A New Approach to Calorimetry in Space-Based Experiments for High-Energy Cosmic Rays
Authors: Bigongiari Gabriele , Adriani Oscar , Albergo Sebastiano , Ambrosi Giovanni , Auditore Lucrezia , Basti Andrea , Berti Eugenio , Bonechi Lorenzo , Bonechi Simone , Bongi Massimo , Bonvicini Valter , Bottai Sergio , Brogi Paolo , Cappello Gigi , Cattaneo Paolo Walter , D’Alessandro Raffaello , Detti Sebastiano , Duranti Matteo , Fasoli Mauro , Finetti Noemi , Formato Valerio , Ionica Maria , Italiano Antonio , Lenzi Piergiulio , Maestro Paolo , Marrocchesi Pier Simone , Mori Nicola , Orzan Giulio , Olmi Miriam , Pacini Lorenzo , Papini Paolo , Pellegriti Maria Grazia , Rappoldi Andrea , Ricciarini Sergio Bruno , Sciuto Antonella , Silvestre Gianluigi , Starodubtsev Oleksandr , Stolzi Francesco , Suh Jung Eun , Sulaj Arta , Tiberio Alessio , Tricomi Alessia , Trifirò Antonio , Trimarchi Marina , Vannuccini Elena , Vedda Anna , Zampa Gianluigi , Zampa Nicola 
Published: March 2019

Precise measurements of the energy spectra and of the composition of cosmic rays in the PeV region could improve our knowledge regarding their origin, acceleration mechanism, propagation, and composition. At the present time, spectral measurements in this region are mainly derived from data collected by ground-based detectors, because of the very low particle rates at these energies. Unfortunately, these results are affected by the high uncertainties typical of indirect measurements, which depend on the complicated modeling of the interaction of the primary particle with the atmosphere. A space experiment dedicated to measurements in this energy region has to achieve a balance between the requirements of lightness and compactness, with that of a large acceptance to cope with the low particle rates. CaloCube is a four-year-old R&D project, approved and financed by the Istituto Nazionale di Fisica Nucleare (INFN) in 2014, aiming to optimize the design of a space-borne calorimeter. The large acceptance needed is obtained by maximizing the number of entrance windows, while thanks to its homogeneity and high segmentation this new detector achieves an excellent energy resolution and an enhanced separation power between hadrons and electrons. In order to optimize detector performances with respect to the total mass of the apparatus, comparative studies on different scintillating materials, different sizes of crystals, and different spacings among them have been performed making use of MonteCarlo simulations. In parallel to simulations studies, several prototypes instrumented with CsI(Tl) (Caesium Iodide, Tallium doped) cubic crystals have been constructed and tested with particle beams. Moreover, the last development of CaloCube, the Tracker-In-Calorimeter (TIC) project, financed by the INFN in 2018, is focused on the feasibility of including several silicon layers at different depths in the calorimeter in order to reconstruct the particle direction. In fact, an important requirement for γ -ray astronomy is to have a good angular resolution in order to allow precise identification of astrophysical sources in space. In respect to the traditional approach of using a tracker with passive material in front of the calorimeter, the TIC solution can save a significant amount of mass budget in a space satellite experiment, which can then be exploited to improve the acceptance and the resolution of the calorimeter. In this paper, the status of the project and perspectives for future developments are presented.