Charge identification in CR-39 nuclear track detector using relativistic lead ion fragmentation

Three stacks of plastic CR-39 Nuclear Track Detectors (NTD) were exposed to 158 A GeV Pb-207 ions at the CERN-SPS beam facility. The main purpose of t his experiment was the calibration of the CR-39 for the search of atmospher ic magnetic monopoles. Different targets (Al, Cu and Pb) were used to produ ce a large spectrum of charge ions for the purpose of calibration as well a s the study of ultrarelativistic lead ion fragmentation. The exposure of ea ch stack was performed at normal incidence with a fluence of about 1500 ion /cm(2). The total number of lead ions in each spill was about 7.8 x 10(4) a nd there were eight spills incident on each stack. For the stack with the C u target, the lengths of etched cones on one face of the CR-39 were measure d. From this measurement procedure, a new calibration curve has been genera ted for the extended charge region 63 less than or equal to Z less than or equal to 83. The charge resolution to,) achieved by this technique is simil ar to0.18e-0.21e. (C) 2000 Elsevier Science B.V. All rights reserved.