An Instrument to Measure Elemental Energy Spectra of Cosmic Ray Nuclei up to 1016 eV

Abstract A longstanding goal of cosmic-ray research is to measure the elemental energy spectra of cosmic rays up to and through the “knee” (≈3×10 15 eV). It is not currently feasible to achieve this goal with an ionisation calorimeter because the mass required to be deployed in Earth orbit is very large (at least 50 tonnes). An alternative method is presented. This is based on measuring the primary particle energy by determining the angular distribution of secondaries produced in a target layer using silicon microstrip detector technology. The proposed technique can be used over a wide range of energies (10 11 –10 16 eV) and gives an energy resolution of 60% or better. Based on this technique, a design for a new lightweight instrument with a large aperture (KLEM) is described.