Iterated finite-orbit Monte Carlo simulations with full-wave fields for modeling tokamak ion cyclotron resonance frequency wave heating experiments

M Choi,M Podesta,J M Park,L L Lao,L A Berry,W W Heidbrink,D N Smithe,V S Chan,D Liu,D Green,R I Pinsker,P Bonoli,Rf Scidac And Swim Team ,F Jaeger,R Harvey

doi:10.1063/1.3314336

Abstract

The five-dimensional finite-orbit Monte Carlo code ORBIT-RF [M. Choi et al., Phys. Plasmas 12, 1 (2005)] is successfully coupled with the two-dimensional full-wave code all-orders spectral algorithm (AORSA) [E. F. Jaeger et al., Phys. Plasmas 13, 056101 (2006)] in a self-consistent way to achieve improved predictive modeling for ion cyclotron resonance frequency (ICRF) wave heating experiments in present fusion devices and future ITER [R. Aymar et al., Nucl. Fusion 41, 1301 (2001)]. The ORBIT-RF/AORSA simulations reproduce fast-ion spectra and spatial profiles qualitatively consistent with fast ion D-alpha [W. W. Heidbrink et al., Plasma Phys. Controlled Fusion 49, 1457 (2007)] spectroscopic data in both DIII-D [J. L. Luxon, Nucl. Fusion 42, 614 (2002)] and National Spherical Torus Experiment [M. Ono et al., Nucl. Fusion 41, 1435 (2001)] high harmonic ICRF heating experiments. This work verifies that both finite-orbit width effect of fast-ion due to its drift motion along the torus and iterations between fast-ion distribution and wave fields are important in modeling ICRF heating experiments.

Highlights

Ion cyclotron resonance frequencyICRFwave is one of main auxiliary plasma heating methods in present tokamak experiments and future ITER.1 In particular, the ICRF wave with frequency equivalent to high ion cyclotron harmonic number has been used to heat background thermal electrons and drive noninductively plasma current in the DIII-DRef. 2͒ and National Spherical Torus ExperimentNSTX ͑Ref. 3͒ devices
In Fig. 8͑b, structure and magnitude of E+ component of ICRF wave field computed from AORSA using the particle distribution function as given in Fig. 8͑aare shown as a dotted curve
A peak in radial fast-ion density profile measured from FIDA spectroscopy indicated outward radial shift from primary resonance layer near magnetic axis, whereas zero-orbit theory predicts a peak near magnetic axis

Summary

Introduction

Ion cyclotron resonance frequencyICRFwave is one of main auxiliary plasma heating methods in present tokamak experiments and future ITER. In particular, the ICRF wave with frequency equivalent to high ion cyclotron harmonic number has been used to heat background thermal electrons and drive noninductively plasma current in the DIII-DRef. 2͒ and National Spherical Torus ExperimentNSTX ͑Ref. 3͒ devices. Primary damping of ICRF wave is expected to occur on thermal electrons, theory predicts that partial damping of ICRF wave may occur on fast-ions when a large population of fast-ions exists in the form of injected neutral beam ion and fusion born alpha due to kЌ␳ Ն 1 ͑kЌ is the perpendicular wave number and ␳ is the fast-ion Larmor radius, which results in a reduction of current drive efficiency. This theoretical prediction has been observed in both DIII-D4,5 and NSTX6,7 high harmonic ICRF wave heating experiments in neutral beam preheated plasma aimed at full noninductive current drive. A first indication is enhanced neutron emission rate measured from neutron detector, increasing by a factor of 2 in DIII-D4,5 and a factor of 3 in a

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