Resonant increase of x-ray emission in a microwave discharge at half-gyrofrequency

Described in the present paper is the observation of a resonant increase of x-ray emission in a microwave discharge at half-gyrofrequency, where the equality omega=1/2 omega(Be) is satisfied (here, omega is the microwave frequency and omega(Be) is the gyrofrequency of electrons). These experiments show, for the first time, that the x-ray flux produced at subharmonic resonance is five times higher than that produced at the cyclotron resonance, the photon energy being higher. (C) 2002 American Institute of Physics.