arXiv subjects

A. McPhail

Publications and source records attributed to A. McPhail.

5 recordsLinked to original sources

arXiv2026

The Murchison Widefield Array Phase III upgrade: Sensitivity Doubled, Number of Baselines Quadrupled, Flexibility Enhanced, and EoR Observations Optimised

We describe the latest iteration of upgrades (designated Phase III) to the Murchison Widefield Array (MWA), in the fourth paper in a series that covers the evolution of the telescope from design concept to initial operational facility, and through two major upgrades. As part of the Phase III upgrade of the MWA, we report the completion of work to design, build, and deploy a new fleet of digital receivers that further optimise the MWA for Epoch of Reionisation observations. These receivers complement existing receivers, such that the MWA now supports the full correlation of all 256 antenna tiles currently in the array. This step releases the MWA from the prior constraint of having to correlate only 128 of the 256 tiles at any given time, which means that the maximum instantaneous sensitivity of the MWA is doubled and the maximum number of interferometric baselines is approximately quadrupled. The upgrade is fundamentally enabled by the new MWAX correlator and various other improvements to the MWA sub-systems. In this paper we describe the new digital receivers and the other improvements that result in the Phase III system. A range of operational benefits arise from the upgrade and scientific flexibility is increased. We also comment on the transition from the MWA to the SKA-Low facility near the end of the decade, including a description of some unique science opportunities utilising joint MWA/SKA-Low data during the Science Verification phase of the SKA-Low Array Assembly 2 (AA2) period.

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arXiv2026

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

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.

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arXiv2021

A Southern-Hemisphere all-sky radio transient monitor for SKA-Low prototype stations

We present the first southern-hemisphere all-sky imager and radio-transient monitoring system implemented on two prototype stations of the low-frequency component of the Square Kilometre Array. Since its deployment the system has been used for real-time monitoring of the recorded commissioning data. Additionally, a transient searching algorithm has been executed on the resulting all-sky images. It uses a difference imaging technique, and has enabled identification of a wide variety of transient classes, ranging from human-made radio-frequency interference to genuine astrophysical events. Observations at the frequency 159.4 MHz and higher in a single coarse channel (0.926 MHz) were made with 2s time resolution, and multiple nights were analysed. Despite having modest sensitivity (~few Jy/beam), using a single coarse channel and 2-s imaging, the system detected bright transients from PSR B0950+08, proving that it can be used to detect bright transients of an astrophysical origin. The unusual, extreme activity of the pulsar PSR B0950+08 (up to ~155 Jy/beam) was initially detected in a "blind" search in the 2020-04-10/11 data and later assigned to this specific pulsar. The limitations of our data, however, prevent use from making firm conclusions of the effect being due to a combination of refractive and diffractive scintillation or intrinsic emission mechanisms. The system can routinely collect data over many days without interruptions; the large amount of recorded data at 159.4 and 229.7 MHz allowed us to determine a preliminary transient surface density upper limit of $1.32 \times 10^{-9} \text{deg}^{-2}$ for a timescale and limiting flux density of 2s and 42 Jy, respectively. We plan to extend the observing bandwidth to tens of MHz and improve time resolution to tens of milliseconds in order to increase the sensitivity and enable detections of Fast Radio Bursts below 300 MHz.

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arXiv2021

Dual Polarization Measurements of MWA Beampatterns at 137 MHz

The wide adoption of low-frequency radio interferometers as a tool for deeper and higher resolution astronomical observations has revolutionised radio astronomy. Despite their construction from static, relatively simple dipoles, the sheer number of distinct elements introduces new, complicated instrumental effects. Their necessary remote locations exacerbate failure rates, while electronic interactions between the many adjacent receiving elements can lead to non-trivial instrumental effects. The Murchison Widefield Array (MWA) employs phased array antenna elements (tiles), which improve collecting area at the expense of complex beam shapes. Advanced electromagnetic simulations have produced the Fully Embedded Element (FEE) simulated beam model which has been highly successful in describing the ideal beam response of MWA antennas. This work focuses on the relatively unexplored aspect of various in-situ, environmental perturbations to beam models and represents the first large-scale, in-situ, all-sky measurement of MWA beam shapes at multiple polarizations and pointings. Our satellite based beam measurement approach enables all-sky beam response measurements with a dynamic range of \sim 50 dB, at 137 MHz.

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arXiv2020

The SKA Particle Array Prototype: The First Particle Detector at the Murchison Radio-astronomy Observatory

We report on the design, deployment, and first results from a scintillation detector deployed at the Murchison Radio-astronomy Observatory (MRO). The detector is a prototype for a larger array -- the Square Kilometre Array Particle Array (SKAPA) -- planned to allow the radio-detection of cosmic rays with the Murchison Widefield Array and the low-frequency component of the Square Kilometre Array. The prototype design has been driven by stringent limits on radio emissions at the MRO, and to ensure survivability in a desert environment. Using data taken from Nov.\ 2018 to Feb.\ 2019, we characterize the detector response while accounting for the effects of temperature fluctuations, and calibrate the sensitivity of the prototype detector to through-going muons. This verifies the feasibility of cosmic ray detection at the MRO. We then estimate the required parameters of a planned array of eight such detectors to be used to trigger radio observations by the Murchison Widefield Array.

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