Preliminary beam test results of an LGAD-based 5D sensor array for the next generation of space-borne experiments

Direct measurements of the fluxes and relative abundances of charged cosmic rays carried out in space and on balloons, require the identification of the incoming particle and the measurement of its energy. Detectors in which tracking and particle-identification devices are operated in conjunction with calorimeters are affected by back-scattered radiation from the calorimeter, leading to a degradation of the charge resolution when the same charge-detector element is simultaneously hit by the incident cosmic ray and by the back-scattered component. To address these challenges, the ADA_5D project, funded by the Italian National Institute for Nuclear Physics (INFN), is developing an innovative detector, based on arrays of Low Gain Avalanche Diode (LGAD) pixels, for the simultaneous measurement of the incident particle position, charge, and timing (5D sensor) over a large dynamic range (∼ 1000 MIP) and with sub-nanosecond time-of-flight (ToF) resolution. A large rejection power of the back-scattered background is expected, by leveraging ToF cuts on the late arrival of back-scattered signals on the charge detector with respect to the incident cosmic rays, and on the high granularity of the array. This paper reports the preliminary results of the first beam test of prototypal arrays of LGADs, developed for the ADA_5D project by FBK in Italy, and the performance of a first version of a low-power custom chip for timing and charge front-end processing. A preliminary analysis shows a timing resolution close to 100 ps and a charge resolution of the order of 0.1 charge units for light nuclei.