Construction And Research Of CMB Superconducting Transition Edge Sensor Cryogenic Characteristic Test Platform

The cosmic microwave background radiation(CMB)contains information about the early evolution of the universe,and the B-mode polarization signal in its anisotropic component is direct evidence to verify the original gravitational waves(PGWs).Due to its small proportion in the polarization component,detection is very difficult.Only detectors with extremely low noise equivalent power(NEP)can effectively measure it.At present,superconducting edge detectors(TES)are commonly used domestically and internationally to detect polarization signals in mode B,and large-scale TES arrays are used to improve the observation sensitivity of CMB polarization signals.The research on primary gravitational wave detection technology in China is still in its early stages,and the Ali CMB Polarization Telescope(AliCPT)under construction uses TES arrays provided by the United States.At the same time,there is a lack of necessary testing systems in China to study the performance of produced TES device.Therefore,setting up a platform for testing the cryogenic characteristics of TES and conducting extensive testing on TES can help accelerate the improvement of the preparation process and the speed of device optimization iterations,and achieve the localization of the core technology of primary gravitational wave detection-TES,enabling China to be at the forefront of the field of primary gravitational wave detection and cosmology.Based on the above background,this paper will focus on the construction and testing of the cryogenic test platform for TES detector.Firstly,based on the 8-channel superconducting quantum interference device(SQUID)of STAR Company,we built a multi-channel test system for the Ⅰ-Ⅴ characteristics of TES detectors in the DR refrigeration system,which can be used to measure the energy spectrum resolution of X-ray TES.By improving the ground-connection method of the device and the room temperature electronics of SQUID,the noise interference of the test is controlled within 1mV.Through this system,the saturation power and thermal conductivity of TES with different cantilever length are measured,and the cantilever length of TES and thermal conductivity process parameters are calibrated.Meanwhile,the negative correlation between them is verified.The thermal fluctuation noise equivalent power of TES is estimated by thermal conductivity,which provides a reference for the processing of TES chips in the future.Secondly,based on the lock-in.amplifier,we set up the complex impedance test system of TES in ADR and DR refrigeration systems,which only has about 0.4%interference fluctuation under the set test conditions.Meanwhile,it can measure hundreds of data points with different frequencies in a short time,and realize the simultaneous measurement of TES multi-parameters.It is also the first cryogenic complex impedance test system built in China.Finally,through this system,we test several TES samples with different cantilever lengths,and the TES bias resistance and total loop inductance obtained are consistent with the previous noise spectrum test results.By testing the complex impedance of TES with different cantilever length at different temperatures and bias points,we obtained logarithmic current sensitivity(β),loop gain(L1)and effective thermal time constant(τeff)through fitting.The correlation of fitting parameters is analyzed,and the range of τeff is 1-10ms.These parameters provide an important reference for the selection of bias points and subsequent design of TES.The work of this article has setting up a relatively complete TES deep cryogenic testing platform,which can test the deep cryogenic characteristic parameters of TES.In particular,the preliminary complex impedance testing system has filled the gap in domestic research in this field.The multiple parameters obtained from the testing provide a basis for the optimization design of TES devices,and lays a solid foundation for future TES optical testing.