Near-Quantum-Noise Axion Dark Matter Search at CAPP around 9.5 μ\mueV

We report the results of an axion dark matter search over an axion mass range of 9.39-9.51 ${\mu}$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.Comment: 6 pages, 4 figure

GrAHal-CAPP for axion dark matter search with unprecedented sensitivity in the 1–3 μeV mass range

A collaboration between CNRS-Grenoble and IBS-CAPP Daejeon plans to build a Sikivie’s type haloscope for axion/ALPs dark matter search at the Dine-Fischler-Srednicki-Zhitnitskii sensitivity for the 300–600 MHz range. It will be based on the large-bore superconducting “outsert” coil of the Grenoble hybrid magnet, providing a central magnetic field up to 9 T in an 810-mm warm bore diameter. This magnet has recently been successfully powered up to 8.5 T, achieving the first step of the electrical commissioning phase. The design principles of the cryostat with its double dilution refrigerators to cool below 50 mK, the light Cu RF cavity of 700-mm diameter, and its tuning rod(s) and the first stages of the measurement chain are presented. Perspectives for the targeted sensitivity assuming less than a 2-year integration time are given

Search for the Sagittarius Tidal Stream of Axion Dark Matter around 4.55 μ\mueV

We report the first search for the Sagittarius tidal stream of axion dark matter around 4.55 $\mu$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 $\rho_a\gtrsim0.184$ and $\gtrsim0.025$ GeV/cm$^{3}$, respectively, over a mass range from 4.51 to 4.59 $\mu$eV at a 90% confidence level.Comment: 6 pages, 7 Figures, PRD Letter accepte

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\,$\mu$eV) to 1.185\,GHz (4.91\,$\mu$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.Comment: A detailed axion dark matter article with 27 pages, 22 figure

Circularly Polarized Wideband Uniplanar Crossed-Dipole Antenna With Folded Striplines and Rectangular Stubs

A circularly polarized (CP) wideband uniplanar crossed-dipole antenna is presented in this paper. The antenna constitutes a pair of identical crossed-dipole arms printed on the same plane of a dielectric substrate. Each crossed-dipole component is a pair of thin dipole arms that are perpendicular to each other and connected with a folded stripline for generating CP radiations. A pair of thin rectangular stubs are introduced on one dipole arm at the center of the antenna to improve impedance-matching bandwidth. Another set of rectangular stubs is attached at the sides of the dipole arms to broaden the axial ratio (AR) bandwidth. The antenna in free space is excited via a coaxial probe with a balun. It generates two adjacent AR bands that are merged into a wide AR bandwidth with bidirectional radiation patterns. Full-wave electromagnetic simulations are performed in the design process, and experiments are performed to validate the antenna design. The proposed antenna sized 42.4 mm x 42.4 mm x 0.2032 mm (0.57 lambda(o) x 0.57 lambda(o) x 0.0027 lambda(o) at 4.05 GHz) has an |S11| < -10 dB impedance bandwidth of 2.92-5.15 GHz (55.26%) and a 3 dB AR bandwidth of 2.96-5.12 GHz (53.5%)

Novel Method for Sidelobe Level Suppression in Multielement Angled Dipole Array Antennas

In this paper, we propose a one-dimensional (1D) array antenna with improved sidelobe level (SLL) and cross-polarization (x-pol) characteristics. The array elements constituting the 1D array antenna comprise different numbers of dipole elements, and each array element has a different gain and E-field phase. The positions of the array elements in the z-axis direction are adjusted to equalize their E-field phases in the far field, and the array elements are arranged symmetrically with respect to the z-axis to obtain a low x-pol. The same amount of power is supplied to all the array elements of the 1D array antenna of the proposed structure. Therefore, a complexly structured feeding network is not required to achieve a low SLL and low x-pol. The gain of the proposed array antenna with a corporate feeding network is 15.2 dBi, and its SLL and x-pol level are-21.3 dB and 20.3 dB, respectively. The-10 dB impedance bandwidth of the proposed array antenna is 35.6% (8.3-11.9 GHz)

Non-Uniform Metasurface-Integrated Circularly Polarized End-Fire Dipole Array Antenna

This paper presents a high-gain wideband circularly polarized antenna composed of an end-fire dipole array antenna integrated with a metasurface. The antenna consists of a two-layer cascaded non-uniform metasurface made up of 4 x 4 circular patches with cross-slots of unequal lengths placed above an end-fire dipole array antenna with an air gap between the structures. The end-fire dipole array antenna comprises four equally spaced dipole elements, and each dipole is connected to a parallel stripline printed on the front and back sides of the substrate. The metasurface, which is made up of a circular patch with 2 x 2 center patches that have a different radius than the outer patches, and the cross-slots of unequal lengths are used for the polarization conversion of a linearly polarized wave to a circularly polarized wave. The measured reflection coefficients for |S11| <-10 dB yielded an impedance bandwidth of 25.6-31.8 GHz (21.5%), a 3-dB axial ratio (AR) bandwidth of 26.1-30.5 GHz (15.5%), a 3-dB gain bandwidth of 26.0-31.1 GHz (17.4%) with a peak gain of 11.0 dBic, and a radiation efficiency of more than 80% in the axial ratio bandwidth

Biaxially Textured YBa2Cu3 O7-x Microwave Cavity in a High Magnetic Field for a Dark-Matter Axion Search

A high-quality (Q)-factor microwave resonator in the presence of a strong magnetic field can have a wide range of applications, such as in axion dark matter searches where the two aspects must coexist to enhance the experimental sensitivity. We introduce a polygon-shaped cavity design with biaxially textured YBa2Cu3O7-x superconducting tapes covering the entire inner wall. Using a 12-sided polygon cavity, we obtain substantially improved Q factors of the 6.9-GHz TM010 mode at 4 K with respect to a copper cavity and observe no considerable degradation in the presence of magnetic fields up to 8 T. © 2022 American Physical Society.11Nsciescopu

Optical measurement of biomechanical properties of individual erythrocytes from a sickle cell patient

Sickle cell disease (SCD) is characterized by the abnormal deformation of red blood cells (RBCs) in the deoxygenated condition, as their elongated shape leads to compromised circulation. The pathophysiology of SCD is influenced by both the biomechanical properties of RBCs and their hemodynamic properties in the microvasculature. A major challenge in the study of SCD involves accurate characterization of the biomechanical properties of individual RBCs with minimum sample perturbation. Here we report the biomechanical properties of individual RBCs from a SCD patient using a non-invasive laser interferometric technique. We optically measure the dynamic membrane fluctuations of RBCs. The measurements are analyzed with a previously validated membrane model to retrieve key mechanical properties of the cells: bending modulus; shear modulus; area expansion modulus; and cytoplasmic viscosity. We find that high cytoplasmic viscosity at ambient oxygen concentration is principally responsible for the significantly decreased dynamic membrane fluctuations in RBCs with SCD, and that the mechanical properties of the membrane cortex of irreversibly sickled cells (ISCs) are different from those of the other types of RBCs in SCD.National Institutes of Health (U.S.) (Grant 9P41-EB015871-26A1)National Institutes of Health (U.S.) (Grant R01HL094270)National Institutes of Health (U.S.) (Grant DK083242)Korea Advanced Institute of Science and TechnologyKorea Advanced Institute of Science and Technology. Institute for Optical Science and TechnologyKorea (South). Ministry of Education, Science and Technology (MEST) (Grant 2009-0087691)National Research Foundation of Korea (NRF-2012R1A1A1009082)Singapore-MIT Alliance for Research and Technolog