Ultra-low fluence irradiation with energetic heavy ion pulsed beam using a modified electrostatic raster scanner

Abstract A method for performing low fluence pulsed irradiations with energetic heavy ions is presented. A raster scanner, placed upstream from a sample target chamber, is externally driven by a voltage pulse generated by a function generator. The configuration is similar to an electrostatic chopper, where a voltage difference across the scanner’s electrodes sweeps the beam across the sample, placed slightly off center from the beam axis, resulting in a short irradiation pulse on the sample and a low particle fluence. Such a system was developed at the Centre for Micro Analysis of Materials (CMAM) facility and characterized using 9 MeV F and 18 MeV Cl ions. The system can generate pulses of a few microseconds duration, depending on ion energy and charge state. A diagnostic method for measuring the fluence on the samples by counting etched ion tracks is described. A fluence on the order of 10 6 cm −2 was obtained by this method. This method could be adopted by other tandem ion accelerator facilities through simple and inexpensive modifications of existing beam handling instruments.