Simulations of Racetrack Microtron for Acceleration of Picosecond Electron Pulse

Low emittance sub-picosecond electron pulses are expected to be used in a wide field, such as free electron laser, laser acceleration, femtosecond X-ray generation by inverse Compton scattering, and pulse radiolysis, etc. In order to produce the low emittance sub-picosecond electron pulses, we are developing a compact racetrack microtron (RTM) with a new 5 MeV injection system adopting an laser photo cathode RF gun [1]. The operation of RTM is kept under the steady state of beam loading for long pulse mode so far[2]. We have investigated for the first time by numerical simulation in the case of shortand single-pulse acceleration. As the results, RTM is also useful to accelerate a picosecond electron pulse under a transient state of beam loading. In the simulation, a picosecond electron pulse is accelerated to 139 MeV in RTM for the injection of about 5 MeV pulse with pulse length of 3 picoseconds, charge of 1 nC per pulse, and emittance of 1.8πmm mrad, which corresponds of output of the RF gun.