The Quenching Effect of BGO Crystals on Relativistic Heavy Ions in the DAMPE Experiment

The DArk Matter Particle Explorer (DAMPE) is a satellite-borne, calorimetric-type, high-energy-resolution detector for the precise measurement of high-energy electrons, gamma rays, and nuclei from deep space. The DAMPE electromagnetic calorimeter consists of bismuth germanate (BGO) crystals that can measure incident hadron energies from 50 GeV to 100 TeV. For an inorganic scintillator, such as BGO, the nonlinear fluorescence response when measuring ions contributes to the difference between the experimental data and Monte Carlo simulations. This article reports the BGO quenching nonlinearity occurring in the DAMPE experiment. The ionization energy response of BGO to several kinds of ions lighter than iron is investigated by conducting beam tests and analyzing flight data. We compare the scintillator output with the energy loss according to GEANT4 simulations and determine the quenching parameters. The combined result of beam test and flight experiment shows that the quenching effect strongly depends on the density of the ionization energy loss.