In high-altitude nuclear detonations,the proportion of pulsed X-ray energy can exceed 70%,making it a specific monitoring signal for such events.These pulsed X-rays can be captured using a satellite-borne X-ray detect...In high-altitude nuclear detonations,the proportion of pulsed X-ray energy can exceed 70%,making it a specific monitoring signal for such events.These pulsed X-rays can be captured using a satellite-borne X-ray detector following atmospheric transmission.To quantitatively analyze the effects of different satellite detection altitudes,burst heights,and transmission angles on the physical processes of X-ray transport and energy fluence,we developed an atmospheric transmission algorithm for pulsed X-rays from high-altitude nuclear detonations based on scattering correction.The proposed method is an improvement over the traditional analytical method that only computes direct-transmission X-rays.The traditional analytical method exhibits a maximum relative error of 67.79% compared with the Monte Carlo method.Our improved method reduces this error to within 10% under the same conditions,even reaching 1% in certain scenarios.Moreover,its computation time is 48,000 times faster than that of the Monte Carlo method.These results have important theoretical significance and engineering application value for designing satellite-borne nuclear detonation pulsed X-ray detectors,inverting nuclear detonation source terms,and assessing ionospheric effects.展开更多
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 Tibet.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
A three-dimensional infrared radiation code for exhaust system was developed by the finite volume method coupled with narrow band k-distribution in non-gray absorbing-emitting media.The final infrared signature had co...A three-dimensional infrared radiation code for exhaust system was developed by the finite volume method coupled with narrow band k-distribution in non-gray absorbing-emitting media.The final infrared signature had considered the atmosphere effect,and the simulation values were favorably consistent with testing ones.The results indicate that the relative errors considering the effect of atmosphere compared with that of the contrary condition reduce by 31%,it shows that when simulating the infrared radiation of the target which is received by the infrared detectors,even the calculation band is in atmospheric windows 3～5 μm,the effect of atmospheric transmission on infrared signature of the target should not be neglected.展开更多
文摘In high-altitude nuclear detonations,the proportion of pulsed X-ray energy can exceed 70%,making it a specific monitoring signal for such events.These pulsed X-rays can be captured using a satellite-borne X-ray detector following atmospheric transmission.To quantitatively analyze the effects of different satellite detection altitudes,burst heights,and transmission angles on the physical processes of X-ray transport and energy fluence,we developed an atmospheric transmission algorithm for pulsed X-rays from high-altitude nuclear detonations based on scattering correction.The proposed method is an improvement over the traditional analytical method that only computes direct-transmission X-rays.The traditional analytical method exhibits a maximum relative error of 67.79% compared with the Monte Carlo method.Our improved method reduces this error to within 10% under the same conditions,even reaching 1% in certain scenarios.Moreover,its computation time is 48,000 times faster than that of the Monte Carlo method.These results have important theoretical significance and engineering application value for designing satellite-borne nuclear detonation pulsed X-ray detectors,inverting nuclear detonation source terms,and assessing ionospheric effects.
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 Tibet.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.
文摘A three-dimensional infrared radiation code for exhaust system was developed by the finite volume method coupled with narrow band k-distribution in non-gray absorbing-emitting media.The final infrared signature had considered the atmosphere effect,and the simulation values were favorably consistent with testing ones.The results indicate that the relative errors considering the effect of atmosphere compared with that of the contrary condition reduce by 31%,it shows that when simulating the infrared radiation of the target which is received by the infrared detectors,even the calculation band is in atmospheric windows 3～5 μm,the effect of atmospheric transmission on infrared signature of the target should not be neglected.
