Cosmic-microwave-background(CMB)B-mode measurements may reveal primordial gravitational waves from the earliest phases of the Big Bang.As the first CMB experiment in the northern hemisphere,the Ali CMB polarization te...Cosmic-microwave-background(CMB)B-mode measurements may reveal primordial gravitational waves from the earliest phases of the Big Bang.As the first CMB experiment in the northern hemisphere,the Ali CMB polarization telescope(Ali CPT)will carry out measurements of this kind at Ali(Nagri)in Xizang.It is therefore of particular importance to understand the terahertz atmospheric transmission at this site.Here we report on the measurement results for three consecutive seasons with a Fourier transform spectrometer(FTS)spanning a wide frequency range from 0.75 to 14 THz.The zenith median precipitable-watervapor(PWV)is found to be as low as 1 mm at the Ali CPT site,which appears as good as those CMB B-mode measurement sites in the southern hemisphere such as Chile's Atacama Desert.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.12020101002,and 11925304)Chinese Academy of Sciences(CAS)(Grant No.GJJSTD20210002)+1 种基金National Key R&D Program of China(Grant No.2017YFA0304003)CAS Key Lab for Radio Astronomy。
文摘Cosmic-microwave-background(CMB)B-mode measurements may reveal primordial gravitational waves from the earliest phases of the Big Bang.As the first CMB experiment in the northern hemisphere,the Ali CMB polarization telescope(Ali CPT)will carry out measurements of this kind at Ali(Nagri)in Xizang.It is therefore of particular importance to understand the terahertz atmospheric transmission at this site.Here we report on the measurement results for three consecutive seasons with a Fourier transform spectrometer(FTS)spanning a wide frequency range from 0.75 to 14 THz.The zenith median precipitable-watervapor(PWV)is found to be as low as 1 mm at the Ali CPT site,which appears as good as those CMB B-mode measurement sites in the southern hemisphere such as Chile's Atacama Desert.
