arXiv subjects

K. M. W. Pappas

Publications and source records attributed to K. M. W. Pappas.

6 recordsLinked to original sources

arXiv2026

The Cryogenic System of DMRadio-50L

The DMRadio-50L experiment is designed to search for axion dark matter in the 5 kHz - 5 MHz frequency range using a lumped-element LC resonator and a toroidal magnet and to serve as a testbed for quantum sensors. This paper describes the custom cryogenic system developed to meet the stringent requirements of the experiment within a standard laboratory environment. The system is designed to cool a 200 kg detector assembly to temperatures as low as 50 mK while providing sufficient cooling power at multiple temperature stages. We present the conceptual design, technical implementation, and measured performance of the hybrid cryogenic system, which combines a horizontal dilution refrigerator with a large vertical payload cryostat.

physics.ins-det↗

arXiv2025

Electromagnetic modeling and science reach of DMRadio-m$^3$

DMRadio-m$^3$ is an experiment that is designed to be sensitive to KSVZ and DFSZ QCD axion models in the 10--200\,MHz (41 neV$/c^2$ -- 0.83 $μ$eV/$c^2$) range. The experiment uses a solenoidal dc magnetic field to convert an axion dark-matter signal to an ac electromagnetic response in a coaxial copper pickup. The current induced by this axion signal is measured by dc SQUIDs. In this work, we present the electromagnetic modeling of the response of the experiment to an axion signal over the full frequency range of DMRadio-m$^3$, which extends from the low-frequency, lumped-element limit to a regime where the axion Compton wavelength is only a factor of two larger than the detector size. With these results, we determine the live time and sensitivity of the experiment. The primary science goal of sensitivity to DFSZ axions across 30--200 MHz can be achieved with a $3σ$ live scan time of 2.9 years.

hep-ex↗

arXiv2025

Noise limits for dc SQUID readout of high-$Q$ resonators below 300 MHz

We present the limits on noise for the readout of cryogenic high-$Q$ resonators using dc Superconducting Quantum Interference Devices (SQUIDs) below 300 MHz. This analysis uses realized first-stage SQUIDs (previously published), whose performance is well described by Tesche-Clarke (TC) theory, coupled directly to the resonators. We also present data from a prototype second-stage dc SQUID array designed to couple to this first-stage SQUID as a follow-on amplifier with high system bandwidth. This analysis is the first full consideration of dc SQUID noise performance referred to a high-$Q$ resonator over this frequency range, and is presented relative to the standard quantum limit. We include imprecision, backaction, and backaction-imprecision noise correlations from TC theory, the noise contributed by the second-stage SQUIDs, wiring, and preamplifiers, and optimizations for both on-resonance measurements and off-resonance scan sensitivity. This architecture has modern relevance due to the increased interest in axion searches and the requirements of the DMRadio-m$^3$ axion search, which will use dc SQUIDs in this frequency range.

quant-ph↗

arXiv2023

Axion Dark Matter

Axions are well-motivated dark matter candidates with simple cosmological production mechanisms. They were originally introduced to solve the strong CP problem, but also arise in a wide range of extensions to the Standard Model. This Snowmass white paper summarizes axion phenomenology and outlines next-generation laboratory experiments proposed to detect axion dark matter. There are vibrant synergies with astrophysical searches and advances in instrumentation including quantum-enabled readout, high-Q resonators and cavities and large high-field magnets. This white paper outlines a clear roadmap to discovery, and shows that the US is well-positioned to be at the forefront of the search for axion dark matter in the coming decade.

hep-ex↗

arXiv2022

New Horizons: Scalar and Vector Ultralight Dark Matter

The last decade has seen unprecedented effort in dark matter model building at all mass scales coupled with the design of numerous new detection strategies. Transformative advances in quantum technologies have led to a plethora of new high-precision quantum sensors and dark matter detection strategies for ultralight ($<10\,$eV) bosonic dark matter that can be described by an oscillating classical, largely coherent field. This white paper focuses on searches for wavelike scalar and vector dark matter candidates.

hep-ex↗

arXiv2022

Introducing DMRadio-GUT, a search for GUT-scale QCD axions

The QCD axion is a leading dark matter candidate that emerges as part of the solution to the strong CP problem in the Standard Model. The coupling of the axion to photons is the most common experimental probe, but much parameter space remains unexplored. The coupling of the QCD axion to the Standard Model scales linearly with the axion mass; therefore, the highly-motivated region 0.4-120 neV, corresponding to a GUT-scale axion, is particularly difficult to reach. This paper presents the design requirements for a definitive search for GUT-scale axions and reviews the technological advances needed to enable this program.

hep-ex↗