial power only 1 MW, quickly rising to 2 MW around 200 ms.
Electron temperature up to 5 keV during 2 MW, but only 3 keV during pellet. 1st small pellet injected at 180 ms, 2nd pellet at 800 ms.. |
| Feb 23 1996 08:40:36:280PM | 960223047 | Miklos Porkolab | We got 5.0 keV Te, at 1.8 MW RF power early on, before sawteeth
came on at 200 ms. No pellet in this shot. |
| Feb 23 1996 08:56:30:980PM | 960223048 | Miklos Porkolab | Good shot, 1.9 MW RF power early, at 100 ms, pellet injected at
200 ms, Te drops from 5.0 keV to 3.8 keV, then sawteeth enter. Apparently we have small locked mode activity around 80-90 ms. |
| Feb 23 1996 09:03:59:970PM | 960223048 | Miklos Porkolab | Good shot, 1.9 MW RF power early, at 100 ms, pellet injected at
200 ms, Te drops from 5.0 keV to 3.8 keV, then sawteeth enter. Apparently we have small locked mode activity around 80-90 ms. |
| Feb 23 1996 09:14:03:280PM | 960223049 | Miklos Porkolab | Good shot, slowed down current ramp initially. Did not make much
difference in parameters. |
| Feb 23 1996 09:14:50:920PM | 960223050 | Miklos Porkolab | Fizzle.
|
| Physics Operator Comments | |||
| Feb 23 1996 08:18:21:170AM | Robert Granetz | MP #141, RF edge physics.
SL: Rost/Reardon PO: Granetz EO: V. Bertolino Today's run will study the parametric decay of RF waves at the edge of the plasma. This is most easily studied at low fields in L-mode. About four shots at each of three fields (2.75, 3.40, and 3.00 T) will be required. The plasma current will be 0.55 MA. The plasma composition will be 7.5% H and 92.5% D. RF power will be varied in steps from 0.1 to 0.8 MW. | |
| Feb 23 1996 08:18:42:100AM | Robert Granetz | Run plan:
Load from yesterday's low-field (3.4 T breakdown) shot #960222027, except decrease early Ip programming demand to try and avoid reaching q=3. This particular shot lasted less than 0.2 s, but it's the only recent shot with low-field breakdown and current rise. The low-field breakdown is necessary because of a problem with 2 breakers, which has temporarily left only 2 of 4 TF cabinets operational. This is also why we cannot begin the run with a fiducial plasma shot. If we are successful at getting good 3.4 tesla plasmas, we will switch to hybrid control of the TF so that we can run shots at 3.0 and 2.75 tesla. | |
| Feb 23 1996 08:19:14:300AM | Robert Granetz | Engineering setup for Tuesday 23 Feb 1996:
Discharge clean in helium for a couple of hours before the run. A-side (actually K-side) plenum: 1.5 psi of H2 and 18.5 psi of D2 B-top plenum: 5 psi of deuterium. B-side-lower plenum: 4 psi of argon. NINJA plenum: make sure this is pumped out. Enable hybrid control of A-side, B-top, and B-side-lower valves for start of run. Enable the ECE, VUV, Moly monitor, PCX, and TCX valves, assuming status of each is okay. Use engineering settings from shot 960222027 (low-field breakdown shot from yesterday). After (if?) we establish a 3.4 tesla shot, we will ask for hybrid control of the TF so that we can go to 3.0 and 2.75 tesla. | |
| Feb 23 1996 08:35:34:470AM | 960223001 | Robert Granetz | Shot 01 -- Plasma, but it looks like it got hit by a brick at 0.2 s, leading
to a termination at 0.44 s. q95 stayed above 3.1, and the plasma was well away from the outboard limiter at the brick injection time. Next shot: repeat with no changes. |
| Feb 23 1996 08:49:06:650AM | 960223002 | Robert Granetz | Shot 02 -- Fizzle. Null looks reasonable. Pre-fill pulse duration is 19 ms,
but this is what Joe found was necessary yesterday, so I'll keep it that long for now. Next shot: repeat with no changes. |
| Feb 23 1996 09:03:43:110AM | 960223003 | Robert Granetz | Shot 03 -- Plasma. Good shot, except that the plasma was limited on the
outboard limiter for nearly the entire duration. Ip=0.56 MA, Bt=3.4 T, nl_04=0.68e20 m-2. Next shot: reduce RCUR by 5 mm in order to generate an outer gap of about 1 cm |
| Feb 23 1996 09:20:35:980AM | 960223004 | Robert Granetz | Shot 04 -- Plasma, but a series of moly injections starting at 0.2 s finally
terminates the plasma at 0.46 s. Very similar to shot 001. The injections begin at about the same time that q95 briefly drops to 3.0, so perhaps there's a connection. Next shot: reduce early Ip programming demand to try and keep q95 above 3 at all times. |
| Feb 23 1996 09:22:29:240AM | 960223005 | Robert Granetz | Shot 05 -- Fizzle. No surprise, given the 001/002 shot sequence.
Next shot: repeat with no changes. |
| Feb 23 1996 09:53:00:820AM | 960223006 | Robert Granetz | Shot 06 -- Plasma, good shot. Bt=3.4 T, nl_04=7.3e20 m-2. Density is
higher than previous good shot, even though no changes have been made. Outer gap was only a couple of mm at best. q95 briefly went down to 3.1, but plasma managed to survive this time. RF pulses look very good. Next shot: decrease RCUR by another 4 mm, and decrease early Ip programming again. |
| Feb 23 1996 10:07:27:140AM | 960223007 | Robert Granetz | Shot 07 -- Plasma, but a series of moly injections starting at 0.2 s finally
terminates the plasma at 0.46 s. Very similar to shot 001, even though q95 is no longer flirting with 3.0. Next shot: if I do nothing, I bet there'll be a fizzle, so I'll do something: shorten pre-pulse puff duration from 19 to 17 ms. |
| Feb 23 1996 10:26:41:790AM | 960223008 | Robert Granetz | Shot 08 -- Plasma, but a series of moly injections starting at 0.2 s finally
terminates the plasma at 0.35 s. q95 doesn't go below 3.2. At least it didn't fizzle! Unfortunately, there's no fast infrared camera, so we can't see where these moly injections are coming from. Next shot: no changes. |
| Feb 23 1996 10:32:16:640AM | 960223009 | Robert Granetz | Shot 09 -- Dud. It turns out that for the last several shots we've been having
a small RF pulse at t=0. For this shot, it was turned off. Looks like it might have been doing something after all. Next shot: repeat, except have the RF turned on at t=0. |
| Feb 23 1996 10:43:26:920AM | 960223010 | Robert Granetz | Shot 10 -- Fizzle.
Next shot: increase pre-pulse gas puff durations from 17 to 19 ms. |
| Feb 23 1996 11:00:31:460AM | 960223011 | Robert Granetz | Shot 11 -- Plasma. Good shot. Outer gap is about 1 cm. Good RF performance.
Next shot: repeat with no changes. |
| Feb 23 1996 11:07:27:960AM | 960223012 | Robert Granetz | Shot 12 -- Dud. How's that for reproducibility!
Next shot: increase Br by 0.5 mT (from 4.5 to 5.0 mT). |
| Feb 23 1996 11:21:29:010AM | 960223013 | Robert Granetz | Shot 13 -- Plasma. Good shot. Good RF. Good data.
Next shot: no changes. Jim Reardon is changing his RF probe position. |
| Feb 23 1996 11:25:06:810AM | 960223014 | Robert Granetz | Shot 14 -- Fizzle. %*$#&#@^!!
Next shot: repeat with no changes. |
| Feb 23 1996 11:38:28:400AM | 960223015 | Robert Granetz | Shot 15 -- Fizzle again.
Next shot: on Steve W's suggestion, I'll raise Bz by increasing I_EF4 from -1200 to -1185 amps. |
| Feb 23 1996 11:54:31:590AM | 960223016 | Robert Granetz | Shot 16 -- Plasma. It turned out to be an okay shot, only because it just
barely survived two huge moly injections at 0.2 s. The plasma current trace looks truly bizarre. But the data are good, and there was an additional RF pulse late in the flattop which reached 0.5 MW. Next shot: repeat with no changes. |
| Feb 23 1996 12:26:16:410PM | 960223017 | Robert Granetz | Shot 17 -- Plasma. Disrupted at 0.36 s, accompanied by a large Mo injection.
At this point in the run, the breaker has been repaired, and we are having a short pause to install it. All four TF cabinets will now be available. Next shot: repeat with no changes. Keep the PLC limit at 100 kA (3.4 T startup) |
| Feb 23 1996 12:58:17:660PM | 960223018 | Robert Granetz | Shot 18 -- Plasma. Disrupted at 0.35 s, just like the last shot. The plasma
is hitting the outboard limiter around this time. Next shot: since we now have all four TF cabinets, we will abandon low-field startups and recall a shot which started at 4.8 tesla and ramped down to 2.6 tesla (960118032). However, changes will be made to ramp the field down to 2.75 tesla (under hybrid control), AND THE FLATTOP WILL BE EXTENDED TO 1.5 s! |
| Feb 23 1996 01:03:46:860PM | 960223019 | Robert Granetz | Shot 19 -- Dud. Not surprising, since the startup from 960118032 needed to
be adjusted last Tuesday as well. Next shot: reduce Br from 6.6 to 5.5 mT. |
| Feb 23 1996 01:24:03:950PM | 960223020 | Robert Granetz | Shot 20 -- Plasma. Good shot, except there were H-modes at the higher RF
powers and lower fields. Bt=2.75 T, flattop lasted until the plasma disrupted at t=1.54 s. Outer gap is small. Don't quite know what to do to prevent H-modes. Next shot: tweak RXL at the request of Brian L. |
| Feb 23 1996 01:36:06:120PM | 960223021 | Robert Granetz | Shot 21 -- Plasma. Good shot. Very similar to previous shot. H-modes even
in ohmic phase. Next shot: reduce Ip demand from 580 to 550 kA, and reduce density a bit as well. |
| Feb 23 1996 01:51:01:050PM | 960223022 | Robert Granetz | Shot 22 -- Plasma. Good shot. A little less H-modey than the previous shots,
at least until the higher RF powers. Next shot: slightly lower density. Also bring CLEARIN down faster after t=1.5 s. |
| Feb 23 1996 02:02:11:640PM | 960223023 | Robert Granetz | Shot 23 -- Plasma, but disrupted at t=0.48 s. I don't think this one was
caused by any moly injections. Not sure what caused it. Next shot: tweak up the density around 0.4 s. |
| Feb 23 1996 02:10:25:870PM | 960223024 | Robert Granetz | Shot 24 -- Plasma. Good shot, but there are still some H-modes.
Next shot: lower Ip and nl some more. |
| Feb 23 1996 02:28:11:010PM | 960223025 | Robert Granetz | Shot 25 -- Plasma. Good shot. Ip is now down to 0.50 MA. There are still
H-modes. Next shot: no changes |
| Feb 23 1996 02:42:51:150PM | 960223026 | Robert Granetz | Shot 26 -- Plasma. Good shot. Still have H-modes.
Next shot: reduce Ip to 450 kA. Also increase Bt from 2.75 to 2.82 tesla. |
| Feb 23 1996 02:54:40:820PM | 960223027 | Robert Granetz | Shot 27 -- Plasma, but disrupted at 0.48 s for unknown reasons.
Next shot: repeat with no changes. |
| Feb 23 1996 03:15:13:990PM | 960223028 | Robert Granetz | Shot 28 -- Plasma. Good shot. Ip is now 450 kA. Bt=2.82 T.
Next shot: no changes |
| Feb 23 1996 03:28:13:610PM | 960223029 | Robert Granetz | Shot 29 -- Plasma. Good shot. Same as previous one.
Next shot: no changes |
| Feb 23 1996 03:37:09:950PM | 960223030 | Robert Granetz | Shot 30 -- Fizzle. Null looks okay.
Next shot: repeat |
| Feb 23 1996 03:53:36:180PM | 960223031 | Robert Granetz | Shot 31 -- Plasma, but disrupted at 0.53 s. On the shots that disrupt early,
the density is noticeably lower than on shots which don't disrupt. Next shot: tweak the density up around 0.4 s. |
| Feb 23 1996 04:09:28:150PM | 960223032 | Robert Granetz | Shot 32 -- Plasma. Good shot. Same as 028 and 029.
Next shot: no changes |
| Feb 23 1996 04:15:44:010PM | 960223033 | Robert Granetz | Shot 33 -- Fizzle. Null is okay.
Next shot: repeat with no changes |
| Feb 23 1996 04:24:13:260PM | 960223034 | Robert Granetz | Shot 34 -- Plasma. Good shot. Same as 028, 029, and 032.
Next shot: repeat with no changes |
| Feb 23 1996 04:53:29:760PM | 960223035 | Robert Granetz | Shot 35 -- Plasma, but disrupted at 0.54 s.
Next shot: repeat |
| Feb 23 1996 05:03:05:250PM | 960223036 | Robert Granetz | Shot 36 -- Plasma. Good shot. Same as 028, 029, 032, and 034.
End of this portion of the run (i.e. MP #141) Following this, Steve Wolfe and Miklos Porkolab will take over for the extended portion of today's run, which is devoted to the ERS/PEP MP. |
| Feb 23 1996 05:25:19:100PM | 960223037 | Steve Wolfe | Proposed run plan for ERS/PEP run on 960221. May be modified in progress.
Part I. Negative central shear ------------------------------ Start from a standard fast 800kA startup, like a fiducial, but bring RF on as early as possible. Things to try: reduce early density move position out earlier to match antenna (maybe use loading feedback?) Try small pellet during current rise, before RF. Monitor sawtooth onset, neutron rate. Note that automatic EFIT stored energies will be meaningless for inverted pressure profiles, but we may be able to get something from w_diamagnetic. If we seem to be getting anything reproducible, try popping some Li pellets to get a cigar measurement of Bz(R). |
| Feb 23 1996 05:25:41:750PM | 960223037 | Steve Wolfe | Part II. PEP modes
------------------- If feasible, this part can be started during the late flattop of shots from the first part of the run. Set up standard 800MA plasma. Vary pellet timing relative to RF turn-on to optimize neutron rate. Document it to death, including Sc injections for tau_p. May want to try a pre-pellet Sc injection as well. |
| Feb 23 1996 05:26:47:570PM | 960223037 | Steve Wolfe | Shot 960223037 - Changing experiments in mid-stream. Now going to
MP #125A ERS/PEP SL Porkolab PO wolfe For run plan see Wednesday, 960221 Load shot 960221035 Purge a-side valve and refill with D2 Plasma, H-modes, full length. |
| Feb 23 1996 05:34:03:880PM | 960223037 | Steve Wolfe | Shot 960223037 - only 1MW from RF. Sawteeth start at 180msec. Multiple
h-modes on and off. Next shot - better RF, RF off at .7, pellet at .8 |
| Feb 23 1996 05:48:41:160PM | 960223038 | Steve Wolfe | Shot 960223038 - try for better RF, RF off at .7, No Li pellet at .8
because I forgot to tell them to open the gate valve. Plasma full length. Rf faulting all the way through. On at .13 at 1MW level, 2MW @ .157, sawteeth at .211. |
| Feb 23 1996 06:05:30:910PM | 960223039 | Steve Wolfe | Shot 960223039 - try for better RF, RF off at .7, Li pellet at .8
ONly 1MW in early. Disrupted at .9sec, after pellet. No PEP mode. Next shot drop density at .2sec to ,9e20 (from 1.0) and turn on RF feedback at -1000 at .1sec |
| Feb 23 1996 06:23:38:510PM | 960223040 | Steve Wolfe | Shot 960223040 - try for better RF, RF off at .7, Li pellet at .8,RF on
at .825. Drop density at .2sec to ,9e20 (from 1.0) and turn on RF feedback at -1000 at .1sec Plasma - multiple h-modes. pellet, possible PEP mode. sawteeth at .2sec, when Te=3keV. RF only on at .15sec and only 1MW. |
| Feb 23 1996 06:47:21:970PM | 960223041 | Steve Wolfe | Shot 960223041 - try for better RF, RF off at .7, Li pellet at .8,RF on
at .825 at 1MW. Raise seg1 PG3 to slow current rise a bit, get rid of CR disruption. Got 2MW in at 130msec. sawtoothing at 200msec; it ain't working. PEP mode looks puny. |
| Feb 23 1996 07:02:09:460PM | 960223042 | Steve Wolfe | Shot 960223042 -No pellet this time. Lowered nl04 at .2 to .5e20.
Try to start RF at .12sec. Darren has a problem- low cell air pressure. Sawtoothing at .216, Te=4.7kev. Neutrons peak at 3e13 at .4sec |
| Feb 23 1996 07:22:49:850PM | 960223043 | Steve Wolfe | Shot 960223043 - Try to get RF on at 50msec!
Darren's problem was a frozen air line! Fixed now. Disruption at .9sec No RF before .1, only 1MW until .35. No PEP mode. |
| Feb 23 1996 07:41:31:920PM | 960223044 | Steve Wolfe | Shot 960223044 - Try to get RF on at 50msec!
5.2keV at 220msec when st start; RF on at .07sec (1MW) , 2MW at .1. Early disruption is stil there - see ECE outer channels show MHD Weak PEP mode. |
| Feb 23 1996 08:01:17:200PM | 960223045 | Steve Wolfe | Shot 960223045 - Pop a small pellet at .180sec, fast magnetics to .08-.21
It survived!! Not much pellet effect. Looks similar to 44, but only 4.5keV Might be a fragment |
| Feb 23 1996 08:10:02:820PM | 960223046 | Steve Wolfe | Shot 960223046 - Pop a small pellet at .180sec, fast magnetics to .08-.21
same as 45 except SC injection 10msec before second pellet. Looks similar to 45. Cigar on first pellet looks weird, sort of hollow. Still hardly any density increase???? Second PEP mode still puny. |
| Feb 23 1996 08:25:46:010PM | 960223047 | Steve Wolfe | Shot 960223047 - Pop a BIG pellet at .180sec, fast magnetics to .08-.21
same as 45 except SC injection 10msec before second pellet. Darren's tracking system is screwed up, he needs a pit run to fix it after this shot. No pellets this time - operator error. Joe identifies the current rise disruption as a locked mode. |
| Feb 23 1996 08:42:28:130PM | 960223048 | Steve Wolfe | Shot 960223048 - Pop a BIG pellet at .180sec, fast magnetics to .08-.21
same as 45 except SC injection 10msec before second pellet. Darren's tracking system is probably still screwed up, he couldn't find anything. He may be able to reconstruct. Still only a small density perturbation! Where are the particles? Neutron rate looks lower??? |
| Feb 23 1996 08:58:18:030PM | 960223049 | Steve Wolfe | Shot 960223049 - Drop the OH1 and 2 voltages by 100V and 20V, respectively
Big pellet at 180 instead of 200 this time. It survived. got the pellet in, around 4kev. sawteeth start around the same time. |
| Feb 23 1996 09:09:56:520PM | 960223050 | Steve Wolfe | Shot 960223050 - Two big pellets 180,185 msec.
fizzle. That's all! |
| Engineering Operator Comments | ||||
| Shot | Time | Type | Status | Comment |
| 1 | 08:24:09:630AM | Plasma | Bad | ef2l pulled out |
| 2 | 08:41:16:920AM | Plasma | Ok | |
| 3 | 08:51:36:980AM | Plasma | Ok | |
| 4 | 09:04:31:460AM | Plasma | Ok | |
| 5 | 09:19:17:440AM | Plasma | Ok | |
| 6 | 09:37:36:440AM | Plasma | Ok | |
| 7 | 09:52:46:070AM | Plasma | Ok | |
| 8 | 10:13:44:230AM | Plasma | Ok | |
| 9 | 10:26:37:190AM | Plasma | Ok | |
| 10 | 10:37:50:570AM | Plasma | Ok | |
| 11 | 10:46:08:790AM | Plasma | Ok | |
| 12 | 10:59:25:450AM | Plasma | Ok | |
| 13 | 11:08:53:100AM | Plasma | Ok | |
| 14 | 11:21:26:160AM | Plasma | Ok | |
| 15 | 11:30:32:090AM | Plasma | Ok | |
| 16 | 11:40:10:030AM | Plasma | Ok | |
| 17 | 11:55:55:320AM | Plasma | Ok | |
| 18 | 12:35:41:870PM | Plasma | Ok | |
| 19 | 12:57:32:060PM | Plasma | Ok | |
| 20 | 01:07:46:480PM | Plasma | Ok | |
| 21 | 01:24:20:030PM | Plasma | Ok | |
| 22 | 01:37:53:030PM | Plasma | Ok | |
| 23 | 01:51:17:610PM | Plasma | Ok | |
| 24 | 02:03:20:080PM | Plasma | Ok | |
| 25 | 02:14:34:070PM | Plasma | Ok | |
| 26 | 02:28:27:860PM | Plasma | Ok | |
| 27 | 02:41:47:500PM | Plasma | Ok | |
| 28 | 03:03:59:040PM | Plasma | Ok | |
| 29 | 03:18:08:310PM | Plasma | Ok | |
| 30 | 03:31:50:490PM | Plasma | Ok | |
| 31 | 03:41:41:560PM | Plasma | Ok | |
| 32 | 03:56:00:260PM | Plasma | Ok | |
| 33 | 04:09:45:780PM | Plasma | Ok | |
| 34 | 04:19:49:950PM | Plasma | Ok | |
| 35 | 04:45:20:620PM | Plasma | Ok | |
| 36 | 04:58:22:580PM | Plasma | Ok | comm fault OH1 & OH2L |
| 37 | 05:24:41:670PM | Plasma | Ok | |
| 38 | 05:41:31:570PM | Plasma | Ok | |
| 39 | 05:53:18:980PM | Plasma | Ok | |
| 40 | 06:12:43:940PM | Plasma | Ok | |
| 41 | 06:33:51:830PM | Plasma | Ok | |
| 42 | 06:51:10:260PM | Plasma | Ok | |
| 43 | 07:15:29:530PM | Plasma | Ok | |
| 44 | 07:31:35:560PM | Plasma | Ok | |
| 45 | 07:48:58:170PM | Plasma | Ok | |
| 46 | 08:02:25:120PM | Plasma | Ok | |
| 47 | 08:17:25:560PM | Plasma | Ok | |
| 48 | 08:33:48:450PM | Plasma | Ok | |
| 49 | 08:47:37:200PM | Plasma | Ok | |
| 50 | 09:03:37:040PM | Plasma | Ok | OH2u Bypass comm Fault OH1 self powered fired. |