Deuterium retention in Tore Supra long discharges

Transcription

1 Deuterium retention in Tore Supra long discharges E. Tsitrone, C. Brosset, J. Bucalossi, B. Pégourié, T. Loarer, P. Roubin 2, Y. Corre, E. Dufour, A. Géraud, C. Grisolia, A. Grosman, J. Gunn, J. Hogan 3, C. Lowry, R. Mitteau, V. Philips 4, D. Reiter 4, J. Roth 5, M. Rubel 6, R. Schneider 7, M. Warrier 7 Association -CEA, CEA Cadarache, CEA-DSM-DRFC, F Saint Paul-lez-Durance, France 2 : LPIIM, UMR 6633, Université de Provence, Centre Saint-Jérôme Marseille cedex 20 3 : Fusion Energy Division, ORNL, Oak Ridge, TN USA 4 : Institut für Plasmaphysik, FZ Jülich, Association, D Jülich, Germany 5 : Max Planck Institute für Plasmaphysik, Association, Boltzmannstr. 2, D Garching Germany 6 : Alfven Laboratory, Royal Institute of Technology, Association VR, Stockholm, Sweden 7 : Max Planck Institute für Plasmaphysik, Association, Teilinst. Greifswald, Wendelsteinstrasse 1, D Greifswald Germany Experimental results Particle retention during long discharges Particle recovery (after shot, glows, disruptions) Interpreting the particle balance 1

2 Tore Supra : the CIEL configuration Outboard movable limiter Bumpers Toroidal pump limiter (TPL) CCD imaging of the TPL Plasma loaded zones 15 m 2 of carbon plasma facing components Active cooling : stationary PFC temperature from 120 C (cooling loop) up to 250 C on the limiter for long pulses Active pumping : neutralisers below TPL Shadowed zones Long pulse : LH driven discharge at V loop ~ 0, low plasma current/density low density hot edge plasma (Te ~ 100 ev at the LCFS) 2

3 Particle retention in long discharges Phase 1 (~ 100 s) Decreasing retention rate Phase 2 Constant retention rate (= 50% of injected flux) No saturation after 6 minutes Phase 1 Phase 2 In vessel inventory shot duration in phase 2 (I max = D for 6 minutes) Identical shot to shot behaviour No saturation of in vessel retention after 15 minutes of cumulated plasma time 3

4 Particle recovery after shot Retention phase 1 ~ 100 s Phase 1 Phase 2 Small fraction recovered after shot Recovery > plasma content : the wall releases particles x x Recovery correlated to retention in phase 1 : transient retention mechanism 4

5 Particle recovery after glow discharge and disruptions Recovery after He glow discharge (6 hours) : D < I max Independent of the quantity trapped during the day of experiment Recovery after disruption : up to D < I max Threshold in Ip : Ip < 0.8 MA : ~ after shot recovery Ip > 0.8 MA : increase with Ip dissipated energy high enough to heat D rich deposited layers [D. Whyte, PSI 2004] Large scatter at given Ip : machine history dependent? (highest exhaust in start up phase) Particle exhaust (Pa.m 3 ) Tore Supra - Disruptions Plasma current before disruption (MA) 5

6 Sample analysis : D content Net deposition zone Plasma facing Shadowed Carbon deposits Net erosion zone (main plasma interaction area) < 1 µm Several µms Several µms TPL Neutraliser finger Hot deposits (> 500 C) D/C ~ 1 % N D ~ at/m 2 * S [C. Brosset, PSI 2004] Outboard limiter Cold deposits (~ 120 C) D/C ~ 10 % N D ~ at /m 2 / µm * S * d Net deposition zones TPL deposits analysis still in progress Cold deposits in shadowed areas D reservoir 6

7 Interpreting the particle balance Implantation D C D +, D 0 Progressive saturation of bombarded surfaces (D +, D 0 ) until C Dmax reached Carbon d imp < 0.1 µm Phase 1 Bumpers D 0 D 2 D + 2 Saturation time : from ~ 1s (TPL) to ~ 100 s (bumpers) D + TPL [E. Tsitrone, PSI 2004] BUT : does not explain shot to shot behaviour unless very strong diffusion takes place 7

8 Interpreting the particle balance Filling the CFC porosity D TS deposited layers : 100 times more porous than original CFC [P. Roubin, PSI 2004] D 2, D 0 Phase 1 Extrapolation from lab exp (77 K) : D/g deposits 0.5 g enough to account for phase 1 Adsorption : weak bond ( chemical bond) ok for transient mechanism Outgassing after shot ~ phase 1 duration ( ~ 100s) : ok with filling / emptying the porosity reservoir Adsorption M. Warrier et al., Contrib. Plasma Phys. 44, No. 1-3, (2004) Good candidate for phase 1 BUT : extrapolation from lab to tokamak environment (temperature) 8

9 Interpreting the particle balance Codeposition : physical sputtering chemical sputtering C, D C x D y Carbon deposits Phase Preliminary estimates of carbon erosion sources physical + chemical sputtering by D + and D 0 self sputtering by C n+ (assumed 5% C in D + flux) Distant redeposition (TPL shadowed areas, neutralisers, Erosion outboard limiter ) C/s (phys. + self) C 6+ /s CD 4 /s (chem.) ok with Zeff, ok with low net erosion on TPL (high local redeposition), ok with Local redeposition layers growing rate carbon balance roughly coherent C/s CD 4 /s 9

10 Interpreting the particle balance Codeposition : D balance D/s Phase /3 of produced CD 4 trapped : but high D/C ratio film : not observed Erosion C/s C 6+ /s Local redeposition Distant redeposition (TPL shadowed areas, neutralisers, outboard limiter ) CD 4 /s C/s CD 4 /s If D/C = 0.1 : need C/s of net redeposition : high erosion/redeposition on TPL ( > 100 µm on 4 m 2 ): not observed No coherence between D retention rate / D/C ratio / C erosion/redeposition D rich film created during the discharge subsequently depleted in D (glows, disruptions)? Hard to explain the retention rate in phase 2 with codeposition alone 10

11 Summary D retention : no wall saturation after 15 minutes in high T e / low n e edge plasma D recovery (He glow discharge, disruptions) < in vessel inventory accumulated in a single long discharge Transient retention : recovered after shot Permanent retention : NOT recovered after shot D implantation in C : progressive saturation but not transient Codeposition of D and C : Can hardly explain the retention rate in phase 2 D adsorption in porosity : good candidate, but to be assessed in tokamak environment Phase 1 Phase 2 D content sample analysis : D mainly in cold deposits in shadowed areas (120 C) Missing D not found yet but still a lot to investigate (TPL deposits, pumping ducts ) 11

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13 Tore Supra : well equipped for particle balance dn p /dt = Φ inj Φ pump Φ in vessel D + Gas injection : manometers to pumps Active pumping : 10 neutralisers with turbomolecular pumps equipped with 20 pressure gauges (1 in vertical port, 1 at the pump) + 2 Penning gauges (D 2 /He) + mass spectrometer 2 pressure gauges in the chamber (equatorial ports) pressure gauges in primary exhaust system Systematic calibration procedure : calibrated gas injection in the chamber with/without pumps activated 13

14 Effect of active pumping Pumping on Pumping off Shifted gas injection Same wall inventory Active pumping on Tore Supra : no effect on dynamic wall retention but offset on gas injection 14

15 Inventories (Pa.m 3 ) Particle balance sensitive to LH power loss LH power (MW) Injected flux (Pa.m 3 /s) Extracted Flux (Pa.m3/s) Plasma Content x100 Gas Puffing Vessel Inventory TPL exhaust Vessel Exhaust s Time (s) Shot dn p /dt = Φ inj Φ pump Φ in vessel 15

16 Disruption heats deposited layers T ( C) before/after disruption (20 ms) Shot Net erosion zone (main plasma interaction area) CCD imaging of the TPL Plasma loaded zones T > 220 C Shadowed zones Thickest deposition zone (shadowed/plasma area) Moderate deposition zone (plasma interaction area) 16

17 IR shows cold deposits T C #33067 (t-20ms) T #33067 (disruption) 17

18 D inventory in the machine Estimated D inventory in the machine : From analysed samples : ~ D (80% in cold deposits) From non analysed samples (TPL surface) : ~ D (most of it in TPL shadowed zones) Total : ~ D BUT : surface/depth of layers difficult to assess, samples still to be analysed Estimated D inventory from particle balance integrated over a campaign: From averaged net retention rates : ~ D Glow discharge : ~ D Disruptions : ~ D Total : ~ D BUT : retention rate scenario dependent, not all disruptions recorded, glow D 2 not accounted, cleaning discharges No firm conclusion can be drawn on D balance 18

19 Deuterium retention in Tore Supra long discharges E. Tsitrone, C. Brosset, J. Bucalossi, B. Pégourié, T. Loarer, P. Roubin 2, Y. Corre, E. Dufour, A. Géraud, C. Grisolia, A. Grosman, J. Gunn, J. Hogan 3, C. Lowry, R. Mitteau, V. Philips 4, D. Reiter 4, J. Roth 5, M. Rubel 6, R. Schneider 7, M. Warrier 7 Association -CEA, CEA Cadarache, CEA-DSM-DRFC, F Saint Paul-lez-Durance, France 2 : LPIIM, UMR 6633, Université de Provence, Centre Saint-Jérôme Marseille cedex 20 3 : Fusion Energy Division, ORNL, Oak Ridge, TN USA 4 : Institut für Plasmaphysik, FZ Jülich, Association, D Jülich, Germany 5 : Max Planck Institute für Plasmaphysik, Association, Boltzmannstr. 2, D Garching Germany 6 : Alfven Laboratory, Royal Institute of Technology, Association VR, Stockholm, Sweden 7 : Max Planck Institute für Plasmaphysik, Association, Teilinst. Greifswald, Wendelsteinstrasse 1, D Greifswald Germany ITER in vessel T inventory limit : (retention rate - recovery rate) dt < 350 g Experimental results Particle retention during long discharges Particle recovery (after shot, glows, disruptions) Interpreting the particle balance minimize the retention rate optimize the recovery techniques 19

20 Particle retention in long discharges dn p /dt = Φ inj Φ pump Φ in vessel Phase 1 (~ 100 s) Decreasing retention rate Phase 2 Constant retention rate (= 50% of injected flux) No saturation after 6 minutes Phase 1 Phase 2 In vessel inventory shot duration in phase 2 (I max = D for 6 minutes) Identical shot to shot behaviour No saturation of in vessel retention after 15 minutes of cumulated plasma time 20

21 Neutraliser finger Sample analysis : D content Net deposition zone Plasma facing Shadowed Carbon deposits < 1 µm Several µms Hot deposits (> 500 C) D/C ~ 1 % N D ~ at/m 2 * S [C. Brosset, PSI 2004] Several µms Outboard limiter Cold deposits (~ 120 C) D/C ~ 10 % N D ~ at /m 2 / µm * S * d TPL Net erosion zone (main plasma interaction area) Moderate deposition zone (plasma interaction area) Thickest deposition zone (shadowed area) TPL deposits analysis still in progress Cold deposits in shadowed areas D reservoir D content in analysed samples < D inventory over campaign 21

22 Interpreting the particle balance Codeposition : Estimates of carbon erosion sources C, D C x D y Carbon deposits Phase Physical Chem. sputtering Self sputtering sputtering (C/s) (CD 4 /s) (C/s) D + (10 22 /s) D 0 ( /s) C 6 + ( /s) C source underestimated : no synergy D + /D 0, no localised hot Tsurf, no LH accelerated e- ok with Zeff, ok with high redeposition (low net erosion on TPL), ok with layers growing rate carbon balance roughly coherent Erosion C/s C 6+ /s Local redeposition Distant redeposition (TPL shadowed areas, neutralisers, outboard limiter ) CD 4 /s C/s CD 4 /s 22

23 Sample analysis : D content Net erosion zone Plasma facing Net deposition zone Plasma facing Shadowed < 1 µm Carbon substrate Carbon deposits < 1 µm Several µms hot deposits Several µms cold deposits TPL Neutraliser finger TPL deposits analysis still in progress Cold deposits in shadowed areas Hot deposits (> 500 C) D/C ~ 1 % N D ~ at/m 2 * S [C. Brosset, PSI 2004] Outboard limiter Cold deposits (~ 120 C) D/C ~ 10 % N D ~ at /m 2 / µm * S * d 23

24 Interpreting the particle balance D Filling the CFC porosity TS deposited layers : 100 times more porous than virgin CFC [P. Roubin, PSI 2004] D 2, D 0 Phase 1 Extrapolation from lab exp : D/g deposits 0.5 g enough to account for phase S (s -1 ) dp vessel /dt = S outgas S eff p vessel p vessel S outgas t (s) P (Pa) Adsorption : weak bond ( chemical bond) ok for transient mechanism Recovery ~ phase 1 duration : ok with filling / emptying the porosity reservoir Adsorption M. Warrier et al., Contrib. Plasma Phys. 44, No. 1-3, (2004) Good candidate for phase 1 BUT : extrapolation from lab to tokamak environment (temperature, pressure, incident particles) 24

25 Deuterium retention in Tore Supra long discharges E. Tsitrone, C. Brosset, J. Bucalossi, B. Pégourié, T. Loarer, P. Roubin 2, Y. Corre, E. Dufour, A. Géraud, C. Grisolia, A. Grosman, J. Gunn, J. Hogan 3, C. Lowry, R. Mitteau, V. Philips 4, D. Reiter 4, J. Roth 5, M. Rubel 6, R. Schneider 7, M. Warrier 7 Association -CEA, CEA Cadarache, CEA-DSM-DRFC, F Saint Paul-lez-Durance, France 2 : LPIIM, UMR 6633, Université de Provence, Centre Saint-Jérôme Marseille cedex 20 3 : Fusion Energy Division, ORNL, Oak Ridge, TN USA 4 : Institut für Plasmaphysik, FZ Jülich, Association, D Jülich, Germany 5 : Max Planck Institute für Plasmaphysik, Association, Boltzmannstr. 2, D Garching Germany 6 : Alfven Laboratory, Royal Institute of Technology, Association VR, Stockholm, Sweden 7 : Max Planck Institute für Plasmaphysik, Association, Teilinst. Greifswald, Wendelsteinstrasse 1, D Greifswald Germany ITER in vessel T inventory limit : (retention rate - recovery rate) dt < 360 g Experimental results Particle retention during long discharges Particle recovery (after shot, glows, disruptions) Interpreting the particle balance minimize the retention rate optimize the recovery techniques 25

26 Particle recovery after glow discharge and disruptions Recovery after He glow discharge (6 hours) : D < I max Independent of the quantity trapped during the day of experiment ~ desaturation of 15 m 2 of carbon implanted with D for 300 ev incident He Recovery after disruption : up to D < I max Threshold in Ip : Ip < 0.8 MA : ~ after shot recovery Ip > 0.8 MA : increase with Ip dissipated energy high enough to outgas deposited layers [D. Whyte, PSI 2004] Large scatter at given Ip : machine history dependent? (highest exhaust in start up phase) Particle exhaust (Pa.m 3 ) Tore Supra - Disruptions Plasma current before disruption (MA) 26

27 Interpreting the particle balance Implantation D C D +, D 0 Progressive saturation of bombarded surfaces (D +, D 0 )at C Dmax = f(e inc, T surf ) Saturation time : from ~ 1s (TPL) to ~ 100 s (bumpers) Carbon d imp < 0.1 µm Phase 1 Bumpers D + D 0 D 2 D + 2 Implantation of D 0 in bumpers TPL [E. Tsitrone, PSI 2004] BUT : does not explain shot to shot behaviour unless very strong diffusion takes place 27