Estimation method for beam size of superconducting transition edge detector

Abstract

Owing to its extremely low noise equivalent power, superconducting transition edge detectors have been widely used in various international cosmic microwave background polarization observation projects in recent years. In order to ensure that the detector works in the best performance range, the saturation power value of the detector needs to be adjusted according to the meteorological conditions of the observation site and the observation band, and the structural size of the detector beam directly determines the saturation power. Owing to process differences and other reasons, the beam sizes obtained under different processing schemes often cannot be directly used for horizontal comparison. In previous observation projects, a series of devices with different sizes were generally processed and measured one by one, and then the actual required size was inferred by fitting the relationship between the measured saturated power and the beam size. In order to match the target value, multiple machining iterations are often required. In this work, the boundary-restricted phonon transport model is used to successfully integrate the device parameters from previous observation projects to estimate the size of the transition edge sensor (TES) beam. According to the estimated value, the TES detector chips for detecting cosmic microwave background polarization signal are fabricated for the first time in China. Measurements show that its parameters deviate slightly from the target value. This method can well estimate the sizes of similar TES detectors, and thus has guiding significance for designing TES detectors in the future.