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Benchmarking of NBI/ASTRA and NUBEAM/TRANSP

Benchmarking of NBI/ASTRA and NUBEAM/TRANSP. A. Polevoi, E. Barbato, I. Voitsekhovitch. Motivations for update of NBI in ASTRA. MUTUAL IO-JET INTERESTS: IO = validation vs JET experiments JET = fast accurate time dependent simulations of JET experiments PREVIOUS FP NBI-ASTRA VERSION :

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Benchmarking of NBI/ASTRA and NUBEAM/TRANSP

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  1. Benchmarking of NBI/ASTRA and NUBEAM/TRANSP A. Polevoi, E. Barbato, I. Voitsekhovitch

  2. Motivations for update of NBI in ASTRA MUTUAL IO-JET INTERESTS: • IO = validation vs JET experiments • JET = fast accurate time dependent simulations of JET experiments PREVIOUS FP NBI-ASTRA VERSION: • Beam-plasma fusion reactions were available only for 1 MeV D-NBI (not applicable to multi-energy JET NBI) • Beam-plasma fusion reactions were in cold ion approximation (Ti = 0) (not accurate for multi-energy JET NBI with Eb<120 keV, Ti ~10 keV) • Treatment of trapped particles for driven current density is satisfactory w/o orbit averaging, but was not accurate for nearly perpendicular NBI of JET in the option with orbit averaging

  3. Motivations for NBI update • 79698 (3.6 T,4.5 MA, n/nGW0.6, PNBI =23 MW): • reference H-mode for DT campaign • 50% of bulk D is replaced by T • D beams • Alpha-particles from beam-plasma and beam-beam reactions are not taken into account – under-estimated alpha-heating • Alpha-heating from beam-plasma interaction is important for JET • More accurate calculation of beam driven current • Output for neutron yield I. Voitsekhovitch et al, ISM WS 2010 79698 (13 s): ASTRA,TRANSP  Palpha_astra = 0.412 MW Palpha_transp = 0.8 MW

  4. NUBEAM (MC) Absorption: with multi step ionization, with plasmarotation Orbital effects: FLR, g.c. drift, fast ion spatial diffusion Ion slowing down: Monte-Carlo, with plasmarotation, sink to thermal at E= 1.5 Ti CX loss with CX recapturing Fusion reactions : beam-plasma, beam-beam Sources: Snbi, Pnbi, Pnbe, jNBCD, torque are orbit averaged Snbe at birth .

  5. ASTRA-NBI (Updated) Absorption: stopping cross section with multistep ionisation (Suzuki) Orbital effects (all in fast first orbit approximation): FLR - coarse internal NBI grid: step =DLarmor(Enb,max) GC - first orbit ion g.c. averaging (optional) for jNB,Pnbi,Pnbe Orb.Loss/Trapping/Ripple loss (optional) Sources: Pnbi, Pnbe, jNBCD with orbit averaging Snbi (=Snbe), Storque are w/o g.c. orb. averaging (can be modified) Fast ion slowing down: steady-state 2-D FP solver optional time dependent 2-D FP solver with straightforward linearization CX loss (optional, only for time dependent FP, no CX recapturing) Fusion reactions: Primary beam-plasma and secondary reactions are in thin orbit steady-state (slowing down) approximations Neglects: rotation, space diffusion, beam-beam fusion

  6. JET 79698, 10.85 s, <ne>=4.3e19 m-3 Sbe_transp=1.45e21 1/s Sbe_astra=1.45e21 1/s Pa_transp=0.64 MW Pa_astra=0.72 MW

  7. JET 79698, <ne>=4.3e19 m-3 T_transp=9.6 T_astra=7.73 Inbi_transp=0.136 MA Inbi_astra=0.173 MA Neutrons: ASTRA TRANSP D beam – D target: 4.4e15, 4.11e15 D beam – T target: 1.14e18 1.013e18 DD thermal: 5.5e14 5.44e14 DT thermal: 1.3e17 1.48e17

  8. JET 79698, 11.7 s, <ne>=7.3e19 m-3

  9. JET 79698, 11.7 s, <ne>=7.3e19 m-3 Neutrons: ASTRATRANSP D beam – D target: 4.28e15 4.e15 D beam – T target: 1.138e18 9.94e17 DD thermal: 1.7e15 1.2e15 DT thermal: 4.73e17 4.81e17

  10. Comparison old NBI ASTRA/TRANSP; ≠77601 profiles, t=5s JNBI ASTRA TRANSP PNBI IT=321kA, QT=20MW , IA=382KA, QA=12MW E. Barbato ISM meeting 24/10/12

  11. New NBI_A version results 77601 t=5s JNBI ASTRA TRANSP PNBI IT=319kA, QT=20MW , IA=415KA, QA=15.MW

  12. Temporal behavior; comparison of total quantities (I, Qabs) IP INBI ASTRA TRANSP QABS TRANSP ASTRA

  13. ≠79698, t=10.9s, <ne>=4.5 1019m-3 electron source • Total beam electron source Sbe= 144 1019m-3s-1

  14. (ASTRA/TRANSP) ≠79698, t=10.9s, <ne>=4.5 1019m-3 PNBI to electrons JNBI PNBIto ions • IT=132kA, QT=22.5MW , IA=167KA, QA=21.7MW • Power to electrons ~ 1MW less in NBI_A

  15. (ASTRA/TRANSP) ≠79698, t=11.8s, <ne>=8 1019m-3 • Total beam electron source Sbe= 144 1019m-3s-1

  16. (ASTRA/TRANSP) ≠79698, t=11.8s, <ne>=8 1019m-3 PNBI to electrons JNBI PNBIto ions IT=38kA, QT=22.2MW , IA=77KA, QA=22MW

  17. Summary • Updated version of the FP-NBI ASTRA solver looks more appropriate for validation with JET experiments • It includes plasma heating and neutron sources from beam-plasma and secondary fusion reactions for all energies + gc averaging for Jnbcd • Relatively good agreement between NBI and NUBEAM is shown for profiles of heating, beam density, fusion reactions, beam driven current in the region 0.1 <  • Strong difference in the electron source Snbe (not sensitive to the orbit averaging) near the centre ( < 0.1) could have 2 reasons: 1) difference in equilibria used in NUBEAM and ASTRA simulations; 2) inaccurate prescription of JET NBI geometry in terms of the NBI ASTRA solver (at least for the equatorial NBIs). Further studies are required • Torque conservation in ASTRA assumes the conservation of the volume integrals of the torque source at ionization. Difference in global torque source (~ 20 %) requires further analysis.

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