Noise Temperature Measurements of Josephson Parametric Amplifiers for the Axion Search at IBS/CAPP

Josephson parametric amplifiers (JPAs) are promising devices for amplifying the weak signal of the axion in haloscopes due to their low noise amplification and tunable resonant frequency. For the axion experiment, the noise temperature of the JPA needs to be determined at various frequencies, which requires altering the noise source temperature. Optimizing the time required to collect this data is crucial for this experiment. Two methods were used to estimate the noise temperature of the JPA and calculate the standard deviation of the fitted data. First, a modified Y-factor method was developed to calculate the noise temperature using only two noise source temperatures. Then, a method using curve fitting to estimate the noise temperature was applied, utilizing all fifty-three noise source temperature spectra, and the standard deviation was calculated. The fitting method provided much more accurate results, but the measurement time was significantly longer than what would be required for the Y-factor method.