13 research outputs found
Search for the Cosmic Axion Background with ADMX
We report the first result of a direct search for a Cosmic
Background CB - a relativistic background of axions that is not dark matter
- performed with the axion haloscope, the Axion Dark Matter eXperiment (ADMX).
Conventional haloscope analyses search for a signal with a narrow bandwidth, as
predicted for dark matter, whereas the CB will be broad. We introduce a
novel analysis strategy, which searches for a CB induced daily modulation in
the power measured by the haloscope. Using this, we repurpose data collected to
search for dark matter to set a limit on the axion photon coupling of the CB
originating from dark matter decay in the 800-995 MHz frequency range. We find
that the present sensitivity is limited by fluctuations in the cavity readout
as the instrument scans across dark matter masses. Nevertheless, we demonstrate
that these challenges can be surmounted with the use of superconducting qubits
as single photon counters, and allow ADMX to operate as a telescope searching
for axions emerging from the decay of dark matter. The daily modulation
analysis technique we introduce can be deployed for various broadband RF
signals, such as other forms of a CB or even high-frequency gravitational
waves.Comment: 9 pages, 4 figure
Low Frequency (100-600 MHz) Searches with Axion Cavity Haloscopes
We investigate reentrant and dielectric loaded cavities for the purpose of
extending the range of axion cavity haloscopes to lower masses, below the range
where the Axion Dark Matter eXperiment (ADMX) has already searched. Reentrant
and dielectric loaded cavities were simulated numerically to calculate and
optimize their form factors and quality factors. A prototype reentrant cavity
was built and its measured properties were compared with the simulations. We
estimate the sensitivity of axion dark matter searches using reentrant and
dielectric loaded cavities inserted in the existing ADMX magnet at the
University of Washington and a large magnet being installed at Fermilab.Comment: 33 pages, 24 figure
Non-Virialized Axion Search Sensitive to Doppler Effects in the Milky Way Halo
The Axion Dark Matter eXperiment (ADMX) has previously excluded
Dine-Fischler-Srednicki-Zhitnisky (DFSZ) axions between 680-790 MHz under the
assumption that the dark matter is described by the isothermal halo model.
However, the precise nature of the velocity distribution of dark matter is
still unknown, and alternative models have been proposed. We report the results
of a non-virialized axion search over the mass range 2.81-3.31 {\mu}eV,
corresponding to the frequency range 680-800 MHz. This analysis marks the most
sensitive search for non-virialized axions sensitive to Doppler effects in the
Milky Way Halo to date. Accounting for frequency shifts due to the detector's
motion through the Galaxy, we exclude cold flow relic axions with a velocity
dispersion of order 10^-7 c with 95% confidence
Search for invisible axion dark matter in the 3.3-4.2 μeV mass range
We report the results from a haloscope search for axion dark matter in the 3.3-4.2 μeV mass range. This search excludes the axion-photon coupling predicted by one of the benchmark models of "invisible"axion dark matter, the Kim-Shifman-Vainshtein-Zakharov model. This sensitivity is achieved using a large-volume cavity, a superconducting magnet, an ultra low noise Josephson parametric amplifier, and sub-Kelvin temperatures. The validity of our detection procedure is ensured by injecting and detecting blind synthetic axion signals