A system for Alfvén-eigenmode spectroscopy using electrodes inserted into the compact helical system heliotron/torsatron plasma.

A system for Alfve´n-eigenmode spectroscopy in the compact helical system heliotron/torsatron is presented. In this system, four electrodes inserted near the last closed flux surface are employed as the exciter of Alfve´n eigenmodes (AEs). A set of magnetic probes is employed as the detectors of excited magnetic fluctuations. An alternating current path along the confinement magnetic field line is generated in the plasma edge between two electrodes which intersect with a specified magnetic field line. Another two electrodes also produce another current path. The polarity between these two current paths is adjusted to specify the toroidal mode number of the excited field perturbations. The frequency of the alternating current is in the range of 10–250 kHz. The possibility of the excitation of AEs by this system is discussed. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]