Energy Spread Monitoring for the JLAB Experimental Program: Synchrotron Light Interferometers, Optical Transition Radiation Monitors, and Wire Scanners

The hypernuclear physics program at JLAB requires an electron beam with small transverse size ( ~ 100 mum) and an upper limit on the RMS energy spread of < 3 X 10-5. To measure and monitor these parameters, a beam size and energy spread measurement system has been created. The system consists of a set of wire scanners, Optical Transition Radiation (OTR) detectors, and Synchrotron Light Interferometers (SLI). The energy spread is measured via a set of wire scans performed at specific locations in the transport line, which is an invasive process. During physics operation the energy spread is monitored continuously with the OTR and/or the SLI. These devices are non-invasive [or nearly non-invasive in the case of OTR] and operate over a very wide range of beam energies (1-6 GeV) and currents (~100 muA down to few muA). All components of this system are automated in an EPICS accelerator control environment. The paper presents our operational experience with the beam size and energy spread measurement system and its maintenance.