Abstract-Terahertz Superconducting Radiometric Spectrometer in Tibet for Atmospheric Science

Sheng Li, Qijun Yao, Dong Liu, Wenying Duan, Kun Zhang, Junda Jin, Zhenhui Lin, Feng Wu, Jinping Yang, Wei Miao, Shengcai Shi

https://link.springer.com/article/10.1007/s10762-018-0557-4

Terahertz superconducting radiometric spectrometer (TSRS), as one of seven instruments of the atmospheric profiling synthetic observation system (APSOS) project, was completed in the middle of 2017 after 5 years of development. It is a dual-band heterodyne receiver system based on high sensitive superconductor-insulator-superconductor (SIS) mixers which cover the frequency range of 180 to 380 GHz. With fast Fourier transform spectrometer (FFTS) of each band, real-time observation of 2 GHz bandwidth of high spectral resolution atmospheric molecular emission lines has been demonstrated. TSRS has been deployed at Yangbajing site, which stands on the Qinghai-Tibet Plateau at an altitude of 4300 m in southwestern China, since October 2017. It has been worked in a preliminary observation phase along with other active observation equipment of APSOS. Since then, ozone emission lines around 236 GHz and 358 GHz have been monitored simultaneously. Achieved data will be used to retrieve the in situ vertical distribution of ozone and its movement among different layers of the atmosphere

Abstract-Terahertz direct-detection behavior of niobium nitride superconducting tunnel junctions above liquid helium temperature

Zheng Wang1,2, Dong Liu1,2, Shao-liang Li1,2, Jing Li1,2 and Sheng-Cai Shi1,2

zhwang@pmo.ac.cn http://iopscience.iop.org/0953-2048/27/7/075003scshi@pmo.ac.cn

1 Millimeter & Submillimeter Wave Lab, Purple Mountain Observatory, CAS, Nanjing, Jiangsu, 210008, People's Republic of China
2 Key Laboratory of Radio Astronomy, CAS, Nanjing, Jiangsu, 210008, People's Republic of China 

Niobium nitride (NbN) superconducting tunnel junctions (STJs) have an energy gap nearly double that of niobium STJs, making them potential sensitive detectors that operate at higher frequencies and temperatures. In this paper, we investigate the direct-detection behavior (i.e. the spectral response, current responsivity, noise characteristics, and noise equivalent power (NEP)) of a 500 GHz NbN STJ detector at temperatures from approximately 5 to 9 K. The detector shows an uncorrected NEP of 3.8 × 10−13W/around 5 K and 1.5 × 10−12 W/at 9 K. Its performance can be further improved by adopting a cryogenically cooled readout circuit and fabricating the device with a wiring layer of higher critical-transition temperatures.