A beam position monitor for low current DC beams

The 4-GeV recirculating linac, CEBAF (Continuous Electron Beam Accelerator Facility), is presently under construction and will produce a CW beam with average current between 0.1 and 200 mu A. In order to measure beam position, the beam current will be amplitude-modulated at a frequency of 10 MHz. The modulation is detected by an inductive loop type monitor with electronics sensitive only to the modulation frequency. The first tests with the beam from the CEBAF injector indicate that beam position can be measured with an accuracy of 0.1 mm at a modulated beam current of 1 mu A.<>