EFFICIENCY OF FREQUENCY UP-SHIFTED GYRODEVICES - CYCLOTRON HARMONICS VERSUS CARMS

For gyrodevices with a given operating frequency and a fixed value of the external magnetic field two kinds of operation are compared: Doppl er frequency up-shifted operation at the fundamental cyclotron resonan ce and cyclotron harmonic operation. When the electron velocity spread is negligibly small the maximum efficiency of the Doppler up-shifted operation exceeds that of harmonic operation. However, as the velocity spread grows the Doppler up-shifted efficiency degrades faster. The r elevant quantity when deciding between fundamental, Doppler up-shifted , and harmonic operation turns out to be the velocity spread divided b y the square root of the beam current. If this quantity is small, fund amental, Doppler upshifted operation is more efficient than harmonic o peration; if it is large harmonic operation is more efficient. The eff iciency dependence of both kinds of operation on electron velocity spr ead is studied. A comparative analysis of designs relevant to the plan ned University of Maryland experiments with relativistic gyro-amplifie rs is done.