Suprathermal electrons are an important population of the Martian ionosphere, either produced by photoionization of atmospheric neutrals or supplied from the Solar Wind (SW). This study is dedicated to an in-depth inv...Suprathermal electrons are an important population of the Martian ionosphere, either produced by photoionization of atmospheric neutrals or supplied from the Solar Wind (SW). This study is dedicated to an in-depth investigation of the pitch angle distribution of suprathermal electrons at two representative energies, 19−55 eV and 124−356 eV, using the extensive measurements made by the Solar Wind Electron Analyzer on board the Mars Atmosphere and Volatile Evolution. Throughout the study, we focus on the overall degree of anisotropy, defined as the standard deviation of suprathermal electron intensity among different directions which is normalized by the mean omni-directional intensity. The available data reveal the following characteristics: (1) In general, low energy electrons are more isotropic than high energy electrons, and dayside electrons are more isotropic than nightside electrons;(2) On the dayside, the anisotropy increases with increasing altitude at low energies but remains roughly constant at high energies, whereas on the nightside, the anisotropy decreases with increasing altitude at all energies;(3) Electrons tend to be more isotropic in strongly magnetized regions than in weakly magnetized regions, especially on the nightside. These observations indicate that the anisotropy is a useful diagnostic of suprathermal electron transport, for which the conversion between the parallel and perpendicular momenta as required by the conservation of the first adiabatic invariant, along with the atmospheric absorption at low altitudes, are two crucial factors modulating the observed variation of the anisotropy. Our analysis also highlights the different roles on the observed anisotropy exerted by suprathermal electrons of different origins.展开更多
The energy spectrum of energetic electrons is a key factor representing the dynamic variations of Earth’s Van Allen radiation belts.Increased measurements have indicated that the commonly used Maxwellian and Kappa di...The energy spectrum of energetic electrons is a key factor representing the dynamic variations of Earth’s Van Allen radiation belts.Increased measurements have indicated that the commonly used Maxwellian and Kappa distributions are inadequate for capturing the realistic spectral distributions of radiation belt electrons.Here we adopt the Kappa-type(KT)distribution as the fitting function and perform a statistical analysis to investigate the radiation belt electron flux spectra observed by the Van Allen Probes.By calculating the optimal values of the key KT distribution parameters(i.e.,κandθ2)from the observed spectral shapes,we fit the radiation belt electron fluxes at different L-shells under different geomagnetic conditions.In this manner,we obtain typical values of the KT distribution parameters,which are statistically feasible for modeling the radiation belt electron flux profiles during either geomagnetically quiet or active periods.A comparison of the KT distribution model results with those using the Maxwellian or Kappa distribution reveals the advantage of the KT distribution for studying the overall properties of the radiation belt electron spectral distribution,which has important implications for deepening the current understanding of the radiation belt electron dynamics under evolving geomagnetic conditions.展开更多
The formulae for parameters of a negative electron affinity semiconductor(NEAS)with large mean escape depth of secondary electrons A(NEASLD)are deduced.The methods for obtaining parameters such asλ,B,E_(pom)and the m...The formulae for parameters of a negative electron affinity semiconductor(NEAS)with large mean escape depth of secondary electrons A(NEASLD)are deduced.The methods for obtaining parameters such asλ,B,E_(pom)and the maximumδandδat 100.0 keV≥E_(po)≥1.0 keV of a NEASLD with the deduced formulae are presented(B is the probability that an internal secondary electron escapes into the vacuum upon reaching the emission surface of the emitter,δis the secondary electron yield,E_(po)is the incident energy of primary electrons and E_(pom)is the E_(po)corresponding to the maximumδ).The parameters obtained here are analyzed,and it can be concluded that several parameters of NEASLDs obtained by the methods presented here agree with those obtained by other authors.The relation between the secondary electron emission and photoemission from a NEAS with large mean escape depth of excited electrons is investigated,and it is concluded that the presented method of obtaining A is more accurate than that of obtaining the corresponding parameter for a NEAS with largeλ_(ph)(λ_(ph)being the mean escape depth of photoelectrons),and that the presented method of calculating B at E_(po)>10.0 keV is more widely applicable for obtaining the corresponding parameters for a NEAS with largeλ_(ph).展开更多
Considering the significance of low-energy electrons(LEEs;0–20 eV) in radiobiology, the sensitization potential of gold nanoparticles(AuNPs) as high-flux LEE emitters when irradiated with sub-keV electrons has been s...Considering the significance of low-energy electrons(LEEs;0–20 eV) in radiobiology, the sensitization potential of gold nanoparticles(AuNPs) as high-flux LEE emitters when irradiated with sub-keV electrons has been suggested. In this study, a track-structure Monte Carlo simulation code using the dielectric theory was developed to simulate the transport of electrons below 50 keV in gold. In this code, modifications, particularly for elastic scattering, are implemented for a more precise description of the LEE emission in secondary electron emission. This code was validated using the secondary electron yield and backscattering coefficient. To ensure dosimetry accuracy, we further verified the code for energy deposition calculations using the Monte Carlo toolkit, Geant4. The development of this code provides a basis for future studies regarding the role of AuNPs in targeted radionuclide radiotherapy.展开更多
Aluminum-ion batteries(AIBs)have been highlighted as a potential alternative to lithium-ion batteries for large-scale energy storage due to the abundant reserve,light weight,low cost,and good safety of Al.However,the ...Aluminum-ion batteries(AIBs)have been highlighted as a potential alternative to lithium-ion batteries for large-scale energy storage due to the abundant reserve,light weight,low cost,and good safety of Al.However,the development of AIBs faces challenges due to the usage of AlCl_(3)-based ionic liquid electrolytes,which are expensive,corrosive,and sensitive to humidity.Here,we develop a low-cost,non-corrosive,and air-stable hydrated eutectic electrolyte composed of aluminum perchlorate nonahydrate and methylurea(MU)ligand.Through optimizing the molar ratio to achieve the unique solvation structure,the formed Al(ClO_4)_(3)·9H_(2)O/MU hydrated deep eutectic electrolyte(AMHEE)with an average coordination number of 2.4 can facilely realize stable and reversible deposition/stripping of Al.When combining with vanadium oxide nanorods positive electrode,the Al-ion full battery delivers a high discharge capacity of 320 mAh g^(-1)with good capacity retention.The unique solvation structure with a low desolvation energy of the AMHEE enables Al^(3+)insertion/extraction during charge/discharge processes,which is evidenced by in situ synchrotron radiation X-ray diffraction.This work opens a new pathway of developing low-cost,safe,environmentally friendly and high-performance electrolytes for practical and sustainable AIBs.展开更多
The effect of tearing modes on the confinement of runaway electrons is studied in Experimental Advanced Superconducting Tokamak(EAST).The general tendency of the radial diffusion coefficient of runaway electrons(REs)D...The effect of tearing modes on the confinement of runaway electrons is studied in Experimental Advanced Superconducting Tokamak(EAST).The general tendency of the radial diffusion coefficient of runaway electrons(REs)Dr is derived based on the time response relation between the tearing modes and runaway electrons.The results indicate that,the magnetic fluctuations of tearing modes will enhance the radial diffusion of runaway electrons when the magnetic island is small.Following the increasing of the magnetic fluctuations of the tearing modes,the formed large magnetic island may weaken the radial diffusion of runaway electrons.The results can be important to understand the confinement of runaway electrons when large magnetic islands exist in the plasma.展开更多
To improve the efficiency and stability of chloride immobilization of portland cement paste,hydrated calcium aluminate cement(HCAC)prepared by wet grinding of CAC was added into portland cement paste as an additive.Th...To improve the efficiency and stability of chloride immobilization of portland cement paste,hydrated calcium aluminate cement(HCAC)prepared by wet grinding of CAC was added into portland cement paste as an additive.The immobilized chloride ratio(ICR)was evaluated,and the mechanism of chloride immobilization was researched by XRD,DTG,NMR,and MIP tests.The analysis results demonstrated that HCAC could improve the chloride immobilization capacity of portland cement paste.The mechanism was attributed to the following aspects:chemical binding capacity was enhanced via producing more Kuzel’s salt;physical adsorption capacity was reduced by decreasing the C-S-H gel;migration resistance was enhanced through refining the pore structure.展开更多
Whistler mode waves are critical emissions in magnetized plasmas that usually influence the electron dynamics in a planetary magnetosphere.In this paper,we present a unique event in the Martian magnetosphere in which ...Whistler mode waves are critical emissions in magnetized plasmas that usually influence the electron dynamics in a planetary magnetosphere.In this paper,we present a unique event in the Martian magnetosphere in which enhanced whistler mode waves(~10^(−11) V^(2)/m^(2)/Hz)with frequency of 0.1 f_(ce)-0.5 f_(ce) occurred,based on MAVEN data,exactly corresponding to a significant decrease of suprathermal electron fluxes.The diffusion coefficients are calculated by using the observed electric field wave spectra.The pitch angle diffusion coefficient can approach 10^(−2) s^(−1),which is much larger,by~100 times,than the momentum diffusion coefficient,indicating that pitch angle scattering dominates the whistler-electron resonance process.The current results can successfully explain the dropout of the suprathermal electrons in this event.This study provides direct evidence for whistler-driven electron losses in the Martian magnetosphere.展开更多
In the experiments of actively triggering plasma disruption by massive gas injection, the externally applied resonant magnetic perturbation has been used to mitigate the hazard of runaway electron(RE). Motivated by th...In the experiments of actively triggering plasma disruption by massive gas injection, the externally applied resonant magnetic perturbation has been used to mitigate the hazard of runaway electron(RE). Motivated by the experiment of multimode coupling to suppress REs on J-TEXT, some typical simulation cases with non-ideal MHD with rotation-open discussion(NIMROD) code are carried out to explore the influential mechanism of different relative phases between m/n =2/1 and m/n = 3/1 magnetic islands on the confinement of REs. Results show that the RE confinement is drastically affected by the relative phase between 2/1 and 3/1 magnetic islands. When the O point phase of 2/1 and 3/1 magnetic islands is toroidal 330°, REs can be effectively lost. The fitting curve of the remaining ratio of REs vs. the relative toroidal phase is predicted to approximate a sine-like function dependence. Further studies indicate that the phase difference between coexisting 2/1 and 3/1 islands can affect the radial transport of impurities. The loss of runaway electrons is closely related to the deposition effect of impurity. The impurity is easier to spread into the core region with smaller poloidal phase difference between the radial velocity of impurity and the impurity quantity of Ar.展开更多
基金the National Natural Science Foundation of China through grants 42241114,42274218 and 42304166the B-type Strategic Priority Program No.XDB41000000 funded by the Chinese Academy of Sciences+1 种基金the pre-research project on Civil Aerospace Technologies No.D020105 funded by China’s National Space Administration,the Guangdong Basic and Applied Research Foundation Project 2021A1515110271the Key Laboratory of Geospace Environment,Chinese Academy of Sciences,University of Science&Technology of China.
文摘Suprathermal electrons are an important population of the Martian ionosphere, either produced by photoionization of atmospheric neutrals or supplied from the Solar Wind (SW). This study is dedicated to an in-depth investigation of the pitch angle distribution of suprathermal electrons at two representative energies, 19−55 eV and 124−356 eV, using the extensive measurements made by the Solar Wind Electron Analyzer on board the Mars Atmosphere and Volatile Evolution. Throughout the study, we focus on the overall degree of anisotropy, defined as the standard deviation of suprathermal electron intensity among different directions which is normalized by the mean omni-directional intensity. The available data reveal the following characteristics: (1) In general, low energy electrons are more isotropic than high energy electrons, and dayside electrons are more isotropic than nightside electrons;(2) On the dayside, the anisotropy increases with increasing altitude at low energies but remains roughly constant at high energies, whereas on the nightside, the anisotropy decreases with increasing altitude at all energies;(3) Electrons tend to be more isotropic in strongly magnetized regions than in weakly magnetized regions, especially on the nightside. These observations indicate that the anisotropy is a useful diagnostic of suprathermal electron transport, for which the conversion between the parallel and perpendicular momenta as required by the conservation of the first adiabatic invariant, along with the atmospheric absorption at low altitudes, are two crucial factors modulating the observed variation of the anisotropy. Our analysis also highlights the different roles on the observed anisotropy exerted by suprathermal electrons of different origins.
基金the National Natural Science Foundation of China(Grant Nos.42188101,42025404,41974186,42174188,and 42204160)the National Key R&D Program of China(Grant No.2022YFF0503700)+2 种基金the B-type Strategic Priority Program of the Chinese Academy of Sciences(Grant No.XDB41000000)the Fundamental Research Funds for the Central Universities(Grant Nos.2042022kf1016 and 2042023kf1025)the China Postdoctoral Science Foundation(Grant No.2022M722447)。
文摘The energy spectrum of energetic electrons is a key factor representing the dynamic variations of Earth’s Van Allen radiation belts.Increased measurements have indicated that the commonly used Maxwellian and Kappa distributions are inadequate for capturing the realistic spectral distributions of radiation belt electrons.Here we adopt the Kappa-type(KT)distribution as the fitting function and perform a statistical analysis to investigate the radiation belt electron flux spectra observed by the Van Allen Probes.By calculating the optimal values of the key KT distribution parameters(i.e.,κandθ2)from the observed spectral shapes,we fit the radiation belt electron fluxes at different L-shells under different geomagnetic conditions.In this manner,we obtain typical values of the KT distribution parameters,which are statistically feasible for modeling the radiation belt electron flux profiles during either geomagnetically quiet or active periods.A comparison of the KT distribution model results with those using the Maxwellian or Kappa distribution reveals the advantage of the KT distribution for studying the overall properties of the radiation belt electron spectral distribution,which has important implications for deepening the current understanding of the radiation belt electron dynamics under evolving geomagnetic conditions.
基金Project supported by the National Natural Science Foundation of China(Grant No.11873013)。
文摘The formulae for parameters of a negative electron affinity semiconductor(NEAS)with large mean escape depth of secondary electrons A(NEASLD)are deduced.The methods for obtaining parameters such asλ,B,E_(pom)and the maximumδandδat 100.0 keV≥E_(po)≥1.0 keV of a NEASLD with the deduced formulae are presented(B is the probability that an internal secondary electron escapes into the vacuum upon reaching the emission surface of the emitter,δis the secondary electron yield,E_(po)is the incident energy of primary electrons and E_(pom)is the E_(po)corresponding to the maximumδ).The parameters obtained here are analyzed,and it can be concluded that several parameters of NEASLDs obtained by the methods presented here agree with those obtained by other authors.The relation between the secondary electron emission and photoemission from a NEAS with large mean escape depth of excited electrons is investigated,and it is concluded that the presented method of obtaining A is more accurate than that of obtaining the corresponding parameter for a NEAS with largeλ_(ph)(λ_(ph)being the mean escape depth of photoelectrons),and that the presented method of calculating B at E_(po)>10.0 keV is more widely applicable for obtaining the corresponding parameters for a NEAS with largeλ_(ph).
基金supported by the National Natural Science Foundation of China (Nos. 12004180, 21906083, 11975122, and 22006067)the Natural Science Foundation of Jiangsu Province (No. BK20190384)the Fundamental Research Funds for the Central Universities (Nos. NE2020006, NS2022095)。
文摘Considering the significance of low-energy electrons(LEEs;0–20 eV) in radiobiology, the sensitization potential of gold nanoparticles(AuNPs) as high-flux LEE emitters when irradiated with sub-keV electrons has been suggested. In this study, a track-structure Monte Carlo simulation code using the dielectric theory was developed to simulate the transport of electrons below 50 keV in gold. In this code, modifications, particularly for elastic scattering, are implemented for a more precise description of the LEE emission in secondary electron emission. This code was validated using the secondary electron yield and backscattering coefficient. To ensure dosimetry accuracy, we further verified the code for energy deposition calculations using the Monte Carlo toolkit, Geant4. The development of this code provides a basis for future studies regarding the role of AuNPs in targeted radionuclide radiotherapy.
基金supported by the National Natural Science Foundation of China(52274302)。
文摘Aluminum-ion batteries(AIBs)have been highlighted as a potential alternative to lithium-ion batteries for large-scale energy storage due to the abundant reserve,light weight,low cost,and good safety of Al.However,the development of AIBs faces challenges due to the usage of AlCl_(3)-based ionic liquid electrolytes,which are expensive,corrosive,and sensitive to humidity.Here,we develop a low-cost,non-corrosive,and air-stable hydrated eutectic electrolyte composed of aluminum perchlorate nonahydrate and methylurea(MU)ligand.Through optimizing the molar ratio to achieve the unique solvation structure,the formed Al(ClO_4)_(3)·9H_(2)O/MU hydrated deep eutectic electrolyte(AMHEE)with an average coordination number of 2.4 can facilely realize stable and reversible deposition/stripping of Al.When combining with vanadium oxide nanorods positive electrode,the Al-ion full battery delivers a high discharge capacity of 320 mAh g^(-1)with good capacity retention.The unique solvation structure with a low desolvation energy of the AMHEE enables Al^(3+)insertion/extraction during charge/discharge processes,which is evidenced by in situ synchrotron radiation X-ray diffraction.This work opens a new pathway of developing low-cost,safe,environmentally friendly and high-performance electrolytes for practical and sustainable AIBs.
基金Project partly supported by the Youth Innovation Promotion Association of Chinese Academy of Sciences(Grant No.2021445)the Science Foundation of Institute of Plasma Physics of Chinese Academy of Sciences(Grant No.DSJJ-2022-05)partly supported by the Comprehensive Research Facility for Fusion Technology Program of China(Grant No.2018-000052-73-01-001228).
文摘The effect of tearing modes on the confinement of runaway electrons is studied in Experimental Advanced Superconducting Tokamak(EAST).The general tendency of the radial diffusion coefficient of runaway electrons(REs)Dr is derived based on the time response relation between the tearing modes and runaway electrons.The results indicate that,the magnetic fluctuations of tearing modes will enhance the radial diffusion of runaway electrons when the magnetic island is small.Following the increasing of the magnetic fluctuations of the tearing modes,the formed large magnetic island may weaken the radial diffusion of runaway electrons.The results can be important to understand the confinement of runaway electrons when large magnetic islands exist in the plasma.
基金Funded by the National Natural Science Foundation of China(Nos.52278275 and 52202029)the Major Technical Innovation Project in Hubei Province of China(No.2021BAA060)。
文摘To improve the efficiency and stability of chloride immobilization of portland cement paste,hydrated calcium aluminate cement(HCAC)prepared by wet grinding of CAC was added into portland cement paste as an additive.The immobilized chloride ratio(ICR)was evaluated,and the mechanism of chloride immobilization was researched by XRD,DTG,NMR,and MIP tests.The analysis results demonstrated that HCAC could improve the chloride immobilization capacity of portland cement paste.The mechanism was attributed to the following aspects:chemical binding capacity was enhanced via producing more Kuzel’s salt;physical adsorption capacity was reduced by decreasing the C-S-H gel;migration resistance was enhanced through refining the pore structure.
基金the National Natural Science Foundation of China grants 42230209, 42241136, 42374199, 42204171, 42274212the Natural Science Foundation of Hunan province Grant 2021JJ20010, 2023JJ20038
文摘Whistler mode waves are critical emissions in magnetized plasmas that usually influence the electron dynamics in a planetary magnetosphere.In this paper,we present a unique event in the Martian magnetosphere in which enhanced whistler mode waves(~10^(−11) V^(2)/m^(2)/Hz)with frequency of 0.1 f_(ce)-0.5 f_(ce) occurred,based on MAVEN data,exactly corresponding to a significant decrease of suprathermal electron fluxes.The diffusion coefficients are calculated by using the observed electric field wave spectra.The pitch angle diffusion coefficient can approach 10^(−2) s^(−1),which is much larger,by~100 times,than the momentum diffusion coefficient,indicating that pitch angle scattering dominates the whistler-electron resonance process.The current results can successfully explain the dropout of the suprathermal electrons in this event.This study provides direct evidence for whistler-driven electron losses in the Martian magnetosphere.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 12175078 and 51821005)
文摘In the experiments of actively triggering plasma disruption by massive gas injection, the externally applied resonant magnetic perturbation has been used to mitigate the hazard of runaway electron(RE). Motivated by the experiment of multimode coupling to suppress REs on J-TEXT, some typical simulation cases with non-ideal MHD with rotation-open discussion(NIMROD) code are carried out to explore the influential mechanism of different relative phases between m/n =2/1 and m/n = 3/1 magnetic islands on the confinement of REs. Results show that the RE confinement is drastically affected by the relative phase between 2/1 and 3/1 magnetic islands. When the O point phase of 2/1 and 3/1 magnetic islands is toroidal 330°, REs can be effectively lost. The fitting curve of the remaining ratio of REs vs. the relative toroidal phase is predicted to approximate a sine-like function dependence. Further studies indicate that the phase difference between coexisting 2/1 and 3/1 islands can affect the radial transport of impurities. The loss of runaway electrons is closely related to the deposition effect of impurity. The impurity is easier to spread into the core region with smaller poloidal phase difference between the radial velocity of impurity and the impurity quantity of Ar.
