System for diagnostics of local electron beam losses in microtron-recuperator at Novosibirsk Free Electron Laser beamline via registration of induced X-rays.
The Novosibirsk Free Electron Laser (FEL) is based on a 4-turn microtron-recuperator. To ensure its stable operation and radiation generation, it is necessary to provide a stable mode of electron beam recirculation and minimize beam losses on the vacuum chamber wall on all the way of beam in the accelerator beamline. To fulfil this task it is necessary to know the longitudinal distribution of these losses along the beamline. To this end, a system for registration of beam losses was created. The system applies optical fibers placed along the full length of the vacuum chamber and nearby it. In case of local electron beam losses somewhere in the vacuum chamber, electrons falling to the vacuum chamber wall cause generation of X- and gamma rays. This radiation in turn causes generation of optical radiation in the optic fiber nearby the region of electron “precipitation” on the chamber wall. Then, executing some transformation and processing of the time dependencies of signals from these optic fibers, one can obtain the longitudinal distribution of electron beam losses along the whole accelerator channel in all its 4 turns.