Ben T. McAllister

Axion Dark Matter Coupling to Resonant Photons via Magnetic Field.

We show that the magnetic component of the photon field produced by dark matter axions via the two-photon coupling mechanism in a Sikivie haloscope is an important parameter passed over in previous analysis and experiments. The interaction of the produced photons will be resonantly enhanced as long as they couple to the electric or magnetic mode structure of the haloscope cavity. For typical haloscope experiments the electric and magnetic couplings are equal, and this has implicitly been assumed in past sensitivity calculations. However, for future planned searches such as those at high frequency, which synchronize multiple cavities, the sensitivity will be altered due to different magnetic and electric couplings. We define the complete electromagnetic form factor and discuss its implications for current and future dark matter axion searches over a wide range of masses.

3D Lumped LC Resonators as Low Mass Axion Haloscopes

The axion is a hypothetical particle considered to be the most economical solution to the strong

Higher order reentrant post modes in cylindrical cavities

CP

The ORGAN Experiment

problem. It can also be formulated as a compelling component of dark matter. The haloscope, a leading axion detection scheme, relies on the conversion of galactic halo axions into real photons inside a resonant cavity structure in the presence of a static magnetic field, where the generated photon frequency corresponds to the mass of the axion. For maximum sensitivity it is key that the central frequency of the cavity mode structure coincides with the frequency of the generated photon. As the mass of the axion is unknown, it is necessary to perform searches over a wide range of frequencies. Currently there are substantial regions of the promising preinflationary low-mass axion range without any viable proposals for experimental searches. We show that three-dimensional resonant LC circuits with separated magnetic and electric fields, commonly known as reentrant cavities, can be sensitive dark matter haloscopes in this region, with frequencies inherently lower than those achievable in the equivalent size of empty resonant cavity. We calculate the sensitivity and accessible axion mass range of these experiments, designing geometries to exploit and maximize the separated magnetic and electric coupling of the axion to the cavity mode.

Novel Resonators for Axion Haloscopes

Reentrant cavities are microwave resonant devices employed in a number of different areas of physics. They are appealing due to their simple frequency tuning mechanism, which offers large tuning ranges. Reentrant cavities are, in essence, 3D lumped LC circuits consisting of a conducting central post embedded in a resonant cavity. The lowest order reentrant mode (which transforms from the

Response to “Comment on ‘Higher order reentrant post modes in cylindrical cavities’” [J. Appl. Phys. 123, 226101 (2018)]

TM_{010}

The ORGAN Experiment: An axion haloscope above 15 GHz

mode) has been extensively studied in past publications. In this work we show the existence of higher order reentrant post modes (which transform from the

Tunable Supermode Dielectric Resonators for Axion Dark-Matter Haloscopes

TM_{01n}

Erratum: Axion Dark Matter Coupling to Resonant Photons via Magnetic Field [Phys. Rev. Lett. 116 , 161804 (2016)]

mode family). We characterize these new modes in terms of their frequency tuning, filling factors and quality factors, as well as discuss some possible applications of these modes in fundamental physics tests. The appendix contains a comment on a paper related to this work.

Axion detection with negatively coupled cavity arrays

The Oscillating Resonant Group AxioN experiment (ORGAN), is a haloscope search for high mass axions hosted at the University of Western Australia node of the ARC Centre of Excellence for Engineered Quantum Systems (EQuS). The experiment has received 7 years of funding through EQuS, and will be a collaboration of the various EQuS nodes. We discuss the targeted parameter space of the search, search methodology, some novel resonator design and a scheme for power combining resonators.