An Ion Beam Tracking System based on a Parallel Plate Avalanche Counter

A pair of twin position-sensitive parallel plate avalanche counters have been developed at the Australian National University as a tracking system to aid in the further rejection of unwanted beam particles from a 6.5 T super conducting solenoid separator named SOLEROO. Their function is to track and identify each beam particle passing through the detectors on an event-by-event basis. In-beam studies have been completed and the detectors are in successful operation, demonstrating the tracking capability. A high efficiency 512-pixel wide-angle silicon detector array will then be integrated with the tracking system for nuclear reactions studies of radioactive ions. 1 Radioactive Ion Beams Most of our current understanding in nuclear physics has come from using stable targets and beams. Stable nuclei represent only a small fraction of the total number of nuclei that can exist and do not exhibit many of the exotic properties seen in nuclei far from stability, such as halos [1]. The ability to study unstable nuclei has opened up a vast new range of physics to be explored. Whilst decay of these isotopes makes most of them unsuitable as targets, they can be used as beams, known as Radioactive (or Rare) Isotope Beams (RIB) [2]. The Australian National University (ANU) RIB capability, based on a super-conducting solenoidal separator, is currently being developed [3]. This capability is successfully producing radioactive nuclei such as (He, Li, Be, B) by transfer reactions, which are then transmitted and focussed by the solenoid onto the secondary target position for nuclear reaction studies.