Beam halo-chaos in high-current accelerators has become a key concerned issue because it can cause excessive radioactivity from the accelerators therefore significantly limits their applications in industry,medicine,a...Beam halo-chaos in high-current accelerators has become a key concerned issue because it can cause excessive radioactivity from the accelerators therefore significantly limits their applications in industry,medicine,and national defense.Some general engineering methods for chaos control have been developed in recent years,but they generally are unsuccessful for beam halo-chaos suppression due to many technical constraints.Beam halo-chaos is essentially a spatiotemporal chaotic motion within a high power proton accelerator.In this paper,some efficient nonlinear control methods,including wavelet function feedback control as a special nonlinear control method,are proposed for controlling beam halo-chaos under five kinds of the initial proton beam distributions (i.e.,Kapchinsky-Vladimirsky,full Gauss,3-sigma Gauss,water-bag,and parabola distributions) respectively.Particles-in-cell simulations show that after control of beam halo-chaos,the beam halo strength factor is reduced to zero,and other statistical physical quantities of beam halo-chaos are doubly reduced.The methods we developed is very effective for suppression of proton beam halo-chaos in a periodic focusing channel of accelerator.Some potential application of the beam halo-chaos control in experiments is finally pointed out.展开更多
I study the response of a particle detector coupled to quantized massless complex scalar field in four dimensional Minkowski spacetime through nonlinear Lagrangian. I find that as in the real scalar field： the partic...I study the response of a particle detector coupled to quantized massless complex scalar field in four dimensional Minkowski spacetime through nonlinear Lagrangian. I find that as in the real scalar field： the particle detector will not respond when it is in inertial motion; If accelerated in its own frame reference, it does respond and feel the same temperature. But different from the real scalar field case, the detector＇s transition amplitude is concerned with particle-antiparticle creation, and the response of the detector is （1/α^2 ＋ ε^2）/24π^2 times of that in real scalar field, with 1/α the accelerator of the detector and e the energy gap between the detector＇s two energy level. It is due to the nonlinear property of the coupling Lagrangian. Whether the total charge of the system constructed by the particle detector and vacuum is conserved is also considered and analyzed.展开更多
The pitch-angle distribution of energetic particles is important for space physics studies on magnetic storm and particle acceleration.A‘pin-hole’imaging structure is built with the‘pin-hole’technique and a positi...The pitch-angle distribution of energetic particles is important for space physics studies on magnetic storm and particle acceleration.A‘pin-hole’imaging structure is built with the‘pin-hole’technique and a position sensitive detector,which can be used to measure the pitch angle distribution of energetic particles.To calibrate the angular response of the‘pin-hole’imaging structure,special experiment facilities are needed,such as the particle accelerator with special design.The features of this kind of particle accelerator are:1)The energy range of the outgoing particles should be mid-energy particles(tens keV to several hundred keV);2)the particle flux should be consistent in time-scale;3)the directions of the outgoing particles should be the same and 4)the particle number within the spot should be low enough.In this paper,a method to calibrate the angular response of the‘pin-hole’imaging structure by the90Sr/90Y β source with a collimator is introduced and simulated by Geant4 software.The result of the calibration with the collimated β source is in accord with the Geant4 simulations,which verifies the validity of this method.展开更多
Recent vacuum system development with an XHV condition for the particle accelerators is briefly described. The progress of selecting and treatment of the materials used in XHV systems is introduced,and the choice of t...Recent vacuum system development with an XHV condition for the particle accelerators is briefly described. The progress of selecting and treatment of the materials used in XHV systems is introduced,and the choice of the main pump for an XHV system and some new pumping method are presented.Some leak detection experiences both for the superconducting and warm vacuum systems are recommended and the status of XHV measurement and the gauge calibration are introduced.展开更多
Particle accelerators are widely used in scientific research and industry.Recently,techniques utilized for accelerator are developed rapidly in China.We briefly review the recent progress in this field and primarily f...Particle accelerators are widely used in scientific research and industry.Recently,techniques utilized for accelerator are developed rapidly in China.We briefly review the recent progress in this field and primarily focus on superconducting RF,innovative structures for particle production and acceleration and beam diagnosis.Several advanced compact user facilities are also introduced.展开更多
In the framework of the left-right twin Higgs （LRTH） model, we study the possibilities to detect the new Z＇ boson at the Tevatron and LHC. First, using pp collision data collected by the DO and CDF II detectors, we...In the framework of the left-right twin Higgs （LRTH） model, we study the possibilities to detect the new Z＇ boson at the Tevatron and LHC. First, using pp collision data collected by the DO and CDF II detectors, we find that the LRTH Z＇ boson is excluded with masses below 940 GeV. Then we search for signatures of the Z＇ boson at the LHC from the analysis of some distributions for pp --＊ It＋g- ＋ X, such as the number of events, the differential cross section of the dimuon invariant mass, the distributions of the transverse momentum and the forward-backward charge asymmetry. We do our calculation for two typical values of the LHC center of mass energy （7 and 14 TeV）. The numerical results show that, by applying convenient cuts on some of the observables, the dimuon invariant mass and final particle PT distributions can reveal the presence of the heavy neutral gauge boson Z＇ contribution in the LRTH model.展开更多
In the solar system, our Sun is Nature's most efficient particle accelerator. In large solar flares and fast coronal mass ejections(CMEs), protons and heavy ions can be accelerated to over ~GeV/nucleon. Large flar...In the solar system, our Sun is Nature's most efficient particle accelerator. In large solar flares and fast coronal mass ejections(CMEs), protons and heavy ions can be accelerated to over ~GeV/nucleon. Large flares and fast CMEs often occur together. However there are clues that different acceleration mechanisms exist in these two processes. In solar flares, particles are accelerated at magnetic reconnection sites and stochastic acceleration likely dominates. In comparison, at CME-driven shocks,diffusive shock acceleration dominates. Besides solar flares and CMEs, which are transient events, acceleration of particles has also been observed in other places in the solar system, including the solar wind termination shock, planetary bow shocks, and shocks bounding the Corotation Interaction Regions(CIRs). Understanding how particles are accelerated in these places has been a central topic of space physics. However, because observations of energetic particles are often made at spacecraft near the Earth,propagation of energetic particles in the solar wind smears out many distinct features of the acceleration process. The propagation of a charged particle in the solar wind closely relates to the turbulent electric field and magnetic field of the solar wind through particle-wave interaction. A correct interpretation of the observations therefore requires a thorough understanding of the solar wind turbulence. Conversely, one can deduce properties of the solar wind turbulence from energetic particle observations. In this article I briefly review some of the current state of knowledge of particle acceleration and transport in the inner heliosphere and discuss a few topics which may bear the key features to further understand the problem of particle acceleration and transport.展开更多
文摘Beam halo-chaos in high-current accelerators has become a key concerned issue because it can cause excessive radioactivity from the accelerators therefore significantly limits their applications in industry,medicine,and national defense.Some general engineering methods for chaos control have been developed in recent years,but they generally are unsuccessful for beam halo-chaos suppression due to many technical constraints.Beam halo-chaos is essentially a spatiotemporal chaotic motion within a high power proton accelerator.In this paper,some efficient nonlinear control methods,including wavelet function feedback control as a special nonlinear control method,are proposed for controlling beam halo-chaos under five kinds of the initial proton beam distributions (i.e.,Kapchinsky-Vladimirsky,full Gauss,3-sigma Gauss,water-bag,and parabola distributions) respectively.Particles-in-cell simulations show that after control of beam halo-chaos,the beam halo strength factor is reduced to zero,and other statistical physical quantities of beam halo-chaos are doubly reduced.The methods we developed is very effective for suppression of proton beam halo-chaos in a periodic focusing channel of accelerator.Some potential application of the beam halo-chaos control in experiments is finally pointed out.
基金Supported by National Natural Science Foundation of China under Grant No.10947016
文摘I study the response of a particle detector coupled to quantized massless complex scalar field in four dimensional Minkowski spacetime through nonlinear Lagrangian. I find that as in the real scalar field： the particle detector will not respond when it is in inertial motion; If accelerated in its own frame reference, it does respond and feel the same temperature. But different from the real scalar field case, the detector＇s transition amplitude is concerned with particle-antiparticle creation, and the response of the detector is （1/α^2 ＋ ε^2）/24π^2 times of that in real scalar field, with 1/α the accelerator of the detector and e the energy gap between the detector＇s two energy level. It is due to the nonlinear property of the coupling Lagrangian. Whether the total charge of the system constructed by the particle detector and vacuum is conserved is also considered and analyzed.
基金supported by the National Natural Science Foundation of China(Grant Nos.40704026 and 41374167)
文摘The pitch-angle distribution of energetic particles is important for space physics studies on magnetic storm and particle acceleration.A‘pin-hole’imaging structure is built with the‘pin-hole’technique and a position sensitive detector,which can be used to measure the pitch angle distribution of energetic particles.To calibrate the angular response of the‘pin-hole’imaging structure,special experiment facilities are needed,such as the particle accelerator with special design.The features of this kind of particle accelerator are:1)The energy range of the outgoing particles should be mid-energy particles(tens keV to several hundred keV);2)the particle flux should be consistent in time-scale;3)the directions of the outgoing particles should be the same and 4)the particle number within the spot should be low enough.In this paper,a method to calibrate the angular response of the‘pin-hole’imaging structure by the90Sr/90Y β source with a collimator is introduced and simulated by Geant4 software.The result of the calibration with the collimated β source is in accord with the Geant4 simulations,which verifies the validity of this method.
文摘Recent vacuum system development with an XHV condition for the particle accelerators is briefly described. The progress of selecting and treatment of the materials used in XHV systems is introduced,and the choice of the main pump for an XHV system and some new pumping method are presented.Some leak detection experiences both for the superconducting and warm vacuum systems are recommended and the status of XHV measurement and the gauge calibration are introduced.
文摘Particle accelerators are widely used in scientific research and industry.Recently,techniques utilized for accelerator are developed rapidly in China.We briefly review the recent progress in this field and primarily focus on superconducting RF,innovative structures for particle production and acceleration and beam diagnosis.Several advanced compact user facilities are also introduced.
基金supported by the National Natural Science Foundation of China(Grant No.11147193)
文摘In the framework of the left-right twin Higgs （LRTH） model, we study the possibilities to detect the new Z＇ boson at the Tevatron and LHC. First, using pp collision data collected by the DO and CDF II detectors, we find that the LRTH Z＇ boson is excluded with masses below 940 GeV. Then we search for signatures of the Z＇ boson at the LHC from the analysis of some distributions for pp --＊ It＋g- ＋ X, such as the number of events, the differential cross section of the dimuon invariant mass, the distributions of the transverse momentum and the forward-backward charge asymmetry. We do our calculation for two typical values of the LHC center of mass energy （7 and 14 TeV）. The numerical results show that, by applying convenient cuts on some of the observables, the dimuon invariant mass and final particle PT distributions can reveal the presence of the heavy neutral gauge boson Z＇ contribution in the LRTH model.
基金supported in part by a guest professorship grant from the School of Geophysics and Information Technology, China University of Geosciences (Beijing)
文摘In the solar system, our Sun is Nature's most efficient particle accelerator. In large solar flares and fast coronal mass ejections(CMEs), protons and heavy ions can be accelerated to over ~GeV/nucleon. Large flares and fast CMEs often occur together. However there are clues that different acceleration mechanisms exist in these two processes. In solar flares, particles are accelerated at magnetic reconnection sites and stochastic acceleration likely dominates. In comparison, at CME-driven shocks,diffusive shock acceleration dominates. Besides solar flares and CMEs, which are transient events, acceleration of particles has also been observed in other places in the solar system, including the solar wind termination shock, planetary bow shocks, and shocks bounding the Corotation Interaction Regions(CIRs). Understanding how particles are accelerated in these places has been a central topic of space physics. However, because observations of energetic particles are often made at spacecraft near the Earth,propagation of energetic particles in the solar wind smears out many distinct features of the acceleration process. The propagation of a charged particle in the solar wind closely relates to the turbulent electric field and magnetic field of the solar wind through particle-wave interaction. A correct interpretation of the observations therefore requires a thorough understanding of the solar wind turbulence. Conversely, one can deduce properties of the solar wind turbulence from energetic particle observations. In this article I briefly review some of the current state of knowledge of particle acceleration and transport in the inner heliosphere and discuss a few topics which may bear the key features to further understand the problem of particle acceleration and transport.
