A detector system for discrete nuclide identification of ions with A ⩽ 60

An x−y position-sensitive detector system which provides simultaneous mass and charge identification with discrete nuclide resolution is described. This system is specially suitable for low-energy, medium-mass (E₁ ≈ 1–10 MeV/mu; A ≈ 10–60) heavy tons. Charge identification is determined from a two-element gas-ionization counter coupled with a semiconductor stop detector. The gas-ionization counter employs a simple electron drift time technique to obtain two-dimensional position information. Mass identification is derived from measurement of the fragment time-of-flight with a pair of channel-plate time devices and the fragment energy, as provided by the ΔE_y – ΔE_x – E telescope. This system yields mass and charge resolution ⩽0.7 units in both A and Z and gives position resolutioon <0.5 mm for fragments with A ≲60, as determined from measurements performed with a 7.2 MeV/u ⁵⁶Fe beam incident on ²³⁸U.