On-orbit equalization of the electromagnetic calorimeter of the Alpha Magnetic Spectrometer

Purpose The Alpha Magnetic Spectrometer(AMS-02)will continuously collect data for the lifetime of the International Space Station(ISS).On-orbit equalization must be performed to ensure the accuracy of the AMS energy measurement(~1%)by the electromagnetic calorimeter(ECAL).Methods The equalization is performed using the most probable value(MPV)of the cosmic-ray proton minimum ionizing particle(MIP).Kalman filter technique is used to improve the precision.Results The precision of the equalization with proton MIP is(7.206±0.003)%and improved to(2.388±0.002)%after the Kalman filter.From the toy Monte Carlo(MC)simulation,the error of the energy reconstruction is about 1.4%and 0.5%due to the 7.2%and 2.4%equalization accuracy,respectively.Conclusion About 1.4%error due to~7%equalization precision does not match the AMS requirement.With the improvement from the Kalman filter,the energy reconstruction error from the equalization is reduced to 0.5%,which can fulfill the AMS requirement.