Design of an ionization profile monitor for the SNS accumulator ring

An ionization profile monitor (IPM) has been designed for the Spallation Neutron Source (SNS) accumulator ring with the goal of simplifying current IPM technology to provide accurate high-intensity beam profiles. Utilizing ionized electrons produced by beam-gas ionization, the SNS IPM uses a 120 kV bias potential and uniquely designed electrode to overcome beam space charge and accelerate electrons towards a movable particle detector. A 300 G magnetic field will be used to confine the transverse electron motion, resulting in profile errors at the 7% level. With a system bandwidth of 17.5 MHz, the SNS IPM will be capable of measuring turn-by-turn beam profiles for a fully accumulated beam. This paper presents a description of the system and design.