Observation of Ion Cyclotron Waves

Abstract

The existence of ion cyclotron waves had been inferred from theoretical calculations and indirectly from experimental observations. In this paper direct experimental observations are reported of phenomena appropriate to these waves in a hot plasma. An induction coil energized at 11.5 Mc with approximately 200 000 w of rf power surrounds a deuterium plasma confined in a 16‐kilogauss magnetic field. A single‐turn rf magnetic probe located in the plasma about 50 cm down the axis from the center of the induction coil is used to detect the propagated wave. The probe is movable. Radial motion of the probe shows the expected penetration of the transverse rf field into the center of the plasma. Axial motion of the probe shows a 300‐cm damping length, and an oscillation wavelength 64% longer than the calculated value. The probe signals disappear when the ion cyclotron frequency is less than the induction coil frequency, which is a result predicted from the ion cyclotron wave dispersion relation.