Improving Amplification Bandwidth by Combining Josephson Parametric Amplifiers for Active Axion Search Experiments at IBS/CAPP

Abstract IBS/CAPP in South Korea is home to multiple active axion search experiments using cavity haloscopes that operate within the frequency range of 1-6 GHz. The haloscopes convert axions to photons, resulting in an output power of about 10-24 to 10-22 W. To detect such a small signal amidst noise, quantum-limited noise amplifiers and ultra-low-temperature environment (∼10 mK) are required for all critical read-out components to minimize noise from all of active and passive lossy components. Additionally, operating at low dissipation levels is necessary to maintain the haloscope and amplifier at a temperature of 25-40 mK. Our primary objective is to achieve the highest possible scanning-frequency speed, which includes the time for maintenance and system calibration. For the CAPP-MAX flagship experiment, we achieved a record speed of 3 MHz/day for the DFSZ-level axion sensitivity during uninterrupting measurements. This paper presents the development and operation of low-noise amplifiers for five haloscope experiments targeting different frequency ranges and provides design, operational, and performance details of the amplifiers.