Bunch by Bunch Intensity Monitor for Fermilab Main Ring

Abstract

A bunch-by-bunch intensity monitor has been developed for the Fermilab Main Ring with future intended use in the Energy Doubler/Saver. The input signal is a beam doublet from a quarter wave stripline pickup that varies from 2 to 8 nanoseconds FWHM. The faithful integration of this pulse will produce an intensity signal proportional to the number of protons per bunch. The technique used is a fast integrate, hold, and damp. The intensity output is then made available for digitizing in the Snapshot Digitizer System. Beam losses at various points of the accelerating cycle may then be monitored on a bunch-by-bunch basis. The intensity monitor requires, in addition to the beam doublet, the input of a synchronized VCO. It is important that the group delay of both the VCO and beam input lines be identical so as not to change the phase relationship between the two as the RF is frequency modulated during acceleration. The doublet input dynamic range adjustment is a switched bank of coaxial attenuators. Their selection is based on predicted beam intensity for each accelerator cycle. A block diagram of the intensity monitor is provided.