Radiation 2006. In association with the Polymer Division, Royal Australian Chemical Institute. Incorporating the 21st AINSE Radiation Chemistry Conference and the 18th Radiation Biology Conference, conference handbook

Full text: The Silicon ΔE-E Telescope is a suitable instrument for identification of charged particles with many applications in heavy ion nuclear physics and of recent, radiation protection for prediction of cancer induction. It is well known that for the same absorbed dose, a different biological effect (characterised by cell survival) is observed between densely and weakly ionising radiations. In this situation one must determine the equivalent dose (the dose of the weakly ionising radiation required to observe the same biological effect as a given absorbed dose of densely ionising radiation) and the associated Relative Biological Efficiency (RBE) of radiation. One of the approaches to determining the RBE of a radiation is microdosimetry. Silicon SOI sensors for microdosimetry (and subsequently determination of RBE) have been developed during the last decade at the CMRP and have been used extensively in radiotherapy. Another method is the fluence based approach which suggests the probability of cancer induction is related to the ion's atomic number and energy. Thus identification of ions and their fluence will provide the total probability of cancer induction or the equivalent dose of radiation. In both situations, identification of low energy heavy ions with a range of several microns in silicon is a challenge due to technological problems associated with producing a stand alone ΔE Si detector with the thickness 1-2 microns. The new telescope discussed is a monolithic ΔE - E detector. It is composed of an n-type silicon wafer with a p+ buried region produced by high energy boron implantation. ΔE and E cathodes are formed by As and P implantation on the front and rear surfaces respectively. The response of the new device using a 2 μm diameter microbeam of α particles and protons was tested on the ion microprobe at ANSTO and the results will be presented. Imaging of charge collection in ΔE and E stages separately and also in coincidence showed excellent uniformity within these detectors. The effective thickness of ΔE detector was 1.9μm and the uniformity of thickness is better than 10%; limited by energy resolution and straggling in ΔE channel. The channelling phenomenon is clearly observed. This detector model will be soon implemented in new instrumentation for equivalent dose and RBE determination in space missions and proton therapy