Scanning wire beam position monitor for alignment of a high brightness inverse-Compton x-ray source

摘要

The Free-Electron Laser Laboratory at the University of Hawai`i hasconstructed and tested a scanning wire beam position monitor to aid thealignment and optimization of a high spectral brightness inverse-Comptonscattering x-ray source. X-rays are produced by colliding the 40 MeV electronbeam from a pulsed S-band linac with infrared laser pulses from a mode-lockedfree-electron laser driven by the same electron beam. The electron and laserbeams are focused to 60 {\mu}m diameters at the interaction point to achievehigh scattering efficiency. This wire-scanner allows for high resolutionmeasurements of the size and position of both the laser and electron beams atthe interaction point to verify spatial coincidence. Time resolved measurementsof secondary emission current allow us to monitor the transverse spatialevolution of the e-beam throughout the duration of a 4 {\mu}s macro-pulse whilethe laser is simultaneously profiled by pyrometer measurement of the occultedinfrared beam. Using this apparatus we have demonstrated that the electron andlaser beams can be co-aligned with a precision better than 10 {\mu}m asrequired to maximize x-ray yield.