| Miniproposals | ||||||||||
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| Operators | |
| Session leader(s): | Martin Greenwald |
| Physics operator(s): | Joseph Snipes |
| Engineering operator(s): | Unknown |
| Engineering Operator Run Comment |
| MP #231 Critical Gradients. Greenwald/Snipes/Cochran. |
| Session Leader Plans |
| Physics Operators Plans |
| Session Leader Summaries |
| Entered: Jul 7 2004 03:49:26:070PM |
| Author: To Be Determined |
| Run Summary for 1001219 MP231 - modulated heating Session Leader - M. Greenwald Phys Op - J. Snipes Background and Plan: The idea is to investigate temperature profile stiffness via modulated heating. The amplitude and phase response can be used to get an incremental chi which is usually much higher than the chi computed from power balance. The difference might be attributed to very strong transport that turns on when the normalized temperature gradient is above a threshold. ITG theory, for example, predicts a big increase in transport when R/L_T goes above a R/L_Tcritical - forcing the plasma to marginal stability. These experiments would give us a quantitative measurement of how sharp the transport turn-on is - that is - how strongly the marginal stability condition is enforced. To do help with the data analysis, we will try to synchronize the sawteeth to the modulation of the central heating (at 80 MHz). This would sharpen up the fourier spectrum of the sawteeth. The steps we will follow will be: 1. get a standard EDA H-mode with 80 MHz heating from D and E. (5.4 T, 0.8 MA) 2. Modulate the power from one of these antennas to a frequency slightly higher than the sawtooth frequency. We will want to vary the degree of modulation from 100% to the minimum necessary to achieve synchronization. 3. With the 80 MHz system at the lowest modulation consistent with sawtooth synchronization, turn on the J-Port system (70 MHz). This system will be 100% modulated. 4. If successful, we will vary the net D and E power from the maximum to the minimum consistent with staying in H-mode. 5. If time permits, we would repeat these conditions in L-mode using an upper null configuration. We should be able to run over a larger power range. ============================== Results: Only moderate success. There were just 15 shots today - Time between shots was longer than average - we also had a slightly late start due to some diagnostic problems and experienced a longer delay when the computers scanning the magnet thermocouples decided to go on strike. We were able to synchronize the sawteeth to the ICRF modulation on shots 13,14 and 15. These shots had an ELMfree period followed by an brief H/L transition and a return to EDA H-mode. The sawteeth were synched during the EDA. We ran out of time before we could get the J port modulation going. The sawtooth heat pulses were easy to see on all three ECE systems. Clear, progressive phase delays could be seen on the outer channels which means we should have good data for calculation of the incremental chi. The amplitude was increased with the addition of modulated RF and the phase delay decreased. ================================ Shots suitable for further analysis include: 1001219007 1001219013 1001219014 1001219015 |
| Physics Operator Summaries |
| Entered: Jul 7 2004 04:37:12:897PM |
| Author: To Be Determined |
| Engineering setup and run plan for Thursday 07 Dec 2000. MP #231 Critical Gradients Session leader: Greenwald Physics operator: Snipes ------------------------------------------------------------------------------- Engineering setup: ECDC in D2 for 2 hours before the run. Power systems as on 1001205001. Gas setup: fill B-top with 6 psi of D2 Hybrid enabled fill B-side lower with 1 psi of Ar Hybrid DISABLED fill B-side upper with 35 psi of D2 Hybrid DISABLED, for ECDC fill C-side with 30 psi of D2 Hybrid enabled leave J-bot as is Hybrid DISABLED Enable the following gate valves: ECE, VUV, Beast, DNB Run starts at 09:00 and ends at 17:00. ------------------------------------------------------------------------------- RF Setup: XMTRs 1,2, and 3 should be made ready by 8:00 (run-on). XMTR 4 should be made ready by 6:30 (run-on). ------------------------------------------------------------------------------- Run Plan: Will start with standard 0.8 MA, 5.4 T, nl04 = 1 x 10^20 m^-2 plasmas with ICRF from D and E to get into H-mode. We will then modulate one of the two antennas by at most 50% to attempt to synchronize the sawtooth period with the modulation. Then, we will add 100% modulation of the J-port antenna at 70 MHz to provide off-axis heat pulses to investigate heat transport. If time permits, a power scan will be tried as well and we may go to upper null plasmas (e.g., 1001204018) to have a larger range of power in the same confinement regime (L-mode). Summary: The machine ran very well today. We had no fizzles and no duds and all plasmas went well into flattop. There was a long delay of nearly 2 hours due to a bit being set that inhibited measurements of the magnet temperatures. Bosco tracked it down in the PLC ladder and reset the bit and we started again. We ran on Z meter density feedback control though the TCI did work reliably in the end. We ran a couple of shots with upper null, but they both disrupted shortly after the ICRF reached full power (2.5 MW) apparently due to overheating of the top of the vessel where there are no protection tiles. A third upper null shot (shot 10) ran through O.K. at P_RF = 1.5 MW though there was a large increase in radiated power during the RF. So, it is probably not advisable to run upper null plasmas with more than 1.5 - 2 MW of RF. Attempts were made to synchronize the sawteeth with modulated ICRF at 80 MHz and they all failed even with 1 MW modulation on top of 2 MW background RF. So, the experiment was unsuccessful at determining heat pulse propagation between sawteeth. The 70 MHz RF was not successfully coupled. Shot,Duration(s),Ipmax(MA) Shot,Duration(s),Ipmax 1 0.981 0.784 2 1.782 0.787 3 1.410 0.792 4 1.862 0.797 5 1.883 0.795 6 1.955 0.800 7 1.956 0.800 8 0.740 0.828 9 0.783 0.826 10 1.944 0.792 11 1.952 0.989 12 1.948 0.992 13 1.962 0.992 14 1.961 0.989 15 1.961 0.989 Finished summary for 1001219 Total of 15 shots. 15 shots. 15 plasmas. 0 fizzles. 0 duds. Shot 1: Copied shot 1001205001 and set NL_ZMETER to 0.75, which should correspond to nl04 = 1.0 x 10^20 m^-2 and increased the TF current to 152 kA to reach 5.4 T. Disrupted at 0.97 s. Prad increased just after 0.94 s, probably a brick fell in. Shot 2: Increased RCUR offset to 6500 from 5500 at Wolfe's suggestion since the startup did not look very good. Good shot. Big injection visible on Prad at 0.77 s. Got 1.1 MW out of D and E. Shot 3: Decreased NL_ZMETER to 0.7. Disrupted at 1.4 s. Prad increased at 1.37 s during the RF. Right gap decreases to 0.5 cm during the shot. Shot 4: Put in a 3 mm inward ramp in RCUR from 0.5 s to 1.4 s to try to keep the outer gap constant at 1 cm. Good shot. Started 0.5 MW modulation of 80 MHz RF to attempt to synchronize the sawteeth about 2.3 MW background. Outer gap now steady at 1 cm. Shot 5: Increased Br0 offset from 1.5 mT to 2 mT since the startup is beginning to deteriorate. Long delay due to computer problems with the magnet thermocouple measurements. Good shot. 1 MW modulation of the 80 MHz RF on a background of 2.4 MW, but still no synchronization of the sawteeth. Nice long EDA H-mode. Shot 6: Dropped NL_ZMETER to 0.35 to bring the density down to nl04 = 7 x 10^19 m^-2. Good shot. RF tripped. Stayed in H-mode with hysteresis for several hundred ms after the RF. No synchronization of the sawteeth with the 80 MHz modulation. Shot 7: Repeat. Good shot. Sawteeth still not synchronized with 1 MW modulation of 80 MHz RF on 2 MW background. Nice long EDA H-mode into current rampdown. Shot 8: Change to segment 3 upper null equilibrium. Set TF current in segment 3 to 152 kA. NL_ZMETER was already set to 0.35. Disrupted at 0.73 s. Prad increased from 0.72 s. Rice said it was a moly flake. Density only reached nl04 = 6 x 10^19 m^-2 whereas the equivalent lower null reached 7.5 x 10^19 m^-2. Shot 9: Increased NL_ZMETER to 0.48 to try to make up for the lower density in upper null plasmas. Disrupted at 0.77s. Perhaps the RF is overheating the upper part of the vessel where there are no divertor tiles. Shot 10: Try reducing the RF power to 1.5 MW and moving it to start at 0.8 s. Good shot. Prad increases around 0.85 s looking like it would disrupt with more power. So, it seems that the RF is overheating the top of the vessel. With nearly 1 MW of 80 MHz modulation on top of 1.5 MW background, there is still no synchronization of the sawteeth with the RF. Shot 11: Reloaded shot 7 and reduced Br0 offset from 2 mT to 1.5 mT to tweak the breakdown. Increased Ip to 1 MA. Good shot. 80 MHz modulation is close in frequency to the sawtooth, but the phase does not match, so they are not synchronized. Shot 12: Repeat. Good shot. ELM-free then EDA H-mode. Breakdown nearly didn't make it. Shot 13: Try changing EF4 current from -1300 A to -1290 A to move the plasma inward a bit. Good shot. Breakdown is a bit better. Shot 15: Repeat. Good shot. Obtained near synchronous sawteeth with the RF modulation in the second H-mode. Then, we ran out of time. |
| Session Leader Comments | |||
| Dec 19 2000 09:05:22:560AM | Martin Greenwald | Plan: The idea is to investigate temperature profile stiffness via modulated heating. The amplitude and phase response can be used to get an incremental chi which is usually much higher than the chi computed from power balance. The difference might be attributed to very strong transport that turns on when the normalized temperature gradient is above a threshold. ITG theory, for example, predicts a big increase in transport when R/L_T goes above a R/L_Tcritical - forcing the plasma to marginal stability. These experiments would give us a quantitative measurement of how sharp the transport turn-on is - that is - how strongly the marginal stability condition is enforced. To do help with the data analysis, we will try to synchronize the sawteeth to the modulation of the central heating (at 80 MHz). This would sharpen up the fourier spectrum of the sawteeth. The steps we will follow will be: 1. get a standard EDA H-mode with 80 MHz heating from D and E. (5.4 T, 0.8 MA) 2. Modulate the power from one of these antennas to a frequency slightly higher than the sawtooth frequency. We will want to vary the degree of modulation from 100% to the minimum necessary to achieve synchronization. 3. With the 80 MHz system at the lowest modulation consistent with sawtooth synchronization, turn on the J-Port system (70 MHz). This system will be 100% modulated. 4. If successful, we will vary the net D and E power from the maximum to the minimum consistent with staying in H-mode. 5. If time permits, we would repeat these conditions in L-mode using an upper null configuration. We should be able to run over a larger power range. We also want to take this opportunity to look for the quasi-coherent mode with the heterodyne ECE system. This might require raising the field to 5.4 or 5.5 T to allow this system to see all the way to the edge. A fast digitization window during the EDA phase would be required. | |
| Dec 19 2000 05:21:45:793PM | Martin Greenwald | Results: Only moderate success. There were just 15 shots today - Time between shots was longer than average - we also had a slightly late start due to some diagnostic problems and experienced a longer delay when the computers scanning the magnet thermocouples decided to go on strike. We were able to synchronize the sawteeth to the ICRF modulation on shots 13,14 and 15. These shots had an ELMfree period followed by an brief H/L transition and a return to EDA H-mode. The sawteeth were synched during the EDA. We ran out of time before we could get the J port modulation going. The sawtooth heat pulses were easy to see on all three ECE systems. Clear, progressive phase delays could be seen on the outer channels which means we should have good data for calculation of the incremental chi. The amplitude was increased with the addition of modulated RF and the phase delay decreased. ================================ Shots suitable for further analysis include: 1001219007 1001219013 1001219014 1001219015 | |
| Dec 19 2000 09:45:25:310AM | 1001219001 | Martin Greenwald | disrupts at 1 second .6 MW no H-mode |
| Dec 19 2000 10:13:49:357AM | 1001219002 | Martin Greenwald | Better shot, RF power still low so no H-mode |
| Dec 19 2000 10:49:33:327AM | 1001219003 | Martin Greenwald | H-mode - but not a very good one |
| Dec 19 2000 11:03:55:530AM | 1001219004 | Martin Greenwald | Start RF modulation sawteeth not synched at 1 second st period = 6.89 msec rf period = 6.21 msec |
| Dec 19 2000 12:56:25:717PM | 1001219005 | Martin Greenwald | Similar to shot 5 still no sync |
| Dec 19 2000 01:18:14:607PM | 1001219006 | Martin Greenwald | Lower density problems with RF tune |
| Dec 19 2000 01:35:15:670PM | 1001219007 | Martin Greenwald | Decent H-mode RF stays on for whole pulse but no sync sawteeth at fairly constant freq though and we get good phase shifts on all gpc channels try L-mode with upper null for next shot |
| Dec 19 2000 01:48:30:890PM | 1001219008 | Martin Greenwald | First try with upper null - L-mode disrupts early |
| Dec 19 2000 02:22:08:437PM | 1001219009 | Martin Greenwald | disrupts early |
| Dec 19 2000 03:21:22:123PM | 1001219011 | Martin Greenwald | back to H-mode at 1 MA sawteeth and rf close to same frequency but not quite in sync ~ 100 Hz |
| Dec 19 2000 04:37:32:047PM | 1001219013 | Martin Greenwald | ELMfree phase followed by EDA Seems to be successfully synched from 1.15 to 1.35 which is during EDA |
| Dec 19 2000 04:38:36:810PM | 1001219014 | Martin Greenwald | Similar to previous shot sync less obvious tried to include modulated J port but didn't get any power |
| Dec 19 2000 05:03:06:157PM | 1001219015 | Martin Greenwald | Nothing out of J port again synched from maybe 1.25 to 1.35 |
| Physics Operator Comments | |||
| Dec 19 2000 08:58:02:090AM | Joseph Snipes | Engineering setup and run plan for Thursday 07 Dec 2000. MP #231 Critical Gradients Session leader: Greenwald Physics operator: Snipes ------------------------------------------------------------------------------- Engineering setup: ECDC in D2 for 2 hours before the run. Power systems as on 1001205001. Gas setup: fill B-top with 6 psi of D2 Hybrid enabled fill B-side lower with 1 psi of Ar Hybrid DISABLED fill B-side upper with 35 psi of D2 Hybrid DISABLED, for ECDC fill C-side with 30 psi of D2 Hybrid enabled leave J-bot as is Hybrid DISABLED Enable the following gate valves: ECE, VUV, Beast, DNB Run starts at 09:00 and ends at 17:00. ------------------------------------------------------------------------------- RF Setup: XMTRs 1,2, and 3 should be made ready by 8:00 (run-on). XMTR 4 should be made ready by 6:30 (run-on). ------------------------------------------------------------------------------- Run Plan: Will start with standard 0.8 MA, 5.4 T, nl04 = 1 x 10^20 m^-2 plasmas with ICRF from D and E to get into H-mode. We will then modulate one of the two antennas by at most 50% to attempt to synchronize the sawtooth period with the modulation. Then, we will add 100% modulation of the J-port antenna at 70 MHz to provide off-axis heat pulses to investigate heat transport. If time permits, a power scan will be tried as well and we may go to upper null plasmas (e.g., 1001204018) to have a larger range of power in the same confinement regime (L-mode). | |
| Dec 19 2000 09:49:45:983AM | 1001219001 | Joseph Snipes | Shot 1: Copied shot 1001205001 and set NL_ZMETER to 0.75, which should correspond to nl04 = 1.0 x 10^20 m^-2 and increased the TF current to 152 kA to reach 5.4 T. Disrupted at 0.97 s. Prad increased just after 0.94 s, probably a brick fell in. |
| Dec 19 2000 10:11:42:043AM | 1001219002 | Joseph Snipes | Shot 2: Increased RCUR offset to 6500 from 5500 at Wolfe's suggestion since the startup did not look very good. Good shot. Big injection visible on Prad at 0.77 s. Got 1.1 MW out of D and E. |
| Dec 19 2000 10:39:18:420AM | 1001219003 | Joseph Snipes | Shot 3: Decreased NL_ZMETER to 0.7. Disrupted at 1.4 s. Prad increased at 1.37 s during the RF. Right gap decreases to 0.5 cm during the shot. |
| Dec 19 2000 11:12:38:340AM | 1001219004 | Joseph Snipes | Shot 4: Put in a 3 mm inward ramp in RCUR from 0.5 s to 1.4 s to try to keep the outer gap constant at 1 cm. Good shot. Started 0.5 MW modulation of 80 MHz RF to attempt to synchronize the sawteeth about 2.3 MW background. Outer gap now steady at 1 cm. |
| Dec 19 2000 12:33:55:497PM | 1001219004 | Joseph Snipes | Shot 5: Increased Br0 offset from 1.5 mT to 2 mT since the startup is beginning to deteriorate. Long delay due to computer problems with the magnet thermocouple measurements. Good shot. 1 MW modulation of the 80 MHz RF on a background of 2.4 MW, but still no synchronization of the sawteeth. Nice long EDA H-mode. |
| Dec 19 2000 01:22:14:577PM | 1001219007 | Joseph Snipes | Shot 6: Dropped NL_ZMETER to 0.35 to bring the density down to nl04 = 7 x 10^19 m^-2. Good shot. RF tripped. Stayed in H-mode with hysteresis for several hundred ms after the RF. No synchronization of the sawteeth with the 80 MHz modulation. |
| Dec 19 2000 01:32:08:263PM | 1001219007 | Joseph Snipes | Shot 7: Repeat. Good shot. Sawteeth still not synchronized with 1 MW modulation of 80 MHz RF on 2 MW background. Nice long EDA H-mode into current rampdown. |
| Dec 19 2000 01:59:36:793PM | 1001219008 | Joseph Snipes | Shot 8: Change to segment 3 upper null equilibrium. Set TF current in segment 3 to 152 kA. NL_ZMETER was already set to 0.35. Disrupted at 0.73 s. Prad increased from 0.72 s. Rice said it was a moly flake. Density only reached nl04 = 6 x 10^19 m^-2 whereas the equivalent lower null reached 7.5 x 10^19 m^-2. |
| Dec 19 2000 02:22:06:780PM | 1001219009 | Joseph Snipes | Shot 9: Increased NL_ZMETER to 0.48 to try to make up for the lower density in upper null plasmas. Disrupted at 0.77s. Perhaps the RF is overheating the upper part of the vessel where there are no divertor tiles. |
| Dec 19 2000 02:47:30:157PM | 1001219010 | Joseph Snipes | Shot 10: Try reducing the RF power to 1.5 MW and moving it to start at 0.8 s. Good shot. Prad increases around 0.85 s looking like it would disrupt with more power. So, it seems that the RF is overheating the top of the vessel. With nearly 1 MW of 80 MHz modulation on top of 1.5 MW background, there is still no synchronization of the sawteeth with the RF. |
| Dec 19 2000 03:18:21:327PM | 1001219011 | Joseph Snipes | Shot 11: Reloaded shot 7 and reduced Br0 offset from 2 mT to 1.5 mT to tweak the breakdown. Increased Ip to 1 MA. Good shot. 80 MHz modulation is close in frequency to the sawtooth, but the phase does not match, so they are not synchronized. |
| Dec 19 2000 03:44:26:483PM | 1001219012 | Joseph Snipes | Shot 12: Repeat. Good shot. ELM-free then EDA H-mode. Breakdown nearly didn't make it. |
| Dec 19 2000 04:47:27:483PM | 1001219013 | Joseph Snipes | Shot 13: Try changing EF4 current from -1300 A to -1290 A to move the plasma inward a bit. Good shot. Breakdown is a bit better. |
| Dec 19 2000 04:49:24:920PM | 1001219014 | Joseph Snipes | Shot 14: Increased NL_ZMETER from 0.35 to 0.39 to try to avoid the ELM-free H-mode phase. Good shot. |
| Dec 19 2000 05:38:10:280PM | 1001219015 | Joseph Snipes | Shot 15: Repeat. Good shot. Obtained near synchronous sawteeth with the RF modulation in the second H-mode. Then, we ran out of time. |
| Dec 19 2000 05:40:08:187PM | 1001219015 | Joseph Snipes | Summary: Shot,Duration(s),Ipmax(MA) Shot,Duration(s),Ipmax 1 0.981 0.784 2 1.782 0.787 3 1.410 0.792 4 1.862 0.797 5 1.883 0.795 6 1.955 0.800 7 1.956 0.800 8 0.740 0.828 9 0.783 0.826 10 1.944 0.792 11 1.952 0.989 12 1.948 0.992 13 1.962 0.992 14 1.961 0.989 15 1.961 0.989 Finished summary for 1001219 Total of 15 shots. 15 shots. 15 plasmas. 0 fizzles. 0 duds. |
| Dec 19 2000 05:51:11:873PM | 1001219015 | Joseph Snipes | Summary: The machine ran very well today. We had no fizzles and no duds and all plasmas went well into flattop. There was a long delay of nearly 2 hours due to a bit being set that inhibited measurements of the magnet temperatures. Bosco tracked it down in the PLC ladder and reset the bit and we started again. We ran on Z meter density feedback control though the TCI did work reliably in the end. We ran a couple of shots with upper null, but they both disrupted shortly after the ICRF reached full power (2.5 MW) apparently due to overheating of the top of the vessel where there are no protection tiles. A third upper null shot (shot 10) ran through O.K. at P_RF = 1.5 MW though there was a large increase in radiated power during the RF. So, it is probably not advisable to run upper null plasmas with more than 1.5 - 2 MW of RF. Attempts were made to synchronize the sawteeth with modulated ICRF at 80 MHz and they all failed even with 1 MW modulation on top of 2 MW background RF. So, the experiment was unsuccessful at determining heat pulse propagation between sawteeth. The 70 MHz RF was not successfully coupled. |
| Engineering Operator Comments | ||||
| Shot | Time | Type | Status | Comment |
| 1 | 09:40:13:513AM | Plasma | Ok | |
| 2 | 10:02:42:280AM | Plasma | Ok | |
| 3 | 10:23:13:340AM | Plasma | Ok | |
| 4 | 10:45:03:623AM | Plasma | Ok | |
| 5 | 12:24:31:483PM | Plasma | Ok | |
| 6 | 12:51:21:717PM | Plasma | Ok | |
| 7 | 01:21:13:513PM | Plasma | Ok | |
| 8 | 01:45:48:577PM | Plasma | Ok | |
| 9 | 02:11:35:047PM | Plasma | Ok | |
| 10 | 02:37:15:077PM | Plasma | Ok | |
| 11 | 03:04:18:840PM | Plasma | Ok | |
| 12 | 03:31:58:140PM | Plasma | Ok | |
| 13 | 03:59:09:513PM | Plasma | Ok | |
| 14 | 04:26:30:327PM | Plasma | Ok | |
| 15 | 04:54:41:450PM | Plasma | Ok | |