On-orbit energy calibration of the calorimeter on the ISS-CREAM instrument using the boronated scintillator detector

The Cosmic Ray Energetics And Mass instrument on the International Space Station (ISS-CREAM) aims to measure the energy spectra of cosmic ray (CR) nuclei from Z=1 to Z=26 with energies from 10¹² eV to 10¹⁵ eV. The calorimeter (CAL) was designed to measure the energy of the CR particles. The ISS-CREAM on-orbit data provide evidence that the CAL may have either suffered from an efficiency problem or its absolute energy scale may be in need of calibration. As a result, a careful scrutiny of the absolute energy calibration of the CAL is required. We describe an approach to calibrate the energy scale using the on-orbit data of the boronated scintillator detector, which is independent of the CAL data and reduces potential bias. We discuss the issues revealed by the on-orbit data, demonstrate how this can be corrected using the boronated scintillator detector and present preliminary results.