Proposal for a race-track microtron with high peak current

Abstract

In order to obtain high gain in a free electron laser a high-quality electron beam with high peak current is required. It is well-known that a microtron is able to produce a high-quality beam having low emittance and small energy spread (1%). Because a circular microtron has a limited high-current capability a race-track design is adopted for providing flexibility, better beam quality and of course higher peak current in the microbunch. Space charge problems may be severe in a microtron. It can be shown that bunching on certain specific subharmonic frequencies will lead to a strong reduction of the space charge problems. The general layout of our microtron design will be presented. The characteristics are: energy 25 MeV, micropulse 10° of the rf frequency of 3 GHz. Our aim is to come beyond the present state of the art with the following characteristics: relative energy spread 0.001, emittance 3 mm mrad, current in the micropulse 100 A, macropulse length 50 μs and subharmonic bunching at 1:64.