# The 3 cavity prototypes of RADES, an axion detector using microwave filters at CAST

## TL;DR

This paper describes the design and testing of three microwave cavity prototypes for the RADES axion detector, demonstrating their potential to detect QCD axions at X-Band frequencies.

## Contribution

It introduces three novel cavity prototypes for RADES and presents initial test results, advancing the development of scalable axion detection technology.

## Key findings

- First prototype operated at 8.4 GHz in 2017 at CERN.
- Two new prototypes designed to optimize volume and tuning.
- Results show promising potential for QCD axion sensitivity.

## Abstract

The Relic Axion Detector Experimental Setup (RADES) is an axion search project that uses a microwave filter as resonator for Dark Matter conversion. The main focus of this publication is the description of the 3 different cavity prototypes of RADES. The result of the first tests of one of the prototypes is also presented. The filters consist of 5 or 6 stainless steel sub-cavities joined by rectangular irises. The size of the sub-cavities determines the working frequency, the amount of sub-cavities determine the working volume. The first cavity prototype was built in 2017 to work at a frequency of $\sim$ 8.4 GHz and it was placed at the 9 T CAST dipole magnet at CERN. Two more prototypes were designed and built in 2018. The aim of the new designs is to find and test the best cavity geometry in order to scale up in volume and to introduce an effective tuning mechanism. Our results demonstrate the promising potential of this type of filter to reach QCD axion sensitivity at X-Band frequencies.