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
目的介绍了目前主流的PET散射校正方法,并进行了横向评估,最后讨论了目前散射校正存在的问题和发展方向。方法基于东软医疗系统股份有限公司NeuWise Pro PET/CT产品进行仿真实验,评估视野外核素分布对每种方法的散射估计精度影响。结果...目的介绍了目前主流的PET散射校正方法,并进行了横向评估,最后讨论了目前散射校正存在的问题和发展方向。方法基于东软医疗系统股份有限公司NeuWise Pro PET/CT产品进行仿真实验,评估视野外核素分布对每种方法的散射估计精度影响。结果视野外部分的核素产生的散射事件,对散射的空间分布存在明显影响,应该纳入模型考虑的范围。蒙特卡罗计算法的散射估计精度更高。结论临床上,若视野外临近部分活度较高,如脑部、肝部、肾脏和膀胱等,很可能会导致散射估计出现偏差。考虑视野外核素分布的蒙特卡罗法散射估计,有助于提高散射分布的估计精度。展开更多
Distortions caused by the neutron spectrum and scattered neutrons are major problems in fast neutron radiography and should be considered for improving the image quality. This paper puts emphasis on the removal of the...Distortions caused by the neutron spectrum and scattered neutrons are major problems in fast neutron radiography and should be considered for improving the image quality. This paper puts emphasis on the removal of these image distortions and deviations for fast neutron radiography performed at the NECTAR facility of the research reactor FRM-II in Technische Universit/it Mfinchen （TUM）, Germany. The NECTAR energy spectrum is analyzed and established to modify the influence caused by the neutron spectrum, and the Point Scattered Function （PSeF） simulated by the Monte-Carlo program MCNPX is used to evaluate scattering effects from the object and improve image quality. Good analysis results prove the sound effects of the above two corrections.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.
文摘目的介绍了目前主流的PET散射校正方法,并进行了横向评估,最后讨论了目前散射校正存在的问题和发展方向。方法基于东软医疗系统股份有限公司NeuWise Pro PET/CT产品进行仿真实验,评估视野外核素分布对每种方法的散射估计精度影响。结果视野外部分的核素产生的散射事件,对散射的空间分布存在明显影响,应该纳入模型考虑的范围。蒙特卡罗计算法的散射估计精度更高。结论临床上,若视野外临近部分活度较高,如脑部、肝部、肾脏和膀胱等,很可能会导致散射估计出现偏差。考虑视野外核素分布的蒙特卡罗法散射估计,有助于提高散射分布的估计精度。
基金Supported by National Natural Science Foundation of China(11079001)
文摘Distortions caused by the neutron spectrum and scattered neutrons are major problems in fast neutron radiography and should be considered for improving the image quality. This paper puts emphasis on the removal of these image distortions and deviations for fast neutron radiography performed at the NECTAR facility of the research reactor FRM-II in Technische Universit/it Mfinchen （TUM）, Germany. The NECTAR energy spectrum is analyzed and established to modify the influence caused by the neutron spectrum, and the Point Scattered Function （PSeF） simulated by the Monte-Carlo program MCNPX is used to evaluate scattering effects from the object and improve image quality. Good analysis results prove the sound effects of the above two corrections.
