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
The magnetic proton recoil（MPR）spectrometer is a novel diagnostic instrument with high perfor-mance for measurements of neutron spectra in inertial confinement fusion（ICF）experiments and high power fusion devices....The magnetic proton recoil（MPR）spectrometer is a novel diagnostic instrument with high perfor-mance for measurements of neutron spectra in inertial confinement fusion（ICF）experiments and high power fusion devices.A compact MPR-type spectrometer dedicated to the research of pulsed deuterium-tritium（DT）neutron spectroscopy of special experimental conditions is currently under design.Analyses of the main parameters and performance of the magnetic analysis system through 3-D particle transport calculations and MonteCarlo simulations and calibration of the system performance as a test using CR-39 solid track detector and α particle from 239pu and 226Ra radioactive sources are presented in this paper.The results indicate that the magnetic analysis system will achieve a detection efficiency level of 10-5-10-4 at an energy resolution of 1.5%-2.1%,and fulfills the design goals of the spectrometer.展开更多
The electron energy spectrum is one of the most important characteristics of an electron beam that is extracted from a linear accelerator. The most direct way to determine an electron spectrum would be to use a magnet...The electron energy spectrum is one of the most important characteristics of an electron beam that is extracted from a linear accelerator. The most direct way to determine an electron spectrum would be to use a magnetic spectrometer and this method could also give results with high precision and effectiveness. In this article we describe our design of a new multi-layer absorption method, which is based on the depth-dose curves method that can be used in most irradiation accelerators, and adds the Monte Carlo simulation and iterative algorithm in order to reconstruct the electron energy spectrum. In this article the energy spectrum was measured using these two methods, and good results were acquired. These results could be crosschecked, which made the results more reliable.展开更多
Laser Wakefield plasma acceleration of electrons to energies above 10 GeV, may be possible in the new high power Laser beam facilities. The design of an Electron Spectrometer with an electro-magnet with adjustable mag...Laser Wakefield plasma acceleration of electrons to energies above 10 GeV, may be possible in the new high power Laser beam facilities. The design of an Electron Spectrometer with an electro-magnet with adjustable magnetic field is proposed for the characterization of electron energy spectrum with a precision better than 10% for the entire energy range from 0.5 GeV to 38 GeV. The expected precision in the measurement of the electron energy is calculated as a function of the magnetic field, of the electron energy and of the magnet length. To outline the advantages offered by a pulsed electromagnet with high magnetic fields, the mass and the electric power lost in the coils of a 4 m long electromagnet with continuous current and Iron yoke are calculated.展开更多
Ⅰ. INTRODUCTION In the past experiments on the magnetic quenching of positronium atom （a hydrogenlike bound state of positron and dectron ）, the plastic scintillator and BaF<sub>2</sub> crystal were usu...Ⅰ. INTRODUCTION In the past experiments on the magnetic quenching of positronium atom （a hydrogenlike bound state of positron and dectron ）, the plastic scintillator and BaF<sub>2</sub> crystal were usually used as the detectors in the positron lifetime spectrometer. In those cases, a long light guide between the detector and the photomultiplier was exclusively necessary for keeping展开更多
Alpha magnetic spectrometer (AMS) is the first large magndtic spectrometer in space. Its precursor flioht was completed successfully in June 1998. The key part of AMS is the permanent magnet system, which was built by...Alpha magnetic spectrometer (AMS) is the first large magndtic spectrometer in space. Its precursor flioht was completed successfully in June 1998. The key part of AMS is the permanent magnet system, which was built by the lnstitute of Electric Engineering, the institute of High Energy Physics and the Chinese Academy of Launch Vehicle Technology. This system includes a permanent magnet made of high grade NdFeB and a support structure. The unique design of the permanent magnet based on the magic ring fulfills the severe requirements on the magnetic field leakage and the dipole moment for space experiments. The permanent magnet weighs about 2 tons, and provides a geometric acceptance of 0.6 m2 · sr and an analyzing powerBL 2 of 0.135 T · m2. It works up to 40°C without demagnetization. The main structure is a thin double shell, which undergoes the strong magnetic force and torque of the permanent magnet, as well as the large load during launching and landing. The permanent magnet system fulfills the requirements from AMS, and satisfies the strict safety standards of NASA.展开更多
Portable X-ray fluorescence(pXRF) spectrometry and magnetic susceptibility(MS) via magnetometer have been increasingly used with terrain variables for digital soil mapping. However, this methodology is still emerging ...Portable X-ray fluorescence(pXRF) spectrometry and magnetic susceptibility(MS) via magnetometer have been increasingly used with terrain variables for digital soil mapping. However, this methodology is still emerging in many countries with tropical soils. The objective of this study was to use proximal soil sensor data associated with terrain variables at varying spatial resolutions to predict soil classes using the Random Forest(RF) algorithm. The study was conducted on a 316-ha area featuring highly variable soil classes and complex soil-landscape relationships in Minas Gerais State, Brazil. The overall accuracy and Kappa index were evaluated using soils that were classified at 118 sites, with 90 being used for modeling and 28 for validation. Digital elevation models(DEMs) were created at 5-, 10-, 20-, and 30-m resolutions using contour lines from two sources. The resulting DEMs were processed to generate 12 terrain variables. Total Fe, Ti, and SiO_(2) contents were obtained using pXRF, with MS determined via a magnetometer. Soil class prediction was performed using the RF algorithm. The quality of the soil maps improved when using only the five most important covariates and combining proximal sensor data with terrain variables at different spatial resolutions. The finest spatial resolution did not always provide the most accurate maps. The high soil complexity in the area prevented highly accurate predictions. The most important variables influencing the soil mapping were MS, Fe, and Ti. Proximal sensor data associated with terrain information were successfully used to map Brazilian soils at variable spatial resolutions.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
Ions with different rigidity have different radius of deflection in the same magnetic field, based on this principle the magnetic mass spectrometer, which will be used to analyze the beam quality and the distribution,...Ions with different rigidity have different radius of deflection in the same magnetic field, based on this principle the magnetic mass spectrometer, which will be used to analyze the beam quality and the distribution, can separate mixed ion beams. In order to reduce the energy loss of beam in vacuum pipe, the vacuum pressure level must be less than 1x10?4 Pa.展开更多
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.
基金Supported by Science and Technology Development Foundation of China Academy of Engineering Physics (2008B0103003)
文摘The magnetic proton recoil（MPR）spectrometer is a novel diagnostic instrument with high perfor-mance for measurements of neutron spectra in inertial confinement fusion（ICF）experiments and high power fusion devices.A compact MPR-type spectrometer dedicated to the research of pulsed deuterium-tritium（DT）neutron spectroscopy of special experimental conditions is currently under design.Analyses of the main parameters and performance of the magnetic analysis system through 3-D particle transport calculations and MonteCarlo simulations and calibration of the system performance as a test using CR-39 solid track detector and α particle from 239pu and 226Ra radioactive sources are presented in this paper.The results indicate that the magnetic analysis system will achieve a detection efficiency level of 10-5-10-4 at an energy resolution of 1.5%-2.1%,and fulfills the design goals of the spectrometer.
文摘The electron energy spectrum is one of the most important characteristics of an electron beam that is extracted from a linear accelerator. The most direct way to determine an electron spectrum would be to use a magnetic spectrometer and this method could also give results with high precision and effectiveness. In this article we describe our design of a new multi-layer absorption method, which is based on the depth-dose curves method that can be used in most irradiation accelerators, and adds the Monte Carlo simulation and iterative algorithm in order to reconstruct the electron energy spectrum. In this article the energy spectrum was measured using these two methods, and good results were acquired. These results could be crosschecked, which made the results more reliable.
文摘Laser Wakefield plasma acceleration of electrons to energies above 10 GeV, may be possible in the new high power Laser beam facilities. The design of an Electron Spectrometer with an electro-magnet with adjustable magnetic field is proposed for the characterization of electron energy spectrum with a precision better than 10% for the entire energy range from 0.5 GeV to 38 GeV. The expected precision in the measurement of the electron energy is calculated as a function of the magnetic field, of the electron energy and of the magnet length. To outline the advantages offered by a pulsed electromagnet with high magnetic fields, the mass and the electric power lost in the coils of a 4 m long electromagnet with continuous current and Iron yoke are calculated.
基金Project supported by the National Natural Science Foundation of China.
文摘Ⅰ. INTRODUCTION In the past experiments on the magnetic quenching of positronium atom （a hydrogenlike bound state of positron and dectron ）, the plastic scintillator and BaF<sub>2</sub> crystal were usually used as the detectors in the positron lifetime spectrometer. In those cases, a long light guide between the detector and the photomultiplier was exclusively necessary for keeping
文摘Alpha magnetic spectrometer (AMS) is the first large magndtic spectrometer in space. Its precursor flioht was completed successfully in June 1998. The key part of AMS is the permanent magnet system, which was built by the lnstitute of Electric Engineering, the institute of High Energy Physics and the Chinese Academy of Launch Vehicle Technology. This system includes a permanent magnet made of high grade NdFeB and a support structure. The unique design of the permanent magnet based on the magic ring fulfills the severe requirements on the magnetic field leakage and the dipole moment for space experiments. The permanent magnet weighs about 2 tons, and provides a geometric acceptance of 0.6 m2 · sr and an analyzing powerBL 2 of 0.135 T · m2. It works up to 40°C without demagnetization. The main structure is a thin double shell, which undergoes the strong magnetic force and torque of the permanent magnet, as well as the large load during launching and landing. The permanent magnet system fulfills the requirements from AMS, and satisfies the strict safety standards of NASA.
基金BL Allen Endowment in Pedology at Texas Tech University,USAthe Brazilian funding agencies National Council for Scientific and Technological Development (CNPq) (Nos.301930/2019-8 and 306389/2019-7)+1 种基金the Coordination for the Improvement of Higher Education Personnel (CAPES),Brazil (No.590-2014)Research Support Foundation of the State of Minas Gerais (FAPEMIG),Brazil (No.PPM 00305-17) for the financial support provided。
文摘Portable X-ray fluorescence(pXRF) spectrometry and magnetic susceptibility(MS) via magnetometer have been increasingly used with terrain variables for digital soil mapping. However, this methodology is still emerging in many countries with tropical soils. The objective of this study was to use proximal soil sensor data associated with terrain variables at varying spatial resolutions to predict soil classes using the Random Forest(RF) algorithm. The study was conducted on a 316-ha area featuring highly variable soil classes and complex soil-landscape relationships in Minas Gerais State, Brazil. The overall accuracy and Kappa index were evaluated using soils that were classified at 118 sites, with 90 being used for modeling and 28 for validation. Digital elevation models(DEMs) were created at 5-, 10-, 20-, and 30-m resolutions using contour lines from two sources. The resulting DEMs were processed to generate 12 terrain variables. Total Fe, Ti, and SiO_(2) contents were obtained using pXRF, with MS determined via a magnetometer. Soil class prediction was performed using the RF algorithm. The quality of the soil maps improved when using only the five most important covariates and combining proximal sensor data with terrain variables at different spatial resolutions. The finest spatial resolution did not always provide the most accurate maps. The high soil complexity in the area prevented highly accurate predictions. The most important variables influencing the soil mapping were MS, Fe, and Ti. Proximal sensor data associated with terrain information were successfully used to map Brazilian soils at variable spatial resolutions.
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.
文摘Ions with different rigidity have different radius of deflection in the same magnetic field, based on this principle the magnetic mass spectrometer, which will be used to analyze the beam quality and the distribution, can separate mixed ion beams. In order to reduce the energy loss of beam in vacuum pipe, the vacuum pressure level must be less than 1x10?4 Pa.
