An experimental muon source(EMuS) will be built at the China Spallation Neutron Source(CSNS). In phase I of CSNS, it has been decided that EMuS will provide a proton beam of 5 kW and 1.6 GeV to generate muon beams. A ...An experimental muon source(EMuS) will be built at the China Spallation Neutron Source(CSNS). In phase I of CSNS, it has been decided that EMuS will provide a proton beam of 5 kW and 1.6 GeV to generate muon beams. A 128-channel muon spin rotation/relaxation/resonance(μSR) spectrometer is proposed as a prototype surface muon spectrometer in a sub-branch of EMuS. The prototype spectrometer includes a detection system, sample environment, and supporting mechanics. The current design has two rings located at the forward and backward directions of the muon spin with 64 detectors per ring. The simulation shows that the highest asymmetry of approximately 0.28 is achieved by utilizing two 10-mm-thick brass degraders. To obtain the optimal asymmetry, the two-ring structure is updated to a four-ring structure with 32 segments in each ring. An asymmetry of 0.42 is obtained through the simulation, which is higher than that of all the current μSR spectrometers in the world.展开更多
The experimental muon source on China Spallation Neutron Source(CSNS) is expected to be a high intensity(105μ+/s) surface muon source with a small beam spot of 4-cm diameter.For a practical application of this muon s...The experimental muon source on China Spallation Neutron Source(CSNS) is expected to be a high intensity(105μ+/s) surface muon source with a small beam spot of 4-cm diameter.For a practical application of this muon source,we are devoting to develop the first pulsed μSR spectrometer in China.In this paper,the performance of plastic scintillators in the μSR spectrometer is studied by Monte Carlo simulation.The processes such as positron energy deposition,scintillation photons production,light propagation and photon-electron conversion are carefully considered.According to the results,an optimal dimension of the plastic scintillator is proposed using for our future spectrometer,which has a long-strip shape with the dimension variation range of 50–60 mm length,5–8 mm height,and 10–12 mm width.Finally,we can build a spectrometer with a count rate up to 104e+/s by 100–120 forward and backward segmental detectors in total.The simulation could serve as an important guide for spectrometer construction.展开更多
The REAl(Si,Ge)(RE=rare earth)family,known to break both the inversion-and time-reversal symmetries,represents one of the most suitable platforms for investigating the interplay between correlated-electron phenomena a...The REAl(Si,Ge)(RE=rare earth)family,known to break both the inversion-and time-reversal symmetries,represents one of the most suitable platforms for investigating the interplay between correlated-electron phenomena and topologically nontrivial bands.Here,we report on systematic magnetic,transport,and muon-spin rotation and relaxation(μSR)measurements on(Nd,Sm)AlGe single crystals,which exhibit antiferromagnetic(AFM)transitions at T_(N)=6.1 and 5.9 K,respectively.In addition,NdAlGe undergoes also an incommensurate-to-commensurate ferrimagnetic transition at 4.5 K.Weak transverse-fieldμSR measurements confirm the AFM transitions,featuring a~90%magnetic volume fraction.Zero-field(ZF)μSR measurements reveal a more disordered internal field distribution in NdAlGe than in SmAlGe,reflected in a larger transverse muon-spin relaxation rateλTat T<<T_(N).This may be due to the complex magnetic structure of NdAlGe,which undergoes a series of metamagnetic transitions in an external magnetic field,while SmAlGe shows only a robust AFM order.In NdAlGe,the topological Hall effect(THE)appears between the first and the second metamagnetic transitions for H‖c,while it is absent in SmAlGe.Such THE in NdAlGe is most likely attributed to the field-induced topological spin textures.The longitudinal muon-spin relaxation rateλL,diverges near the AFM order,followed by a clear drop at T<T_N.In the magnetically ordered state,spin fluctuations are significantly stronger in NdAlGe than in SmAlGe.In general,our longitudinal-fieldμSR data indicate vigorous spin fluctuations in NdAlGe,thus providing valuable insights into the origin of THE and of the possible topological spin textures in REAl(Si,Ge)Weyl semimetals.展开更多
基金supported by the National Natural Science Foundation of China(No.11527811)the Key Program of State Key Laboratory of Particle Detection and ElectronicsA part of the work performed in the UKRI ISIS Detector Group was sponsored by the China Scholarship Council
文摘An experimental muon source(EMuS) will be built at the China Spallation Neutron Source(CSNS). In phase I of CSNS, it has been decided that EMuS will provide a proton beam of 5 kW and 1.6 GeV to generate muon beams. A 128-channel muon spin rotation/relaxation/resonance(μSR) spectrometer is proposed as a prototype surface muon spectrometer in a sub-branch of EMuS. The prototype spectrometer includes a detection system, sample environment, and supporting mechanics. The current design has two rings located at the forward and backward directions of the muon spin with 64 detectors per ring. The simulation shows that the highest asymmetry of approximately 0.28 is achieved by utilizing two 10-mm-thick brass degraders. To obtain the optimal asymmetry, the two-ring structure is updated to a four-ring structure with 32 segments in each ring. An asymmetry of 0.42 is obtained through the simulation, which is higher than that of all the current μSR spectrometers in the world.
基金Supported by National Natural Science Foundation of China(No.11075154)
文摘The experimental muon source on China Spallation Neutron Source(CSNS) is expected to be a high intensity(105μ+/s) surface muon source with a small beam spot of 4-cm diameter.For a practical application of this muon source,we are devoting to develop the first pulsed μSR spectrometer in China.In this paper,the performance of plastic scintillators in the μSR spectrometer is studied by Monte Carlo simulation.The processes such as positron energy deposition,scintillation photons production,light propagation and photon-electron conversion are carefully considered.According to the results,an optimal dimension of the plastic scintillator is proposed using for our future spectrometer,which has a long-strip shape with the dimension variation range of 50–60 mm length,5–8 mm height,and 10–12 mm width.Finally,we can build a spectrometer with a count rate up to 104e+/s by 100–120 forward and backward segmental detectors in total.The simulation could serve as an important guide for spectrometer construction.
基金supported by the National Key Research and Development Program of China Nos.2016YFA0300503the National Natural Science Foundation of China No.11774061the Shanghai Municipal Science and Technology(Major Project Grant No.2019SHZDZX01 and No.20ZR1405300).
基金supported by the Natural Science Foundation of Shanghai(Grant Nos.21ZR1420500,and 21JC1402300)the Natural Science Foundation of Chongqing(Grant No.CSTB-2022NSCQ-MSX1678)+3 种基金the National Natural Science Foundation of China(Grant Nos.12374105,and 12350710785)the Fundamental Research Funds for the Central Universitiesthe Schweizerische Nationalfonds zur F?rderung der Wissenschaftlichen Forschung(SNF)(Grant Nos.200021169455,and 200021188706)support from Paul Scherrer Institute Research Grant(Grant No.202101346)。
文摘The REAl(Si,Ge)(RE=rare earth)family,known to break both the inversion-and time-reversal symmetries,represents one of the most suitable platforms for investigating the interplay between correlated-electron phenomena and topologically nontrivial bands.Here,we report on systematic magnetic,transport,and muon-spin rotation and relaxation(μSR)measurements on(Nd,Sm)AlGe single crystals,which exhibit antiferromagnetic(AFM)transitions at T_(N)=6.1 and 5.9 K,respectively.In addition,NdAlGe undergoes also an incommensurate-to-commensurate ferrimagnetic transition at 4.5 K.Weak transverse-fieldμSR measurements confirm the AFM transitions,featuring a~90%magnetic volume fraction.Zero-field(ZF)μSR measurements reveal a more disordered internal field distribution in NdAlGe than in SmAlGe,reflected in a larger transverse muon-spin relaxation rateλTat T<<T_(N).This may be due to the complex magnetic structure of NdAlGe,which undergoes a series of metamagnetic transitions in an external magnetic field,while SmAlGe shows only a robust AFM order.In NdAlGe,the topological Hall effect(THE)appears between the first and the second metamagnetic transitions for H‖c,while it is absent in SmAlGe.Such THE in NdAlGe is most likely attributed to the field-induced topological spin textures.The longitudinal muon-spin relaxation rateλL,diverges near the AFM order,followed by a clear drop at T<T_N.In the magnetically ordered state,spin fluctuations are significantly stronger in NdAlGe than in SmAlGe.In general,our longitudinal-fieldμSR data indicate vigorous spin fluctuations in NdAlGe,thus providing valuable insights into the origin of THE and of the possible topological spin textures in REAl(Si,Ge)Weyl semimetals.
