Beam Current Monitor for the Oak Ridge Electron Linear Accelerator

A toroidal induction monitor was designed for the Oak Ridge Electron Linear Accelerator (ORELA) to provide a visual display of beam current pulses having peak amplitudes up to 15 amp with widths ranging from 3 to 200 nsec. To achieve rise times of about 1 nsec, the monitor was designed to utilize the influence of the electric field of the electron bunch to improve the response time of the magnetically induced output pulse. The final monitor design consists of a Ferroxcube 400T750, ferrite toroidal core of 1.25 in. ID wound with ten symmetrical turns of AWG 26 Formvar copper wire. The toroid is mounted at the end of the last acceleration tube in an assembly which includes a 0.9-in. ID collimator preceding the toroid. For simplicity of mechanical design, the toroid is operated at the vacuum level of the acceleration tube.