arXiv subjects

Seonjeong Oh

Publications and source records attributed to Seonjeong Oh.

17 recordsLinked to original sources

arXiv2026

Extended High-Mass Axion Search with an Auxetically Tuned Higher-Order-Mode Cavity

Conventional high-mass axion haloscopes based on the TM$_{010}$ mode lose detection volume as the resonant frequency increases. We report an extended axion search using a dielectric-restored TM$_{020}$ cavity haloscope with symmetry-preserving auxetic tuning based on a single-degree-of-freedom mechanical architecture. Using a near-quantum-limited microwave receiver, we searched a frequency range of 4.98-5.07 GHz and exclude axion-photon couplings with sensitivity approaching the KSVZ benchmark. Together with two earlier searches, the present scans extend a multi-scan program based on this architecture, yielding nearly 300 MHz of contiguous high-mass axion coverage over 4.98-5.27 GHz, the first broad search reported with a single higher-order-mode haloscope. This work establishes higher-order-mode cavities as a practical, scalable route beyond the TM$_{010}$ volume penalty.

hep-ex↗

arXiv2026

Search for Axion Dark Matter around \texorpdfstring{$15.6\,μ\text{eV}$}{15.6 microeV} with a Broadly Tunable High-Temperature Superconducting Cavity

We report an axion dark matter search in the mass range of $15.30\text{--}15.85\,μ\text{eV}$ using a broadly tunable high-temperature superconducting (HTS) haloscope. By soldering substrate-stripped rare-earth barium copper oxide (REBCO) films onto a copper shell, we achieved a quality factor 3--4 times higher than in copper cavities across its tuning band in an 8\text{-T} magnetic field. We set robust Frequentist 90\%~confidence-level exclusion limits on the axion--photon coupling down to 1.3 times the KSVZ coupling, while a complementary Bayesian analysis achieves KSVZ-level sensitivity.

hep-ex↗

arXiv2026

Extended Haloscope Search and Exclusion of a Candidate Signal near 1.036 GHz

We report a follow-up axion haloscope search near 1.036 GHz that completes and extends our previous work [Phys. Rev. X 14, 031023 (2024)], in which a portion of the HEMT-based data could not be analyzed due to unrecorded experimental information. While recovering this dataset, we identified an excess near 1.036 GHz that satisfied our candidate-selection criteria, motivating dedicated validation studies, including independent cross-checks and re-examination with the original apparatus. The excess did not persist under these investigations and was not confirmed as an axion dark-matter signal. We subsequently extended the search over a 20-MHz band surrounding the candidate using a quantum-noise-limited amplifier, achieving sensitivity close to the Dine-Fischler-Srednicki-Zhitnitsky benchmark. In the absence of a confirmed signal, we set improved 90% confidence-level upper limits on the axion-photon coupling over the frequency range 1.026-1.045 GHz. This work highlights the importance of robust candidate-validation strategies as haloscope searches approach discovery-level sensitivity.

hep-ex↗

arXiv2025

Search for high-frequency gravitational waves via re-analysis of cavity axion data

Monochromatic high-frequency gravitational waves (HFGW) provide a distinctive probe of new physics scenarios, most notably axion clouds around rotating black holes formed via superradiance. We reanalyzed data from the CAPP-12T MC (multi-cell) axion haloscope experiment [Phys. Rev. Lett. 133,051802 (2024)]. The study covers a continuous $2\,$MHz frequency span centered at $5.311\,$GHz. No rescan candidates were found, and we set 90% confidence-level exclusion limits on the gravitational-wave strain, reaching $h_0 \approx 3.9 \times 10^{-21}$ in the most sensitive regions of the sky. Interpreted in the context of black-hole superradiance from axion clouds, the results exclude black holes with mass $M_{\mathrm{BH}} \simeq 1.22 \times 10^{-6}\,M_\odot$ within distances of $O(10^{-2})\,$AU from Earth, under benchmark assumptions. This work demonstrates the potential of electromagnetic resonant cavities as novel detectors of monochromatic HFGW and motivates future searches for both long-lived and transient signals.

hep-ex↗

arXiv2025

Axion Dark Matter Search with Near-KSVZ Sensitivity Using the TM$_{020}$ Mode

Dark matter remains one of the most profound mysteries in modern physics, with axions, a hypothetical particle proposed to resolve the strong CP problem, standing as a compelling candidate. Among various experimental strategies, cavity haloscopes currently offer the most sensitive method to detect axions, though their searches have largely been confined to axion masses below 10 $μ$eV. However, recent theoretical developments suggest that the axion mass lies beyond this range. Higher-order cavity modes have been explored as a methodological approach to expand the search range, albeit with limited success in achieving both high sensitivity and broad tunability. In this work, we present a sensitive search for axions with masses around 21 $μ$eV, utilizing the TM$_{020}$ mode of a cylindrical cavity, which incorporated an innovative tuning mechanism. Our results reached 1.7 times the KSVZ sensitivity over 100 MHz, representing a significant improvement in this mass range and contributing to the experimental search for axion dark matter at higher masses.

hep-ex↗

arXiv2024

Experimental search for invisible dark matter axions around 22 μeV

The axion has emerged as the most attractive solution to two fundamental questions in modern physics related to the charge-parity invariance in strong interactions and the invisible matter component of our universe. Over the past decade, there have been many theoretical efforts to constrain the axion mass based on various cosmological assumptions. Interestingly, different approaches from independent groups produce good overlap between 20 and 30 μeV. We performed an experimental search to probe the presence of dark matter axions within this particular mass region. The experiment utilized a multi-cell cavity haloscope embedded in a 12 T magnetic field to seek for microwave signals induced by the axion-photon coupling. The results ruled out the KSVZ axions as dark matter over a mass range between 21.86 and 22.00 μeV at a 90% confidence level. This represents a sensitive experimental search guided by specific theoretical predictions

hep-ex↗

arXiv2024

Josephson Parametric Amplifier based Quantum Noise Limited Amplifier Development for Axion Search Experiments in CAPP

This paper provides a comprehensive overview of the development of flux-driven Josephson Parametric Amplifiers (JPAs) as Quantum Noise Limited Amplifier for axion search experiments conducted at the Center for Axion and Precision Physics Research (CAPP) of the Institute for Basic Science. It focuses on the characterization, and optimization of JPAs, which are crucial for achieving the highest sensitivity in axion particle detection. We discuss various characterization techniques, methods for improving bandwidth, and the attainment of ultra-low noise temperatures. JPAs have emerged as indispensable tools in CAPPs axion search endeavors, playing a significant role in advancing our understanding of fundamental physics and unraveling the mysteries of the universe.

hep-ex↗

arXiv2024

Extensive search for axion dark matter over 1\,GHz with CAPP's Main Axion eXperiment

We report an extensive high-sensitivity search for axion dark matter above 1\,GHz at the Center for Axion and Precision Physics Research (CAPP). The cavity resonant search, exploiting the coupling between axions and photons, explored the frequency (mass) range of 1.025\,GHz (4.24\,$μ$eV) to 1.185\,GHz (4.91\,$μ$eV). We have introduced a number of innovations in this field, demonstrating the practical approach of optimizing all the relevant parameters of axion haloscopes, extending presently available technology. The CAPP 12\,T magnet with an aperture of 320\,mm made of Nb$_3$Sn and NbTi superconductors surrounding a 37-liter ultralight-weight copper cavity is expected to convert DFSZ axions into approximately $10^2$ microwave photons per second. A powerful dilution refrigerator, capable of keeping the core system below 40\,mK, combined with quantum-noise limited readout electronics, achieved a total system noise of about 200\,mK or below, which corresponds to a background of roughly $4\times 10^3$ photons per second within the axion bandwidth. The combination of all those improvements provides unprecedented search performance, imposing the most stringent exclusion limits on axion--photon coupling in this frequency range to date. These results also suggest an experimental capability suitable for highly-sensitive searches for axion dark matter above 1\,GHz.

hep-ex↗

arXiv2023

Search for the Sagittarius Tidal Stream of Axion Dark Matter around 4.55 $μ$eV

We report the first search for the Sagittarius tidal stream of axion dark matter around 4.55 $μ$eV using CAPP-12TB haloscope data acquired in March of 2022. Our result excluded the Sagittarius tidal stream of Dine-Fischler-Srednicki-Zhitnitskii and Kim-Shifman-Vainshtein-Zakharov axion dark matter densities of $ρ_a\gtrsim0.184$ and $\gtrsim0.025$ GeV/cm$^{3}$, respectively, over a mass range from 4.51 to 4.59 $μ$eV at a 90% confidence level.

hep-ex↗

arXiv2023

Expanding Scanning Frequency Range of Josephson Parametric Amplifier Axion Haloscope Readout with Schottky Diode Bias Circuit

The axion search experiments in the microwave frequency range require high sensitive detectors with intrinsic noise close to quantum noise limit. Josephson parametric amplifiers (JPAs) are the most valuable candidates for the role of the first stage amplifier in the measurement circuit of the microwave frequency range, as they are well-known in superconducting quantum circuits readout. To increase the frequency range, a challenging scientific task involves implementing an assembly with parallel connection of several single JPAs, which requires matching the complex RF circuit at microwaves and ensuring proper DC flux bias. In this publication, we present a new DC flux bias setup based on a Schottky diode circuit for a JPA assembly consisting of two JPAs. We provide a detailed characterization of the diodes at cryogenic temperatures lower than 4 K. Specifically, we selected two RF Schottky diodes with desirable characteristics for the DC flux bias setup, and our results demonstrate that the Schottky diode circuit is a promising method for achieving proper DC flux bias in JPA assemblies.

hep-ex↗

arXiv2023

Four-channel System for Characterization of Josephson Parametric Amplifiers

The axion search experiments based on haloscopes at the Center for Axion and Precision Physics Research (CAPP) of the Institute for Basic Science (IBS) in South Korea are performed in the frequency range from 1 GHz to 6 GHz. In order to perform the experiments in a strong magnetic field of 12 T and a large-volume cavity of close to 40 liters, we use He wet dilution refrigerators with immersed superconducting magnets. The measurements require continuous operation for months without interruptions for microwave component replacements. This is achieved by using different cryogenic engineering approaches including microwave RF-switching. The critical components, defining the scanning rate and the sensitivity of the setup, are the Josephson parametric amplifiers (JPA) and cryogenic low noise amplifiers (cLNA) based on high-electron-mobility-transistor (HEMT) technology. It is desirable for both devices to have a wide frequency range and low noise close to the quantum limit for the JPA. In this paper, we show a recent design of a 4-channel measurement setup for JPA and HEMT measurements. The setup is based on a 4-channel wideband noise source (NS) and is used for both JPA and HEMT gain and noise measurements. The setup is placed at 20 mK inside the dry dilution refrigerator. The NS is thermally decoupled from the environment using plastic spacers, superconducting wires and superconducting coaxial cables. We show the gain and noise temperature curves measured for 4 HEMT amplifiers and 2 JPAs in one cool-down

cond-mat.supr-con↗

arXiv2023

Systematic Approach for Tuning Flux-driven Josephson Parametric Amplifiers for Stochastic Small Signals

Many experiments operating at millikelvin temperatures with signal frequencies in the microwave regime are beginning to incorporate Josephson Parametric Amplifiers (JPA) as their first amplification stage. While there are implementations for a wideband frequency response with a minimal need for tuning, designs using resonant structures with small numbers of Josephson elements still achieve the best noise performance. In a typical measurement scheme involving a JPA, one needs to control the resonance frequency, pump frequency and pump power to achieve the desired amplification and noise properties. In this work, we propose a straightforward approach for operating JPAs with the help of a look-up table (LUT) and online fine-tuning. Using the proposed approach, we demonstrate the operation of a flux-driven JPA with 20 dB gain around 5.9 GHz, covering approximately 100 MHz with 20 kHz tuning steps. The proposed methodology was successfully used in the context of a haloscope axion experiment.

physics.ins-det↗

arXiv2023

Josephson Parametric Amplifier in Axion Experiments

The axion is a hypothetical particle, a promising candidate for dark matter, and a solution to the strong CP problem. Axion haloscope search experiments deal with a signal power comparable to noise uncertainty at millikelvin temperature. We use a flux-driven Josephson parametric amplifier (JPA) with the aim of approaching a noise level near the theoretically allowed limit of half quanta. In our measurements to characterize the JPA we have found the added noise to the system with a JPA as the first-stage amplifier to be lower than 110 mK at the frequencies from 0.938 GHz to 0.963 GHz.

cond-mat.supr-con↗

arXiv2023

Axion Dark Matter Search around 4.55 $μ$eV with Dine-Fischler-Srednicki-Zhitnitskii Sensitivity

We report an axion dark matter search at Dine-Fischler-Srednicki-Zhitnitskii sensitivity with the CAPP-12TB haloscope, assuming axions contribute 100\% of the local dark matter density. The search excluded the axion--photon coupling $g_{aγγ}$ down to about $6.2\times10^{-16}$ GeV$^{-1}$ over the axion mass range between 4.51 and 4.59 $μ$eV at a 90\% confidence level. The achieved experimental sensitivity can also exclude Kim-Shifman-Vainshtein-Zakharov axion dark matter that makes up just 13\% of the local dark matter density. The CAPP-12TB haloscope will continue the search over a wide range of axion masses.

hep-ex↗

arXiv2022

Near-Quantum-Noise Axion Dark Matter Search at CAPP around 9.5 $μ$eV

We report the results of an axion dark matter search over an axion mass range of 9.39-9.51 $μ$eV. A flux-driven Josephson parametric amplifier (JPA) was added to the cryogenic receiver chain. A system noise temperature of as low as 200 mK was achieved, which is the lowest recorded noise among published axion cavity experiments with phase-insensitive JPA operation. In addition, we developed a two-stage scanning method which boosted the scan speed by 26%. As a result, a range of two-photon coupling in a plausible model for the QCD axion was excluded with an order of magnitude higher in sensitivity than existing limits.

hep-ex↗

arXiv2021

First Results from Axion Haloscope at CAPP around 10.7 $μ$eV

The Center for Axion and Precision Physics research at the Institute for Basic Science is searching for axion dark matter using ultra-low temperature microwave resonators. We report the exclusion of the axion mass range 10.7126$-$10.7186 $μ$eV with near Kim-Shifman-Vainshtein-Zakharov (KSVZ) coupling sensitivity and the range 10.16$-$11.37 $μ$eV with about 9 times larger coupling at 90$\%$ confidence level. This is the first axion search result in these ranges. It is also the first with a resonator physical temperature of less than 40 mK.

hep-ex↗

arXiv2021

Characterization of a flux-driven Josephson parametric amplifier with near quantum-limited added noise for axion search experiments

The axion, a hypothetical elementary pseudoscalar, is expected to solve the strong CP problem of QCD and is also a promising candidate for dark matter. The most sensitive axion search experiments operate at millikelvin temperatures and hence rely on instrumentation that carries signals from a system at cryogenic temperatures to room temperature instrumentation. One of the biggest limiting factors affecting the parameter scanning speed of these detectors is the noise added by the components in the signal detection chain. Since the first amplifier in the chain limits the minimum noise, low-noise amplification is of paramount importance. This paper reports on the operation of a flux-driven Josephson parametric amplifier (JPA) operating at around 2.3 GHz with added noise approaching the quantum limit. The JPA was employed as a first stage amplifier in an experimental setting similar to the ones used in haloscope axion detectors. By operating the JPA at a gain of 19 dB and cascading it with two cryogenic amplifiers operating at 4 K, noise temperatures as low as 120 mK were achieved for the whole signal detection chain.

cond-mat.supr-con↗