Development of Beam Profile and Fast Position Monitors for the LEP Injector Linacs

The beam profile monitor is a wire scanner comprising of an isolated L-shaped tungsten wire driven at 45-through the beam by a stepping motor controlled by a microprocessor system. Three measuring methods have been investigated : the secondary emission, the change of resistance of the wire, and the observation with a scintillator of the interactions taking place in the wire. Profiles of beams with 6 × 107 to 3 × 1011 e- have been measured, some of them in the vicinity of the e-/e+ converter at the LAL ORSAY linac. An economical S-band waveguide monitor has been designed to follow the beam position changes during the 12 ns pulse of LIL. It consists of a waveguide pick-up with a 2-4 GHz bandpass, of a voltage controlled phase shifter and of a double-balanced mixer used as a phase detector. The S-band components are located close to the pick-up and are small enough to be easily shielded.