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by J.G. Cordey Based on lecture notes provided by M. Zarnstorff

Neutral Beams in TRANSP. by J.G. Cordey Based on lecture notes provided by M. Zarnstorff. The Monte Carlo technique is described in R.J. Goldston, D.C. McCune, et al. Journal of Computational Physics 43 61 (1981). General Model. Fast Neutral Propagation.

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by J.G. Cordey Based on lecture notes provided by M. Zarnstorff

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  1. Neutral Beams in TRANSP by J.G. Cordey Based on lecture notes provided by M. Zarnstorff The Monte Carlo technique is described in R.J. Goldston, D.C. McCune, et al. Journal of Computational Physics 43 61 (1981)

  2. General Model Fast Neutral Propagation Monte Carloincludes tracking of NB ATOMS from ‘SOURCE’ Fast Neutral Deposition (Ionisation & CX) FAST ION ORBITING EITHER • MONTE CARLO BEAM MODEL (MORE ACCURATE) COLLISIONS WITH PLASMA or THERMALISATION LOSS VIA HITTING BOUNDARY or RIPPLE MODEL • FOKKER PLANCK BEAM MODEL (FASTER)

  3. IN GENERAL: Very Sophisticated Models LOTS OF CONTROL KNOBS AVAILABLE IN MOST CASES, MOST OF THE CONTROLS ARE SET UP BY AN EXPERT AND ARE THEN INVISIBLE TO THE USER. (e.g. TIME-STEPS, BEAM GEOMETRY, …….

  4. DEPOSITION • TYPICALLY 500 DEPOSITIONS CALCULATED/TIMESTEP CONTROLABLE, BUT SEEMS INSENSITIVE. DEALS WITH FULL, 1/2 AND 1/3 ENERGY COMPONENTS. • IONISATION AND CX CALCULATED IN THE PLASMA FRAME (i.e. including rotation effects). • FAST NEUTRALS CAN ALSO BE GENERATED BY CX LOSS OF FAST IONS. TRACKED AS FAST NEUTRALS . AND CAN BE RE-ABSORBED BY CX OR IONISATION OR LOST TO WALL. ONLY AVAILABLE IN MONTE CARLO BEAM MODEL.

  5. Deposition rate of Beam Ions Example TFTR Dº injection into H+ thermal plasma A) Impact ionisation on electrons, ions and impurities. B) Charge Exchange with D+ background ions. C) Charge Exchange with H+ background ions. D) Beam - Beam charge exchange. E) Beam - Beam impact ionisation.

  6. BEAM ORBITING (MONTE CARLO ONLY) • INCLUDES Er EFFECTS • ACCUMULATES FBM FOR BEAM-BEAM NEUTRONS AND OTHER SIMULATIONS. • CALCULATES ORBIT LOSSES. • CALCULATES STOCHASTIC RIPPLE DIFFUSION AT TRAPPED PARTICLE TURNING POINTS (REDI et al, WHITE et al, GOLDSTON-WHITE-BOOZER.) - HAS A FIXED NUMBER OF SIMULATED PARTICLES AT ALL TIMES. - LOST PARTICLES ARE REPLACED WITH NEW PARTICLES

  7. BEAM ION COLLISIONS • TRANSFER OF ENERGYAND MOMENTUM TO THERMAL SPECIES (e.g. BULK IONS, IMPURITY). • NO BEAM-BEAM COLLISIONS. • COLLISION OPERATOR CALCULATED IN PLASMA FRAME (for Vø‡0) • WHEN BEAM PARTICLE REACHES 3/2 Ti IT IS THERMALISED. -JOINS THERMAL ION POPULATION VIA Si th -BRINGS POWER TO THERMAL ION POPULATION VIA PBTH ~ Si th (3/2 Ti) -BRINGS THERMALISATION TORQUE FOR HIGHLY ROTATING PLASMAS 1/3 ENERGY BEAM IONS MAY PROMPLTLY THERMALISE.

  8. A Monte Carlo beam particle pitch angle scattering, charge exchanging and finally thermalising in PLT.

  9. Fast ion power losses versus time BPSHI, BPLIM, BPCXI,BPCXX, BPTH

  10. Fast ion power losses versus time D T

  11. ACfiles - Timeslice Output for Higher Dimensional Data • By setting special namelist controls, the user can request “Acfile” output at up to five different times in the course of a TRANSP run. • The Acfile contains an image of TRANSP COMMON, which includes a number of higher dimensional items such as fast ion distribution functions which are not accessible by RPLOT. • Named items in the Acfile can be time averaged, as an option for improving statistics on Monte Carlo generated outputs. • In general, special software is needed to access AC file output. Some software exists for examination of: • Monte Carlo fast ion distribution functions. • Fokker Planck bounce averaged RF fast ion distibution functions. • Beam deposition distribution functions. • 3d fast neutral density profiles in front of selected beamlines.

  12. Ion Power Balance

  13. D-T and D-D Fusion Code follows D, T fast particles and alphas with separate Monte Carlo calculations. This can be time consuming. Calculates beam-beam, beam-thermal and thermal contributions to fusion yield. JET Highest Fusion power (16MW) pulse

  14. Comparison with measured line integral of neutron emission TRANSP basic philosophy is to check consistency of data from different diagnostics. Code contains simulated output of several diagnostics

  15. Comparison measured diamagnetic energy with that calculated by TRANSP from kinetic data

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