1 TORE SUPRA Association Euratom-Cea A. Ekedahl et al Progress Report DITS project : 13 July 2007 Operational Limits during the TPL Deuterium Loading Experiment _______________________ F. Saint-Laurent, F. Rimini, A. Ekedahl, E. Tsitrone, A. Triay-Alcouffe, P. Monier-Garbet et al Overview of the 10 days experiment (talk E. Tsitrone) Main Limitation: Disruptions Revised scenario Probability of UFOs and Disruptions Appearance of UFOs Origin of UFOs Analysis of IR and CCD films Conclusions

2 TORE SUPRA Association Euratom-Cea A. Ekedahl et al Progress Report DITS project : 13 July 2007 Performance evolution over 10 days [F. Saint-Laurent, F. Rimini] Day Number of UFOs % Disruptions Scenario 2 Scenario 1: I p = 0.6MA, P LH = 2MW, 120 s pulse duration Scenario 2: P LH reduced, ~80 s duration

3 TORE SUPRA Association Euratom-Cea A. Ekedahl et al Progress Report DITS project : 13 July 2007 Probability of UFOs and disruptions Day Disruption probability follows the number of UFOs % of UFOs lead to disruption Definition of UFO: Increase in P rad > 20% TS #39928 Prad (MW) Time (s) threshold # of UFOs per 100s of plasma # of disruption per 100s of plasma

4 TORE SUPRA Association Euratom-Cea A. Ekedahl et al Progress Report DITS project : 13 July /05/07 (Day 3) : clean pulses Appearance of UFOs: Scenario 1 [E. Tsitrone]

5 TORE SUPRA Association Euratom-Cea A. Ekedahl et al Progress Report DITS project : 13 July /05/07 (day 3) : almost no UFOs … 01/06/07 (Day 7): lots of UFOs, and disruptions. UFOs appear when P LH is first applied, then more sporadic Appearance of UFOs: Scenario 1 [E. Tsitrone] LH power is switched off by the safety system when UFOs appear

6 TORE SUPRA Association Euratom-Cea A. Ekedahl et al Progress Report DITS project : 13 July 2007 Day 10 : Search of power limit Scenario 2: P LH limited to MW [E. Tsitrone] Reduced P LH No UFOs

7 TORE SUPRA Association Euratom-Cea A. Ekedahl et al Progress Report DITS project : 13 July 2007 Time distribution of UFOs 29 shots with LH power 117 UFOs 24 shots with LH power33 UFOs Day 7 Day 3 3 disruptions 19 disruptions

8 TORE SUPRA Association Euratom-Cea A. Ekedahl et al Progress Report DITS project : 13 July 2007 IR analysis of disruptions Number of disruptions62 Disruptions with IR data available59 1 st origin Arcs in front of launcher prior to disruption1830% Carbon flakes from side protections prior to arcing10 2 nd origin Hot spot on TPL prior to disruption (Q6 and Q5)14 Hot spot on TPL prior to disruption (Q6 => 1/6 of TPL)1017% Both origins simultaneously0 IR cameras to monitor : both LH launchers 1/6 of the TPL (Q6) ~1/18 of the TPL with high resolution (Q5) [A. Ekedahl]

9 TORE SUPRA Association Euratom-Cea A. Ekedahl et al Progress Report DITS project : 13 July 2007 Disruption precursor: Arcs IR camera observation of LH launchers Flaking of co-deposited layer from launcher side protections Induce arcing in front of launchers C2 Impurity safety system detects Cu in the plasma. IR safety system detects arcing. LH power is switched off. Impurity safety system was later modified to act on all impurities (C, Cu,Fe, …) to try to avoid disruptions due to UFOs. Increase of electron density and radiated power 30% of the disruptions were preceded by arcs in front of launchers. 70% of disruptions can NOT be attributed to arcing. LH launcher safety: Plasma safety:

10 TORE SUPRA Association Euratom-Cea A. Ekedahl et al Progress Report DITS project : 13 July 2007 IR camera observation : localized at vertical port in Q6 Overheating of co-deposited layers prior to disruption Disruption precursor: TPL Pulse 39918, t = s Localised hot spot on TPL appears around 4.0s. Followed by overheating of the co- deposited layer. P Rad and CIV increase at 4.2s. P LH is switched off at 4.25s (plasma safety). No arcs in front of launchers.

11 TORE SUPRA Association Euratom-Cea A. Ekedahl et al Progress Report DITS project : 13 July 2007 Overheating of TPL starts ~100ms before increase in P Rad and n e. Increase in P Rad is associated with carbon release. Disruption precursor: TPL 39868, t=5.0s 39868, t=6.0s 39868, t=6.4s 39868, t=5.56s Heating on high field side on TPL prior to disruption Overheating of co-deposited layers prior to disruption

12 TORE SUPRA Association Euratom-Cea A. Ekedahl et al Progress Report DITS project : 13 July 2007 bolo3/bolo14 HFSLFS 3 14 P LH Zeff-2 Ip b3/b14 nl 0-100ms before LH is cut off steady phase TS39868 A MARFE is triggered before the disruption [P. Monier-Garbet] The ratio of the signals from two bolometer sight-lines indicate the roll-over of the radiation towards the HFS (MARFE)

13 TORE SUPRA Association Euratom-Cea A. Ekedahl et al Progress Report DITS project : 13 July 2007 Appearance of UFO (IR camera) Overheating of CFC tile on TPL => UFO Hot spot on TPL appears at ~48.3s. Increase of electron density and radiated power (UFO). Then the tile remains overheated, but n e and P rad are recovered until the plasma disrupts ~50s later , t = 48.5s Q6A

14 TORE SUPRA Association Euratom-Cea A. Ekedahl et al Progress Report DITS project : 13 July 2007 Appearance of UFOs (visible CCD camera) T1 T2 T3 T4 T5 T6 Origin Unknown : 30 % From TPL : 70 % Localisation of UFOs from TPL for 2 days 1/3 rd of TPL is observed Number of UFOs : 01/06/07 (day 7) : 598 (CCD) [117 from P rad ] 07/06/07 (day 10) : 325 (CCD) [80 from P rad ] 1/18th = if equal repartition T1 T2T3T4T5T6 Percentage [A. Triay-Alcouffe]

15 TORE SUPRA Association Euratom-Cea A. Ekedahl et al Progress Report DITS project : 13 July 2007 Conclusions The TPL loading campaign was limited by disruptions, induced by UFOs. Two strategies were applied : - Modified impurity safety system (fast switch-off of LH power) P LH reduced for all impurity influx (C, Cu, Fe, …) not enough. - Reduced P LH in beginning of pulse, followed by slow P LH ramp-up 80s pulse duration OK until end of campaign. LH power limit : ~1.6 MW at the end of the campaign. - Statistical limit : associated with the probability of UFOs to appear % of the UFOs lead to disruption. - Dynamical limit : the power threshold seemed to decreased with time. Analysis of CCD and IR films indicate that most UFOs seem to originate from the TPL. Day 8 Day 4

16 TORE SUPRA Association Euratom-Cea A. Ekedahl et al Progress Report DITS project : 13 July 2007 Appearance of UFOs Shot number [F. Rimini] UFO : Increase in P rad > 20% Data averaged over 5 shots Scenario 2 Scenario 1