PERFORMANCE OF AN ACOUSTOOPTIC BRAGG CELL UNDER ION MICROBEAM IRRADIATION

An acousto-optic (AO) deflector composed of PbMoO4 was exposed to 4 Me V protons while operating under Bragg angle conditions. An ion beam in air of 1 mm width was directed normal to the crystal face and laser b eam. Between exposures, the approximately 13 mm x 8.5 mm AO deflector was mechanically translated in two dimensions in front of the fixed io n beam. The AO diffraction efficiency was mapped and was observed to c hange as a function of ion beam location and dose rate. These effects are attributed to the induced change in the temperature distribution o f the crystal, which changed the sonic velocity and refractive index. Similar effects were observed when the ion beam was directed at the ac oustic transducer.