Results from the SLAC Lasertron

Rf power at 2856 MHz has been obtained from the SLAC proof of principle lasertron. Experiments show that the electron beam is well bunched when the laser beam is well dispersed, the voltage high, and the current density low. However, if any of the these criteria is not met, space charge forces can cause significant debunching. The maximum beam power to rf power conversion efficiency was 12.3%, and the maximum rf power was 2 kW. Both maxima were obtained under the same operating conditions, at a beam voltage of 75 kV. When the maximum efficiency was obtained, it was limited by the poor match of the beam impedance to the cavity impedance. The rf measurements, the technical problems that limit available current and voltage, and the theory of the coupling between the beam and the cavity are discussed.