Beam-driven energetic particle modes in advanced tokamak plasmas

摘要

A major goal of the DIII-D program is to study 'advanced tokamak' plasma with good confinement, large normalized β, and a large fraction of self-sustained current. Many of these plasmas have large beam pressures (≤1/3 of the total pressure) and weak magnetic shear; alfven instabilities with laboratory frequencies of 100-250 kHz are often observed. The instabilities correlate with reductions in the neutron rate below the classically expected value, complicating determination of the pressure and current profiles.