The accumulation of^(222)Rn and^(220)Rn progeny in poorly ventilated environments poses the risk of natural radiation exposure to the public.A previous study indicated that satisfactory results in determining the^(222...The accumulation of^(222)Rn and^(220)Rn progeny in poorly ventilated environments poses the risk of natural radiation exposure to the public.A previous study indicated that satisfactory results in determining the^(222)Rn and^(220)Rn progeny concentrations by measuring the total alpha counts at five time intervals within 560 min should be expected only in the case of high progeny concentrations in air.To complete the measurement within a relatively short period and adapt it for simultaneous measurements at comparatively lower^(222)Rn and^(220)Rn progeny concentrations,a novel mathematical model was proposed based on the radioactive decay law.This model employs a nonlinear fitting method to distinguish nuclides with overlapping spectra by utilizing the alpha particle counts of non-overlapping spectra within consecutive measurement cycles to obtain the concentrations of^(222)Rn and^(220)Rn progeny in air.Several verification experiments were conducted using an alpha spectrometer.The experimental results demonstrate that the concentrations of^(222)Rn and^(220)Rn progeny calculated by the new method align more closely with the actual circumstances than those calculated by the total count method,and their relative uncertainties are all within±16%.Furthermore,the measurement time was reduced to 90 min,representing an acceleration of 84%.The improved capability of the new method in distinguishing alpha particles with similar energies emitted from ^(218)Po and^(212)Bi,both approximately 6 MeV,contributed to realizing more accurate results.The proposed method has the potential advantage of measuring relatively low concentrations of^(222)Rn and^(220)Rn progeny in air more quickly via air filtration.展开更多
High-temperature warnings frequently occurred at the Power Distribution System(PDS)of the Alpha Magnetic Spectrometer(AMS).To investigate the fundamental reasons,a theoretical model for the AMS PDS was established und...High-temperature warnings frequently occurred at the Power Distribution System(PDS)of the Alpha Magnetic Spectrometer(AMS).To investigate the fundamental reasons,a theoretical model for the AMS PDS was established under the International Space Station(ISS)normal and special operating conditions.With the model,the study investigated the external heat fluxes and the temperature responses of the PDS.The effects of ISS special operations on the PDS’s thermal environment were also investigated.Results reveal that the total external heat flux at the PDS reaches its maximum value when the angleβis around–25°,where high-temperature warning frequently occurs.Under the ISS normal operating condition,the temperature response hysteresis at the PDS varies from 116 s to 230 s.When the ISS performed special operations,locking the ISS solar arrays had the greatest influence on the PDS’s external heat fluxes,and the average temperature at the PDS fell by 1.7°C.When the ISS performed multiple special operations,simultaneously locking the ISS solar arrays and adjusting the ISS flight attitude were the most frequent operations,of which the influences on the PDS temperature were the largest,i.e.,the changes in peak temperature reached up to+2.5°C.展开更多
Loop heat pipes （LHPs） were designed for the alpha magnetic spectrometer （AMS-02） to dissipate heat from the cryocoolers. A bypass valve is applied to the LHP to keep the cryocooler temperature above its limit （...Loop heat pipes （LHPs） were designed for the alpha magnetic spectrometer （AMS-02） to dissipate heat from the cryocoolers. A bypass valve is applied to the LHP to keep the cryocooler temperature above its limit （-20℃） in cold environment. Extensive experiments were performed on operation characteristics of LHPs with the bypass valve for AMS-02 during thermal vacuum and thermal balance （TVTB） test. We found that the bypass valve can start up successfully in cold environment. With the bypass valve, the evaporator temperature is stable and can meet the requirement of the cryocooler. We analyzed three operating modes of the bypass valve. Set point temperature and regulation temperature shifts were observed and their relations with the bypass valve temperature were given.展开更多
基金supported by the National Natural Science Foundation of China(No.12075112)Natural Science Foundation of Hunan(No.2023JJ50121),Natural Science Foundation of Hunan Province(No.2023JJ50091)Key Projects of Hunan Provincial Department of Education(No.23A0516).
文摘The accumulation of^(222)Rn and^(220)Rn progeny in poorly ventilated environments poses the risk of natural radiation exposure to the public.A previous study indicated that satisfactory results in determining the^(222)Rn and^(220)Rn progeny concentrations by measuring the total alpha counts at five time intervals within 560 min should be expected only in the case of high progeny concentrations in air.To complete the measurement within a relatively short period and adapt it for simultaneous measurements at comparatively lower^(222)Rn and^(220)Rn progeny concentrations,a novel mathematical model was proposed based on the radioactive decay law.This model employs a nonlinear fitting method to distinguish nuclides with overlapping spectra by utilizing the alpha particle counts of non-overlapping spectra within consecutive measurement cycles to obtain the concentrations of^(222)Rn and^(220)Rn progeny in air.Several verification experiments were conducted using an alpha spectrometer.The experimental results demonstrate that the concentrations of^(222)Rn and^(220)Rn progeny calculated by the new method align more closely with the actual circumstances than those calculated by the total count method,and their relative uncertainties are all within±16%.Furthermore,the measurement time was reduced to 90 min,representing an acceleration of 84%.The improved capability of the new method in distinguishing alpha particles with similar energies emitted from ^(218)Po and^(212)Bi,both approximately 6 MeV,contributed to realizing more accurate results.The proposed method has the potential advantage of measuring relatively low concentrations of^(222)Rn and^(220)Rn progeny in air more quickly via air filtration.
基金support from Shandong Universitysponsored by the Fundamental Research Fund of Shandong University,China。
文摘High-temperature warnings frequently occurred at the Power Distribution System(PDS)of the Alpha Magnetic Spectrometer(AMS).To investigate the fundamental reasons,a theoretical model for the AMS PDS was established under the International Space Station(ISS)normal and special operating conditions.With the model,the study investigated the external heat fluxes and the temperature responses of the PDS.The effects of ISS special operations on the PDS’s thermal environment were also investigated.Results reveal that the total external heat flux at the PDS reaches its maximum value when the angleβis around–25°,where high-temperature warning frequently occurs.Under the ISS normal operating condition,the temperature response hysteresis at the PDS varies from 116 s to 230 s.When the ISS performed special operations,locking the ISS solar arrays had the greatest influence on the PDS’s external heat fluxes,and the average temperature at the PDS fell by 1.7°C.When the ISS performed multiple special operations,simultaneously locking the ISS solar arrays and adjusting the ISS flight attitude were the most frequent operations,of which the influences on the PDS temperature were the largest,i.e.,the changes in peak temperature reached up to+2.5°C.
基金supported by the Major Project of Technology Transfer of Shandong Province (Grant No. 2009ZHZX1A1105)
文摘Loop heat pipes （LHPs） were designed for the alpha magnetic spectrometer （AMS-02） to dissipate heat from the cryocoolers. A bypass valve is applied to the LHP to keep the cryocooler temperature above its limit （-20℃） in cold environment. Extensive experiments were performed on operation characteristics of LHPs with the bypass valve for AMS-02 during thermal vacuum and thermal balance （TVTB） test. We found that the bypass valve can start up successfully in cold environment. With the bypass valve, the evaporator temperature is stable and can meet the requirement of the cryocooler. We analyzed three operating modes of the bypass valve. Set point temperature and regulation temperature shifts were observed and their relations with the bypass valve temperature were given.
