An Injection and Acceleration System of a Pulsed Race-Track Microtron

A pulsed race-track microtron (RTM) with a maximum beam energy of 70 MeV 1] is described. This device was developed at the Research Institute of Nuclear Physics of Moscow State University (Russia) in cooperation with World Physics Technologies Inc. (USA). For this project, several new elements, including bending magnets (based on rare-earth permanent magnets) 2], a system for injection of the bunched electron beam through a compact -magnet (also based on permanent magnets 3]), and a rectangular cavity biperiodic structure (RCBS) 4, 5], were developed. Unlike axially symmetric accelerating structures, the RCBS has small transverse dimensions and, as a result, does not present an obstacle for the electron beam traveling in the first orbit. Moreover, the RCBS possesses a quadrupole focusing with the value and sign of the focal power depending on the relationship between the size of the drift aperture and the dimensions of the microtron cavity and on the phase of the microwave field. These properties substantially simplify the RTM design and tuning. Tests, the tuning procedure, and measured characteristics of the injection and acceleration systems of the race-track microtron are described.