Bulk etch rate measurements and calibrations of CR39 and Makrofol nuclear track detectors

We developed a new method for determining the bulk etch rate velocity based on both cone height and base diameter measurements of the etched tracks. This method is applied here for the calibration of CR39 and Makrofol nuclear track detectors exposed to 158 A GeV In^{49+} and Pb^{82+} ions, respectively. For CR39 the peaks corresponding to indium ions and their different fragments are well separated from Z/beta = 7 to 49: the detection threshold is at REL ~ 50 MeV cm^2 g^{-1}, corresponding to a nuclear fragment with Z/beta = 7. The calibration of Makrofol with Pb^{82+} ions has shown all peaks due to lead ions and their fragments from Z/beta ~ 51 to 83 (charge pickup). The detection threshold of Makrofol is at REL ~ 2700 MeV cm^2 g^{-1}, corresponding to a nuclear fragment with Z/beta = 51.