The High Energy cosmic-Radiation Detection (HERD) Facility onboard China's Future Space Station

TL;DR

The HERD facility onboard China's space station is designed for high-precision cosmic ray, gamma-ray, and dark matter research, featuring advanced calorimeter and tracker systems with expected high performance in energy resolution and particle identification.

Contribution

This paper introduces the design and scientific objectives of the HERD space-based detector, highlighting its innovative calorimeter and tracker configurations for cosmic ray and gamma-ray measurements.

Findings

HERD achieves 1% energy resolution for electrons and gamma-rays above 100 GeV.

Proton energy measurement accuracy from 100 GeV to 1 PeV with 20% resolution.

Electron/proton separation power better than 10^-5.

Abstract

The High Energy cosmic-Radiation Detection (HERD) facility is one of several space astronomy payloads of the cosmic lighthouse program onboard China's Space Station, which is planned for operation starting around 2020 for about 10 years. The main scientific objectives of HERD are indirect dark matter search, precise cosmic ray spectrum and composition measurements up to the knee energy, and high energy gamma-ray monitoring and survey. HERD is composed of a 3-D cubic calorimeter (CALO) surrounded by microstrip silicon trackers (STKs) from five sides except the bottom. CALO is made of about 10$^4$ cubes of LYSO crystals, corresponding to about 55 radiation lengths and 3 nuclear interaction lengths, respectively. The top STK microstrips of seven X-Y layers are sandwiched with tungsten converters to make precise directional measurements of incoming electrons and gamma-rays. In the baseline design, each of the four side SKTs is made of only three layers microstrips. All STKs will also be used for measuring the charge and incoming directions of cosmic rays, as well as identifying back scattered tracks. With this design, HERD can achieve the following performance: energy resolution of 1\% for electrons and gamma-rays beyond 100 GeV, 20\% for protons from 100 GeV to 1 PeV; electron/proton separation power better than $10^{-5}$; effective geometrical factors of $>$3 ${\rm m}^{2}{\rm sr}$ for electron and diffuse gamma-rays, $>$2 $ {\rm m}^{2}{\rm sr}$ for cosmic ray nuclei. R\&D is under way for reading out the LYSO signals with optical fiber coupled to image intensified CCD and the prototype of one layer of CALO.