M. Okamoto

N. Nakajima

S. "Murakami

U." Gasparino

National Institute for Fusion Science (NIFS-Repository)

§ 14. Development of Monte Carlo Simulation Code for ECR Heating in Non-axisymmetric Devices Murakami, S., Nakajima, N., Okamoto, M. Gasparino, U. (Max-Planck-Institut fur Plasma physik, Germany) Although linear theory predicts a local absorp-tion ofECR heating power, broader heating pro-files and changes in the radial electric field, pos-sibly due to enhanced electron flux, are observed in electron cyclotron heating of low density plas-mas in both heliotrons and stellarators. The drift motions across the magnetic sur-faces related to the heating of ripple trapped electrons can play an important role in these phenomena. However, this drift motion effect has not been sufficiently analyzed in literatures due to the difficulty in solving the electron or-bits and the radial electric field consistently. We have developed a Monte Carlo simulation code in which a complex magnetic field configuration, the :finite-,8 effect, and the radial electric field are consistently included. The analysis is based on a technique similar to the adjoint equation for dynamic linearized problems. In the linearized kinetic equation, the wave-induced flux in velocity space (quasi-linear diffusion term) is assumed to be known (e.g., from ray-tracing calculations) and the steady-state distribution function is evaluated through a convolution with a characteristic time dependent "Green's function". The com-plex magnetic field configuration and :finite-,8 ef-fects on the electron motion are included us-ing the Boozer coordinates based on the three-dimensional MHD equilibrium. Ai3 a test of our Monte Carlo based simula-tion code we have compared our results with Fokker-Planck simulation results by eliminat-ing the orbit effects. Figure 1 shows the contours of Green's function; Monte Carlo simulation (up) and Fokker-Planck simulation (down). We can see the good agreements between them. The 152 time development of parallel momentum with the quasi-linear diffusion term depending k 11 is shown in Fig. 2. The results also show a good agreement. We are now applying this code for study of orbit effects in non-axisymmetric con-figurations. Fig. 1: Comparison of Green's function; MC re-sult (up) and F-P result (down). pcalld liiOIDeii!IIUI [mls) -f- -----f+ ..... . oL-~~~~--~~~~~ 0 So-050.0001.0001~.000Q.()()()'m.0008.0003G.OOOO.<XX>4e.OOOS a- [s) Fig. 2: Time development of parallel momen-tum; MC result( dashed line) and F-P result (solid line). References 1) N.J. Fisch, Phys. Fluids 29 (1986) 172. 2) S. Murakami, et al., Nuclear Fusion 34 (1994) 913. 

Development of Monte Carlo Simulation Code for ECR Heating in Non-axisymmetric Devices

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