The μeV-scale axion is a compelling cold dark matter candidate. The Axion Dark Matter eXperiment (ADMX) searches for axions by stimulating the decay of galactic dark matter halo axions into ...detectable microwave photons by their conversion in a resonant cavity permeated by a strong, static magnetic field. The signal depends on properties of the Milky Way’s dark matter halo; the choice of halo model has significant implications for the sensitivity of direct detection searches, e.g., ADMX. This paper explores the sensitivity of the data taken by ADMX from 2008 to 2010 to various dark matter halo models. New models for the phase-space distribution of local axions are considered; the analysis demonstrates that certain assumptions about the dark matter halo improve limits on axion–photon coupling. In addition, new ADMX data covering 860–892 MHz are included in the analysis.
The recently developed technique of Cyclotron Radiation Emission Spectroscopy (CRES) uses frequency information from the cyclotron motion of an electron in a magnetic bottle to infer its kinetic ...energy. Here we derive the expected radio-frequency signal from an electron in a waveguide CRES apparatus from first principles. We demonstrate that the frequency-domain signal is rich in information about the electron's kinematic parameters and extract a set of measurables that in a suitably designed system are sufficient for disentangling the electron's kinetic energy from the rest of its kinematic features. This lays the groundwork for high-resolution energy measurements in future CRES experiments, such as the Project 8 neutrino mass measurement.
It has been understood since 1897 that accelerating charges should emit electromagnetic radiation. Cyclotron radiation, the particular form of radiation emitted by an electron orbiting in a magnetic ...field, was first derived in 1904. Despite the simplicity of this concept, and the enormous utility of electron spectroscopy in nuclear and particle physics, single-electron cyclotron radiation has never been observed directly. Here we demonstrate single-electron detection in a novel radiofrequency spectrometer. We observe the cyclotron radiation emitted by individual electrons that are produced with mildly-relativistic energies by a gaseous radioactive source and are magnetically trapped. The relativistic shift in the cyclotron frequency permits a precise electron energy measurement. Precise beta electron spectroscopy from gaseous radiation sources is a key technique in modern efforts to measure the neutrino mass via the tritium decay endpoint, and this work is a proof-of-concept for future neutrino mass experiments using this technique.
Scalar fields with a"chameleon" property, in which the effective particle mass is a function of its local environment, are common to many theories beyond the standard model and could be responsible ...for dark energy. If these fields couple weakly to the photon, they could be detectable through the afterglow effect of photon-chameleon-photon transitions. The ADMX experiment was used in the first chameleon search with a microwave cavity to set a new limit on scalar chameleon-photon coupling beta_gamma excluding values between 2x109 and 5x1014 for effective chameleon masses between 1.9510 and 1:9525 micro eV.
Axions in the {mu}eV mass range are a plausible cold dark matter candidate and may be detected by their conversion into microwave photons in a resonant cavity immersed in a static magnetic field. The ...first result from such an axion search using a superconducting first-stage amplifier (SQUID) is reported. The SQUID amplifier, replacing a conventional GaAs field-effect transistor amplifier, successfully reached axion-photon coupling sensitivity in the band set by present axion models and sets the stage for a definitive axion search utilizing near quantum-limited SQUID amplifiers.
This paper reports on a surface impedance measurement of a niobium titanium superconducting radio frequency (SRF) cavity in a magnetic field (up to \(10\,{\rm T}\)). A novel method is employed to ...decompose the surface resistance contributions of the cylindrical cavity end caps and walls using measurements from multiple \(TM\) cavity modes. The results confirm that quality factor degradation of a NbTi SRF cavity in a high magnetic field is primarily from surfaces perpendicular to the field (the cavity end caps), while parallel surface resistances (the walls) remain relatively constant. This result is encouraging for applications needing high Q cavities in strong magnetic fields, such as the Axion Dark Matter eXperiment (ADMX), because it opens the possibility of hybrid SRF cavity construction to replace conventional copper cavities.
Phys. Rev. D 106, 102002 (2022) Dark matter makes up 85% of the matter in the universe and 27% of its energy
density, but we do not know what comprises dark matter. It is possible that
dark matter ...may be composed of either axions or dark photons, both of which can
be detected using an ultra-sensitive microwave cavity known as a haloscope. The
haloscope employed by ADMX consists of a cylindrical cavity operating at the
TM$_{010}$ mode and is sensitive to the QCD axion with masses of few $\mu$eV.
However, this haloscope design becomes challenging to implement for higher
masses. This is because higher masses require smaller-diameter cavities,
consequently reducing the detection volume which diminishes the detected signal
power. ADMX-Orpheus mitigates this issue by operating a tunable,
dielectrically-loaded cavity at a higher-order mode, allowing the detection
volume to remain large. This paper describes the design, operation, analysis,
and results of the inaugural ADMX-Orpheus dark photon search between 65.5
$\mu$eV (15.8 GHz) and 69.3 $\mu$eV (16.8 GHz), as well as future directions
for axion searches and for exploring more parameter space.
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