Absolute beam current monitoring in endstation c

The first few experiments at CEBAF require approximately 1% absolute measurements of beam currents expected to range from 10-25{mu}A. This represents errors of 100-250 nA. The initial complement of beam current monitorsare of the non intercepting type. CEBAF accelerator division has provided a stripline monitorand a cavity monitor, and the authors have installed an Unser monitor(parametric current transformeror PCT). After calibrating the Unser monitorwith a precision current reference, the authors plan to transfer this calibration using CW beam to the stripline monitorsand cavity monitors. It is important that this be done fairly rapidly because while the gain of the Unser monitoris quite stable, the offset may drift on the order of .5{mu}A per hour. A summary of what the authors have learned about the linearity, zero drift, and gain drift of each type of current monitorwill be presented.