CVD diamond detectors for nuclear and dosimetric applications

The recent availability of single crystal (sc) CVD diamond samples of very good quality and suitable thickness and surface area has opened new application fields in nuclear detection and dosimetry such as hadron radiotherapy and neutron spectrometry in fusion reactors. At the same time, dot, strip, and pixel detectors with unprecedented performances have been successfully realized and exploited in the framework of high energy physics (HEP). While the goal of a charge collection distance (ccd) of 200 μm was reached with polycrystalline (pc) samples in the year 2000, values of ccd up to 0.42 mm at 0.2 V/μm are now reported for the new sc samples. From the point of view of “detector quality,” the mobility-lifetime product for carriers is now approaching that of one of the best nonsilicon detector materials like CdTe, but it seems still far from that of Si. The most important point seems to be related to the homogeneity of new sc samples, which now in some cases displays an energy resolution down to 0.4% for Am-241 alpha particles and of 2.9% for 14.1 MeV neutrons. CVD single crystal beam monitors are now currently running in HEP experiments and their performances are compared with more recent radiation hard Si detectors. CVD diamond detectors are quoted to be capable to withstand particle fluxes over 1015 cm−2 (which corresponds to a 10-year experiment run) with no counting losses and only a small reduction in S/N ratio. A more intriguing question is concerning priming, which is very important for detector performances: while no priming seems necessary for sc samples, in the case of pc samples, a simple priming with blue light instead of X-rays or beta-rays is possible, with the issue of different or better detector performances. The paper will review the more recent history of CVD diamond nuclear detectors with respect to material quality and priming. Some detectors and dosimeter performances in different top level fields will be quoted and possible future scenarios will be described.