A major goal of the DIII-D program is to study `advanced tokamak' plasmas with good confinement, large normalized β, and a large fractionof self-sustained current. Many of these plasmas have large beam pressures(≲(1/3) of the total pressure) and weak magnetic shear; Alfvén instabilities with laboratory frequencies of 100-250 kHz are oftenobserved. The instabilities correlate with reductions in the neutron ratebelow the classically expected value, complicatingdetermination of the pressure and current profiles. Quantitative analysis of onecase suggests that two types of energetic particle modes are destabilized: the resonant toroidicity-induced Alfvén eigenmode and theresonant kinetic ballooning mode. The strong dependence on neutralbeam injection parameters and the variability in mode frequency arequalitatively consistent with this identification. Further analysis andmeasurements are planned.
Investigation of beam– and wave–plasma interactions in spherical tokamak Globus-M