A novel high power vacuum diode with a focusing electrode for effective operation in a low guiding magnetic field.

A novel diode featuring an annular cathode and a ring-shaped focusing electrode and operating in a low guiding magnetic field (GMF) has been developed. It was found that the breakdown threshold for a focusing electrode made of titanium was 140 kV/cm higher than a stainless steel electrode for the same operating conditions. Comparison of the diode current measured by a Rogowski coil and the beam current measured by a Faraday cup at the collector indicated that an intense relativistic electron beam was transmitted effectively even in a GMF of as low as 0.21 T. In addition, a photo of the cathode plasma and the targeting results indicated that the emission uniformity of the graphite cathode was satisfactory.