A precision toroidal charge monitor for SLAC

A charge monitor system which utilizes a ferrite toroid operated in a reso-nant mode is described. The system is designed to monitor electron and posi-tron beam pulses of,< 2 psec duration having peak intensities of 50 PA to 50 mA, at a maximum rate of 360 pps. The digital accumulator which totalizes charge is bidirectional in order to reduce the effects of noise. For runs of 10 4 samples ( N 30 seconds at 360 pps), the error due to noise is,< 0.1 percent of reading over a 1OOO:l signal range. Faraday cup comparisons for currents greater than 1 mA peak show agreement to < 1 percent, with a standard deviation of < 0.1 percent. The system includes a built-in calibration and test facility; toroid tem-perature stabilization; digital displays for total charge, charge per beam pulse, and number of beam pulses; and digital outputs to a computer. Work supported by the U. S. Atomic Ener,v Commission (Presented at the Symposium on Beam Intensity Measurement, T)aresbury Nuclea