1Annual meeting SEWG Transient Heat Loads, Ljubljana, 1 st /2 nd October 2009 TORE SUPRA Association Euratom-CEA J. Bucalossi Report on Tore Supra activities on Mitigation of disruptions loads for ITER WP09-PWI-08-01/08-02 J. Bucalossi, F. Saint-Laurent, C. Reux and Tore Supra team Institute for Research on Magnetic Fusion Association Euratom-CEA Annual meeting of the SEWG Transient Heat Loads Ljubljana, 1 st /2 nd October 2009

2Annual meeting SEWG Transient Heat Loads, Ljubljana, 1 st /2 nd October 2009 TORE SUPRA Association Euratom-CEA J. Bucalossi Outline Mitigation of disruption loads with massive gas injection Control of runaway electron beams Activities in 2010

3Annual meeting SEWG Transient Heat Loads, Ljubljana, 1 st /2 nd October 2009 TORE SUPRA Association Euratom-CEA J. Bucalossi Outline Mitigation of disruption loads with massive gas injection Control of runaway electron beams Activities in 2010

4Annual meeting SEWG Transient Heat Loads, Ljubljana, 1 st /2 nd October 2009 TORE SUPRA Association Euratom-CEA J. Bucalossi Previously on TS Non-mitigated disruptions Helium Neon Argon Mix He/Ar With MGI reduction of dI p /dt for all gases (~50%), mild reduction of eddy current in toroidal pumped limiter (TPL) Ne and Ar MGI have no effect on RE production He (He/Ar) MGI are very efficient at suppressing RE even in small amount ( Pa.m 3, plasma ~25m 3, vacuum vessel ~50 m 3 ) NB: MGI triggered disruptions on stable plasmas

5Annual meeting SEWG Transient Heat Loads, Ljubljana, 1 st /2 nd October 2009 TORE SUPRA Association Euratom-CEA J. Bucalossi Fuelling efficiency N e was estimated using fast FIR interferometer and approximate integration of several chords He assimilation much higher (measurement not possible up to TQ) N e ~ 2x plasma e content with Ar N e > 6x plasma e content with He TQ at higher density with He Only a fraction of the injected gas reaches the plasma before TQ NB: fuelling efficiency estimated assuming single ionization and that all the gas reached the plasma before TQ

6Annual meeting SEWG Transient Heat Loads, Ljubljana, 1 st /2 nd October 2009 TORE SUPRA Association Euratom-CEA J. Bucalossi Gas penetration Determined using a Fast framing visible camera and interference filters for low ionized species (He II nm, Ar II nm, He I nm) cold front poloidal plane parallel to the endoscope lens

7Annual meeting SEWG Transient Heat Loads, Ljubljana, 1 st /2 nd October 2009 TORE SUPRA Association Euratom-CEA J. Bucalossi Gas jet dynamics Penetration depth nearly independent of nature and amount of gas (5 to 500 Pa.m 3 in He) Penetration speed higher for higher amount of gas (consistent with density measurement) but smaller than gas sound speed (He~1000m/s and Ar~320m/s)

8Annual meeting SEWG Transient Heat Loads, Ljubljana, 1 st /2 nd October 2009 TORE SUPRA Association Euratom-CEA J. Bucalossi Safety factor influence Stopping surface q ρ Penetration depth nearly constant in safety factor (stop near q = 2) Scan in q profile (I p / B t variations) Same He MGI 25 Pa.m 3 q profile reconstructed with CRONOS

9Annual meeting SEWG Transient Heat Loads, Ljubljana, 1 st /2 nd October 2009 TORE SUPRA Association Euratom-CEA J. Bucalossi Thermal energy influence Scan in LH power (1 to 3.5 MW) Same He MGI 25 Pa.m 3 q profile reconstructed with CRONOS Penetration depth more sensitive to q profile than thermal energy LH power [MW] Energy stored between plasma edge and gas stopping surface [kJ] ohmic , , ,534

10Annual meeting SEWG Transient Heat Loads, Ljubljana, 1 st /2 nd October 2009 TORE SUPRA Association Euratom-CEA J. Bucalossi Penetration bounce (a) (b) (c) (d) 8.8 ms 15.1 ms 18.8 ms 24.4 ms TQ He 25 Pa.m3 PLH = 3.5 MW Soft X-ray analysis Core and edge chords behavior correlated with the movement of the cold front Heat pulse from the core to the edge triggered by the perturbation of the q = 2 rational surface (MHD)

11Annual meeting SEWG Transient Heat Loads, Ljubljana, 1 st /2 nd October 2009 TORE SUPRA Association Euratom-CEA J. Bucalossi Outline Mitigation of disruption loads with massive gas injection Control of runaway electron beams Activities in 2010

12Annual meeting SEWG Transient Heat Loads, Ljubljana, 1 st /2 nd October 2009 TORE SUPRA Association Euratom-CEA J. Bucalossi RE creates a cold plasma Time (s) PlasmacurrentIp(MA) LineintegratedElectron Density(10 19 m -2 ) for 2chords TS#33707 Photoneutron (s -1 ) ( Ntn /s ) Time (s) PlasmacurrentIp(x100 kA) LineintegratedElectron Density(10 19 m -2 ) for 2chords TS#33707 Photoneutron (s -1 ) ( Ntn /s ) Line averaged density recovers after the disruption without any gas puffing (RE density ~ only a few m -2 from RE current) A cold background plasma is generated: RE-neutrals collisions (ionization on C dusts and D atoms)? RE-wall interaction?

13Annual meeting SEWG Transient Heat Loads, Ljubljana, 1 st /2 nd October 2009 TORE SUPRA Association Euratom-CEA J. Bucalossi RE beam in action 450 ms plateau Exp: 495 µs

14Annual meeting SEWG Transient Heat Loads, Ljubljana, 1 st /2 nd October 2009 TORE SUPRA Association Euratom-CEA J. Bucalossi Interaction with dust TS#43493 Ip( 100 kA) nl(10 19 m -2 )chord#3 Time (s) neutron (s -1 ) nl(10 19 m -2 )chord# TS#43493 Ip( 100 kA) nl(10 19 m -2 )chord#3 Time (s) neutron (s -1 ) nl(10 19 m -2 )chord#4 Many photoneutron peaks, large peaks associated to density rises and radiating events Radiating events associated to transverse transport of RE Filamentary events observed using fast visible camera Location and radial size of RE beam can be estimated

15Annual meeting SEWG Transient Heat Loads, Ljubljana, 1 st /2 nd October 2009 TORE SUPRA Association Euratom-CEA J. Bucalossi Controlling beam position Controlling the beam position is an important issue Active position control on current channel barycentre was implemented 30 ms after the disruption (no I p control nor fuelling so far) More time to apply mitigation technique on the RE beam

16Annual meeting SEWG Transient Heat Loads, Ljubljana, 1 st /2 nd October 2009 TORE SUPRA Association Euratom-CEA J. Bucalossi Decelerating electric field Variation of the central solenoid voltage with RE beam position control Reduction of the plateau duration with a small voltage (~0.5 V/turn) Photoneutrons reduced (~30%) but still a neutron burst at the end Further studies required

17Annual meeting SEWG Transient Heat Loads, Ljubljana, 1 st /2 nd October 2009 TORE SUPRA Association Euratom-CEA J. Bucalossi Effect of MGI on RE beam Tabulated using an averaged RE energy E = 10 MeV faster decrease of RE current increase of the photoneutron flux slowing down by neutrals not effective Increase of the RE transverse transport towards the wall: Multiple Coulomb scattering = stochastic effect larger interacting area lower heat loads Beneficial effect for mitigating RE Simple assumption of a free stopping in neutral gas

18Annual meeting SEWG Transient Heat Loads, Ljubljana, 1 st /2 nd October 2009 TORE SUPRA Association Euratom-CEA J. Bucalossi Damages on CFC tiles large energy deposit leads to vaporization of CFC bulk and fast expulsion of carbon fragments ( m/s) Detailed Monte-Carlo simulation of RE-carbon interaction in progress

19Annual meeting SEWG Transient Heat Loads, Ljubljana, 1 st /2 nd October 2009 TORE SUPRA Association Euratom-CEA J. Bucalossi Outline Mitigation of disruption loads with massive gas injection Control of runaway electron beams Activities in 2010

20Annual meeting SEWG Transient Heat Loads, Ljubljana, 1 st /2 nd October 2009 TORE SUPRA Association Euratom-CEA J. Bucalossi Activities in 2010 MGI –radiated power analysis with faster bolometers –better characterization of the gas jet –modeling effort (CRONOS, JOREK, etc.) RE beam control –improve statistics (reliable RE beam creation) –study of mitigation of RE beams with MGI –modeling of RE beam damping IR fast camera (from ASDEX Upgrade) –analysis of SOL widening on the TPL during disruption –estimation of conducted heat loads on the TPL during TQ

21Annual meeting SEWG Transient Heat Loads, Ljubljana, 1 st /2 nd October 2009 TORE SUPRA Association Euratom-CEA J. Bucalossi Summary MGI –Fuelling efficiency estimated –Data gathered on gas penetration Runaway electrons –Cold background plasma observed –Interaction with dusts observed –Active position control achieved –Mitigation techniques applied to created RE beam 2010 –More experiments planned –New diagnostic (fast IR camera) –Modeling effort