A scanner for gamma-ray detectors based on principles of positron tomography

The rapid development of the novel gamma-ray detectors and detector clusters based on principles of gammaray tracking opens new broad perspectives to nuclear spectroscopy. An increase of the efficiency and a gain of the Peak/Total [1] alongside with a possibility for an efficient linear polarimetry and imaging are expected to produce a significant impact on future experiments. The HPGe arrays like AGATA [2], GRETA [3] and DESPEC [4] will determine a new cutting edge of nuclear spectroscopy. The core principle of these detectors is an application of the pulse shape analysis (PSA) [e.g. 5,6]. Although one may say that this principle is nowadays well established, its verification and steady performance still poses big difficulties and uncertainties. The only reliable solution to its verification is a full 3D scanning of the detectors which experimentally determines pulse shapes from every given position inside the active volume. Easy sounding it turned out to be an extremely lengthy procedure with a timescale of months which may postpone the real experimental application of the PSA and tracking techniques. As one of the possible ways to speed up this process we proposed and implemented a first detector scanner based on principles of positron emission tomography [7]. An application of the Na source emitting pairs of 511 keV gammas in opposite directions allows creating a “collimator-free” scanner where many lines across the detector or even the whole detector is scanned simultaneously, see figure 1.