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 Pb and In 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 measurement is adequate to identify nuclear fragments in the interval 7 ≤ Z/β ≤ 49. For CR39 the detection threshold is at REL ∼ 50 MeV cm g, corresponding to a nuclear fragment with Z/β ∼ 7. Base cone area distributions for Makrofol foils exposed to Pb 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 ÷ 83 (charge pickup). The Makrofol detection threshold is at REL ∼ 2700 MeV cm g, corresponding to a nuclear fragment with Z/β ∼ 50. PACS: 29.40.Wk; 34.90.+q