| Miniproposals | ||||||||||
|
| Operators | |
| Session leader(s): | Tuomas Tala |
| Physics operator(s): | Steve Scott |
| Engineering operator(s): | Andy Pfeiffer,Bill Parkin,Bill Byford |
| Engineering Operator Run Comment |
| MP 609a SL Rice PO Steve Scott |
| Session Leader Plans |
| Entered: Jan 12 2011 05:54:13:890PM |
| Author: Tuomas Tala |
| Essential diagnostics: DNB, CXRS, Hirex-Sr, Thomson
1. Start with the locked-mode shot number 1110105018 for calibration purpose. Bt=5.4T, Ip=0.8MA and nl04=0.6e20m^-2. B-side lower enabled, 1 psi Ar. 2. LH modulation tests: Run shot 1101021009 (Bt=5.4T, Ip=0.8MA, nl04=0.8e20m^-2) Repeat with 50% higher density (Bt=5.4T, Ip=0.8MA, nl04=1.2e20m^-2) Repeat with 50% lower density (Bt=5.4T, Ip=0.8MA, nl04=0.5e20m^-2) Repeat the 3 shots above by adding 2MW of ICRF at 80MHz 3. SSEP sweep tests: Run shot 1080314009 (Bt=5.4T, Ip=0.8MA, nl04=1.3e20m^-2) Repeat at a factor of 2 higher density (Bt=5.4T, Ip=0.8MA, nl04=2.5e20m^-2) Repeat at higher Bt and Ip (Bt=7T, Ip=1MA, nl04=1.3e20m^-2) Repeat at lower Bt and Ip (Bt=3.4T, Ip=0.5MA, nl04=1.3e20m^-2) 4. DNB modulation tests: Run the shot of Bob Granetz with DNB modulation If modulation visible in the core rotation, vary density, Bt and ICRF power (at Bt=5.4T) The order of points 2-4 can be changed if needed. After these initial tests, the best perturbation is chosen and the collisonality, R/Ln and q profile scans are carried out in the best possible way operationally feasible following the physics ideas presented in the miniproposal 609a. |
| Physics Operators Plans |
| Entered: Jan 12 2011 05:38:41:867PM |
| Author: Steve Scott |
| -----------------
Engineering Setup ----------------- Run begins at 09:00 and ends at 17:00 Power systems as on: 1110105018 Noote: the first several parts of this MP call for operation at 5.4 Tesla. So the TF limit should be set for the usual 5.4 Tesla value. A later part of the experiment calls for operation at 7.0 Tesla. We will ask for a change in the engineering limit to the TF current if we reach that part of the expt. Acoil: +Dtop -Dbot -Jtop +Jbot (standard) Hybrid Enabled Gas setup: B-Top 6 psi D2 Hybrid enabled (PG4) B-side lower 1 psi Ar H Hybrid disabled (PG1) B-main 40 psi D2 Hybrid enabled (PG3) fill NINJA with 10 psi D2 DISABLED leave B-side lower upper as-is. Hybrid DISABLED (PG2) Enable gate-valves and shutters: ECE, VUV, HiREX Sr, Xeus Leave z-bolo shutter as is (should be open) Torvac gatevalve toggle (yes/no): no Boronization(yes/no): no Overnight ECDC (yes/no): yes, if possible. This may not be possible, since MIT is officially closed today. If possible, could we get 2 hours of ecdc before the run, using the conditions from last Friday (January 7). ICRF(yes/no): yes LH(yes/no): yes Cryopump (yes/no): yes DNB (yes/no): yes Vessel temperature: 35/35/35 ------------------------------ ECDC Parameters (if requested) ------------------------------ gas and pressure: He at 1.e-4 Torr sweep: 45/43/103 cm scan: 20/120 s This is a temporary version of the physOp plan, it will be updated thru the evening. We'll start with an evaluation of the suitability of locked mode shot 1110105018 for momentum-pinch studies. Then we'll move to the use of Lower Hybrid modulation, as on shot 1101021009. We will vary the density up and down a factor of two. Also, we will explore the use of 2 MW of ICF at 80 MHz. Then we'll progress to ssep sweeps as on shot 1080314009. Start with an exact duplicate shot, then increase density NeL demand a factor of 2. Assuming success & available time, we'll then proceed to varying the TF. (down to 3 T, up to 7 T). At that time we will ask that the engineering limits on the TF supply be changed. |
| Session Leader Summaries |
| Entered: Jan 14 2011 04:07:29:823PM |
| Author: Tuomas Tala |
| The session explored 3 different techniques to create a periodic perturbation in the plasma, LHCD modulation, DNBI modulation and SSEP modulation.
In addition, impurity transport was studied in most of the discharges, with the idea to compare the impurity transport with the momentum transport. After the kind of slowish start of the session, 14 shots (005-018) were performed with LHCD modulation. The first shots with 250kW power modulation did not create any visble rotation modulation. Even LHCD modulation at 500kW of power (shot 008) did not have enough modulation to be a useful physics shot. Just after increasing the LHCD power modulation to 750-800kW, a very clear v_tor modulation appeared. Good LH modulation shots with a clear v_tor modulation are the following ones: 011, probably the best shot, low density case; 013, density 25% higher than in 011; 016, density further 30% up, but it looks like the rotation modulation is really small at these higher densities, nebar= 1.05e21m^-2 and 018, as in 011 but add 1.4Mw of ICRF, looks again like v_tor modulation is much smaller. 017 is a reference shot to 011 with constant LH power of 450kW, a proxy of the averaged LH power in 011 to see the steady-state rotation level without rotation. The shots 019-024 were devoted to DNBI modulation. The first part 0.6-1.0s was ohmic phase and the latter part of shots 019-021 was planned to be EDA H-mode with 2.6MW of ICRF power. No clear v_tor modulation was observed in any of the pulses. There are some hints on a possible modulation in shots 020 and 021, but further analysis, probably with some smoothing or Fourier analysis is required to confirm or unconfirm a possible modulation. In any case, it looks like this modulation method is not useful for momentum transport studies on C-Mod. The shots 025-035 were surveying the SSEP modulation technique. Pulses 025-029 disrupted either due to the SSEP modulation amplitude being too large or the rise and down times being too small. Shot number 030 is a very good shot, no disruption and a clear v_tor modulation visible with 10 good cycles. Other pulses were modulation visible although not as well as in 030 are 031, 032 and possibly 035 which is at higher density. It looked like having Cryo ON or OFF did not make much difference in the observed v_tor modulation. Impurity puffs were carried out for most of the shots, but as most of the time were spent on developing the rotation modulation techniques, the actual scans were not carried out in htat extent planned. Therefore, the comparision whether the parametric dependencies of momentum and impurity transport are the same or not remains to be done when the scans will be performed. A comparison between impurity and momentum confinement times can be done already for those pulses where the rotation modulation was successful. Executive summary: LHCD modulation creates a good v_tor modulation but the questions remains whether it perturbs too much things like ne and Te as well. Quick analysis suggests 10-15% modulation in ne and Te which is not too much. DNBI modulation is not applicable to momentum transport studies. SSEP modulation looks like an ideal technique as it does not create any other visible perturbation in the plasma. Further run time is needed to optimise its use, like the optimum SSEP modulation amplitude and rise/fall times and the its use with ICRF power. A new run day is needed to carry out the collisionality, R/Ln and q profile scans to study the dependence of the momentum pinch and diffusivity on these using the SSEP technique and possibly LHCD technique. |
| Physics Operator Summaries |
| Entered: Jan 13 2011 08:24:50:093AM |
| Author: Steve Scott |
| this is a place holder for the summary |
| Entered: Jan 13 2011 06:17:13:847PM |
| Author: Steve Scott |
| Physics Operator summary for MP609a:
If you are shopping this expt for good plasma startups, please note that the cryopump was on for shots 1-31 and 35. The cryopump was off for shots 32-34. To fix the fizzle that occurred on shot 33, we made a small adjustment to the EF4 current programming (-1290 --> -1300). This resulted in a nice (bounce-free) startup (cryopump off). The next and final shot (35) had the cryopump on, and it was also a nice startup. So this is a good startup if you need the cryopump. But note that shot 35 isn't so great if you use it in its entirety: the NeL demand was set for 1.9e20, but because (a) the plasma was near double null; and (b) because the cryopump was on, the plasma density got to only about 1.1e20 despite the fact that the gas valve was wide open for most of the shot. Scorecard Test shots ....... 1 fizzles, duds ..... 3 plasmas ........... 31 full length* .......... 24 disruptions ........... 7 (shots 6, 15, 25, 26, 28, 29, 34) * plasma survives at least into Ip rampdown This was a reasonably successful run. We explored three methods of perturbing the toroidal velocity: shots 3-4 locked mode to establish zero-offset of HIREX 5-18 modulated LH to perturb vphi 19-24 modulated DNB to perturb vphi 25-35 ssep sweeps to perturb vphi MODULATED LH perturbations (shots 5 --> 18) We successfully applied modulated LH. We covered a range of NeL from about 3.6e19 to about 7.e19, with modulated LH power up to about 800 kW. The scan also included one shot with constant LH power (shot 17) and one shot which had both modulated LH plus some ICRF (shot 18, about 1.3 MW). The LH ran reasonably well, although we did have to make some adjustments to RCUR to adjust the size of the outer gap as we varied the plasma density. These shots had a number of 'bounces' in the startup. I decreased the prefill a little, and the bounces went away. Then later in the day, they came back. So at the suggestion of Steve Wolfe, I increased the prefill, and the bounces went away again. So today's experience doesn't provide much clarity on how to eliminate bounces. There was also some adjustment of the size (duration) of the argon puff in this series of shots. Since it was John Rice's run, we were generally pretty generous with the argon puffing. MODULATED DNB (shots 19 --> 24) The objective here was to inject a modulated DNB into a steady EDA H-mode plasma. The hope was that having a steady plasma would make the small velocity perturbations expected from the small DNB torque visible above the noise, and having an Hmode would give CXRS enough signal to make a precision measurement. We basically continued with the same equilibrium from the previous series, and just increased the NeL demand and added ~2.6 MW of ICRF power. Shot 21 is a 'trophy' from the perspective of it being an excellent steady EDA plasma, but alas the DNB didn't work so well. Some shots (e.g. 20, 24) had RF problems which reduced the RF power to 1.3 MW, and so the plasma remained in Lmode. On shot22 there was no RF power at all. Shot 23 had a series of ELM-free periods with the usual impurity accumulation followed by radiative collapse. SSEP sweeps (shots 25 --> 35) This was the most challenging part of the experiment. We chose to impose the ssep sweeps by varying the zcur demand, without touching the clearin controls. The original perturbations resulted in disruptions, because the EFC power supply railed. By reducing the magnitude of the sawtooth-like perturbation and by decreasing the up/down ramp rate, we managed to get some full-length plasmas with 10 ssep perturbations, see e.g. shots 30, 31, 32, 33 and one shot (27) with a single step-like ssep perturbation. On the last shot we attempted to significantly increase the collisionality by doubling the NeL demand, but alas the cryopump ate all the gas, and so the density increased only to about 1.1e20. |
| Session Leader Comments | |||
| Jan 13 2011 08:55:16:783AM | 1110113001 | Tuomas Tala | No power shot. Was OK. |
| Jan 13 2011 09:35:05:093AM | 1110113002 | Tuomas Tala | Non-shot. |
| Jan 13 2011 09:37:28:220AM | 1110113003 | Tuomas Tala | Start with the locked-mode shot number 1110105018 for calibration purpose. Bt=5.4T, Ip=0.8MA and nl04=0.6e20m^-2. B-side lower enabled, 1 psi Ar. Locked-mode reproduced. Too little Argon for good v_tor and Ti measurements. |
| Jan 13 2011 09:51:29:460AM | 1110113004 | Tuomas Tala | Start with the locked-mode shot number 1110105018 for calibration purpose. Bt=5.4T, Ip=0.8MA and nl04=0.6e20m^-2. B-side lower enabled, 1 psi Ar. Shot OK for calibration pruposes. The scientific program can start with a LHCD modulation shot at 10Hz frequency with n||=1.6. |
| Jan 13 2011 10:11:34:927AM | 1110113005 | Tuomas Tala | Repeat LH reference shot 1101021009 (Bt=5.4T, Ip=0.8MA, nl04=0.6e20m^-2), but with modulation at 10Hz. Good modulation of 250kW, but modulation not visible in rotation, rotation only changed when LH was switched on and off. Increase LH power and decrease density. |
| Jan 13 2011 10:19:13:897AM | 1110113006 | Tuomas Tala | Increase LH power and decrease density from previous shot. Density down by about 20%, more than requested. No LH power modulation, LH system trip. Repeat the shot with LH modulation ON and 10% higher density. |
| Jan 13 2011 12:07:51:660PM | 1110113007 | Tuomas Tala | Repeat the previous shot with LH modulation ON and 10% higher density. Decrease teh outer gap to increase the density in front of the LH grill.
Disrupted at 0.6s. Repeat the same pulse, but at higher density to avoid possible lock-modes. |
| Jan 13 2011 10:56:52:523AM | 1110113008 | Tuomas Tala | Repeat the previous shot 005, but with LH modulation ON and higher density (back to pulse 005). LH modulation of about 0.5MW, but not very visible modulation in v_tor though there is a hint of mudulation. Increase LH power to get a more clear modulation. |
| Jan 13 2011 11:24:17:920AM | 1110113010 | Tuomas Tala | LH trip. Repeat previous shot with LH power ramp-up in the first modulation cycle. |
| Jan 13 2011 12:07:36:697PM | 1110113011 | Tuomas Tala | Good pulse. LH power now 900kW. Really clear modulation in v_tor in the plasma center. Looks like in the anti-phase with LH power modulation.
Increase density 25% to nbar=8e19m^-2 to try to move the LH power modulation to the edge and to create the rotation modulation also there. |
| Jan 13 2011 11:55:26:610AM | 1110113012 | Tuomas Tala | Density almost identical to 011 as the density increase request was not uploaded. Locked-mode as well. Repeat it with 25% higher density nbar=8e19m^-2. |
| Jan 13 2011 12:12:42:750PM | 1110113013 | Tuomas Tala | Good pulse. Density nbar=8e19m^-2, up by 25%. v_tor modulation clearly smaller than in 011, but still visible. Increase density further. |
| Jan 13 2011 12:16:45:667PM | 1110113014 | Tuomas Tala | Density nbar=1.05e21m^-2 as requested. LH power modulation not good. Increase outer gap to improve LH. |
| Jan 13 2011 12:40:38:207PM | 1110113015 | Tuomas Tala | Disrupted at very early phase. Repeat the pulse. |
| Jan 13 2011 12:55:10:323PM | 1110113016 | Tuomas Tala | Good pulse, but it seems that at this high density, no modulation visible in v_tor any longer. This is the end of the density scan with LH. |
| Jan 13 2011 01:02:58:990PM | 1110113017 | Tuomas Tala | as in pulse 011, but no LH modulation reference shot at half LH power 450kW. Density turns out to be a bit higher than 011 although no gas is puffed. Now add ICRF power to decrease the collisionality. |
| Jan 13 2011 01:22:15:260PM | 1110113018 | Tuomas Tala | As for shot 011, but add ICRF power 1.4MW as requested. Looks like rotation modulation more or less absent. End of LH modulation part of the run. Go to DNBI modulation. |
| Jan 13 2011 01:43:39:230PM | 1110113019 | Tuomas Tala | DNBI modulation, ohmic 0.6s-1.0s, EDA H-mode 1.0s-1.4s with 2.6MW of ICRF. ICRH power increase slow, the first part of H-mode not good, not in EDA mode. No clear DNBI modulation. Repeat at higher density. |
| Jan 13 2011 01:47:00:250PM | 1110113020 | Tuomas Tala | DNBI modulation, ohmic 0.6s-1.0s, EDA H-mode 1.0s-1.4s with 2.6MW of ICRF. ICRH produced only half of the power. There could be a hint that some sort of modulation is visible in the core rotation signal. |
| Jan 13 2011 01:56:47:450PM | 1110113021 | Tuomas Tala | DNBI modulation, ohmic 0.6s-1.0s, EDA H-mode 1.0s-1.4s with 2.6MW of ICRF.
DNBI did not fire in the Ohmic phase, in the H-mode phase, DNBI fired 4 modulation cycles at lower voltage around 40kV. ICRF power waveform good. |
| Jan 13 2011 02:16:19:430PM | 1110113022 | Tuomas Tala | DNBI modulation, ohmic throughout, no ICRH to maximize the number of modulation cycles under the same plasma conditions. Technically good pulse. It seems that no visible rotation modulation seen in the core v_tor signal. Repeat with 2.6MW of ICRF power in H-mode. |
| Jan 13 2011 02:29:49:777PM | 1110113023 | Tuomas Tala | DNBI modulation, with 2.6MW of ICRF power.
Unintentional L-H transition modulation between the ELM free H-mode and L-mode. Very visible rotation modulation seen in the core v_tor signal due the L-H trnasition modulation. Repeat the pulse with increased ne to stay in EDA H-mode. |
| Jan 13 2011 02:43:14:960PM | 1110113024 | Tuomas Tala | Repeat shot 023, but at higher ne. DNBI modulation, with 2.6MW of ICRF power. No steady EDA H-mode. No clear rotation modulation at 10Hz DNBI modulation frequency. Move to the SSEP part of the program. |
| Jan 13 2011 03:08:39:630PM | 1110113025 | Tuomas Tala | SSEP part of the program.
Disrupted at 1.05s around the upper null - single null transition. Lower null - upper null transition created some 10km/s decrease in v_tor, which is large enough perturbation. Density too low. Decrease the amplitude of SSEP and increase density. |
| Jan 13 2011 03:07:51:940PM | 1110113026 | Tuomas Tala | Disrupted at 1.05s around the upper null - single null transition. Lower null - upper null transition created some 10km/s decrease in v_tor, which is large enough perturbation. Same problem again. Need to slow down the upper null-lower null transition from 20ms to 30ms to avoid disruption. |
| Jan 13 2011 03:43:10:320PM | 1110113027 | Tuomas Tala | SSEP modulation at 20Hz, 20ms lower-upper null, 30ms upper-lower null. Disrupted at 0.8s. |
| Jan 13 2011 03:46:49:103PM | 1110113028 | Tuomas Tala | Repeat 027. SSEP modulation at 20Hz, 20ms lower-upper null, 30ms upper-lower null. Disrupted at 0.8s.
Rotation at the first modulation step behaves in an unexpected as rotation increases there. Increase modulation time from 50ms to 70ms. |
| Jan 13 2011 03:45:43:510PM | 1110113029 | Tuomas Tala | Repeat 027. SSEP modulation at 20Hz, 20ms lower-upper null, 30ms upper-lower null. Disrupted at 0.8s. The only successful modulation step is fine, v_tor goes down as expected. |
| Jan 13 2011 04:08:49:583PM | 1110113030 | Tuomas Tala | Successful modulation with respect to disruptions. Good pulse, clear modulation signal in v_tor. 10 good cycles. |
| Jan 13 2011 04:17:26:457PM | 1110113031 | Tuomas Tala | Good pulse, not so clear modulation signal in v_tor. Not undertood why the v_tor modulation signal is weaker even if there is more Ar in the plasma. 10 cycles. |
| Jan 13 2011 04:39:37:230PM | 1110113032 | Tuomas Tala | No cryopump and less Ar puff. Disrupted in the landing at 1.9s (no issue for physics analysis).
v_tor modulation signal larger, but not too visible. Increase the SSEP modulation amplitude by 50% and decrease density by 10%. |
| Jan 13 2011 04:39:19:167PM | 1110113033 | Tuomas Tala | Increase the SSEP modulation amplitude by 50% and decrease density by 10%.
Disrupted very early. Repeat with modified gas prefill. |
| Jan 13 2011 04:56:18:430PM | 1110113034 | Tuomas Tala | Increase the SSEP modulation amplitude by 50% and decrease density by 10%. Disrupted at 0.9s, a few modulation cycles available. v_tor modulation signal does not look very clear. |
| Jan 13 2011 05:28:12:940PM | 1110113035 | Tuomas Tala | Go back to shot 030 and increase density a factor of 2. Went through successfully, but density not as much higher as requested. No clear modulation signal. |
| Physics Operator Comments | |||
| Jan 13 2011 08:56:44:480AM | 1110113001 | Steve Scott | first shot will be a no-power shot to verify that the gas values work.
On the physics-operator side, shot 1110105018 has been loaded. Bt=5.4 Tesla, Ip=0.8 MA, Nel demand = 6.e19. Acoil current is ramped from 0 to 4000 amps between 0.4 and 0.5 sec to generate the locked mode. Result: success. gas valve worked. next: proceed to experiment using shot 1110105018 as the reference |
| Jan 13 2011 09:14:09:927AM | 1110113002 | Steve Scott | Loaded 1100105018.
result: no plasma. permissive problem. Next shot: try again for a repeat of 1100105018. |
| Jan 13 2011 09:41:05:313AM | 1110113003 | Steve Scott | Loaded 1110105018.
Result: full length plasma. Using iscope, verified that we got the same plasma. Alas, operator error: forgot to enable the Argon valve. Next shot: repeat, but this time with argon. |
| Jan 13 2011 09:55:24:080AM | 1110113004 | Steve Scott | Result: good repeat of previous shot. Got the argon puff.
Argon level sufficient for HIREX. So we have calibrated the zero offset for hirex. Next shot: load segment 2 from 1101021009 into segment 2. 5.4 Tesla, 0.8 MA, nl04=0.8e20. Modulated LH. |
| Jan 13 2011 10:07:43:677AM | 1110113005 | Steve Scott | Loaded from 1101021009. Full length shot.
Got modulated LH at about 200 kW. Next: Reduce NeL demand in segment 2 from 4.0e19 to 3.6e19. Also, try to increase the LH power. |
| Jan 13 2011 10:34:28:567AM | 1110113006 | Steve Scott | Result: plasma was OK, but little or no LH power.
The decrease in NeL was a little more than requested ... NeL decreased to 3.2e19. So on the next shot, increase the NeL demand from 3.6 to 3.75e19 also, increase RCUR from 0.662 to 0.6645 in order to reduce the outer gap by 5 mm. result: disrupted early. Next shot: increase NeL demand back to 4.e19 |
| Jan 13 2011 10:35:47:557AM | 1110113008 | Steve Scott | Increase NeL demand back to its original value of 4.0e19. |
| Jan 13 2011 10:53:47:940AM | 1110113008 | Steve Scott | Increase NeL demand back to its original value of 4.0e19.
Result: good plasma. |
| Jan 13 2011 11:02:54:220AM | 1110113009 | Steve Scott | Increase argon puff from duration 100 to 150 ms.
try to increase rf power. result: some bounce on the startup at 10-20 ms, but plasma survived. |
| Jan 13 2011 11:17:52:417AM | 1110113010 | Steve Scott | Increase Argon puff again, from 150 to 200 ms. Also try to raise the LH power.
also decrease prepuff by 4 ms Result: full length plasma. There is still a bobble at startup, slightly better than previous shot. But got no LH power. |
| Jan 13 2011 11:22:48:880AM | 1110113011 | Steve Scott | Reduce prefill another 4 ms. Now set at 42 ms. |
| Jan 13 2011 11:32:51:027AM | 1110113012 | Steve Scott | Increase NeL demand from 4.0e19 to 5.0e19. |
| Jan 13 2011 11:52:54:920AM | 1110113012 | Steve Scott | Increase NeL demand from 4.0e19 to 5.0e19. Oops, operator error.
I changed the Nel demand but forgot to load the change. |
| Jan 13 2011 11:54:52:337AM | 1110113012 | Steve Scott | Increase NeL demand from 4.0e19 to 5.0e19. Oops, operator error.
I changed the Nel demand but forgot to load the change. result: locked mode throughout the shot. also, the shot had an early "bounce" |
| Jan 13 2011 12:02:47:447PM | 1110113013 | Steve Scott | Loaded the Nel demand to 5.e19. also reduced rcur demand by 2mm in order
to increase the outer gap by 4 mm. Result: good plasma. Got the requested density increase. PLH=800 kW modulated. This being an odd shot number, the early bounce seems to be absent. |
| Jan 13 2011 12:15:05:943PM | 1110113014 | Steve Scott | Increase NeL demand to 7.e19. No change in RCUR.
Result: nice plasma. got desired density. No bounce in the startup. Alas, got only a little LH power. |
| Jan 13 2011 12:30:06:590PM | 1110113015 | Steve Scott | Decrease RCUR by 2mm in order to increase the outer gap from 1.0 cm to 1.4 cm.
result: high hard x-rays early. plasma disrupts very early, at about 0.2 sec |
| Jan 13 2011 12:42:04:507PM | 1110113016 | Steve Scott | Increase prefill by 5 ms.
Result: got rid of the hard x-rays and the disruption. Also, there is no early bounce. |
| Jan 13 2011 12:59:19:353PM | 1110113017 | Steve Scott | Reload shot 11 from today. half power LH, but continuous.
Good shot, but we didn't quite reproduce the NeL that obtained on shot 11 ... the density on this shot is a little higher. Next: go back to modulated LH and add some RF power. If successful, shot 18 will be the end of this part of the experiment |
| Jan 13 2011 01:32:41:543PM | 1110113019 | Steve Scott | Start DNB-modulation part of the experiment.
Continue with same equilibrium. Increase NeL demand to 8.e19 and decrease argon puff to duration=100 ms (was 200 ms in previous shot). Looking to get a nice EDA H-mode. RF = 2.6 MW from 1.0 to 1.4 sec LH is now off, and will remain off for the remainder of today. result: not too bad. Need to get rid of the RF trips. |
| Jan 13 2011 01:48:05:350PM | 1110113020 | Steve Scott | Increase prefill back to 50 ms, hoping to get rid of the bounce.
also, increase NeL demand to 9.e19. Extend RF to 1.5 sec. Result: D-antenna did not fire. so plasma remained in Lmode. But we did get rid of the bounce. |
| Jan 13 2011 01:53:37:343PM | 1110113021 | Steve Scott | increased argon puff to 150 ms
result: plasma is beautiful EDA H-mode, but the DNB wasn't so good. Next: increase argon puff to 200 ms and turn off rf |
| Jan 13 2011 02:08:22:060PM | 1110113022 | Steve Scott | Good ohmic plasma. Had a couple of small injections at circa 0.8 and 0.9 sec.
DNB wasn't perfect, but good enough. The early 'bounce' seems to be absent. |
| Jan 13 2011 02:22:48:950PM | 1110113023 | Steve Scott | Add the rf power back in. No changes by the physics operator.
We should get a nice EDA plasma, like shot 21. RF will be on from 0.6 to 1.5 sec. Result: got a series of ELM-free periods, followed by impurity accumulation, radiative collapse, etc. Next shot: as per suggestion of Steve Wukitch, increase the target NeL from 9.e19 to 1.e20 in order to force the plasma back to EDA H-mode. No other DPCS changes. |
| Jan 13 2011 02:37:37:177PM | 1110113024 | Steve Scott | Increase target NeL to 1.0e20.
Result: got only 1/2 the RF power. Energy confinement remains L-mode This terminates this part of the experiment (velocity modulations via DNB modulation). Proceed to the third component of today's expt: ssep modulations |
| Jan 13 2011 02:38:35:170PM | 1110113025 | Steve Scott | Maintain same segment #1 from previous shot.
Load segment #2 from 1080314009, then updated the magnetics calculators. |
| Jan 13 2011 02:48:19:230PM | 1110113025 | Steve Scott | Maintain same segment #1 from previous shot.
Load segment #2 from 1080314009, then updated the magnetics calculators. NeL demand is left at its value in 1080314009, NeL = 1.0e20. result: plasma disrupts just after 1.0 sec. |
| Jan 13 2011 03:04:10:477PM | 1110113026 | Steve Scott | change perturbed zcur from -0.013 to -0.010 (in both perturbations)
also increased nel demand to 9.5e19 result: as in the previous shot, this shot disrupts shortly after the 2nd perturbation. |
| Jan 13 2011 03:07:15:980PM | 1110113027 | Steve Scott | Change: Increase zcur time scale for 2nd perturbation from 20 to 30 ms, i.e. the end of the zcur perturbation is moved from 1.02 to 1.03 sec. |
| Jan 13 2011 03:31:17:343PM | 1110113028 | Steve Scott | replaced 2-piece square-wave perturbation to zcur by a 10 sawtooth perturbation, 20 ms rise, 30 ms fall, starting 700 ms. no change to clearin programming.
also added a 50 ms argon puff at 1.0 sec, because the cryopump eats the argon result: plasma disrupts at 0.80 sec |
| Jan 13 2011 03:32:45:610PM | 1110113028 | Steve Scott | replaced 2-piece square-wave perturbation to zcur by a 10 sawtooth perturbation, 20 ms rise, 30 ms fall, starting 700 ms. no change to clearin programming.
also added a 50 ms argon puff at 1.0 sec, because the cryopump eats the argon result: disrupts at 0.8 sec. EFC rails. |
| Jan 13 2011 03:39:14:860PM | 1110113029 | Steve Scott | change modulation of zcur: go to a 70 ms moculation period, 30 ms rise, 30 ms fall, 5 ms at the top and bottom.
also, extend the early argon puff to 250 ms and eliminate the second argon puff |
| Jan 13 2011 03:55:39:930PM | 1110113030 | Steve Scott | changed programming on zcur modulation again: reduce amplitude from 0.013 to 0.007 and also increase the minimum from 0 to 0.003.
result: BINGO! this worked, in the sense that the plasma survived all ten modulation periods. |
| Jan 13 2011 04:05:34:217PM | 1110113031 | Steve Scott | Double the argon puff. No other changes.
result: |
| Jan 13 2011 04:23:48:313PM | 1110113032 | Steve Scott | 1. turn cryo pump off
2. reduce argon puff by factor 2 (back to 250 ms) 3. reduce prefill to 25 ms result: good plasma, disrupted in rampdown at 1.8 sec (0.4 MA). prefill pressure a little higher than previous shot, so reduce prefill on the next shot. |
| Jan 13 2011 04:24:45:360PM | 1110113033 | Steve Scott | 1. decrease prefill from 25 to 21 ms.
2. double the argon puff 3. reduce NeL demand to 8e19. |
| Jan 13 2011 04:29:17:843PM | 1110113033 | Steve Scott | 1. decrease prefill from 25 to 21 ms.
2. double the argon puff 3. reduce NeL demand to 8e19. 4. increase amplitude of zcur modulation from 0.007 to 0.010 by changing the minimum of the modulation from 0.03 to 0.00 |
| Jan 13 2011 04:48:39:973PM | 1110113034 | Steve Scott | increased prefill to 25 ms and increased ef4 to -1300
result: disruption at 0.92 seconds. |
| Jan 13 2011 05:24:21:320PM | 1110113035 | Steve Scott | reload shot 30.
increase nel demand to 1.9e20 reset EF4 to -1300 turned cryopump back on result: interesting. The plasma went through, but we didn't get the desired demand NeL despite the fact that the gas valve was wide open. Apparently, when the plasma is close to double null, the cryopump is a very efficient pump in ohmic plasmas. |
| Engineering Operator Comments | ||||
| Shot | Time | Type | Status | Comment |
| 1 | 08:51:56:357AM | Test | Ok | Gas only |
| 2 | 09:09:31:347AM | Plasma | Bad | No alternator shot permissive |
| 3 | 09:31:07:810AM | Plasma | Ok | |
| 4 | 09:43:37:310AM | Plasma | Ok | |
| 5 | 09:56:22:197AM | Plasma | Ok | |
| 6 | 10:09:59:430AM | Plasma | Ok | |
| 7 | 10:30:21:690AM | Plasma | Ok | |
| 8 | 10:45:33:077AM | Plasma | Ok | |
| 9 | 10:58:54:797AM | Plasma | Ok | |
| 10 | 11:12:53:213AM | Plasma | Ok | |
| 11 | 11:26:02:183AM | Plasma | Ok | |
| 12 | 11:43:01:300AM | Plasma | Ok | |
| 13 | 11:56:34:467AM | Plasma | Ok | |
| 14 | 12:09:36:940PM | Plasma | Ok | |
| 15 | 12:22:51:207PM | Plasma | Ok | |
| 16 | 12:38:49:690PM | Plasma | Ok | |
| 17 | 12:52:36:947PM | Plasma | Ok | |
| 18 | 01:06:26:743PM | Plasma | Ok | |
| 19 | 01:20:54:170PM | Plasma | Ok | |
| 20 | 01:33:59:653PM | Plasma | Ok | |
| 21 | 01:47:11:113PM | Plasma | Ok | |
| 22 | 02:01:48:713PM | Plasma | Ok | |
| 23 | 02:15:00:467PM | Plasma | Ok | |
| 24 | 02:29:13:543PM | Plasma | Ok | |
| 25 | 02:43:43:320PM | Plasma | Ok | |
| 26 | 03:00:23:230PM | Plasma | Ok | |
| 27 | 03:13:04:023PM | Plasma | Ok | |
| 28 | 03:27:44:353PM | Plasma | Ok | |
| 29 | 03:40:11:770PM | Plasma | Ok | |
| 30 | 03:52:36:710PM | Plasma | Ok | |
| 31 | 04:05:16:587PM | Plasma | Ok | |
| 32 | 04:18:41:393PM | Plasma | Ok | |
| 33 | 04:32:31:870PM | Plasma | Ok | |
| 34 | 04:46:22:427PM | Plasma | Ok | |
| 35 | 04:58:43:340PM | Plasma | Ok | |
| System Availability | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Jan 13 2011 08:51:42:170AM | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||