Life test of EBS diode at 200 - 300 W dissipation

This paper reports life test data on the highest CW power EBS device demonstrated to date. A silicon EBS diode of 60 mm²active area, but with only 10 mm²under electron bombardment, mounted on a water-cooled heatsink, was operated at 200 to 250 W dissipation for 5000 hours. During this period, reverse leakage characteristics were stable but current gain declined in the first 1000 hours. From 5000 to 8000 hours, dissipation was raised to 300 W with a junction temperature which ultimately proved to be over 200°C. Leakage current increased substantially during this period. Cathode deterioration forced a reduction of power to 250 W after 8000 hours. The diode was short-circuited after 9360 hours by the growth of a crystalline projection outside the area of bombardment. Prior to the beginning of the life test, the diode temperature was measured in EBS operation by an infrared pyrometer technique. A theoretical prediction of CW performance for EBS amplifiers is also given.