Turn-by-turn transverse phase space measurements in real time

The South Hall Ring at the MIT-Bates Linear Accelerator is a 190 m circumference 1 GeV electron ring for use by nuclear physics experiments. Real-time turn-by-turn measurements of the beam transverse phase space in the ring are made using an EPICS based BPM data acquisition system, interfaced with a C/Motif application for data analysis and operator interface. Data acquisition is performed such that multiple BPMs acquire data synchronously. By acquiring data at a rate many times the ring revolution frequency, it is possible to make reliable turn-by-turn beam position measurements, even in the case of varying beam conditions. The application program uses an efficient algorithm for data reduction, and provides various modes for presenting data to the user. Details of the system design, including data acquisition, analysis, and the graphical user interface, are presented.