The simultaneous measurement of the spatial profile and spectrum of laser-accelerated protons is important for further optimization of the beam qualities and applications.We report a detailed study regarding the under...The simultaneous measurement of the spatial profile and spectrum of laser-accelerated protons is important for further optimization of the beam qualities and applications.We report a detailed study regarding the underlying physics and regular procedure of such a measurement through the radioactivation of a stack composed of aluminum,copper,and CR-39 plates as well as radiochromic films(RCFs).After being radioactivated,the copper plates are placed on imaging plates(IPs)to detect the positrons emitted by the reaction products through contact imaging.The spectrum and energy-dependent spatial profile of the protons are then obtained from the IPs and confirmed by the measured ones from the RCFs and CR-39 plates.We also discuss the detection range,influence of electrons,radiation safety,and spatial resolution of this measurement.Finally,insights regarding the extension of the current method to online measurements and dynamic proton imaging are also provided.展开更多
Laser-driven proton-induced x-ray emission(laser-PIXE) is a nuclear analysis method based on the compact laser ion accelerator. Due to the transient process of ion acceleration, the laser-PIXE signals are usually spur...Laser-driven proton-induced x-ray emission(laser-PIXE) is a nuclear analysis method based on the compact laser ion accelerator. Due to the transient process of ion acceleration, the laser-PIXE signals are usually spurted within nanoseconds and accompanied by strong electromagnetic pulses(EMP), so traditional multi-channel detectors are no longer applicable.In this work, we designed a reflective elliptical crystal spectrometer for the diagnosis of laser-PIXE. The device can detect the energy range of 1 keV–11 ke V with a high resolution. A calibration experiment was completed on the electrostatic accelerator of Peking University using samples of Al, Ti, Cu, and ceramic artifacts. The detection efficiency of the elliptical crystal spectrometer was obtained in the order of 10-9.展开更多
Many isotopes of Np,Pu,Am,and Cm around the N=126 shell still have not been produced in the laboratory.This study aims to investigate the cross sections and yields of the neutron-deficient nuclei of Np,Pu,Am,and Cm pr...Many isotopes of Np,Pu,Am,and Cm around the N=126 shell still have not been produced in the laboratory.This study aims to investigate the cross sections and yields of the neutron-deficient nuclei of Np,Pu,Am,and Cm produced in the proton-induced spallations of transuranium elements.The isospin-dependent quantum molecular dynamics(IQMD)model is applied to study the dynamical process of reaction,and the subsequent decay process is simulated by the GEMINI++model.The IQMD-GEMINI++model is applied to calculate the cross section,kinetic energy,and angular distribution of the isotopic productions around N=126.The Lindhand,Scharff,and Schiott theory is applied to calculate the energy loss of different heavy nuclei in the target material.A comparison between the data and the calculations shows that the IQMD-GEMINI++model can reproduce the production cross sections of the neutron-deficient nuclei in spallation within approximately 1.5 orders of magnitude.The maximum cross section of the undiscovered isotopes of Np,Pu,Am,and Cm is about 10-5 mb,while the kinetic energies of the productions are all less than 16 MeV.The angular distribution shows that the emission direction of production is mostly at a backward angle.The range of production in the target is within the range of 10-7to 10-5cm.This range is the effective target thickness for the online identification of undiscovered isotopes.Based on the effective thickness of the target and assuming an intensity of 120μA for the proton beam,the yields of the undiscovered neutron-deficient nuclei are calculated.Productions of the undiscovered isotopes of Np,Pu,Am,and Cm by the proton-induced spallations of transuranium elements are feasible.However,experimental techniques for online identification of neutron-deficient nuclei produced in proton-induced spallation should be developed.展开更多
Proton-induced scattering of 238U nuclei,with spheroidal deformations at beam energies above 100 MeV,is simulated using an improved quantum molecular dynamics model.The angular distribution of the deflected protons is...Proton-induced scattering of 238U nuclei,with spheroidal deformations at beam energies above 100 MeV,is simulated using an improved quantum molecular dynamics model.The angular distribution of the deflected protons is highly sensitive to the orientation of the symmetrical long axis of the target nuclei with respect to the beam direction.As a result,in reverse kinematic reactions,an orientation dichroism effect is predicted,implying that the absorption rate of the 238U beam by a proton target discerns between the parallel and perpendicular orientations of the deformed 238U nuclei.展开更多
By combing the time-dependent density functional calculations for electrons with molecular dynamics simulations for ions(TDDFT-MD)nonadiabatically in real time,we investigate the microscopic mechanism of collisions be...By combing the time-dependent density functional calculations for electrons with molecular dynamics simulations for ions(TDDFT-MD)nonadiabatically in real time,we investigate the microscopic mechanism of collisions between cytosine and low-energy protons with incident energy ranging from 150 e V to 1000 e V.To explore the effects of the collision site and the proton incident energy on irradiation processes of cytosine,two collision sites are specially considered,which are N and O both acting as the proton receptors when forming hydrogen bonds with guanine.Not only the energy loss and the scattering angle of the projectile but also the electronic and ionic degrees of freedom of the target are identified.It is found that the energy loss of proton increases linearly with the increase of the incident energy in both situations,which are14.2%and 21.1%of the incident energy respectively.However,the scattering angles show different behaviors in these two situations when the incident kinetic energy increases.When proton collides with O,the scattering angle of proton is larger and the energy lost is more,while proton captures less electrons from O.The calculated fragment mass distribution shows the high counts of the fragment mass of 1,implying the production of H+fragment ion from cytosine even for proton with the incident energy lower than keV.Furthermore,the calculated results show that N on cytosine is easier to be combined with low-energy protons to form NH bonds than O.展开更多
1 Introduction Esophageal cancer is one of the major malignant diseases in China and its etiology isstill unclear. Some reports have shown that trace elements play important roles in thecausation and development of th...1 Introduction Esophageal cancer is one of the major malignant diseases in China and its etiology isstill unclear. Some reports have shown that trace elements play important roles in thecausation and development of the cancer. Hair is generally considered to be an indicarorof the trace elements in human bodies. The contents of trace elements in human scalphair can be determined by means of proton-induced X-ray emission (PIXE), a novel tech-展开更多
More than 20 hair strands obtained from several people are analyzed by non-invasive micro-proton induced X-ray emission (PIXE) for probing calcium and sulfur distribution and pattern. The sulfur con- tent in woman’s ...More than 20 hair strands obtained from several people are analyzed by non-invasive micro-proton induced X-ray emission (PIXE) for probing calcium and sulfur distribution and pattern. The sulfur con- tent in woman’s hair along the longitudinal axis shows a monthly rhythm whereas the level of Ca is much higher in the medulla core and exhibits a daily rhythm both in male and female hair. The Ca content gradually decreases from the tip to the root position in the shedding process and more Ca can be found in black hair compared to white hair.展开更多
Dust events occurred frequently in Beijing in recent years. In this work, 120 aerosol samples were collected in two typical dust events (21-22 March and 15 May) and a non-dust period in Beijing from March to May 2001....Dust events occurred frequently in Beijing in recent years. In this work, 120 aerosol samples were collected in two typical dust events (21-22 March and 15 May) and a non-dust period in Beijing from March to May 2001. Samples were analyzed for major elemental components by the Proton Induced X-ray Emission (PIXE) method. Results show that the enrichment factors of crustal elements such as Mg, Al, and Ti had little differences between the dust period and the non-dust period in Beijing, while the enrichment factors of other elements that have a relation to anthropogenic emissions were very low during the dust period. The results derived by using multivariate factor analysis from the observation data show that the sources such as soil dust, industry, and fuel combustion were among the major contributors to the particles in Beijing.展开更多
基金supported by the Institute for Basic ScienceKorea under the project code IBS-R012-D1by the Ultrashort Quantum Beam Facility(UQBF)operation program(No.140011)through APRI,GIST。
文摘The simultaneous measurement of the spatial profile and spectrum of laser-accelerated protons is important for further optimization of the beam qualities and applications.We report a detailed study regarding the underlying physics and regular procedure of such a measurement through the radioactivation of a stack composed of aluminum,copper,and CR-39 plates as well as radiochromic films(RCFs).After being radioactivated,the copper plates are placed on imaging plates(IPs)to detect the positrons emitted by the reaction products through contact imaging.The spectrum and energy-dependent spatial profile of the protons are then obtained from the IPs and confirmed by the measured ones from the RCFs and CR-39 plates.We also discuss the detection range,influence of electrons,radiation safety,and spatial resolution of this measurement.Finally,insights regarding the extension of the current method to online measurements and dynamic proton imaging are also provided.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 11975037 and 11921006)the National Grand Instrument Project of China (Grant Nos. 2019YFF01014400 and 2019YFF01014404)。
文摘Laser-driven proton-induced x-ray emission(laser-PIXE) is a nuclear analysis method based on the compact laser ion accelerator. Due to the transient process of ion acceleration, the laser-PIXE signals are usually spurted within nanoseconds and accompanied by strong electromagnetic pulses(EMP), so traditional multi-channel detectors are no longer applicable.In this work, we designed a reflective elliptical crystal spectrometer for the diagnosis of laser-PIXE. The device can detect the energy range of 1 keV–11 ke V with a high resolution. A calibration experiment was completed on the electrostatic accelerator of Peking University using samples of Al, Ti, Cu, and ceramic artifacts. The detection efficiency of the elliptical crystal spectrometer was obtained in the order of 10-9.
基金Supported by the Open Project of Guangxi Key Laboratory of Nuclear Physics and Nuclear Technology(NLK2020-02)the National Natural Science Foundation of China(11875328,12075327)the Fundamental Research Funds for the Central Universities,Sun Yat-Sen University(22qntd1801)。
文摘Many isotopes of Np,Pu,Am,and Cm around the N=126 shell still have not been produced in the laboratory.This study aims to investigate the cross sections and yields of the neutron-deficient nuclei of Np,Pu,Am,and Cm produced in the proton-induced spallations of transuranium elements.The isospin-dependent quantum molecular dynamics(IQMD)model is applied to study the dynamical process of reaction,and the subsequent decay process is simulated by the GEMINI++model.The IQMD-GEMINI++model is applied to calculate the cross section,kinetic energy,and angular distribution of the isotopic productions around N=126.The Lindhand,Scharff,and Schiott theory is applied to calculate the energy loss of different heavy nuclei in the target material.A comparison between the data and the calculations shows that the IQMD-GEMINI++model can reproduce the production cross sections of the neutron-deficient nuclei in spallation within approximately 1.5 orders of magnitude.The maximum cross section of the undiscovered isotopes of Np,Pu,Am,and Cm is about 10-5 mb,while the kinetic energies of the productions are all less than 16 MeV.The angular distribution shows that the emission direction of production is mostly at a backward angle.The range of production in the target is within the range of 10-7to 10-5cm.This range is the effective target thickness for the online identification of undiscovered isotopes.Based on the effective thickness of the target and assuming an intensity of 120μA for the proton beam,the yields of the undiscovered neutron-deficient nuclei are calculated.Productions of the undiscovered isotopes of Np,Pu,Am,and Cm by the proton-induced spallations of transuranium elements are feasible.However,experimental techniques for online identification of neutron-deficient nuclei produced in proton-induced spallation should be developed.
基金Supported by the National Natural Science Foundation of China(11875174,11890712,11965004,11947413,U1867212,11711540016)Natural Science Foundation of Guangxi(2016GXNSFFA380001,2017GXNSFGA198001)Foundation of Guangxi innovative team and distinguished scholar in institutions of higher education。
文摘Proton-induced scattering of 238U nuclei,with spheroidal deformations at beam energies above 100 MeV,is simulated using an improved quantum molecular dynamics model.The angular distribution of the deflected protons is highly sensitive to the orientation of the symmetrical long axis of the target nuclei with respect to the beam direction.As a result,in reverse kinematic reactions,an orientation dichroism effect is predicted,implying that the absorption rate of the 238U beam by a proton target discerns between the parallel and perpendicular orientations of the deformed 238U nuclei.
基金supported by the National Natural Science Foundation of China(Grant Nos.11905160 and 11635003)the‘333’Project of Jiangsu Province,China(Grant No.BRA2020327)the Science Foundation of Wuxi Institute of Technology(Grant No.ZK201903)。
文摘By combing the time-dependent density functional calculations for electrons with molecular dynamics simulations for ions(TDDFT-MD)nonadiabatically in real time,we investigate the microscopic mechanism of collisions between cytosine and low-energy protons with incident energy ranging from 150 e V to 1000 e V.To explore the effects of the collision site and the proton incident energy on irradiation processes of cytosine,two collision sites are specially considered,which are N and O both acting as the proton receptors when forming hydrogen bonds with guanine.Not only the energy loss and the scattering angle of the projectile but also the electronic and ionic degrees of freedom of the target are identified.It is found that the energy loss of proton increases linearly with the increase of the incident energy in both situations,which are14.2%and 21.1%of the incident energy respectively.However,the scattering angles show different behaviors in these two situations when the incident kinetic energy increases.When proton collides with O,the scattering angle of proton is larger and the energy lost is more,while proton captures less electrons from O.The calculated fragment mass distribution shows the high counts of the fragment mass of 1,implying the production of H+fragment ion from cytosine even for proton with the incident energy lower than keV.Furthermore,the calculated results show that N on cytosine is easier to be combined with low-energy protons to form NH bonds than O.
基金National Natural Science Foundation of China (NSFC) partly supported by Laboratory of Nuclear Analysis Techniques. Academia Sinica (LNAT).
文摘1 Introduction Esophageal cancer is one of the major malignant diseases in China and its etiology isstill unclear. Some reports have shown that trace elements play important roles in thecausation and development of the cancer. Hair is generally considered to be an indicarorof the trace elements in human bodies. The contents of trace elements in human scalphair can be determined by means of proton-induced X-ray emission (PIXE), a novel tech-
基金Supported by the National Natural Science Foundation of China (Grant Nos. 30471652 and 10675159)and Nanyang Technological University
文摘More than 20 hair strands obtained from several people are analyzed by non-invasive micro-proton induced X-ray emission (PIXE) for probing calcium and sulfur distribution and pattern. The sulfur con- tent in woman’s hair along the longitudinal axis shows a monthly rhythm whereas the level of Ca is much higher in the medulla core and exhibits a daily rhythm both in male and female hair. The Ca content gradually decreases from the tip to the root position in the shedding process and more Ca can be found in black hair compared to white hair.
基金supported by China National Key Basic Research Science Foundation Project(G1999043400)the Hundred Talents Program(Global Environmental Change)by the Chinese Academy of Sciences+1 种基金the National Natural Science Foundation of China(No.40205017)Social Commonweal Research Project(2002DIA20012)by the Ministry of Science and Technology of China.
文摘Dust events occurred frequently in Beijing in recent years. In this work, 120 aerosol samples were collected in two typical dust events (21-22 March and 15 May) and a non-dust period in Beijing from March to May 2001. Samples were analyzed for major elemental components by the Proton Induced X-ray Emission (PIXE) method. Results show that the enrichment factors of crustal elements such as Mg, Al, and Ti had little differences between the dust period and the non-dust period in Beijing, while the enrichment factors of other elements that have a relation to anthropogenic emissions were very low during the dust period. The results derived by using multivariate factor analysis from the observation data show that the sources such as soil dust, industry, and fuel combustion were among the major contributors to the particles in Beijing.
