Nuclear Instruments and Methods in Physics Research A285 (1989) 71-75 71 North-Holland, Amsterdam PROPOSAL FOR A RACE-TRACK MICROTRON WITH HIGH PEAK CURRENT

In order to obtain high gain m 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 etntttance and small energy spread (1%0). Because a circular nucrotron has a linuted high-current capability a race-track design is adopted for providing flexibility, better beam quality and of course higher peak current m the nucrobunch . 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, macropulse 10 ° of the rf frequency of 3 GHz. Our am is to come beyond the present state of the art with the following characteristics : relative energy spread 0.001, enuttance 3 mm mrad, current m the nucropulse 100 A, macropulse length 50 ls and subharmonic bunching at 1 :64.