and

The 4 GeV recirculating linac, CEBAF, is presently under construction and will produce a CW beam with averagecurrent between.1 and 200 PA. 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 beam from the CEBAF injector indicate that beam position can be measured with an accuracy of.l mm at a modulated beam current of 1 PA