Development Of The Cryogenic Phased Array Feed System

Five hundred meters Aperture Spherical Radio Telescope(FAST)is the largest single antenna Radio Telescope in the world with the largest aperture,resolution and sensitive.Phase array feed is one of the new feed technology of radio astronomy.The whole performance of the telescope can be further improved by reducing the noise temperature of the system.This paper studies the phase array feed cryogenic system which is to be applied to FAST.Based on the development of traditional receiver cryogenic system,the design of the cryogenic system is designed according to the shape and performance of the phase array feed.Firstly,the basic structure of phase array feed receiver is introduced,and the method to improve the performance of phase array feed is analyzed.Secondly,the structure of the phase array feed cryogenic system is introduced,and the thermal load of dewar is analyzed by theoretical calculation and software simulation.The calculation of the total thermal load of the cryogenic phased array feed shows that the total heat transfer load can satisfy the phase array feed receiving unit cooling temperature of 70 K and low noise amplifier 20 K.Finally compared the performance of the phase array feed cryogenic before and after,it is concluded that after cryogenic the phase array feed signal-to-noise ratio increased about 3 times,the system noise temperature dropped by about 3 times,survey speed increased about 9 times.The design and experimental process of dewar provide the experience and experimental data for the future phase array feed cryogenic system.