CaloCube: a highly segmented calorimeter for space based observation of high energy cosmic rays.
Future research in High Energy Cosmic Ray Physics concerns fundamental questions on their origin, acceleration mechanism,and composition.Unambiguous measurements of the energy spectra and of composition of cosmic rays at the “knee” region are expected to answer the above questions. Ground based experiments have systematic limitations to the precision of the measurement and thus they must be complemented by space-based experiemtns. A calorimeter based space experiment can provide not only flux measurements but also energy thus overcoming some of the limitations of the ground based experiments. Large acceptance is required, but this contrasts with the limitations in weight and size of space based experiments. A novel idea in calorimetry is discussed here which addresses these issues compatibly with the constraints. Simulation and beam test results with prototypes are reported.
Future satellite-based experiments dedicated to the observation of high-energy gamma and charged cosmic rays will increasingly rely on highly performing calorimetry, and their physics performance will depend on the geometrical dimensions and the energy resolution of the calorimeter. Thus an important issue is the optimization of the geometrical acceptance, the granularity and the absorption depth with respect to the total mass of the apparatus which is a crucial constraint for space based experiments. The design studied in CaloCube satisfies those criteria while retaining a total mass below 1.6 tons. It is a homogeneous calorimeter with active material Cesium Iodide (CsI) crystals, whith a cubic and isotropic geometry, to be sensitive to particles from every direction in space. Granularity is defined by the small size of the cubic CsI crystals. The total radiation length in all directions is sufficient for measurement of electromagnetic particles, whilst the interaction length is sufficient to allow a precise reconstruction of hadronic showers. This configuration requires original solutions in the read-out system, which must cope with a verylarge dynamic range, and with calibration requirements that are tackled by a LED base system. Results of prototypes built with different crystal materials in beam test with electrons, hadrons and muons are presented.