Global-gyrokinetic study of finite beta effects on linear microinstabilities
Electromagnetic micoinstabilities in tokamak plasmas are studied by means of a linear global eigenvalue numerical code. Ion dynamics is described by the gyrokinetic equation, so that finite Larmor radius effects are taken into account to all orders. Non-adiabatic electrons are included in the model, with passing particles described by the drift-kinetic equation and trapped particles through the bounce averaged drift-kinetic equation. A large aspect ratio plasma with circular shifted surfaces is considered for the numerical implementation. The effects of an electromagnetic perturbation on toroidal Ion Temperature Gradient driven (ITG) modes are studied, confirming the stabilisation of these modes with increasing beta (parameter identifying the ratio of the plasma pressure to the magnetic pressure). The threshold for the destabilisation of an electromagnetic mode, the so-called kinetic ballooning mode (KBM) or Alfvénic Ion Temperature Gradient mode (AITG) is identified. Moreover, owing to the global formulation, the radial structure of these electromagnetic modes is observed for the first time. Finally, the contributions of trapped electron dynamics and the effects of the Shafranov shift are addressed.
Bibliographic Reference: EPFL Internal report LRP 752/03, March 2003. pp.33.
Availability: Available free of charge from: École Polytechnique Fédérale de Lausanne (EPFL), Ecublens, CH-1015 Lausanne Fax +41-21-6934747
ISBN: ISSN: 0458-5895
Record Number: 200316119 / Last updated on: 2003-03-31
Original language: en
Available languages: en