Non-Intercepting Monitor of Beam Current and Position

Abstract

A compact monitor has been developed which measures beam current and beam position without intercepting or appreciably affecting the particle beam being measured. It is a broad band device which prevents the development of beam disturbing resonant modes. Although developed specifically for use on a short-pulse electron induction accelerator, it might be applied to other accelerator beams of pulsed or rf-bunched nature. The monitor consists of a resistive band inserted in the beam pipe wall with connections for reading the voltage across the band at each vertical and horizontal axis intercept. For pulsed or rf beams, return current equal in magnitude to the beam current flows on the beam pipe inside wall and through the resistive band. If the beam is centered, equal voltage appears on all four monitor connections. If the beam is off-center, the return currents are unsymmetrical and unequal voltages appear at the monitor connections. Beam current is proportional to the sum of all monitor voltages, while beam position is approximately proportional to the difference in voltage at opposing monitors. Tests and operating experience confirm its operation.