A Particle Detector Array deployed to the Murchison Widefield Array in the Murchison Radio-astronomy Observatory

TL;DR

This paper presents the design, deployment, and initial results of a particle detector array at the Murchison Radio-astronomy Observatory, capable of detecting and reconstructing high-energy cosmic ray air showers, and serving as a pathfinder for future large-scale detectors.

Contribution

It introduces a new particle detector array integrated with the MWA, demonstrating its ability to identify cosmic ray air showers and its potential for future large-scale cosmic ray detection projects.

Findings

Successfully detected 35,500 EAS events over 13 days

Can reconstruct arrival directions and energies of cosmic rays above 4 PeV

Reliable triggering and data capture for radio analysis

Abstract

We report the design and functionality of the Murchison Widefield Array Particle Detector Array (MWA PDA), an array of eight particle scintillation detectors deployed to Inyarrimanha Ilgari Bundara, the Murchison Radio-astronomy Observatory (MRO). The purpose of the instrument is to identify cosmic ray extensive air showers (EAS) occurring over the core of the MWA radio telescope, and generate a trigger to allow radio data on the event to be captured and analysed. The system also acts as a pathfinder for a much larger instrument to be deployed in the core of the low-frequency component of the Square Kilometre Array, SKA-Low, by the SKA's ultra-high-energy particles science working group. Here, we describe the instrument and associated infrastructure, which has been verified to comply with the strict radio-frequency emissions requirements of the MRO, and was deployed in November 2024. We present calibration data, which demonstrates the ability of each detector to identify individual atmospheric muons at the expected rate, and we characterise the temperature dependence of the system. We describe a sample of 35,500 EAS identified using multi-detector coincidence over a 13-day period, and show how the detector data can be used to reconstruct the arrival directions and approximate energies of these events. We conclude that the PDA can reliably trigger on and reconstruct EAS contained within the $\sim 103 \times 90$ m$^2$ core region, arriving within 20$^{\circ}$ of zenith, at primary cosmic ray energies above $\sim 4$ PeV. We have also verified that the detector array can generate triggers, allowing the capture of radio data from the MWA correlator for offline analysis.