Nuclear physics experiments at Thomas Jefferson National Accelerator Facility's CEBAF rely on high polarization electron beams. We describe a recently commissioned system for prequalifying and studying photocathodes for CEBAF with a load-locked, low-voltage polarized electron source coupled to a compact retarding-field Mott polarimeter. The polarimeter uses simplified electrode structures and operates from 5 to 30kV. The effective Sherman function for this device has been calibrated by comparison with the CEBAF 5 MeV Mott polarimeter. For elastic scattering from a thick gold target at 20keV, the effective Sherman function is 0.201(5). Its maximum efficiency at 20keV, defined as the detected count rate divided by the incident particle current, is 5.4(2) × 10-4, yielding a figure-of-merit, or analyzing power squared times efficiency, of 1.0(1) × 10-5. The operating parameters of this new polarimeter design are compared to previously published data for other compact Mott polarimeters of the retarding-field type.
|Original language||English (US)|
|Number of pages||7|
|Journal||Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment|
|State||Published - Jun 1 2010|
ASJC Scopus subject areas
- Nuclear and High Energy Physics