Axion CDM cavity experiment with ultra-low noise at 2.3 GHz frequency

Abstract

In this dissertation, we present the result of axion haloscope cavity experiment with ultra-low noise and an advanced scanning method around 2.3 GHz. Axion is a pseudo-scalar particle originally introduced to explain strong CP problem. The identification of the axion is important because it is also a good dark matter candidate. The Center for Axion and Precision Physics Research (CAPP) of IBS at KAIST Munji Campus is launching a microwave axion search experiment, aiming 2.27 – 2.30 GHz region. For cavity experiments it is critical to minimize system noise because of the small expected power of axion signal, which is in order of $10^{-23}$ W at GHz scale. For this purpose, we introduce Josephson Parametric Amplifier (JPA) of which the noise can go down to quantum noise level. After implementing JPA to the system the total noise is estimated to be 204 mK, which corresponds to less than two noise photon number at given frequency. Together with controlled ultra-low noise and OFHC copper cavity the experimental run is done under 8 T magnetic field. In addition, we propose a scanning method based on a new axion candidate criterion, which boosts the scan speed by around 26%. As a result, we exclude axion parameter map above 2.7 KSVZ coupling strength in 9.3906 – 9.5130 μeV axion mass range with 90% confidence level.