Position and collision point measurement system for Fermilab’s interaction regions

Abstract

A higher resolution beam position monitor (BPM) system has been developed at FNAL to measure the transverse position of the beam at opposite ends of the Collision Hall. A secondary function is to measure the longitudinal location of the collision point. This system is called the Collision Point Monitor (CPM). The transverse positions are determined by software rectification and integration of a BPM signal obtained from a sampling oscilloscope. A difference over sum calculation of the A and B signals yields the position. The longitudinal location is obtained by measuring the difference in time between the proton and antiproton bunches at both ends of the Collision Hall. The downstream difference is then subtracted from the upstream difference and the result is multiplied by half the speed of light to yield the collision point error.