New bunch length monitor utilizing a detection of electromagnetic fields in millimeter-wave region

A new nondestructive bunch-length monitor has been numerically investigated. The monitor detects electromagnetic fields generated through a ceramic gap of a vacuum pipe when a charged particle beam passes through the pipe gap. The frequency spectrum of the electromagnetic fields detected in wave zone spreads over a millimeter-wave length from a microwave length region for a short-pulsed beam with a bunch length of picosecond range. The frequency spectrum strongly depends on the bunch length of a relativistic charged beam if the geometrical structure of the pipe gap is fixed. The detection principle of the bunch-length monitor and some numerical analysis results applied to a single-bunch electron beam of the KEKB injector linac are described in this report. (author)