An improved self-consistent, multi-component, and one-dimensional plasma model for simulating atmospheric pressure argon glow discharge is presented. In the model, both the plasma hydrodynamics model and chemical mode...An improved self-consistent, multi-component, and one-dimensional plasma model for simulating atmospheric pressure argon glow discharge is presented. In the model, both the plasma hydrodynamics model and chemical model are considered. The numerical simulation is carried out for parallel-plate geometry with a separation of 0.06 cm. The results show that Ar* plays a major role in the discharge, which is mainly produced by ground state excitation reaction. The electron temperature reaches its maximum in the cathode sheath but maintains a low value (0.23 eV) in bulk plasma. Elastic collision is the dominant volumetric electron energy loss in atmosphere argon glow discharge, which is negligible in low pressure argon glow discharge. The metastable step-wise ionization is the main mechanism for electron production to sustain the discharge. However, the highest contribution to electron production rate is ground state ionization reaction. The bremsstrahlung power density is related to electric voltage. With the increase of the electric voltage, the bremsstrahlung power density increases, namely, the strength of ultraviolet radiation spectrum enhances in the cathode sheath.展开更多
Inverse Bremsstrahlung absorption(IBA) of an intense laser field in plasma containing Maxwellian and nonMaxwellian(with Kappa and q-nonextensive distribution functions) electrons is studied analytically. Our results s...Inverse Bremsstrahlung absorption(IBA) of an intense laser field in plasma containing Maxwellian and nonMaxwellian(with Kappa and q-nonextensive distribution functions) electrons is studied analytically. Our results show that IBA decreases with an increase in temperature at high intensities and a decrease in plasma density for all kinds of distribution functions. Another striking result is that IBA is independent of the laser intensity at low intensity but is dependent on it when the intensity is going to rise. Also, it could be find that the behavior of the absorption as the function of laser intensity for the Kappa distribution with κ= 10 at low intensity is close to that for the Maxwellian distribution, but at high intensity it is close to that in the presence of q-nonextensive electrons with q = 0.9. These results provide insights into the inverse Bremsstrahlung absorption in the laser-plasma interactions.展开更多
This paper reports on the results of calculations using a Monte Carlo code (MCNP5) to study the properties of photons, electrons and photoneutrons obtained in the converted target and their transportations in x-ray ...This paper reports on the results of calculations using a Monte Carlo code (MCNP5) to study the properties of photons, electrons and photoneutrons obtained in the converted target and their transportations in x-ray radiography. A comparison between measurements and calculations for bremsstrahlung and photoneutrons is presented. The radiographic rule and the effect of the collimator on the image are studied with the experimental model. The results provide exact parameters for the optimal design of radiographic layout and shielding systems.展开更多
In this paper, TLD (LiF: Mg, Cu, P) is used as detector. A multi-layer absorption (MLA) model is designed. Combined with Monte-Carlo processes, a bremsstrahlung X-ray spectrum is reconstructed by an iterative met...In this paper, TLD (LiF: Mg, Cu, P) is used as detector. A multi-layer absorption (MLA) model is designed. Combined with Monte-Carlo processes, a bremsstrahlung X-ray spectrum is reconstructed by an iterative method; the reconstructed results agree with the results of simulations by the MCNP process essentially, especially in middle energy region.展开更多
In this work, characteristics of X/γ-ray radiations by intense laser interactions with high-Z solids are investigated by means of a newlydeveloped particle-in-cell (PIC) simulation code. The PIC code takes advantage ...In this work, characteristics of X/γ-ray radiations by intense laser interactions with high-Z solids are investigated by means of a newlydeveloped particle-in-cell (PIC) simulation code. The PIC code takes advantage of the recently developed ionization and collision dynamicsmodels, which make it possible to model different types of materials based on their intrinsic atomic properties. Within the simulations, bothbremsstrahlung and nonlinear Compton scatterings have been included. Different target materials and laser intensities are considered forstudying the parameter-dependent features of X/γ-ray radiations. The relative strength and angular distributions of X/γ ray productions frombremsstrahlung and nonlinear Compton scatterings are compared to each other. The threshold under which the nonlinear Compton scatteringsbecome dominant over bremsstrahlung is also outlined.展开更多
An algorithm for Monte Carlo simulation of bremsstrahlung emission by electrons based on the framework of Super MC is presented in this paper with efficient and accurate methods to sample the angular distribution and ...An algorithm for Monte Carlo simulation of bremsstrahlung emission by electrons based on the framework of Super MC is presented in this paper with efficient and accurate methods to sample the angular distribution and energy of bremsstrahlung photons. The photon energy is sampled according to scaled energy-loss differential cross sections tabulated by Seltzer and Berger. A novel hybrid model for photon angular distribution by low-and high-energy incident electrons is developed. The model uses Tsai's full form of angular distribution function with atomic form factors for high-energy incident electrons. For electrons o\500 ke V, a simple efficient and accurate analytical distribution function is developed, using adjustable parameters determined from the fitting of numerical values of the shape functions tabulated by Kissel et al. The efficiency of sampling photon energy is 80%. Our angular sampling algorithm for high-energy electron bremsstrahlung based on Tsai distribution function is very efficient(sampling efficiency*70%) in the useful photon energy range.展开更多
A novel real time fast electron bremsstrahlung (FEB) diagnostic system based on the lutetium yttrium oxyorthosilicate scintillators (LYSO) and silicon photomultipliers (SiPM) has been developed for tokamak.The diagnos...A novel real time fast electron bremsstrahlung (FEB) diagnostic system based on the lutetium yttrium oxyorthosilicate scintillators (LYSO) and silicon photomultipliers (SiPM) has been developed for tokamak.The diagnostic system is dedicated to study the FEB emission in the hard x-ray (HXR) energy range between 10 and 200 keV during the lower hybrid current drive.The system consists of a detection module and three data acquisition and processing (DAP)boards.The detection module consists of annulus LYSO-SiPM detector array and a 12-channel preamplifier module.The DAP boards upload the data to the host computer for displaying and storing through PXI bus.The time and space resolutions of the system are 10 ms and 4 cm,respectively.The experimental results can show the evolution over time and the spatial distribution of FEB.This paper presents the system performance and typical discharge results.展开更多
The quantization of circuits has received to be rather attractive in domains of solid state—molecular—and biophysics, since the quanta referred to as Q-bits play a significant role in the design of the quantum compu...The quantization of circuits has received to be rather attractive in domains of solid state—molecular—and biophysics, since the quanta referred to as Q-bits play a significant role in the design of the quantum computer and entangled structures. Quantized circuits cannot be applied without modifications, since the energy differences are not equidistant and the polarization of the excited states has to be accounted for having particular importance for the creation of virtual states. Applications of the presented theory are scanning methods in radiotherapy without multi-leaf collimators, which may be realized in tomo-scanning radiotherapy and in the keV domain, which provides a new design of CT. The problem of lateral scatter in the target and energy storage by heat production is significantly reduced by a multilayer system with focusing the impinging electrons at the walls and by a magnetic field. The verification of the Heisenberg-Euler scatter of crossing beams of 9 MV is a central problem of photon physics and can be solved by the new bremsstrahlung technique. A comparison with GEANT 4 Monte-Carlo data indicates that the presented method also works in the GeV domain, and a multi-target can improve the bremsstrahlung yield. GEANT 4 provides the spatial distribution, whereas the virtual oscillator states only show the created energy spectrum. In every case, the exploitation yield can be drastically improved by the superiority of the focused multitarget system compared to a single standard target, and the door to new technologies is opened.展开更多
The yield of bremsstrahlung (BS) from collisions of fast electrons (energy at least 6 MeV) with a Tungsten target can be significantly improved by exploitation of Tungsten wall scatter in a multi-layered target. A sim...The yield of bremsstrahlung (BS) from collisions of fast electrons (energy at least 6 MeV) with a Tungsten target can be significantly improved by exploitation of Tungsten wall scatter in a multi-layered target. A simplified version of a previously developed principle is also able to focus on small angle scattered electrons by a Tungsten wall. It is necessary that the thickness of each Tungsten layer does not exceed 0.04 mm—a thickness of 0.03 mm is suitable for accelerators in medical physics. Further focusing of electrons results from suitable magnetic fields with field strength between 0.5 Tesla and 1.2 Tesla (if the cone with multi-layered targets is rather narrow). Linear accelerators in radiation therapy only need to be focused by wall scatter without further magnetic fields (a standard case: 31 plates with 0.03 mm thickness and 1 mm distance between the plates). We considered three cases with importance in medical physics: A very small cone with an additional magnetic field for focusing (the field diameter at 90 cm depth: 6 cm), a medium cone with an optional magnetic field (field diameter at 90 cm depth: 13 cm) and a broad cone without a magnetic field (the field diameter at 90 cm depth: 30 cm). All these cases can be positioned in a carousel. Measurements have been performed in the existing carousel positioned in the plane of the flattening filter and scatter foils for electrons.展开更多
Transmission data for 12 MV bremsstrahlung beams produced by the process for continuous-pulsed 12 MV electrons coming from a linear accelerator hitting a 1.2mm thick plane tantalum target have been acquired with a com...Transmission data for 12 MV bremsstrahlung beams produced by the process for continuous-pulsed 12 MV electrons coming from a linear accelerator hitting a 1.2mm thick plane tantalum target have been acquired with a combination of iron and Telfon attenuators. Two solid state dosimeters with LiF-TLD material surrounded Telfon were used as detectors. It has been checked that the experimental system achieves reasonably narrow-beam geometry by Monte Carlo simulations. From these transmission data, the original energy photon spectrum has been reconstructed using the iterative least-squares technique and compared with the spectrum calculated with Monte Carlo code system EGSnrc. The comparison shows that the numerical technique for analysis of transmission data can represent 12 MV bremsstrahlung spectrum acceptably well. The purpose of our work is to provide an effective way to reconstruct an unknown photon spectrum with high energy component and prove the correctness of this way.展开更多
In this study,experiments were performed at bremsstrahlung end-point energies of 10-23 MeV with the beam from the MT-25 microtron using theγ-activation technique.The experimental values of relative yields were compar...In this study,experiments were performed at bremsstrahlung end-point energies of 10-23 MeV with the beam from the MT-25 microtron using theγ-activation technique.The experimental values of relative yields were compared with theoretical results obtained on the basis of TALYS with the standard parameters and the combined model of photonucleon reactions.Including isospin splitting in the combined model of photonucleon reactions allows describing experimental data on reactions with proton escape in the energy range from 10 to 23 MeV.Therefore,taking into account isospin splitting is necessary for a correct description of the decay of the giant dipole resonance.展开更多
The ^(nat)Mo(γ,xnp)^(95m,g)Nb photonuclear reaction was studied using the electron beam from the NSC KIPT linear accelerator LUE-40.The experiment was performed using the activation and off-line γ-ray spectrometric ...The ^(nat)Mo(γ,xnp)^(95m,g)Nb photonuclear reaction was studied using the electron beam from the NSC KIPT linear accelerator LUE-40.The experiment was performed using the activation and off-line γ-ray spectrometric technique.The experimental isomeric yield ratio(IR) was determined for the reaction products ^(95m,g)Nb at the bremsstrahlung end-point energy E_(γmax) range of 38-93 MeV.The obtained values of IR are in satisfactory agreement with the results of other studies and extend the range of previously known data.The theoretical values of the yields Y_(m,g)(E_(γmax)) and the IR for the isomeric pair ^(95m,g)Nb from the ^(nat)Mo(γ,xnp) reaction were calculated using the partial cross-sections σ(E) from the TALYS1.95 code for six different level density models.For the investigated range of E_(γmax),the theoretical dependence of IR on energy was confirmed-the IR smoothly increases with increasing energy.The comparison showed a noticeable difference(more than 3.85 times) in the experimental IR relative to all theoretical estimates.展开更多
The energetic bremsstrahlung photons up to 100 MeV produced in heavy ion collisions can be used as a sensitive probe for short-range correlation in atomic nuclei. The energy of the γ-rays can be measured by collectin...The energetic bremsstrahlung photons up to 100 MeV produced in heavy ion collisions can be used as a sensitive probe for short-range correlation in atomic nuclei. The energy of the γ-rays can be measured by collecting the Čerenkov light in the medium induced by the fast electrons generated in the Compton scattering or electromagnetic shower of the incident γray. Two types of detectors based on pure water and lead glass as sensitive materials were designed for this purpose. The γresponse and optical photon propagation in the detectors were simulated based on electromagnetic and optical processes in Geant4. The inherent energy resolutions of 0.022(4) + 0.51(2)∕E^(1/2)_(γ) for water and 0.0026(3) + 0.446(3)∕E^(1/2)_(γ) for lead glass were obtained. The geometry sizes of the lead glass and water were optimized to 30 cm × 30 cm × 30 cm and 60 cm × 60 cm ×120 cm, respectively, to detect high-energy γ-rays at 160 MeV. The Hough transform method was applied to reconstruct the direction of the incident γ-rays, providing the ability to experimentally distinguish the high-energy γ-rays produced in the reactions on the target from random background cosmic-ray muons.展开更多
Objective:This study is aimed to measure the Bremsstrahlung spectrum produced by ^(204)Tl in barium compounds such as BaCl_(2),BaCO_(3),Ba(NO_(3))_(2),BaSO_(4) and BaTiO_(3).It is also aimed to study the attenuation o...Objective:This study is aimed to measure the Bremsstrahlung spectrum produced by ^(204)Tl in barium compounds such as BaCl_(2),BaCO_(3),Ba(NO_(3))_(2),BaSO_(4) and BaTiO_(3).It is also aimed to study the attenuation of bremsstrahlung in the given compounds.Materials and methods:Bremsstrahlung spectrum and yield ^(204)Tl in barium compounds such as BaCl_(2),BaCO_(3),Ba(NO_(3))_(2),BaSO_(4) and BaTiO_(3) have been measured using NaI(Tl)detector and multichannel analyzer(MCA).The beta stopper technique is employed to measure the bremsstrahlung spectrum.Liden-Starfelt procedure is used to unfold the measured raw spectrum.The unfolded spectra were compared with Tseng–Pratt theory.Results:The measured spectra agree with the theory at low energy end of spectrum and some deviation(less than 10%)at higher energy end of spectrum.Attenuation of the bremsstrahlung,excited by ^(204)Tl beta emitters in the same compounds,is also studied.The measured attenuation parameter is not constant with absorber thickness and it increases with increasing Zmod of the absorber.Conclusion:The discrepancy between measured spectrum and theory increases with Zmod of the target compound and photon energy.The attenuation of bremsstrahlung may be represented as a combination of a large number of exponential terms rather than single term.展开更多
Laser-solid interactions are highly suited as a potential source of high energy X-rays for nondestructive imaging.A bright,energetic X-ray pulse can be driven from a small source,making it ideal for high resolution X-...Laser-solid interactions are highly suited as a potential source of high energy X-rays for nondestructive imaging.A bright,energetic X-ray pulse can be driven from a small source,making it ideal for high resolution X-ray radiography.By limiting the lateral dimensions of the target we are able to confine the region over which X-rays are produced,enabling imaging with enhanced resolution and contrast.Using constrained targets we demonstrate experimentally a(20±3)μm X-ray source,improving the image quality compared to unconstrained foil targets.Modelling demonstrates that a larger sheath field envelope around the perimeter of the constrained targets increases the proportion of electron current that recirculates through the target,driving a brighter source of X-rays.展开更多
In the framework of the isospin-dependent quantum molecular dynamics transport model (QMD), the effects of symmetry potential on the collision number and the neutron-proton bremsstrahlung photon in the reactions of ...In the framework of the isospin-dependent quantum molecular dynamics transport model (QMD), the effects of symmetry potential on the collision number and the neutron-proton bremsstrahlung photon in the reactions of 40Ca+40Ca, 124Sn+124Sn, 40Ca+64Zn, 40Ca+124Sn at different incident beam energies are studied. It is found that the collision number shows moderate sensitivity to the stiffness of the symmetry potential and the number of hard photons calculated with stiff symmetry potential is obviously smaller than that with soft symmetry potential. Thus, the neutron-proton bremsstrahlung photons produced in heavy-ion collisions may be a useful probe for the high-density behavior of the nuclear symmetry potential.展开更多
基金supported by the Major State Basic Research Development Program of China (973 Program) (No. 2011CB20941)Scientific Research Foundation of State Key Lab. of Power Transmission Equipment and System Security of China (No. 2007DA10512709102)+1 种基金National Natural Science Foundation of China (No. 51007096)the Fundamental Research Funds for the Central Universities of China(No. CDJZR10150001)
文摘An improved self-consistent, multi-component, and one-dimensional plasma model for simulating atmospheric pressure argon glow discharge is presented. In the model, both the plasma hydrodynamics model and chemical model are considered. The numerical simulation is carried out for parallel-plate geometry with a separation of 0.06 cm. The results show that Ar* plays a major role in the discharge, which is mainly produced by ground state excitation reaction. The electron temperature reaches its maximum in the cathode sheath but maintains a low value (0.23 eV) in bulk plasma. Elastic collision is the dominant volumetric electron energy loss in atmosphere argon glow discharge, which is negligible in low pressure argon glow discharge. The metastable step-wise ionization is the main mechanism for electron production to sustain the discharge. However, the highest contribution to electron production rate is ground state ionization reaction. The bremsstrahlung power density is related to electric voltage. With the increase of the electric voltage, the bremsstrahlung power density increases, namely, the strength of ultraviolet radiation spectrum enhances in the cathode sheath.
文摘Inverse Bremsstrahlung absorption(IBA) of an intense laser field in plasma containing Maxwellian and nonMaxwellian(with Kappa and q-nonextensive distribution functions) electrons is studied analytically. Our results show that IBA decreases with an increase in temperature at high intensities and a decrease in plasma density for all kinds of distribution functions. Another striking result is that IBA is independent of the laser intensity at low intensity but is dependent on it when the intensity is going to rise. Also, it could be find that the behavior of the absorption as the function of laser intensity for the Kappa distribution with κ= 10 at low intensity is close to that for the Maxwellian distribution, but at high intensity it is close to that in the presence of q-nonextensive electrons with q = 0.9. These results provide insights into the inverse Bremsstrahlung absorption in the laser-plasma interactions.
基金Project supported by the National Natural Science Foundation of China (Grant No.10576006)the Foundation of China Academy of Engineering Physics (Grant Nos.2007A01001 and 2009B0202020)
文摘This paper reports on the results of calculations using a Monte Carlo code (MCNP5) to study the properties of photons, electrons and photoneutrons obtained in the converted target and their transportations in x-ray radiography. A comparison between measurements and calculations for bremsstrahlung and photoneutrons is presented. The radiographic rule and the effect of the collimator on the image are studied with the experimental model. The results provide exact parameters for the optimal design of radiographic layout and shielding systems.
文摘In this paper, TLD (LiF: Mg, Cu, P) is used as detector. A multi-layer absorption (MLA) model is designed. Combined with Monte-Carlo processes, a bremsstrahlung X-ray spectrum is reconstructed by an iterative method; the reconstructed results agree with the results of simulations by the MCNP process essentially, especially in middle energy region.
基金This work was supported by Science Challenge Project(No.TZ2016005)National Natural Science Foundation of China(No.11605269,11674341 and 11675245)National Basic Research Program of China(Grant No.2013CBA01504).
文摘In this work, characteristics of X/γ-ray radiations by intense laser interactions with high-Z solids are investigated by means of a newlydeveloped particle-in-cell (PIC) simulation code. The PIC code takes advantage of the recently developed ionization and collision dynamicsmodels, which make it possible to model different types of materials based on their intrinsic atomic properties. Within the simulations, bothbremsstrahlung and nonlinear Compton scatterings have been included. Different target materials and laser intensities are considered forstudying the parameter-dependent features of X/γ-ray radiations. The relative strength and angular distributions of X/γ ray productions frombremsstrahlung and nonlinear Compton scatterings are compared to each other. The threshold under which the nonlinear Compton scatteringsbecome dominant over bremsstrahlung is also outlined.
基金supported by the National Natural Science Foundation of China(No.81101132 and 11305203)the Strategic Priority Research Program of Chinese Academy of Sciences(No.XDA03040000)the Natural Science Foundation of Anhui Province of China(No.1508085QH180)
文摘An algorithm for Monte Carlo simulation of bremsstrahlung emission by electrons based on the framework of Super MC is presented in this paper with efficient and accurate methods to sample the angular distribution and energy of bremsstrahlung photons. The photon energy is sampled according to scaled energy-loss differential cross sections tabulated by Seltzer and Berger. A novel hybrid model for photon angular distribution by low-and high-energy incident electrons is developed. The model uses Tsai's full form of angular distribution function with atomic form factors for high-energy incident electrons. For electrons o\500 ke V, a simple efficient and accurate analytical distribution function is developed, using adjustable parameters determined from the fitting of numerical values of the shape functions tabulated by Kissel et al. The efficiency of sampling photon energy is 80%. Our angular sampling algorithm for high-energy electron bremsstrahlung based on Tsai distribution function is very efficient(sampling efficiency*70%) in the useful photon energy range.
基金National Natural Science Foundation of China (No. 11575184).
文摘A novel real time fast electron bremsstrahlung (FEB) diagnostic system based on the lutetium yttrium oxyorthosilicate scintillators (LYSO) and silicon photomultipliers (SiPM) has been developed for tokamak.The diagnostic system is dedicated to study the FEB emission in the hard x-ray (HXR) energy range between 10 and 200 keV during the lower hybrid current drive.The system consists of a detection module and three data acquisition and processing (DAP)boards.The detection module consists of annulus LYSO-SiPM detector array and a 12-channel preamplifier module.The DAP boards upload the data to the host computer for displaying and storing through PXI bus.The time and space resolutions of the system are 10 ms and 4 cm,respectively.The experimental results can show the evolution over time and the spatial distribution of FEB.This paper presents the system performance and typical discharge results.
文摘The quantization of circuits has received to be rather attractive in domains of solid state—molecular—and biophysics, since the quanta referred to as Q-bits play a significant role in the design of the quantum computer and entangled structures. Quantized circuits cannot be applied without modifications, since the energy differences are not equidistant and the polarization of the excited states has to be accounted for having particular importance for the creation of virtual states. Applications of the presented theory are scanning methods in radiotherapy without multi-leaf collimators, which may be realized in tomo-scanning radiotherapy and in the keV domain, which provides a new design of CT. The problem of lateral scatter in the target and energy storage by heat production is significantly reduced by a multilayer system with focusing the impinging electrons at the walls and by a magnetic field. The verification of the Heisenberg-Euler scatter of crossing beams of 9 MV is a central problem of photon physics and can be solved by the new bremsstrahlung technique. A comparison with GEANT 4 Monte-Carlo data indicates that the presented method also works in the GeV domain, and a multi-target can improve the bremsstrahlung yield. GEANT 4 provides the spatial distribution, whereas the virtual oscillator states only show the created energy spectrum. In every case, the exploitation yield can be drastically improved by the superiority of the focused multitarget system compared to a single standard target, and the door to new technologies is opened.
文摘The yield of bremsstrahlung (BS) from collisions of fast electrons (energy at least 6 MeV) with a Tungsten target can be significantly improved by exploitation of Tungsten wall scatter in a multi-layered target. A simplified version of a previously developed principle is also able to focus on small angle scattered electrons by a Tungsten wall. It is necessary that the thickness of each Tungsten layer does not exceed 0.04 mm—a thickness of 0.03 mm is suitable for accelerators in medical physics. Further focusing of electrons results from suitable magnetic fields with field strength between 0.5 Tesla and 1.2 Tesla (if the cone with multi-layered targets is rather narrow). Linear accelerators in radiation therapy only need to be focused by wall scatter without further magnetic fields (a standard case: 31 plates with 0.03 mm thickness and 1 mm distance between the plates). We considered three cases with importance in medical physics: A very small cone with an additional magnetic field for focusing (the field diameter at 90 cm depth: 6 cm), a medium cone with an optional magnetic field (field diameter at 90 cm depth: 13 cm) and a broad cone without a magnetic field (the field diameter at 90 cm depth: 30 cm). All these cases can be positioned in a carousel. Measurements have been performed in the existing carousel positioned in the plane of the flattening filter and scatter foils for electrons.
文摘Transmission data for 12 MV bremsstrahlung beams produced by the process for continuous-pulsed 12 MV electrons coming from a linear accelerator hitting a 1.2mm thick plane tantalum target have been acquired with a combination of iron and Telfon attenuators. Two solid state dosimeters with LiF-TLD material surrounded Telfon were used as detectors. It has been checked that the experimental system achieves reasonably narrow-beam geometry by Monte Carlo simulations. From these transmission data, the original energy photon spectrum has been reconstructed using the iterative least-squares technique and compared with the spectrum calculated with Monte Carlo code system EGSnrc. The comparison shows that the numerical technique for analysis of transmission data can represent 12 MV bremsstrahlung spectrum acceptably well. The purpose of our work is to provide an effective way to reconstruct an unknown photon spectrum with high energy component and prove the correctness of this way.
文摘In this study,experiments were performed at bremsstrahlung end-point energies of 10-23 MeV with the beam from the MT-25 microtron using theγ-activation technique.The experimental values of relative yields were compared with theoretical results obtained on the basis of TALYS with the standard parameters and the combined model of photonucleon reactions.Including isospin splitting in the combined model of photonucleon reactions allows describing experimental data on reactions with proton escape in the energy range from 10 to 23 MeV.Therefore,taking into account isospin splitting is necessary for a correct description of the decay of the giant dipole resonance.
文摘The ^(nat)Mo(γ,xnp)^(95m,g)Nb photonuclear reaction was studied using the electron beam from the NSC KIPT linear accelerator LUE-40.The experiment was performed using the activation and off-line γ-ray spectrometric technique.The experimental isomeric yield ratio(IR) was determined for the reaction products ^(95m,g)Nb at the bremsstrahlung end-point energy E_(γmax) range of 38-93 MeV.The obtained values of IR are in satisfactory agreement with the results of other studies and extend the range of previously known data.The theoretical values of the yields Y_(m,g)(E_(γmax)) and the IR for the isomeric pair ^(95m,g)Nb from the ^(nat)Mo(γ,xnp) reaction were calculated using the partial cross-sections σ(E) from the TALYS1.95 code for six different level density models.For the investigated range of E_(γmax),the theoretical dependence of IR on energy was confirmed-the IR smoothly increases with increasing energy.The comparison showed a noticeable difference(more than 3.85 times) in the experimental IR relative to all theoretical estimates.
基金This work was supported by the Ministry of Science and Technology(No.2020YFE0202001)by the National Natural Science Foundation of China(Nos.11961141004 and 12205160)Tsinghua University Initiative Scientific Research Program.
文摘The energetic bremsstrahlung photons up to 100 MeV produced in heavy ion collisions can be used as a sensitive probe for short-range correlation in atomic nuclei. The energy of the γ-rays can be measured by collecting the Čerenkov light in the medium induced by the fast electrons generated in the Compton scattering or electromagnetic shower of the incident γray. Two types of detectors based on pure water and lead glass as sensitive materials were designed for this purpose. The γresponse and optical photon propagation in the detectors were simulated based on electromagnetic and optical processes in Geant4. The inherent energy resolutions of 0.022(4) + 0.51(2)∕E^(1/2)_(γ) for water and 0.0026(3) + 0.446(3)∕E^(1/2)_(γ) for lead glass were obtained. The geometry sizes of the lead glass and water were optimized to 30 cm × 30 cm × 30 cm and 60 cm × 60 cm ×120 cm, respectively, to detect high-energy γ-rays at 160 MeV. The Hough transform method was applied to reconstruct the direction of the incident γ-rays, providing the ability to experimentally distinguish the high-energy γ-rays produced in the reactions on the target from random background cosmic-ray muons.
文摘Objective:This study is aimed to measure the Bremsstrahlung spectrum produced by ^(204)Tl in barium compounds such as BaCl_(2),BaCO_(3),Ba(NO_(3))_(2),BaSO_(4) and BaTiO_(3).It is also aimed to study the attenuation of bremsstrahlung in the given compounds.Materials and methods:Bremsstrahlung spectrum and yield ^(204)Tl in barium compounds such as BaCl_(2),BaCO_(3),Ba(NO_(3))_(2),BaSO_(4) and BaTiO_(3) have been measured using NaI(Tl)detector and multichannel analyzer(MCA).The beta stopper technique is employed to measure the bremsstrahlung spectrum.Liden-Starfelt procedure is used to unfold the measured raw spectrum.The unfolded spectra were compared with Tseng–Pratt theory.Results:The measured spectra agree with the theory at low energy end of spectrum and some deviation(less than 10%)at higher energy end of spectrum.Attenuation of the bremsstrahlung,excited by ^(204)Tl beta emitters in the same compounds,is also studied.The measured attenuation parameter is not constant with absorber thickness and it increases with increasing Zmod of the absorber.Conclusion:The discrepancy between measured spectrum and theory increases with Zmod of the target compound and photon energy.The attenuation of bremsstrahlung may be represented as a combination of a large number of exponential terms rather than single term.
基金supported by EPSRC grants EP/K022415/1and EP/R006202/1the STFC IPS grant ST/P000177/1
文摘Laser-solid interactions are highly suited as a potential source of high energy X-rays for nondestructive imaging.A bright,energetic X-ray pulse can be driven from a small source,making it ideal for high resolution X-ray radiography.By limiting the lateral dimensions of the target we are able to confine the region over which X-rays are produced,enabling imaging with enhanced resolution and contrast.Using constrained targets we demonstrate experimentally a(20±3)μm X-ray source,improving the image quality compared to unconstrained foil targets.Modelling demonstrates that a larger sheath field envelope around the perimeter of the constrained targets increases the proportion of electron current that recirculates through the target,driving a brighter source of X-rays.
基金Supported by National Natural Science Foundation of China(10905041,11005157)China Scholarship Council Foundation(201208310156)the Innovation Fund and Project For Graduate Student of Shanghai(JWCXSL1202)
文摘In the framework of the isospin-dependent quantum molecular dynamics transport model (QMD), the effects of symmetry potential on the collision number and the neutron-proton bremsstrahlung photon in the reactions of 40Ca+40Ca, 124Sn+124Sn, 40Ca+64Zn, 40Ca+124Sn at different incident beam energies are studied. It is found that the collision number shows moderate sensitivity to the stiffness of the symmetry potential and the number of hard photons calculated with stiff symmetry potential is obviously smaller than that with soft symmetry potential. Thus, the neutron-proton bremsstrahlung photons produced in heavy-ion collisions may be a useful probe for the high-density behavior of the nuclear symmetry potential.