Supported by. Validation of a new fast ion transport model for TRANSP. M. Podestà - PPPL

Transcription

1 NSTX-U Supported by Validation of a new fast ion transport model for TRANSP Coll of Wm & Mary Columbia U CompX General Atomics FIU INL Johns Hopkins U LANL LLNL Lodestar MIT Lehigh U Nova Photonics Old Dominion ORNL PPPL Princeton U Purdue U SNL Think Tank, Inc. UC Davis UC Irvine UCLA UCSD U Colorado U Illinois U Maryland U Rochester U Tennessee U Tulsa U Washington U Wisconsin X Science LLC M. Podestà - PPPL acknowledgments: M. Gorelenkova, R. White, D. Darrow, E. Fredrickson, N. Gorelenkov and NSTX-U Energetic Particles Topical Science Group US/EU Transport Task Force Workshop Apr. 28 th -May 1 st, 2015 Salem, MA Supported by US DoE FES, grant no. DE-AC02-09CH11466 Culham Sci Ctr York U Chubu U Fukui U Hiroshima U Hyogo U Kyoto U Kyushu U Kyushu Tokai U NIFS Niigata U U Tokyo JAEA Inst for Nucl Res, Kiev Ioffe Inst TRINITI Chonbuk Natl U NFRI KAIST POSTECH Seoul Natl U ASIPP CIEMAT FOM Inst DIFFER ENEA, Frascati CEA, Cadarache IPP, Jülich IPP, Garching ASCR, Czech Rep

2 Integrated Modeling of tokamak discharges requires consistent treatment of energetic particle (EP) physics Classical EP physics is already accounted for in most IM tools (e.g. TRANSP) Uncertainty remains when effects other than classical affect EP behavior E.g. transport by MHD & other EP-driven instabilities > A new approach is being pursued in TRANSP Use reduced information from detailed analysis to evolve EP distribution in the presence of instabilities -> kick model 2

3 Outline Basic ideas of kick model Status of kick model Discussion and future work 3

4 Instabilities introduce fundamental constraints on particle dynamics From Hamiltonian formulation single resonance: P ne = const. P / E = n/ ω=2πf, mode frequency n, toroidal mode number E, energy P ζ mrv par -Ψ, canonical angular momentum µ v perp2 /(2B), magnetic moment where Ψ : poloidal flux R : major radius m : mass These effects are not accounted for by ad-hoc diffusive models. Kick model aims at including them in integrated modeling. 4

5 Use constants of motion E, P ζ, µ for concise description of wave-particle interaction Effects of multiple TAE modes R. B. White, Theory of toroidally confined plasmas, Imperial College Press (2014) P ζ 5

6 Particle-following codes are used to extract distribution of kicks ΔE, ΔP ζ for each bin (E,P ζ,µ) - ORBIT code: record E,P ζ,µ vs. time for each particle - Compute average kicks over multiple wave periods - Re-bin for each (E,P ζ,µ) region Effects of multiple TAE modes ΔP ζ1 ΔP ζ3 ΔE 1 ΔE N ΔP ζn ΔE 2 ΔE 3 ΔP ζ2 P ζ [Podestà, PPCF 2014] 6

7 New kick model uses a probability distribution function to describe particle transport in (E,P ζ,µ) space Kicks ΔE, ΔP ζ are described by which includes the effects of multiple modes, resonances. correlated random walk in E, P ζ Effects of multiple TAE modes 3 TAE modes (ORBIT code modeling) µ B 0 /E P ζ [Podestà, PPCF 2014] 7

8 Outline Basic ideas of kick model Status of kick model Discussion and future work 8

9 NSTX test-case for initial TRANSP simulations NSTX # magnetics Target NSTX scenario features several instabilities TAEs in weakly chirping regime TAE avalanches Low-f kink-like modes 9

10 TRANSP tests with kick model look promising for long time-scale, time-dependent simulations [Podestà, NF 2015] 10

11 EP redistribution in phase space is important for accurate simulation of NB current drive Use ad-hoc diffusive model Use kick model [Podestà, NF 2015] 11

12 EP evolution also critical for power balance analysis in NB-heated plasmas EP physics determines the source term for thermal transport studies Inferred thermal transport vary substantially with proper treatment of sources! [Podestà, NF 2015] 12

13 Outline Basic ideas of kick model Status of kick model Discussion and future work 13

14 Test version implemented in NUBEAM/TRANSP; debugging & validation is in progress Model being tested/debugged for scenarios on NSTX, DIII-D TAE avalanches TAEs in stationary & weakly chirping regimes Low-f kinks (, NTMs) Initial tests are guiding further improvements E.g., consolidate kicks into orbiting (scattering, slowing down) scripts Procedure more resilient to choice of NB time step duration in simulation Better handling of losses (crucial when first orbit losses are high) Define standards for input quantities Identify useful outputs from simulation E.g. power balance terms, power exchanged between EPs and modes Considering longer-term improvements Use power balance for more consistent A(t) evolution Compute A(t) from marginal stability condition: zero net power to/from modes Still requires probability matrix as input; would require estimate of (total) damping rate 14

15 Future work: estimate mode amplitude evolution from energetics, damping rate(s) 15

16 Reduced models offer advantages for Integrated Modeling, plasma control over first-principles codes First-principles codes not (yet) suitable for extensive scans with multiple shots, long time-scale simulations Inclusion in real-time control schemes also unpractical IM codes (e.g. TRANSP) have accurate treatment of atomic physics, classical mechanisms Reduced models for EP transport are good complement IM codes have much broader scope than just EP physics Physics-based reduced models improve accuracy of simulations, retaining generality of IM codes 16