Blue light sensitization of CVD diamond detectors

CVD diamond needs to be 'primed' or 'pumped' by X-rays or by high energy electrons in order to be qualified for nuclear detection. In this 'pumped' state, CVD diamond detector performances are reported to be more reproducible, homogeneous and averagely better. The pumping effect is usually attributed to filling of (hole) traps, which are responsible for the charge collection efficiency of the detector. In this work, the possibility of filling traps selectively by light has been systematically investigated, in order to find the kind of 'background light' in which the detectors could preserve their performances indefinitely in time. Irradiation by the blue light before or/and during the detection of nuclear particles seems to avoiding the large doses needed for pumping. Other wavelengths seem to be totally inefficient from this point of view. It turns out that electrons are responsible for charge transport during blue light priming, while holes give the largest contribution during X-ray priming. The results will be presented as maps of charge collection efficiency in CVD diamond detectors as obtained by IBIC (Ion Beam Induced Charge) carried out by using a proton microbeam.