The Plastic Scintillator Detector of the HERD space mission

Abstract

The High Energy cosmic-Radiation (HERD) detector is one of the prominent space-borne instruments to be installed on-board the Chinese Space Station (CSS), around 2027. Primary scientific goals regarding this initiative include: precise measurements of cosmic ray (CR) energy spectra and mass composition, at energies up to the PeV range; contributions to high energy gamma-ray astronomy and transient studies; as well as indirect searches for Dark Matter (DM) particles via their possible annihilation/decay to detectable products. HERD is configured to accept incident particles from both its top and four lateral sides. Owing to its pioneering design, an order of magnitude increase in acceptance is foreseen, with respect to previous and ongoing experiments. The Plastic Scintillator Detector (PSD) constitutes an important sub-detector of HERD, particularly aimed towards anti-coincidence (discriminating incident photons from charged particles), while providing precise charge measurement of incoming cosmic-ray nuclei in a range of Z = 1 -26. Main requirements concerning its design, include: high detection efficiency, broad dynamic range and good energy resolution. In order to select the optimal layout, two geometries are currently under investigation: one based on long scintillator bars and the other on square tiles, with both layouts being readout by Silicon Photomultipliers (SiPMs). Ongoing activities and future plans regarding the HERD PSD will be presented in this work.

Cosmic rays and gamma rays with DAMPE and HERD

“…Thanks to its unprecedented acceptance, HERD will achieve fundamental and frontier objectives in dark matter search, cosmic ray physics and gamma-ray astronomy. To improve the detector design, several simulation works and tests both in laboratory and with particle beams are ongoing [13][14][15][16][17].…”

Overview of the HERD space mission

“…The HERD PSD [4] envelops the detectors illustrated above and serves an anti-coincidence (discriminating incident photons from charged particles), while providing an essential charge measurement of incoming cosmic-ray nuclei in a range of Z = 1 − 26. Practically, thin and light materials (i.e., organic scintillators) can be an optimal choice for this task.…”

“…The bar layout [4] in its current design is instrumented with 2 layers of scintillator bars orthogonally interleaved (in X and Y axes), in order to assist in track identification and charge measurement. For the top surface, a total of 134 bars (67 for each layer) and size of 174.2 × 3 × 0.5 cm 3 will be instrumented.…”

The High Energy Cosmic-Radiation Detection (HERD) facility for direct cosmic-ray measurements.

“…The main aim of the PSD [20] is to provide a veto (both online and offline) to identify gamma rays. The current design is made of rectangular tiles read out by SiPMs, and is currently being optimized for hermeticity.…”