The main “bottleneck” limiting the beam power in circular machines is caused by space charge effects that produce beam instabilities. To increase maximally the beam power of a “proton driver”, it is proposed to bu...The main “bottleneck” limiting the beam power in circular machines is caused by space charge effects that produce beam instabilities. To increase maximally the beam power of a “proton driver”, it is proposed to build a facility consisting solely of a 2.5 GeV injector linac (PI) and a 20 GeV pulsed superconducting linac (SCL). Such a facility could be constructed using the existing KEK accelerator infrastructure. The PI, based on the European Spallation Source (ESS) linac, would serve both as an injector to the SCL and a source of proton beams that could be used to copiously produce, e.g., muons and “cold” neutrons. Protons accelerated by the SCL would be transferred through the KEK Tristan ring in order to create neutrino, kaon and muon beams for fixed-target experiments. At a later stage, a 70 GeV proton synchrotron could be installed inside the Tristan ring. The SCL, comprising 1.3 GHz ILC-type rf cavities, could also accelerate polarized or unpolarized electron beams. After acceleration, electrons could be used to produce polarized positrons, or may traverse an XFEL undulator.展开更多
Magnetization,specific heat,and muon spin relaxation(μSR)experiments have been carried out on the Cr-based nitride superconductor La_(3)Cr_(10-x)N_(11),which exhibits a number of unconventional superconducting proper...Magnetization,specific heat,and muon spin relaxation(μSR)experiments have been carried out on the Cr-based nitride superconductor La_(3)Cr_(10-x)N_(11),which exhibits a number of unconventional superconducting properties.The susceptibilityχ(T)shows nearly perfect superconducting diamagnetism(4πχ(T=0)≈-1)and a remarkably high upper critical fieldμ_(0)Hc_(2)=11.2 T.The specific heat displays activated exponential behavior exp(-Δ0/kBT),together with a large and field-dependent residual Sommerfeld coefficient.Transverse-field muon spin relaxation(μSR)measurements suggest s+s-wave or p-wave pairing symmetry,ruling out single s-wave pairing.Zero-fieldμSR yields no statistically significant evidence for time reversal symmetry breaking(TRSB),and places an upper bound of 1.5(1.3)ms-1 on any TRSB-induced muon relaxation rate at T=0.Our results suggest that the unconventional superconductivity in Ln_(3)Cr_(10-x)N_(11),Ln=La and Pr,is mainly due to Cr 3d electrons and is similar in both compounds,whereas Pr 4f electrons are primarily responsible for the TRSB superconductivity observed in Pr_(3)Cr_(10-x)N_(11).展开更多
The ATF2 project is the final focus system prototype for the ILC and CLIC linear collider projects, with the purpose of reaching a 37nm vertical beam size at the interaction point. In the nanometer beam size regime, h...The ATF2 project is the final focus system prototype for the ILC and CLIC linear collider projects, with the purpose of reaching a 37nm vertical beam size at the interaction point. In the nanometer beam size regime, higher order multipoles in magnets become a crucial point for consideration. The strength and rotation angle of the ATF2 QEA magnets were reconstructed from the IHEP measurements and compared with the KEK ones to be identical. Based on the study of the skew multipoles sensitivity, we report on the analysis of the possible mitigation of the measured multipoles. A suggestion is given which will benefit the ATF2 present commissioning to reach the goal beam size, and also the reduced β optics in future.展开更多
In this proceeding,we will first outline the experimental setup and main results of the most recent hypernuclear γ-ray spectroscopy experiment (KEK-E566) performed at KEK-PS K6 beam line. The main feature and charact...In this proceeding,we will first outline the experimental setup and main results of the most recent hypernuclear γ-ray spectroscopy experiment (KEK-E566) performed at KEK-PS K6 beam line. The main feature and characteristics of this type of research will be emphasised. After that,the approved experimental proposal (E13) at J-PARC facility will be introduced briefly.展开更多
The coherent muon-to-electron transition(COMET)experiment is a leading experiment for the coherent conversion of μ^(-)N→e^(-)N using a high-intensity pulsed muon beamline,produced using innovative slow-extraction te...The coherent muon-to-electron transition(COMET)experiment is a leading experiment for the coherent conversion of μ^(-)N→e^(-)N using a high-intensity pulsed muon beamline,produced using innovative slow-extraction techniques.Therefore,it is critical to measure the muon beam characteristics.We set up a muon beam monitor(MBM),where scintillating fibers woven in a cross shape were coupled to silicon photomultipliers to measure the spatial profile and timing structure of the extracted muon beam for the COMET.The MBM detector was tested successfully with a proton beamline at the China Spallation Neutron Source and took data with good performance in the commissioning run.The development of the MBM,including its mechanical structure,electronic readout,and beam measurement results,are discussed.展开更多
Controlling Li ion transport in glasses at atomic and molecular levels is key to realizing all-solid-state batteries,a promising technology for electric vehicles.In this context,Li_(3)PS_(4)glass,a promising solid ele...Controlling Li ion transport in glasses at atomic and molecular levels is key to realizing all-solid-state batteries,a promising technology for electric vehicles.In this context,Li_(3)PS_(4)glass,a promising solid electrolyte candidate,exhibits dynamic coupling between the Li^(+)cation mobility and the PS_(4)^(3-)anion libration,which is commonly referred to as the paddlewheel effect.In addition,it exhibits a concerted cation diffusion effect(i.e.,a cation-cation interaction),which is regarded as the essence of high Li ion transport.However,the correlation between the Li^(+)ions within the glass structure can only be vaguely determined,due to the limited experimental information that can be obtained.Here,this study reports that the Li ions present in glasses can be classified by evaluating their valence oscillations via Bader analysis to topologically analyze the chemical bonds.It is found that three types of Li ions are present in Li_(3)PS_(4)glass,and that the more mobile Li ions(i.e.,the Li3-type ions)exhibit a characteristic correlation at relatively long distances of 4.0-5.0A.Furthermore,reverse Monte Carlo simulations combined with deep learning potentials that reproduce X-ray,neutron,and electron diffraction pair distribution functions showed an increase in the number of Li3-type ions for partially crystallized glass structures with improved Li ion transport properties.Our results show order within the disorder of the Li ion distribution in the glass by a topological analysis of their valences.Thus,considering the molecular vibrations in the glass during the evaluation of the Li ion valences is expected to lead to the development of new solid electrolytes.展开更多
To reduce the energy demand and operation cost for circular electron positron collider(CEPC), the high efficiency klystrons are being developed at Institute of High Energy Physics, Chinese Academy of Sciences. A 800-k...To reduce the energy demand and operation cost for circular electron positron collider(CEPC), the high efficiency klystrons are being developed at Institute of High Energy Physics, Chinese Academy of Sciences. A 800-k W continuous wave(CW) klystron operating at frequency of 650-MHz has been designed. The results of beam–wave interaction simulation with several different codes are presented. The efficiency is optimized to be 65% with a second harmonic cavity in three-dimensional(3D) particle-in-cell code CST. The effect of cavity frequency error and mismatch load on efficiency of klystron have been investigated. The design and cold test of reentrant cavities are described, which meet the requirements of RF section design. So far, the manufacturing and high-power test of the first klystron prototype have been completed.When the gun operated at DC voltage of 80 k V and current of 15.4 A, the klystron peak power reached 804 k W with output efficiency of about 65.3% at 40% duty cycle. The 1-d B bandwidth is ±0.8 MHZ. Due to the crack of ceramic window, the CW power achieved about 700 kW. The high-power test results are in good agreement with 3D simulation.展开更多
This paper presents the first phase of design, analysis, and simulation for the klystron coaxial radio frequency（RF）output window. This study is motivated by 800 kW continuous wave（CW）, 650 MHz klystrons for the f...This paper presents the first phase of design, analysis, and simulation for the klystron coaxial radio frequency（RF）output window. This study is motivated by 800 kW continuous wave（CW）, 650 MHz klystrons for the future plan of circular electron–positron collider（CEPC） project. The RF window which is used in the klystron output section has a function to separate the klystron from the inner vacuum side to the outside, and high RF power propagates through the window with small power dissipation. Therefore, the window is a key component for the high power klystron. However, it is vulnerable to the high thermal stress and multipacting, so this paper presents the window design and analysis for these problems. The microwave design has been performed by using the computer simulation technology（CST） microwave studio and the return loss of the window has been established to be less than-90 d B. The multipacting simulation of the window has been carried out using MultiPac and CST particles studio. Through the multipacting analysis, it is shown that with thin coating of TiN, the multipacting effect has been suppressed effectively on the ceramic surface. The thermal analysis is carried out using ANSYS code and the temperature of alumina ceramic is lower than 310 K with water cooling.The design result successfully meets the requirement of the CEPC 650 MHz klystron. The manufacturing and high power test plan are also described in this paper.展开更多
Radio frequency windows are developed and evaluated for a 650 MHz continuous-wave multibeam klystron.Thin-pillbox windows with alumina and beryllia disks are designed with an average RF power of CW 400 kW.Results of a...Radio frequency windows are developed and evaluated for a 650 MHz continuous-wave multibeam klystron.Thin-pillbox windows with alumina and beryllia disks are designed with an average RF power of CW 400 kW.Results of a cold test and tuning procedures are described.The final measured S11 curves under the required bandwidth are less than-32.0 and-26.9 dB for alumina and beryllia windows,respectively.The windows are tested up to CW 143 kW for traveling waves and CW 110 kW for standing waves using a solid-state amplifier as an RF power source.Multipactor simulations for windows and benchmark studies for the thermal analysis of ceramic disks are introduced.展开更多
High-entropy alloys are characteristic of extensive atomic occupational disorder on high-symmetric lattices,differing from traditional alloys.Here,we investigate the magnetic and thermal transport properties of the pr...High-entropy alloys are characteristic of extensive atomic occupational disorder on high-symmetric lattices,differing from traditional alloys.Here,we investigate the magnetic and thermal transport properties of the prototype face-centered-cubic high-entropy alloy CrMnFeCoNi by combining physical properties measurements and neutron scattering.Direct-current and alternating-current magnetizations measurements indicate a mictomagnetic behavior with coexisting antiferromagnetic and ferromagnetic interactions below room temperature and three anomalies are found at about 80,40,and 20 K,which are related to the paramagnetic to antiferromagnetic transition,the antiferromagnetic to ferromagnetic transition,and the spin freezing,respectively.The electrical and thermal conductivities are significantly reduced compared to Ni,and the temperature dependence of lattice thermal conductivity exhibits a glasslike plateau.Inelastic neutron scattering measurements suggest weak anharmonicity so that the thermal transport is expected to be dominated by the defect scattering.展开更多
Ductal carcinoma in-situ (DCIS) has been visualized by 2D XDFI (X-ray dark-field imaging) and further by a 3D X-ray CT, and the data was acquired by the X-ray optics DEI (diffraction-enhanced imaging). A newly made al...Ductal carcinoma in-situ (DCIS) has been visualized by 2D XDFI (X-ray dark-field imaging) and further by a 3D X-ray CT, and the data was acquired by the X-ray optics DEI (diffraction-enhanced imaging). A newly made algorithm was used for CT. Data of 900 projections with interval of 0.2 degrees were used. Ductus lactiferi, microcalci-fication in a 3D form have been clearly visible. The spatial resolution available was approximately 30μm.展开更多
By using a path-integral theory, the photoemission spectra of the electron-phonon (e-ph) coupled systems are calculated exactly. The spectral properties of the e-ph coupled systems based on the 1D and 2D Holstein mode...By using a path-integral theory, the photoemission spectra of the electron-phonon (e-ph) coupled systems are calculated exactly. The spectral properties of the e-ph coupled systems based on the 1D and 2D Holstein models are systematically studied under various conditions. The electronic band structure is found to be greatly modified by the multiple scattering effect of electron with phonons, so as to produce a spectral evolution from broad Gaussian at band bottom to two-headed Lorentzian near the Fermi energy. This evolution reflects a transition of electronic states from localized incoherent one to the extended coherent one near the Fermi energy. The results qualitatively agree with recent experiments of high resolution ARPES on the Be (0001) surface and Bi2Sr2CaCu2O8.展开更多
Review of X-ray dark-field imaging under development is presented. Its goal is its application to clinical diagnosis of organs that have been invisible by the ordinary techniques. In order to clinically visualize tiss...Review of X-ray dark-field imaging under development is presented. Its goal is its application to clinical diagnosis of organs that have been invisible by the ordinary techniques. In order to clinically visualize tissues in detail one needs high contrast and high spatial resolution say ～50 μm. This X-ray optics comprises a Bragg asymmetric monochro-collimator and a Bragg case or a Laue case filter with capability of analyzing angle in a parallel position. Their diffraction index is 4,4,0 and the X-ray energy 35 keV (λ= 0.0354 nm). The filter has 0.6 mm thickness in the Bragg case or 1.075 mm or 2.15 mm thickness in the Laue case. Under this condition only the refracted X-rays from object can transmit through the filter while the beam that may receive absorption and/or phase change will not. Soft tissues at human joints thus taken show high contrast images so that the DFI is promising for clinical diagnosis. Preliminary X-ray absorption images of another clinical candidates of ear bones are also shown.展开更多
A historical review is presented on the experimental and theoretical studies on Zn under high pressure. Based on our high-pressure powder x-ray diffraction experiments that have been done for nearly a decade, we descr...A historical review is presented on the experimental and theoretical studies on Zn under high pressure. Based on our high-pressure powder x-ray diffraction experiments that have been done for nearly a decade, we describe the structural change of Zn up to 126 GPa at room temperature. Although several experimental and theoretical studies indicated an anomalous change of the c/a axial ratio with pressure, we found no such an anomaly within our experimental uncertainty. Our high-pressure low-temperature experiments up to 18 GPa at 40 K also gave no evidence of the c/a anomaly. We suspect that the pressure-transmitting media played an important role in producing the anomaly. The structural anisotropy of Zn is drastically reduced at high pressures, which would be a general trend for hexagonal close-packed (hcp) metals.展开更多
The assessment of activated concrete is particularly difficult during the decommissioning of an accelerator facility.Destructive analysis by core boring is the only method of investigating the activity of concrete mat...The assessment of activated concrete is particularly difficult during the decommissioning of an accelerator facility.Destructive analysis by core boring is the only method of investigating the activity of concrete material.To address this problem,an in-situ and nondestructive analysis method was developed to determineγ-ray-emitting nuclides and their specific activities in the concrete walls and floor by using a portable germanium semiconductor detector.In this work,we examined a substitute for Ge detector to establish a simpler and more convenient method.As candidates,we focused on some scintillation type spectrometers,and the possibility of a substitute for a Ge detector was examined by both simulation and experiment.The detection limits were roughly estimated through Monte Carlo simulation for various scintillation crystals,and it was found that 1.5-inch LaBr3,CeBr3,and SrI2 could distinguish the clearance level.It was confirmed that the 1.5-inch LaBr3 could reproduce the calibration curve of the Ge detector in the experiment.The required thickness and length of the radiation shield for suppressing the background radiation during the measurement was also determined for the convenience of an actual decommissioning work.展开更多
文摘The main “bottleneck” limiting the beam power in circular machines is caused by space charge effects that produce beam instabilities. To increase maximally the beam power of a “proton driver”, it is proposed to build a facility consisting solely of a 2.5 GeV injector linac (PI) and a 20 GeV pulsed superconducting linac (SCL). Such a facility could be constructed using the existing KEK accelerator infrastructure. The PI, based on the European Spallation Source (ESS) linac, would serve both as an injector to the SCL and a source of proton beams that could be used to copiously produce, e.g., muons and “cold” neutrons. Protons accelerated by the SCL would be transferred through the KEK Tristan ring in order to create neutrino, kaon and muon beams for fixed-target experiments. At a later stage, a 70 GeV proton synchrotron could be installed inside the Tristan ring. The SCL, comprising 1.3 GHz ILC-type rf cavities, could also accelerate polarized or unpolarized electron beams. After acceleration, electrons could be used to produce polarized positrons, or may traverse an XFEL undulator.
基金funded by the National Key Research and Development Program of China(Grant No.2022YFA1402203)the National Natural Science Foundations of China(Grant No.12174065)+1 种基金the Innovation Program for Quantum Science and Technology(Grant No.2024ZD0300104)the Shanghai Municipal Science and Technology Major Project(Grant No.2019SHZDZX01).
文摘Magnetization,specific heat,and muon spin relaxation(μSR)experiments have been carried out on the Cr-based nitride superconductor La_(3)Cr_(10-x)N_(11),which exhibits a number of unconventional superconducting properties.The susceptibilityχ(T)shows nearly perfect superconducting diamagnetism(4πχ(T=0)≈-1)and a remarkably high upper critical fieldμ_(0)Hc_(2)=11.2 T.The specific heat displays activated exponential behavior exp(-Δ0/kBT),together with a large and field-dependent residual Sommerfeld coefficient.Transverse-field muon spin relaxation(μSR)measurements suggest s+s-wave or p-wave pairing symmetry,ruling out single s-wave pairing.Zero-fieldμSR yields no statistically significant evidence for time reversal symmetry breaking(TRSB),and places an upper bound of 1.5(1.3)ms-1 on any TRSB-induced muon relaxation rate at T=0.Our results suggest that the unconventional superconductivity in Ln_(3)Cr_(10-x)N_(11),Ln=La and Pr,is mainly due to Cr 3d electrons and is similar in both compounds,whereas Pr 4f electrons are primarily responsible for the TRSB superconductivity observed in Pr_(3)Cr_(10-x)N_(11).
基金Supported by Agence Nationale de la Recherche of the French Ministry of Research(Programme Blanc,Project ATF2-IN2P3-KEK,contract,ANR-06-BLAN-0027)National Natural Science Foundation of China(11175192)support in part by the USDepartment of Energy(DE-AC02-76SF00515)
文摘The ATF2 project is the final focus system prototype for the ILC and CLIC linear collider projects, with the purpose of reaching a 37nm vertical beam size at the interaction point. In the nanometer beam size regime, higher order multipoles in magnets become a crucial point for consideration. The strength and rotation angle of the ATF2 QEA magnets were reconstructed from the IHEP measurements and compared with the KEK ones to be identical. Based on the study of the skew multipoles sensitivity, we report on the analysis of the possible mitigation of the measured multipoles. A suggestion is given which will benefit the ATF2 present commissioning to reach the goal beam size, and also the reduced β optics in future.
文摘In this proceeding,we will first outline the experimental setup and main results of the most recent hypernuclear γ-ray spectroscopy experiment (KEK-E566) performed at KEK-PS K6 beam line. The main feature and characteristics of this type of research will be emphasised. After that,the approved experimental proposal (E13) at J-PARC facility will be introduced briefly.
基金supported in part by Fundamental Research Funds for the Central Universities(23xkjc017)at Sun Yat-sen Universitythe National Natural Science Foundation of China(No.12075326)JSPS KAKENHI(No.22H00139)。
文摘The coherent muon-to-electron transition(COMET)experiment is a leading experiment for the coherent conversion of μ^(-)N→e^(-)N using a high-intensity pulsed muon beamline,produced using innovative slow-extraction techniques.Therefore,it is critical to measure the muon beam characteristics.We set up a muon beam monitor(MBM),where scintillating fibers woven in a cross shape were coupled to silicon photomultipliers to measure the spatial profile and timing structure of the extracted muon beam for the COMET.The MBM detector was tested successfully with a proton beamline at the China Spallation Neutron Source and took data with good performance in the commissioning run.The development of the MBM,including its mechanical structure,electronic readout,and beam measurement results,are discussed.
基金partially supported by JSPS KAKENHI(Grant Numbers 19 K05025,19H05814,19H05815,19H05816,20H02430,21H02038,and 21H05549)
文摘Controlling Li ion transport in glasses at atomic and molecular levels is key to realizing all-solid-state batteries,a promising technology for electric vehicles.In this context,Li_(3)PS_(4)glass,a promising solid electrolyte candidate,exhibits dynamic coupling between the Li^(+)cation mobility and the PS_(4)^(3-)anion libration,which is commonly referred to as the paddlewheel effect.In addition,it exhibits a concerted cation diffusion effect(i.e.,a cation-cation interaction),which is regarded as the essence of high Li ion transport.However,the correlation between the Li^(+)ions within the glass structure can only be vaguely determined,due to the limited experimental information that can be obtained.Here,this study reports that the Li ions present in glasses can be classified by evaluating their valence oscillations via Bader analysis to topologically analyze the chemical bonds.It is found that three types of Li ions are present in Li_(3)PS_(4)glass,and that the more mobile Li ions(i.e.,the Li3-type ions)exhibit a characteristic correlation at relatively long distances of 4.0-5.0A.Furthermore,reverse Monte Carlo simulations combined with deep learning potentials that reproduce X-ray,neutron,and electron diffraction pair distribution functions showed an increase in the number of Li3-type ions for partially crystallized glass structures with improved Li ion transport properties.Our results show order within the disorder of the Li ion distribution in the glass by a topological analysis of their valences.Thus,considering the molecular vibrations in the glass during the evaluation of the Li ion valences is expected to lead to the development of new solid electrolytes.
基金Project supported by Yifang Wang’s Science Studio of the Ten Thousand Talents Project。
文摘To reduce the energy demand and operation cost for circular electron positron collider(CEPC), the high efficiency klystrons are being developed at Institute of High Energy Physics, Chinese Academy of Sciences. A 800-k W continuous wave(CW) klystron operating at frequency of 650-MHz has been designed. The results of beam–wave interaction simulation with several different codes are presented. The efficiency is optimized to be 65% with a second harmonic cavity in three-dimensional(3D) particle-in-cell code CST. The effect of cavity frequency error and mismatch load on efficiency of klystron have been investigated. The design and cold test of reentrant cavities are described, which meet the requirements of RF section design. So far, the manufacturing and high-power test of the first klystron prototype have been completed.When the gun operated at DC voltage of 80 k V and current of 15.4 A, the klystron peak power reached 804 k W with output efficiency of about 65.3% at 40% duty cycle. The 1-d B bandwidth is ±0.8 MHZ. Due to the crack of ceramic window, the CW power achieved about 700 kW. The high-power test results are in good agreement with 3D simulation.
基金Project supported by Yifang Wang’s Science Studio of the Ten Thousand Talents Project,China
文摘This paper presents the first phase of design, analysis, and simulation for the klystron coaxial radio frequency（RF）output window. This study is motivated by 800 kW continuous wave（CW）, 650 MHz klystrons for the future plan of circular electron–positron collider（CEPC） project. The RF window which is used in the klystron output section has a function to separate the klystron from the inner vacuum side to the outside, and high RF power propagates through the window with small power dissipation. Therefore, the window is a key component for the high power klystron. However, it is vulnerable to the high thermal stress and multipacting, so this paper presents the window design and analysis for these problems. The microwave design has been performed by using the computer simulation technology（CST） microwave studio and the return loss of the window has been established to be less than-90 d B. The multipacting simulation of the window has been carried out using MultiPac and CST particles studio. Through the multipacting analysis, it is shown that with thin coating of TiN, the multipacting effect has been suppressed effectively on the ceramic surface. The thermal analysis is carried out using ANSYS code and the temperature of alumina ceramic is lower than 310 K with water cooling.The design result successfully meets the requirement of the CEPC 650 MHz klystron. The manufacturing and high power test plan are also described in this paper.
文摘Radio frequency windows are developed and evaluated for a 650 MHz continuous-wave multibeam klystron.Thin-pillbox windows with alumina and beryllia disks are designed with an average RF power of CW 400 kW.Results of a cold test and tuning procedures are described.The final measured S11 curves under the required bandwidth are less than-32.0 and-26.9 dB for alumina and beryllia windows,respectively.The windows are tested up to CW 143 kW for traveling waves and CW 110 kW for standing waves using a solid-state amplifier as an RF power source.Multipactor simulations for windows and benchmark studies for the thermal analysis of ceramic disks are introduced.
基金financially supported by the Liaoning Revitalization Talents Program(No.XLYC1807122)the National Natural Science Foundation of China(Nos.11804346,12005243,and 51771197)+1 种基金the Key Research Program of Frontier Sciences of Chinese Academy of Sciences(No.ZDBS-LY-JSC002)the Ministry of Science and Technology of China(No.2020YFA0406002)
文摘High-entropy alloys are characteristic of extensive atomic occupational disorder on high-symmetric lattices,differing from traditional alloys.Here,we investigate the magnetic and thermal transport properties of the prototype face-centered-cubic high-entropy alloy CrMnFeCoNi by combining physical properties measurements and neutron scattering.Direct-current and alternating-current magnetizations measurements indicate a mictomagnetic behavior with coexisting antiferromagnetic and ferromagnetic interactions below room temperature and three anomalies are found at about 80,40,and 20 K,which are related to the paramagnetic to antiferromagnetic transition,the antiferromagnetic to ferromagnetic transition,and the spin freezing,respectively.The electrical and thermal conductivities are significantly reduced compared to Ni,and the temperature dependence of lattice thermal conductivity exhibits a glasslike plateau.Inelastic neutron scattering measurements suggest weak anharmonicity so that the thermal transport is expected to be dominated by the defect scattering.
文摘Ductal carcinoma in-situ (DCIS) has been visualized by 2D XDFI (X-ray dark-field imaging) and further by a 3D X-ray CT, and the data was acquired by the X-ray optics DEI (diffraction-enhanced imaging). A newly made algorithm was used for CT. Data of 900 projections with interval of 0.2 degrees were used. Ductus lactiferi, microcalci-fication in a 3D form have been clearly visible. The spatial resolution available was approximately 30μm.
文摘By using a path-integral theory, the photoemission spectra of the electron-phonon (e-ph) coupled systems are calculated exactly. The spectral properties of the e-ph coupled systems based on the 1D and 2D Holstein models are systematically studied under various conditions. The electronic band structure is found to be greatly modified by the multiple scattering effect of electron with phonons, so as to produce a spectral evolution from broad Gaussian at band bottom to two-headed Lorentzian near the Fermi energy. This evolution reflects a transition of electronic states from localized incoherent one to the extended coherent one near the Fermi energy. The results qualitatively agree with recent experiments of high resolution ARPES on the Be (0001) surface and Bi2Sr2CaCu2O8.
文摘Review of X-ray dark-field imaging under development is presented. Its goal is its application to clinical diagnosis of organs that have been invisible by the ordinary techniques. In order to clinically visualize tissues in detail one needs high contrast and high spatial resolution say ～50 μm. This X-ray optics comprises a Bragg asymmetric monochro-collimator and a Bragg case or a Laue case filter with capability of analyzing angle in a parallel position. Their diffraction index is 4,4,0 and the X-ray energy 35 keV (λ= 0.0354 nm). The filter has 0.6 mm thickness in the Bragg case or 1.075 mm or 2.15 mm thickness in the Laue case. Under this condition only the refracted X-rays from object can transmit through the filter while the beam that may receive absorption and/or phase change will not. Soft tissues at human joints thus taken show high contrast images so that the DFI is promising for clinical diagnosis. Preliminary X-ray absorption images of another clinical candidates of ear bones are also shown.
文摘A historical review is presented on the experimental and theoretical studies on Zn under high pressure. Based on our high-pressure powder x-ray diffraction experiments that have been done for nearly a decade, we describe the structural change of Zn up to 126 GPa at room temperature. Although several experimental and theoretical studies indicated an anomalous change of the c/a axial ratio with pressure, we found no such an anomaly within our experimental uncertainty. Our high-pressure low-temperature experiments up to 18 GPa at 40 K also gave no evidence of the c/a anomaly. We suspect that the pressure-transmitting media played an important role in producing the anomaly. The structural anisotropy of Zn is drastically reduced at high pressures, which would be a general trend for hexagonal close-packed (hcp) metals.
文摘The assessment of activated concrete is particularly difficult during the decommissioning of an accelerator facility.Destructive analysis by core boring is the only method of investigating the activity of concrete material.To address this problem,an in-situ and nondestructive analysis method was developed to determineγ-ray-emitting nuclides and their specific activities in the concrete walls and floor by using a portable germanium semiconductor detector.In this work,we examined a substitute for Ge detector to establish a simpler and more convenient method.As candidates,we focused on some scintillation type spectrometers,and the possibility of a substitute for a Ge detector was examined by both simulation and experiment.The detection limits were roughly estimated through Monte Carlo simulation for various scintillation crystals,and it was found that 1.5-inch LaBr3,CeBr3,and SrI2 could distinguish the clearance level.It was confirmed that the 1.5-inch LaBr3 could reproduce the calibration curve of the Ge detector in the experiment.The required thickness and length of the radiation shield for suppressing the background radiation during the measurement was also determined for the convenience of an actual decommissioning work.
