Abstract
We present results of the Relic Axion Dark-Matter Exploratory Setup (RADES), a detector which is part of the CERN Axion Solar Telescope (CAST), searching for axion dark matter in the 34.67 μeV mass range. A radio frequency cavity consisting of 5 sub-cavities coupled by inductive irises took physics data inside the CAST dipole magnet for the first time using this filter-like haloscope geometry. An exclusion limit with a 95% credibility level on the axion-photon coupling constant of gaγ ≳ 4 × 10−13 GeV−1 over a mass range of 34.6738 μeV < ma< 34.6771 μeV is set. This constitutes a significant improvement over the current strongest limit set by CAST at this mass and is at the same time one of the most sensitive direct searches for an axion dark matter candidate above the mass of 25 μeV. The results also demonstrate the feasibility of exploring a wider mass range around the value probed by CAST-RADES in this work using similar coherent resonant cavities.
Highlights
The axion signal generated in the cavity would appear as an increment over the background thermal noise
We present results of the Relic Axion Dark-Matter Exploratory Setup (RADES), a detector which is part of the CERN Axion Solar Telescope (CAST), searching for axion dark matter in the 34.67 μeV mass range
A radio frequency cavity consisting of 5 sub-cavities coupled by inductive irises took physics data inside the CAST dipole magnet for the first time using this filter-like haloscope geometry
Summary
The CAST-RADES detector used in this work consists of a 316LN stainless steel cavity, coated with a 30 μm thick copper layer. Port P1 is connected with coaxial cables to a 40 decibels (dB) TXA4000 cryogenic low noise amplifier (LNA) manufactured by TTI Norte located in a copper vessel at the end cap of the CAST magnet, in a region with negligible magnetic field (B 0.01 T), but still at cryogenic temperatures. Both P1 and P2 are connected with semi-rigid coaxial cables to. The coupling β, noise temperature Tsys and QL were inferred from single measurements They are assumed to have been stable over the data-taking period of 103 hours taken within a period of 20 days. Since our cavity did not undergo any mechanical changes during the data-taking period, the assumption of stability of these parameters is justified
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