Report on the one-megawatt, CW, X-band project

A two-year program has been undertaken to develop a klystron amplifier operating at 8 kMc and delivering one megawatt of CW power. The final tube will employ four cavities of the extended-interaction type. It is designed to operate at 10 kilovolts and a microperveance of 0.3. This paper will deal with the results of three major experiments which were performed during the first year of the program in order to establish the final design. These experiments were: 1. Evaluation of the electron gun in a specially designed beam analyzer. 2. The construction and experimental evaluation of a beam tester operating at full beam power. 3. The construction and testing of a pulsed klystron employing an extended-interaction output cavity and operating at one megawatt of peak power with a duty factor of 0.001. As a result of the first experiment a gun design was evolved which produced a beam having the desired size and uniformity. In the second experiment this gun was used to focus a beam through a drift tube with a transmission exceeding 99.9% at average beam power levels up to 2 megawatts. The general design of the beam analyzer will be given along with a discussion of the design and operation of the multimegawatt beam tester and collector. In the third experiment the same beam was employed in the pulsed klystron. Efficiencies exceeding 50 per cent were obtained with no instabilities at voltages between 125 and 150 kv. In view of the above results and the properties of the extended-interaction cavities, it would appear that the final design of the one-megawatt CW klystron could result in a successful tube.