High-power T. P.O. M. amplifiers

The TPOM, which is a forward wave crossed field amplifier, is characterised by a wide bandwidth, a relatively high gain and a notable efficiency. The pulsed tube is! suitable for obtaining peak powers of several megawatts and average powers of several tens of kilowatts. It works at low voltage and high current if compared to solid beam klystrons or travelling wave tubes, has a good phase stability, and satisfies the following features: the current is obtained from an injection gun; the non-reentrant beam needs the use of a col lector; the delay structure which has good, thermal dissipation properties is, for some tubes, even cooled by means of a liquid; but in fact in the pulsed TPOM’s developed for ‘L’ and ‘S’ bands the limits of the performance charts come from two factors which are the low beam impedance and the r. f. power of slow or fast waves existing in all the parts of the tube where an electric field is applied: namely the gun, the sole to line gap, the collector. This appears as oscillations, noise and voltage breakdowns, and limits the gain, the bandwidth and the maximum peak power.