Monolithic arrays of SDDs and low noise CMOS readout for X-ray spectroscopy measurements in nuclear physics experiments

This work deals with the development of Silicon Drift Detectors (SDDs) of different sizes and low noise CMOS read-out preamplifiers in view of their use in nuclear physics experiments, like the SIDDHARTA upgrade supported by Italian INFN. In this work we report about the recent SDDs and CMOS preamplifiers development, with particular emphasis on X-ray measurements at cryogenic temperatures. The SDDs presented are designed as single square shaped units of different areas 64 mm(2) (8 mm x 8 mm) or 144 mm(2) (12 mm x 12 mm) and also as monolithic arrays of 9 elements (8 mm x 8 mm each, total area 26 mm x 26 mm) in a 3 x 3 format. The detectors have been designed and manufactured by the Fondazione Bruno Kessler (FBK). The read-out of the SDDs is based on the CMOS preamplifier (CUBE) for both the single unit and the 3 x 3 array. The CMOS technology is intrinsically more robust at lower temperatures with respect to the more conventional JFET transistor used in SDDs readout. A measured resolution of 123 eV on the Mn-K alpha line with the optimum shaping time and a resolution of 126.4 eV with 250 ns shaping time have been obtained with round shaped 10 mm(2) SDDs detectors. This last result leads to excellent spectroscopy performances even with very high input count rates making the SDD+CUBE combination very attractive also for synchrotron applications. The nine detectors array in addition to the preamplifiers the use of a multichannel ASIC for signal shaping and peak detection of all the units and of a custom Data Acquisition System. Also preliminary measurements of low energies lines are reported in order to prove the possibility of soft X-ray detection.