Use of CR-39 plastic dosimeters for beam ion halo measurements

The first testing of CR-39 solid-state nuclear track dosimeters for beam halo measurement were performed at the SARAF phase I accelerator with ~ 2 MeV proton beams. Beam pulses of 90 nA peak intensity of the shortest possible duration (15 ns) available at SARAF were used for direct irradiation of standard CR-39 personal dosimetry tags. The lowest intensity and duration were used to minimize the beam core saturation on CR-39 tags. Other irradiations were done with beam pulses of 200 ns and 1 mA peak intensity. Specially prepared large area CR-39 plates with central hole for the beam core transport were used in the latter tests. Weak beam structures were clearly observed in both types of irradiation. The tests showed feasibility of low energy beam halo measurements down to resolution level of a single proton. Different CR-39 etching conditions were studied. The advantages and drawback of the method are discussed.