Faraday cup for measuring the electron beams of TWT guns

A compact Faraday cup reported in this paper is designed to investigate the current distributions of the electron beams of Traveling Wave Tube’s guns. It consists of a 0.06 mm thick molybdenum aperture plate and a copper shield with a graphite collector inside. There are plates with different laser-cut aperture holes that were 100 μm, 50 μm, 20 μm and 10 μm in diameter for measuring electron beams with different sizes. The thermal analysis of the Faraday cup with pulse beam heating was performed and discussed in this paper. The pulse test shows that this device has fast response and small dissipation. A 0.58 beam perveance (μP) electron gun with expected minimum beam radius 1.0 mm was measured with the Faraday cup and the three-dimensional current density distribution and beam envelope were presented. The experiment results show that the design is reasonable for measuring the electron beam with a high resolution.