Longitudinally segmented shashlik calorimeters with SiPM embedded readout

Shashlik calorimeters are sampling calorimeters using wavelength shifting fibers running perpendicularly to the scintillating/absorber plates for the light readout. These devices are cost-effective, easy to assemble, and characterized by a good flexibility in terms of energy resolution. On the contrary, the perpendicular optical fiber readout and the resulting fiber bundling to the photosensor pose a strong limitation to the longitudinal segmentation. Recently, the fast development of solid state photosensors allowed for the integration of the readout system directly in the bulk of the calorimeter, opening new possibilities in terms of longitudinal segmentation (SCENTT INFN R &D). In an ultra-compact module every single fiber segment is directly connected to a SiPM; the SiPMs are arranged in arrays on custom PCBs and readout by a fast electronics based on waveform digitizers. This detector technology is the baseline option for ENUBET: a 5 year project (2016-2021) funded by the European Research Council aiming to demonstrate the possibility of a complete instrumentation of the decay tunnel of conventional neutrino beam. This technique allows for a ten-fold reduction on the neutrino flux normalization error. In the talk we will present the results and a detailed performance assessment of the novel ultra-compact design obtained with a prototype of longitudinally segmented shashlik calorimeter, readout with SiPMs embedded in the calorimeter bulk. Tests performed at the CERN PST9 beamline in the 1-5 GeV energy range in November 2016 provided results in terms of linearity, energy resolution and e/π discrimination at various beam angles reproducing the grazing incident conditions typical of neutrino beam decay tunnels. We will also present results from a neutron irradiation campaign of our Silicon Photomultipliers at the INFN-LNL CN accelerator allowing to test neutron fluences of O(10
¹²
/cm
²
) using 5 MeV protons on a Be target.