Analysis of toroidal Alfven eigenmode-induced fast ion losses in Globus-M2 spherical tokamak

Abstract

With an increase of magnetic field up to 0.8 T and plasma currentto 400 kA, fast ion losses rate in the discharges with toroidal Alfveneigenmodes decreased in tokamak Globus-M2 comparing with Globus-M tokamakdischarges. Taking into account the data on the discharges with increasedmagnetic field and plasma current, the regression fit of neutral particleanalyzer flux drop in energy channel close to neutral beam energy onrelative eigenmode magnitude, the value of magnetic field and plasma currentwas analyzed. The power of flux drop dependence on TAE magnitude was foundto be ~0.5 and inverse proportional on the value of product of magneticfield and plasma current, which is highly likely is determined only byplasma current due to weak dependence on magnetic field. The resultobtained indicates that fast ion losses in Globus-M2, stimulated by toroidalAlfven eigenmodes are mostly determined by the shift of passing orbits tothe plasma edge. With the increase of plasma current and magnetic field,neutron flux drops arising in the moments of toroidal mode bursts have alsodecreased. Keywords: TAE, NPA, spherical tokamak, fast ion losses\