Testing of a Raster Magnet System for Expanding the Apt Proton Beam

A method of expanding the 1700 MeV, 100 mA proton beam of the APT linear accelerator onto the 19 by 190 cm target has been devised using eight ferrite dipole magnets. These magnets deflect the beam in the x and y-plane, and thereby paint the target area uniformly with a rastered pattern. Insulated Gate Bipolar Transistor (IGBT)-based power modulators drive the raster magnets with triangular current waveforms that are synchronized using voltage controlled crystal oscillators and phase-locked loops (PLLs). Redundant fault detection circuits monitor both the ac magnet currents and magnetic fields to ensure proper operation. This paper presents the test results taken on an integrated prototype system including eight magnets, the associated modulators, the master clock and the fault detection circuitry.