Performance assessment of the HERD calorimeter with a photo-diode read-out system for high-energy electron beams

TL;DR

This paper evaluates the HERD calorimeter's photo-diode read-out system using CERN beam tests, demonstrating excellent energy resolution for high-energy electrons and validating simulation models for future cosmic ray measurements.

Contribution

It presents the performance assessment of the HERD calorimeter's photo-diode read-out system with beam test results and simulation comparison, advancing space-based cosmic ray detection technology.

Findings

Energy resolution better than 1% at 250 GeV

Successful validation of Monte Carlo simulations

Demonstrated detector's capability for high-energy electron measurement

Abstract

The measurement of cosmic rays at energies exceeding 100 TeV per nucleon is crucial for enhancing the understanding of high-energy particle propagation and acceleration models in the Galaxy. HERD is a space-borne calorimetric experiment that aims to extend the current direct measurements of cosmic rays to unexplored energies. The payload is scheduled to be installed on the Chinese Space Station in 2027. The primary peculiarity of the instrument is its capability to measure particles coming from all directions, with the main detector being a deep, homogeneous, 3D calorimeter. The active elements are read out using two independent systems: one based on wavelength shifter fibers coupled to CMOS cameras, and the other based on photo-diodes read-out with custom front-end electronics. A large calorimeter prototype was tested in 2023 during an extensive beam test campaign at CERN. In this paper, the performance of the calorimeter for high-energy electron beams, as obtained from the photo-diode system data, is presented. The prototype demonstrated excellent performance, e.g., an energy resolution better than 1% for electrons at 250 GeV. A comparison between beam test data and Monte Carlo simulation data is also presented.