Calibration of Tuffak polycarbonate track detector for identification of relativistic nuclei

Abstract

We discuss response of Tuffak polycarbonate to relativistic heavy nuclei using two methods, measurement of the minor axis diameter and of the length of the track cone, to determine charge resolution. At Z = 92 (0.95 GeV/u 238U) both methods give about 0.9 e charge resolution for a single cone measurement. Multiple cone measurements along the ion's trajectory have yielded a charge resolution σ z ⩽ 0.25 e (16 cones) when stripping foils (Cu) are interleaved between plastic sheets to minimize sheet-to-sheet charge state correlations. As the charge of the incident ion decreases to Z ≈ 52–57, the single-cone charge resolution improves (σ z ∼ 0.29 e). The angular response of Tuffak is fairly constant for zenith angles of incidence from 0° to 48°. Range measurements of stopping relativistic 238U in Tuffak deviate by ∼5% from that predicted by the Bethe-Bloch formula, as expected from recent relativistic calculations. We conclude that Tuffak is an excellent track detector for identification of nuclear charges of relativistic heavy nuclei with 50 ≤ Z ≤ 92.