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Modulation of Commercial Hollow Cathode Lamps by a Magnetic Field in a Magnetron Configuration

Volume 42, Number 6 (Aug. 1988) Page 1032-1039

Simonneau, Regis; Sacks, Richard

An oscillating magnetic field generated by an underdamped capacitive discharge in a large coil is used to modulate the intensity of commercial hollow cathode lamps. Lamps are oriented in the coil so that the magnetic field is coaxial with the hollow cathode. This results in a pseudo-magnetron configuration where the magnetic field is normal to the electric field in the cathode space charge. This configuration results in ExB and diamagnetic drift motions of positive ions and electrons, so that these particles are trapped in circular orbits parallel to the cathode surface. Radiation intensity vs. time profiles are presented for Mn, Cr, Hg, Ag, and V lamps. With relatively high magnetic field strengths and low lamp current, periods of very low lamp intensity are obtained with high-intensity spikes occurring when the magnetic field changes direction. With lower field strengths and higher lamp current, a variety of patterns of intensity modulation is observed.