First microdosimetric measurements with a TEPC based on a gem

A new type of mini multi-element tissue-equivalent proportional counter (TEPC) based on a gas electron multiplier (GEM) has been designed and constructed. This counter is in particular suitable to be constructed with a small sensitive volume so that it can be used for microdosimetry in intense pulsed radiation fields to measure the microdosimetric spectrum in the beam of, for instance, a clinical linear accelerator. The concept lends itself also for a mini multi-element version of the counter to be used for applications in which a high sensitivity is required. In this paper, we present the first microdosimetric measurements of this novel counter exposed to a 14 MeV monoenergetic neutron beam and a californium (Cf-252) source for a counter cavity diameter of 1.8 mm simulating 1.0 mum tissue site size. The measured spectra showed an excellent agreement with spectra from the literature. The specific advantages of the TEPC-GEM are discussed

Novel low-temperature processing of low noise SDDs with on-detector electronics

\u3cp\u3eWe have developed a fabrication process (SMART700° process) for monolithic integration of p-channel JFETs and silicon detectors. Processing steps of the SMART700° do not exceed 700°C. The integrated p-JFET has a minimum gate length of 1 μm. A relatively large width can be chosen to achieve a reasonable transconductance, while the JFET capacitance still matches the small capacitance of a detector. The feedback capacitor was also realized on-chip as a double-metal capacitor. In this paper we describe DC and noise characteristics of a silicon drift detector (SDD) with a p-JFET (W/L = 100/1) and a feedback capacitor integrated in the read-out anode (smart-SDD). The device has a transconductance of 1-3 mS, a top gate capacitance of ∼140 fF and a low leakage current (<10 nA/cm\u3csup\u3e2\u3c/sup\u3e at room temperature). The smart-SDD with an active area of 3.8 mm\u3csup\u3e2\u3c/sup\u3e has reached an energy resolution of ∼50 rms electrons at a temperature of 213 K. This relatively poor energy resolution is due to generation-recombination noise caused by defects produced by a deep n-implantation. Rapid thermal annealing (RTA) and excimer laser annealing (ELA) techniques are experimented to remove the implantation damage. The noise of p-JFETs annealed with RTA and ELA is also presented.\u3c/p\u3