A modular focal plane detector system for the heavy ion reaction analyzer at NSC, New Delhi

Abstract

Abstract A detector system has been developed for the focal plane of the HIRA. It consists of two independent detectors, a low-pressure multiwire proportional counter (LP-MWPC) followed by a split-anode ionization detector. Details of the design and test results are presented. Using slow preamplifiers, the position resolution is 21 mm and the time resolution is estimated to be 1.5 ns for the LP-MWPC. The ionization detector gives 2.4% energy resolution for 150 MeV “Si scattered off a gold target and the AZ/Z obtained for 28Si+27A1 is l/42 for Z= 14. Some results for fusion and transfer studies for the 48Ti+58Ni and 28Si+68Zn systems, respectively, at energies around the Coulomb barrier, are presented to highlight the performance of the detector system. 1. Introduction Recoil mass spectrometers (RMS) are versatile tools for heavy ion reaction studies [ 1,2]. Coupled to a high rejection for beam-like particles is the excellent mass resolution with large solid angle, and space and energy focusing. They are ideally suited for studying reactions which are forward peaked and have found good application in the study of fusion and transfer reactions around the Coulomb barrier, spectroscopy by residue tagging, etc. The heavy ion reaction analyzer (HIRA) at the Nuclear Science Centre is a large solid angle RMS, details of which are presented elsewhere [3]. An important part of such spec- trometers is the focal plane detector system (see Refs. [4,5] and references therein). At the focal plane, the HlRA brings to focus particles of varying values of