Bulk etch rate measurements and calibrations of plastic nuclear track detectors

New calibrations of CR39 and Makrofol nuclear track detectors have been obtained using 158 A GeV Pb82+ and In49+ions; a new method for the bulk etch rate determination, using both cone height and base diameter measurements, was developed. The CR39 charge resolution based on the etch-pit base area measurements is adequate to identify nuclear fragments in the interval 7 ⩽ Z/β ⩽ 49. For CR39 the detection threshold is at REL ∼50 MeV cm2 g−1, corresponding to a nuclear fragment with Z/β ∼ 7. Base cone area distributions for Makrofol foils exposed to Pb82+ ions have shown for the first time all peaks due to nuclear fragments with Z > 50; the distribution of the etched cone heights shows well separated individual peaks for Z/β ∼ 78 to 83 (charge pick-up). The Makrofol detection threshold is at REL ∼2700 MeV cm2 g−1, corresponding to a nuclear fragment with Z/β = 50.