Pelletron-based MeV-range electron beam recirculation

In this paper we describe the successful recirculation of a DC electron beam at energies 1–1.5 MeV and currents up to 0.7 A with typical relative losses of 5–20×10−6. Currents of 200 mA were maintained for periods of up to five hours without a single breakdown. We found that the aperture-limiting diaphragm in the gun anode significantly increased the stability of the recirculation. We also found that the stability depended strongly on vacuum pressure in the beamline. The performance of the collector with transverse magnetic fields was found to be adequate for beam currents up to 0.6 A, which is in agreement with our low-energy bench test results.