Study of linearity of LYSO crystal for HERD calorimeter

TL;DR

This study evaluates the linearity of LYSO crystal-based calorimeter cells for the HERD space mission, demonstrating they maintain better than 10% linearity over a wide energy range from 30 MeV to 1,100 TeV.

Contribution

The paper provides the first beam test results confirming the linear response of LYSO crystals over an unprecedented energy range for space-based cosmic ray detection.

Findings

Linearity of HCC is better than 10% from 30 MeV to 1.1×10^3 TeV.

No saturation effects observed in the tested energy range.

Results meet the requirements for HERD's cosmic ray observation objectives.

Abstract

The High Energy cosmic Radiation Detection (HERD) facility is a space mission designed for detecting cosmic ray (CR) electrons, $\gamma$-rays up to tens of TeV and CR nuclei from proton to iron up to several PeV. The main instrument of HERD is a 3-D imaging calorimeter (CALO) composed of nearly ten thousand cubic LYSO crystals. A large dynamic range of single HERD CALO Cell (HCC) is necessary to achieve HERD's PeV observation objectives, which means that the response of HCC should maintain a good linearity from minimum ionizing particle (MIP) calibration to PeV shower maximum. In order to study the linearity of HCC over such a large energy range, a beam test has been implemented at the E2 and E3 beam lines of BEPC. High intensity pulsed electron beam provided by E2 line are used for producing high energy density within HCC; $\pi^{+}$/proton provided by E3 line are used for HCC calibration. The results show that no saturation effect occurs and the linearity of HCC is better than 10% from 30 MeV (1 MIP) to 1.1$\times$10$^{3}$ TeV (energy density is 93 TeV/cm$^{3}$), which can meet the requirement mentioned above.