A micrometric thickness silicon diode proposed as a microdosimeter

A thin silicon diode formed by a deep p+ implantation under a shallow n+ one is proposed as a solid state microdosimeter. The thickness of the sensitive layer of the tested device is about two micrometers and the active area is about 10 mm
²
. Due to the very large electric capacitance of the diode (about 1 nF) a low noise read-out circuit based on a discrete JFET has been developed. The noise due to the parasitic resistance of the detector itself dominates and fixes the lower threshold of the energy spectrum. A prototype of the proposed microdosimeter covered with a polyethylene converter has been irradiated with fast monoenergetic neutrons at the INFN-Legnaro Labs (I). The first experimental spectra are in good agreement with the simulated ones. The effect of direct interactions of thermal neutrons in silicon has been measured