Abstract
Parallel momentum conserving collision model is developed for GNET code, in which a linearized drift kinetic equation is solved in the five dimensional phase-space to study the electron cyclotron current drive (ECCD) in helical plasmas. In order to conserve the parallel momentum, we introduce a field particle collision term in addition to the test particle collision term. Two types of the field particle collision term are considered. One is the high speed limit model, where the momentum conserving term does not depend on the velocity of the background plasma and can be expressed in a simple form. The other is the velocity dependent model, which is derived from the Fokker-Planck collision term directly. In the velocity dependent model the field particle operator can be expressed using Legendre polynominals and, introducing the Rosenbluth potential, we derive the field particle term for each Legendre polynominals. In the GNET code, we introduce an iterative process to implement the momentum conserving collision operator. The high speed limit model is applied to the ECCD simulation of the heliotron-J plasma. The simulation results show a good conservation of the momentum with the iterative scheme.
Highlights
Efficient current dive by the electron cyclotron heating (ECH) is an important issue in tokamaks and, helical devices
We have studied the radial transport of supra-thermal electrons by the ECH[1, 2] and the electron cyclotron current drive (ECCD)[3] in helical plasmas
One is the high speed limit model, where the momentum conserving term does not depend on the velocity of the background plasma, and is easy to implement
Summary
Efficient current dive by the electron cyclotron heating (ECH) is an important issue in tokamaks and, helical devices. We have studied the radial transport of supra-thermal electrons by the ECH[1, 2] and the electron cyclotron current drive (ECCD)[3] in helical plasmas. In the present GNET code, a linear Monte Carlo collision operator is applied. This operator consider the collisional effect between test particle and background particle only as the pitch angle scatter and energy scattering. In order to study ECCD quantitatively, we develop the model conserving the parallel momentum for GNET. In order to conserve the parallel momentum, we introduce the field particle collision term in addition to the test particle one. We apply the developed model to the ECCD in the Heliotron J plasma with the momentum conserving operators
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