Improved magnetron injection guns for gyrotrons

All efficient, vacuum, RF sources required a high quality electron beam for efficient interaction. Non uniform cathode emission occurs when either the temperature or the work function varies over the cathode surface. If the non-uniformity exceeds certain limits, the RF source cannot perform according the specifications. Magnetron injection guns for gyrotrons were built that separate the emission surface from the heater circuit, with both components being replaceable. Temperature variations over the surface are predicted to be less than 1 degree centigrade, and recent measurements indicated variations in work function are less than 6%. The MIG designs will be described and available test results will be presented. CCR´s MIG test chamber was modified to improve measurements of surface emission and temperature.