ABSTRACT
Evidence is presented for a multitude of discrete frequency Alfvén waves in the core of magnetically confined high-temperature fusion plasmas. Multiple diagnostic instruments confirm wave excitation over a wide spatial range from the device size at the longest wavelengths down to the thermal ion Larmor radius. At the shortest scales, the poloidal wavelengths are comparable to the scale length of electrostatic drift wave turbulence. Theoretical analysis confirms a dominant interaction of the modes with particles in the thermal ion distribution traveling well below the Alfvén velocity.
ABSTRACT
The expansion of a dense (initially, n(lpp)/n(0)>>1) laser-produced plasma into an ambient magnetized plasma ( n(0) = 2 x 10(12) cm(-3)) capable of supporting Alfvén waves has been studied. The interaction results in the production of shear Alfvén waves as well as large density perturbations (Delta n/n(0) approximately 0.3) associated with the moving dense plasma. The waves propagate away from the target and are observed to become plasma-column resonances. Spatial patterns of the wave magnetic fields are measured and are used to estimate the coupling efficiency of the laser energy and the kinetic energy of the dense plasma into wave energy.
