Electrostatic Design and Fabrication a New Tunable Perveance Pierce Electron Gun

Abstract

The perveance, ${K}$ , one of the Pierce electron gun (PEG) outputs, is completely dependent on geometric features, including the anode-cathode spherical distance, ${D}_{\text {ac}}$ . If the measured ${K}$ is not desirable after assembling, or the center of the cathode is not aligned with the anode axis, the PEG should be disassembled. In this article, with respect to the effects of spherical aberration and thermal velocity, a PEG is designed, simulated by computer simulation technologies (CSTs)-particle studio (PS) software, and manufactured for an ${S}$ -band klystron with ${K} = 1.5\,\,\mu $ and variable ${D}_{\text {ac}}$ . A new part in the PEG is designed that is called the spring film. It can move the cathode ±1 mm in the ${z}$ -direction while the other components are fixed and the vacuum of PEG does not change. The initial design leads to ${D}_{\text {ac }}$ to be 3.6 mm, but since ${K}$ is not expected as what we were looking for, so the desired ${K}$ is obtained by changing ${D}_{\text {ac}}$ , also the other parameters changing with ${D}_{\text {ac}}$ are examined and their values are estimated from the simulation. Finally, it is concluded that with the newly designed electron gun, unlike conventional PEGs, some parameters like perveance, cathode current, cathode lifetime, and body current are not fixed and they can be changed or improved.