In this work,the high-energy-density plasmas(HEDP)evolved from joule-class-femtosecond-laser-irradiated nanowire-array(NWA)targets were numerically and experimentally studied.The results of particle-in-cell simulation...In this work,the high-energy-density plasmas(HEDP)evolved from joule-class-femtosecond-laser-irradiated nanowire-array(NWA)targets were numerically and experimentally studied.The results of particle-in-cell simulations indicate that ions accelerated in the sheath field around the surfaces of the nanowires are eventually confined in a plasma,contributing most to the high energy densities.The protons emitted from the front surfaces of the NWA targets provide rich information about the interactions that occur.We give the electron and ion energy densities for broad target parameter ranges.The ion energy densities from NWA targets were found to be an order of magnitude higher than those from planar targets,and the volume of the HEDP was several-fold greater.At optimal target parameters,8%of the laser energy can be converted to confined protons,and this results in ion energy densities at the GJ/cm^(3) level.In the experiments,the measured energy of the emitted protons reached 4 MeV,and the changes in energy with the NWA’s parameters were found to fit the simulation results well.Experimental measurements of neutrons from 2H(d,n)3He fusion with a yield of(24±18)×10^(6)/J from deuterated polyethylene NWA targets also confirmed these results.展开更多
In our published letter,[1]we have identified a minor error in Figs.2 and 3.Instead,we have 2111 events in these two plots with 646,249,382,and 834 events in Run 9(20.0 ton·day),Run 10(19.4 ton·day),Run 11–...In our published letter,[1]we have identified a minor error in Figs.2 and 3.Instead,we have 2111 events in these two plots with 646,249,382,and 834 events in Run 9(20.0 ton·day),Run 10(19.4 ton·day),Run 11–1(24.2 ton·day),and Run 11–2(37.1 ton·day).The mistake is due to an incorrect application of a small energy non-linearity(known as the BLS non-linearity)in making plots,but has no impact to the final results.Figures 2 and 3 are now updated in this note.展开更多
We report a search for new physics signals using the low energy electron recoil events in the complete data set from PandaX-Ⅱ,in light of the recent event excess reported by XENON1 T.The data correspond to a total ex...We report a search for new physics signals using the low energy electron recoil events in the complete data set from PandaX-Ⅱ,in light of the recent event excess reported by XENON1 T.The data correspond to a total exposure of 100.7 ton·day with liquid xenon.With robust estimates of the dominant background spectra,we perform sensitive searches on solar axions and neutrinos with enhanced magnetic moment.It is found that the axionelectron coupling gAe<4.6×10^(-12) for an axion mass less than 0.1 keV/c^(2) and the neutrino magnetic moment μv<4.9×10^(-11)μB at 90%confidence level.The observed excess from XENON1 T is within our experimental constraints.展开更多
There are a number of puzzles concerning physics on the scale of nanometers to femtometers,including the neutron lifetime,the proton charge radius,and the possible existence of the deep Dirac level.With the developmen...There are a number of puzzles concerning physics on the scale of nanometers to femtometers,including the neutron lifetime,the proton charge radius,and the possible existence of the deep Dirac level.With the development of high-intensity laser technology,lasers today can induce extremely strong electromagnetic fields.Electrons in the deep shells of atoms as well as the atomic nucleus itself can be affected by these fields.This may provide a new experimental platform for studies of physical processes on the femto-to nanometer scale,where atomic physics and nuclear physics coexist.In this paper,we review possible new opportunities for studying puzzles on the femto-to nanometer scale using highintensity lasers.展开更多
Self-interacting dark matter(SIDM)is a leading candidate proposed to solve discrepancies between predictions of the prevailing cold dark matter theory and observations of galaxies.Many SIDM models predict the existenc...Self-interacting dark matter(SIDM)is a leading candidate proposed to solve discrepancies between predictions of the prevailing cold dark matter theory and observations of galaxies.Many SIDM models predict the existence of a light force carrier that mediates strong dark matter self-interactions.If the mediator couples to the standard model particles,it could produce characteristic signals in dark matter direct detection experiments.We report searches for signals of SIDM models with a light mediator using the full dataset of the PandaX-II experiment,basing on a total exposure of 132 tonne-days.No significant excess over background is found,and our likelihood analysis leads to a strong upper limit on the dark matter-nucleon coupling strength.We further combine the PandaX-II constraints and those from observations of the light element abundances in the early universe,and show that direct detection and cosmological probes can provide complementary constraints on dark matter models with a light mediator.展开更多
We report the dark matter search results obtained using the full 132 ton·day exposure of the PandaX-II experiment,including all data from March 2016 to August 2018.No significant excess of events is identified ab...We report the dark matter search results obtained using the full 132 ton·day exposure of the PandaX-II experiment,including all data from March 2016 to August 2018.No significant excess of events is identified above the expected background.Upper limits are set on the spin-independent dark matter-nucleon interactions.The lowest 90%confidence level exclusion on the spin-independent cross section is 2.2×10−46 cm2 at a WIMP mass of 30 GeV/c2.展开更多
Precise measurement of two-neutrino double beta decay(DBD)half-life is an important step for the searches of Majorana neutrinos with neutrinoless double beta decay.We report the measurement of DBD half-life of 136xe u...Precise measurement of two-neutrino double beta decay(DBD)half-life is an important step for the searches of Majorana neutrinos with neutrinoless double beta decay.We report the measurement of DBD half-life of 136xe using the Pandax-4T dual-phase Time Projection Chamber(TPC)with 3.7-tonne natural xenon and the first 94.9-day physics data release.展开更多
The Panda X-4T experiment, a 4-ton scale dark matter direct detection experiment, is being planned at the China Jinping Underground Laboratory. In this paper we present a simulation study of the expected background in...The Panda X-4T experiment, a 4-ton scale dark matter direct detection experiment, is being planned at the China Jinping Underground Laboratory. In this paper we present a simulation study of the expected background in this experiment. In a 2.8-ton fiducial mass and the signal region between 1-10 keV electron equivalent energy, the total electron recoil background is found to be 4.9 × 10^(-5) kg^(-1) d^(-1) keV^(-1). The nuclear recoil background in the same region is 2.8 × 10^(-7) kg^(-1) d^(-1) keV^(-1). With an exposure of 5.6 ton-years, the sensitivity of Panda X-4 T could reach a minimum spin-independent dark matter-nucleon cross section of 6 × 10^(-48) cm^2 at a dark matter mass of 40 Ge V/c^2.展开更多
Jinping Underground laboratory for Nuclear Astrophysics(JUNA) will take the advantage of the ultra-low background of CJPL lab and high current accelerator based on an ECR source and a highly sensitive detector to dire...Jinping Underground laboratory for Nuclear Astrophysics(JUNA) will take the advantage of the ultra-low background of CJPL lab and high current accelerator based on an ECR source and a highly sensitive detector to directly study for the first time a number of crucial reactions occurring at their relevant stellar energies during the evolution of hydrostatic stars. In its first phase, JUNA aims at the direct measurements of^(25)Mg(p,γ)^(26)Al,^(19)F(p,α)^(16)O,^(13)C(α,n)^(16)O and ^(12)C(α,γ)^(16)O reactions. The experimental setup,which includes an accelerator system with high stability and high intensity, a detector system, and a shielding material with low background, will be established during the above research. The current progress of JUNA will be given.展开更多
In 2014, the National Natural Science Foundation of China(NSFC) approved the Jinping Underground Nuclear Astrophysics laboratory(JUNA) project, which aims at direct cross-section measurements of four key stellar nucle...In 2014, the National Natural Science Foundation of China(NSFC) approved the Jinping Underground Nuclear Astrophysics laboratory(JUNA) project, which aims at direct cross-section measurements of four key stellar nuclear reactions right down to the Gamow windows. In order to solve the observed fluorine overabundances in Asymptotic Giant Branch(AGB) stars, measuring the key ^(19)F( p,α)^(16)O reaction at effective burning energies(i.e., at Gamow window) is established as one of the scientific research sub-projects. The present paper describes this sub-project in details, including motivation, status, experimental setup, yield and background estimation, aboveground test, as well as other relevant reactions.展开更多
A novel method of initiating nuclear fusion reactions in a full plasma environment was suggested, and a proof-of-concept experiment was carried out with the D t D ! n t3 He reaction. In this new approach, two plasma j...A novel method of initiating nuclear fusion reactions in a full plasma environment was suggested, and a proof-of-concept experiment was carried out with the D t D ! n t3 He reaction. In this new approach, two plasma jets generated by high-intensity lasers collide headon-head. The center-of-mass energy of the nuclei increases accordingly, and therefore, reaction products can be significantly enhanced, especially in the sub-Coulomb barrier ranges. As a result of the fusion reaction, up to 7:6 105 neutrons had been observed. This new type of ‘‘plasma collider'' could provide an innovative tool to study nuclear reactions under astrophysical conditions.展开更多
We report the Neutrino-less Double Beta Decay(NLDBD)search results from PandaX-II dual-phase liquid xenon time projection chamber.The total live time used in this analysis is 403.1 days from June 2016 to August 2018.W...We report the Neutrino-less Double Beta Decay(NLDBD)search results from PandaX-II dual-phase liquid xenon time projection chamber.The total live time used in this analysis is 403.1 days from June 2016 to August 2018.With NLDBD-optimized event selection criteria,we obtain a fiducial mass of 219 kg of natural xenon.The accumulated xenon exposure is 242 kg·yr,or equivalently 22.2 kg·yr of 136Xe exposure.At the region around 136Xe decay Q-value of 2458 keV,the energy resolution of PandaX-II is 4.2%.We find no evidence of NLDBD in PandaX-II and establish a lower limit for decay half-life of 2.1 ×10^23 yr at the 90%confidence level,which corresponds to an effective Majorana neutrino mass mββ<(1.4-3.7) eV.This is the first NLDBD result reported from a dual-phase xenon experiment.展开更多
A pulsed fast neutron source is critical for applications of fast neutron resonance radiography and fast neutron absorption spectroscopy.However,due to the large transversal source size(of the order of mm)and long pul...A pulsed fast neutron source is critical for applications of fast neutron resonance radiography and fast neutron absorption spectroscopy.However,due to the large transversal source size(of the order of mm)and long pulse duration(of the order of ns)of traditional pulsed fast neutron sources,it is difficult to realize high-contrast neutron imaging with high spatial resolution and a fine absorption spectrum.Here,we experimentally present a micro-size ultra-short pulsed neutron source by a table-top laser-plasma wakefield electron accelerator driving a photofission reaction in a thin metal converter.A fast neutron source with source size of approximately 500μm and duration of approximately 36 ps has been driven by a tens of MeV,collimated,micro-size electron beam via a hundred TW laser facility.This micro-size ultra-short pulsed neutron source has the potential to improve the energy resolution of a fast neutron absorption spectrum dozens of times to,for example,approximately 100 eV at 1.65 MeV,which could be of benefit for high-quality fast neutron imaging and deep understanding of the theoretical model of neutron physics.展开更多
In dark matter direct detection experiments,neutron is a serious source of background,which can mimic the dark matter-nucleus scattering signals.In this paper,we present an improved evaluation of the neutron backgroun...In dark matter direct detection experiments,neutron is a serious source of background,which can mimic the dark matter-nucleus scattering signals.In this paper,we present an improved evaluation of the neutron background in the PandaX-II dark matter experiment by a novel approach.Instead of fully relying on the Monte Carlo simulation,the overall neutron background is determined from the neutron-induced high energy signals in the data.In addition,the probability of producing a dark-matter-like background per neutron is evaluated with a complete Monte Carlo generator,where the correlated emission of neutron(s)andγ(s)in the(α,n)reactions and spontaneous fissions is taken into consideration.With this method,the neutron backgrounds in the Run 9(26-ton-day)and Run 10(28-ton-day)data sets of PandaX-II are estimated to be(0.66±0.24)and(0.47±0.25)events,respectively.展开更多
We present a systematic determination of the responses of PandaX-Ⅱ,a dual phase xenon time projection chamber detector,to low energy recoils.The electron recoil(ER) and nuclear recoil(NR) responses are calibrated,res...We present a systematic determination of the responses of PandaX-Ⅱ,a dual phase xenon time projection chamber detector,to low energy recoils.The electron recoil(ER) and nuclear recoil(NR) responses are calibrated,respectively,with injected tritiated methane or 220Rn source,and with 241Am-Be neutron source,in an energy range from 1-25 keV(ER) and 4-80 keV(NR),under the two drift fields,400 and 317 V/cm.An empirical model is used to fit the light yield and charge yield for both types of recoils.The best fit models can describe the calibration data significantly.The systematic uncertainties of the fitted models are obtained via statistical comparison to the data.展开更多
Ⅰ.INTRODUCTION The direct detection of dark matter particles,especially the weakly interacting massive particles(WIMPs),is being actively carried out by a couple of experiments worldwide[1].In recent years,the PandaX...Ⅰ.INTRODUCTION The direct detection of dark matter particles,especially the weakly interacting massive particles(WIMPs),is being actively carried out by a couple of experiments worldwide[1].In recent years,the PandaX-Ⅱ experiment located in the China Jinping Underground Laboratory(CJPL)[1-3],which uses the technology of dual phase liquid xenon time projection chambers(TPCs),has pushed the limits of the cross section between WIMPs and nucleons to a new level for most of the possible WIMP masses;other experiments of the same type are also being performed[4–10].展开更多
The dark matter puzzle is one of the most important fundamental physics questions in the 21st century.There is no doubt that solving the puzzle will be a new milestone for human beings in achieving a deeper understand...The dark matter puzzle is one of the most important fundamental physics questions in the 21st century.There is no doubt that solving the puzzle will be a new milestone for human beings in achieving a deeper understanding of nature.Herein,we propose the use of the Shanghai laser electron gamma source(SLEGS)to search for dark matter candidate particles,including dark pseudoscalar particles,dark scalar particles,and dark photons.Our simulations indicate that,with some upgrading,electron facilities such as SLEGS could be competitive platforms in the search for light dark matter particles with a mass below tens of keV.展开更多
Neutron-induced nuclear recoil background is critical to dark matter searches in the PandaX-4T liquid xenon experiment.In this study,we investigate the features of neutron background in liquid xenon and evaluate its c...Neutron-induced nuclear recoil background is critical to dark matter searches in the PandaX-4T liquid xenon experiment.In this study,we investigate the features of neutron background in liquid xenon and evaluate its contribution in single scattering nuclear recoil events using three methods.The first method is fully based on Monte Carlo simulations.The last two are data-driven methods that also use multiple scattering signals and high energy signals in the data.In the PandaX-4T commissioning data with an exposure of 0.63 tonne-year,all these methods give a consistent result,i.e.,there are 1.15±0.57 neutron-induced backgrounds in the dark matter signal region within an approximated nuclear recoil energy window between 5 and 100 keV.展开更多
Astrophysical collisionless shocks are amazing phenomena in space and astrophysical plasmas, where supersonic flows generate electromagnetic fields through instabilities and particles can be accelerated to high energy...Astrophysical collisionless shocks are amazing phenomena in space and astrophysical plasmas, where supersonic flows generate electromagnetic fields through instabilities and particles can be accelerated to high energy cosmic rays. Until now, understanding these micro-processes is still a challenge despite rich astrophysical observation data have been obtained. Laboratory astrophysics, a new route to study the astrophysics, allows us to investigate them at similar extreme physical conditions in laboratory. Here we will review the recent progress of the collisionless shock experiments performed at SG-Ⅱ laser facility in China. The evolution of the electrostatic shocks and Weibel-type/filamentation instabilities are observed. Inspired by the configurations of the counter-streaming plasma flows, we also carry out a novel plasma collider to generate energetic neutrons relevant to the astrophysical nuclear reactions.展开更多
Over one hundred years have passed since the nuclear isomer was first introduced,in analogy with chemical isomers to describe long-lived excited nuclear states.In 1921,Otto Hahn discovered the first nuclear isomerPa.A...Over one hundred years have passed since the nuclear isomer was first introduced,in analogy with chemical isomers to describe long-lived excited nuclear states.In 1921,Otto Hahn discovered the first nuclear isomerPa.After that,step by step,it was realized that different types of nuclear isomers exist,including spin isomer,K isomer,seniority isomers,and"shape and fission"isomer[1,2].展开更多
基金This work was supported by the NSFC innovation group project(Grant No.11921006)the National Grand Instrument Project(Grant No.2019YFF01014402)+1 种基金the United States Department of Energy(Grant No.DE-FG03-93ER40773)the NNSA(Grant No.DENA0003841)(CENTAUR).The PIC simulations were carried out using the High-Performance Computing Platform of Peking University。
文摘In this work,the high-energy-density plasmas(HEDP)evolved from joule-class-femtosecond-laser-irradiated nanowire-array(NWA)targets were numerically and experimentally studied.The results of particle-in-cell simulations indicate that ions accelerated in the sheath field around the surfaces of the nanowires are eventually confined in a plasma,contributing most to the high energy densities.The protons emitted from the front surfaces of the NWA targets provide rich information about the interactions that occur.We give the electron and ion energy densities for broad target parameter ranges.The ion energy densities from NWA targets were found to be an order of magnitude higher than those from planar targets,and the volume of the HEDP was several-fold greater.At optimal target parameters,8%of the laser energy can be converted to confined protons,and this results in ion energy densities at the GJ/cm^(3) level.In the experiments,the measured energy of the emitted protons reached 4 MeV,and the changes in energy with the NWA’s parameters were found to fit the simulation results well.Experimental measurements of neutrons from 2H(d,n)3He fusion with a yield of(24±18)×10^(6)/J from deuterated polyethylene NWA targets also confirmed these results.
文摘In our published letter,[1]we have identified a minor error in Figs.2 and 3.Instead,we have 2111 events in these two plots with 646,249,382,and 834 events in Run 9(20.0 ton·day),Run 10(19.4 ton·day),Run 11–1(24.2 ton·day),and Run 11–2(37.1 ton·day).The mistake is due to an incorrect application of a small energy non-linearity(known as the BLS non-linearity)in making plots,but has no impact to the final results.Figures 2 and 3 are now updated in this note.
基金Supported in part by the National Key R&D Program of China(Grant No.2016YFA0400301)the National Natural Science Foundation of China(Grant Nos.11525522,11775141,and 11755001)+5 种基金the Double First Class Plan of the Shanghai Jiao Tong University,the China Postdoctoral Science Foundation(Grant No.2018M640036)the Office of Science and Technology,Shanghai Municipal Government(Grant Nos.11DZ2260700,16DZ2260200,and 18JC1410200)the Key Laboratory for Particle Physics,Astrophysics and Cosmology,Ministry of Education,for important supportsponsorship from the Chinese Academy of Sciences Center for Excellence in Particle Physics(CCEPP)the Hongwen Foundation in Hong Kongthe Tencent Foundation in China。
文摘We report a search for new physics signals using the low energy electron recoil events in the complete data set from PandaX-Ⅱ,in light of the recent event excess reported by XENON1 T.The data correspond to a total exposure of 100.7 ton·day with liquid xenon.With robust estimates of the dominant background spectra,we perform sensitive searches on solar axions and neutrinos with enhanced magnetic moment.It is found that the axionelectron coupling gAe<4.6×10^(-12) for an axion mass less than 0.1 keV/c^(2) and the neutrino magnetic moment μv<4.9×10^(-11)μB at 90%confidence level.The observed excess from XENON1 T is within our experimental constraints.
基金This work is supported by the National Nature Science Foundation of China(Grant No.11875191)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB16).
文摘There are a number of puzzles concerning physics on the scale of nanometers to femtometers,including the neutron lifetime,the proton charge radius,and the possible existence of the deep Dirac level.With the development of high-intensity laser technology,lasers today can induce extremely strong electromagnetic fields.Electrons in the deep shells of atoms as well as the atomic nucleus itself can be affected by these fields.This may provide a new experimental platform for studies of physical processes on the femto-to nanometer scale,where atomic physics and nuclear physics coexist.In this paper,we review possible new opportunities for studying puzzles on the femto-to nanometer scale using highintensity lasers.
基金This work was supported by a Double Top-class grant from Shanghai Jiao Tong University,and the National Natural Science Foundation of China(Grant No.11875190)Department of Energy(Grant No.de-sc0008541)the John Templeton Foundation(Grant No.#61884).
文摘Self-interacting dark matter(SIDM)is a leading candidate proposed to solve discrepancies between predictions of the prevailing cold dark matter theory and observations of galaxies.Many SIDM models predict the existence of a light force carrier that mediates strong dark matter self-interactions.If the mediator couples to the standard model particles,it could produce characteristic signals in dark matter direct detection experiments.We report searches for signals of SIDM models with a light mediator using the full dataset of the PandaX-II experiment,basing on a total exposure of 132 tonne-days.No significant excess over background is found,and our likelihood analysis leads to a strong upper limit on the dark matter-nucleon coupling strength.We further combine the PandaX-II constraints and those from observations of the light element abundances in the early universe,and show that direct detection and cosmological probes can provide complementary constraints on dark matter models with a light mediator.
基金Supported by a Double Top-class grant from Shanghai Jiao Tong University,grants from National Science Foundation of China(11435008,11525522,11775141,11755001)a grant from the Ministry of Science and Technology of China(2016YFA0400301)the Office of Science and Technology,Shanghai Municipal Government(11DZ2260700,16DZ2260200,18JC1410200)。
文摘We report the dark matter search results obtained using the full 132 ton·day exposure of the PandaX-II experiment,including all data from March 2016 to August 2018.No significant excess of events is identified above the expected background.Upper limits are set on the spin-independent dark matter-nucleon interactions.The lowest 90%confidence level exclusion on the spin-independent cross section is 2.2×10−46 cm2 at a WIMP mass of 30 GeV/c2.
基金This project is supported in part by grants from the Ministry of Science and Technology of China(No.2016YFA0400301 and 2016YFA0400302)grants from National Science Foundation of China(Nos.12090061,12090062,12005131,11905128,and 11925502)by Office of Science and Technology,Shanghai Municipal Government(grant No.18JC1410200).
文摘Precise measurement of two-neutrino double beta decay(DBD)half-life is an important step for the searches of Majorana neutrinos with neutrinoless double beta decay.We report the measurement of DBD half-life of 136xe using the Pandax-4T dual-phase Time Projection Chamber(TPC)with 3.7-tonne natural xenon and the first 94.9-day physics data release.
基金supported by a 985-Ⅲ grant from Shanghai Jiao Tong University,the National Natural Science Foundation of China(Grant Nos.11435008,11455001,11505112,11525522,11775141,and 11755001)the Ministry of Science and Technology of China(Grant No.2016YFA0400301)+2 种基金the Office of Science and Technology,Shanghai Municipal Government(Grant Nos.11DZ2260700,and 16DZ2260200)the Key Laboratory for Particle Physics,Astrophysics and Cosmology,Ministry of Educationsupported in part by the Chinese Academy of Sciences Center for Excellence in Particle Physics(CCEPP)and Hongwen Foundation in Hong Kong
文摘The Panda X-4T experiment, a 4-ton scale dark matter direct detection experiment, is being planned at the China Jinping Underground Laboratory. In this paper we present a simulation study of the expected background in this experiment. In a 2.8-ton fiducial mass and the signal region between 1-10 keV electron equivalent energy, the total electron recoil background is found to be 4.9 × 10^(-5) kg^(-1) d^(-1) keV^(-1). The nuclear recoil background in the same region is 2.8 × 10^(-7) kg^(-1) d^(-1) keV^(-1). With an exposure of 5.6 ton-years, the sensitivity of Panda X-4 T could reach a minimum spin-independent dark matter-nucleon cross section of 6 × 10^(-48) cm^2 at a dark matter mass of 40 Ge V/c^2.
基金supported by the National Natural Science Foundation of China(Grant Nos.11490560 and 11321064)the National Basic Research Program of China(Grant No.2013CB834406)
文摘Jinping Underground laboratory for Nuclear Astrophysics(JUNA) will take the advantage of the ultra-low background of CJPL lab and high current accelerator based on an ECR source and a highly sensitive detector to directly study for the first time a number of crucial reactions occurring at their relevant stellar energies during the evolution of hydrostatic stars. In its first phase, JUNA aims at the direct measurements of^(25)Mg(p,γ)^(26)Al,^(19)F(p,α)^(16)O,^(13)C(α,n)^(16)O and ^(12)C(α,γ)^(16)O reactions. The experimental setup,which includes an accelerator system with high stability and high intensity, a detector system, and a shielding material with low background, will be established during the above research. The current progress of JUNA will be given.
基金supported by the National Natural Science Foundation of China(Grant Nos.114905621149056011135005 and 11321064)
文摘In 2014, the National Natural Science Foundation of China(NSFC) approved the Jinping Underground Nuclear Astrophysics laboratory(JUNA) project, which aims at direct cross-section measurements of four key stellar nuclear reactions right down to the Gamow windows. In order to solve the observed fluorine overabundances in Asymptotic Giant Branch(AGB) stars, measuring the key ^(19)F( p,α)^(16)O reaction at effective burning energies(i.e., at Gamow window) is established as one of the scientific research sub-projects. The present paper describes this sub-project in details, including motivation, status, experimental setup, yield and background estimation, aboveground test, as well as other relevant reactions.
基金supported by the National Basic Research Program of China(2013CBA01501 and2013CB834401)the National Natural Science Foundation of China(11135012 and 11135005)+1 种基金the Doctoral Fund of Ministry of Education of China(20120073110065)Shanghai Municipal Science and Technology Commission(11DZ2260700)for the supports
文摘A novel method of initiating nuclear fusion reactions in a full plasma environment was suggested, and a proof-of-concept experiment was carried out with the D t D ! n t3 He reaction. In this new approach, two plasma jets generated by high-intensity lasers collide headon-head. The center-of-mass energy of the nuclei increases accordingly, and therefore, reaction products can be significantly enhanced, especially in the sub-Coulomb barrier ranges. As a result of the fusion reaction, up to 7:6 105 neutrons had been observed. This new type of ‘‘plasma collider'' could provide an innovative tool to study nuclear reactions under astrophysical conditions.
基金Supported by grants from the Ministry of Science and Technology of China(2016YFA0400301,2016YFA0400302)a Double Top-class grant from Shanghai Jiao Tong University,grants from National Science Foundation of China(11435008,11505112,11525522,11775142,11755001)+3 种基金grants from the Office of Science and Technology,Shanghai Municipal Government(11DZ2260700,16DZ2260200,18JC1410200)the support from the Key Laboratory for Particle Physics,Astrophysics and Cosmology,Ministry of Educationsupported in part by the Chinese Academy of Sciences Center for Excellence in Particle Physics(CCEPP)Hongwen Foundation in Hong Kong
文摘We report the Neutrino-less Double Beta Decay(NLDBD)search results from PandaX-II dual-phase liquid xenon time projection chamber.The total live time used in this analysis is 403.1 days from June 2016 to August 2018.With NLDBD-optimized event selection criteria,we obtain a fiducial mass of 219 kg of natural xenon.The accumulated xenon exposure is 242 kg·yr,or equivalently 22.2 kg·yr of 136Xe exposure.At the region around 136Xe decay Q-value of 2458 keV,the energy resolution of PandaX-II is 4.2%.We find no evidence of NLDBD in PandaX-II and establish a lower limit for decay half-life of 2.1 ×10^23 yr at the 90%confidence level,which corresponds to an effective Majorana neutrino mass mββ<(1.4-3.7) eV.This is the first NLDBD result reported from a dual-phase xenon experiment.
基金supported by the Science Challenge Project(No.TZ2018005)the National Natural Science Foundation of China(Nos.11875191,11991073,11890710,and 11721404)+2 种基金the Strategic Priority Research Program of the CAS(Nos.XDB1602 and XDA01020304)the Key Program of CAS(Nos.XDA01020304 and XDB17030500)the National Key R&D Program of China(No.2017YFA0403301)。
文摘A pulsed fast neutron source is critical for applications of fast neutron resonance radiography and fast neutron absorption spectroscopy.However,due to the large transversal source size(of the order of mm)and long pulse duration(of the order of ns)of traditional pulsed fast neutron sources,it is difficult to realize high-contrast neutron imaging with high spatial resolution and a fine absorption spectrum.Here,we experimentally present a micro-size ultra-short pulsed neutron source by a table-top laser-plasma wakefield electron accelerator driving a photofission reaction in a thin metal converter.A fast neutron source with source size of approximately 500μm and duration of approximately 36 ps has been driven by a tens of MeV,collimated,micro-size electron beam via a hundred TW laser facility.This micro-size ultra-short pulsed neutron source has the potential to improve the energy resolution of a fast neutron absorption spectrum dozens of times to,for example,approximately 100 eV at 1.65 MeV,which could be of benefit for high-quality fast neutron imaging and deep understanding of the theoretical model of neutron physics.
基金supported by the Double Top-class of Shanghai Jiao Tong University,the National Natural Science Foundation of China(Grant Nos.11435008,11505112,11525522,11775141,and 11755001)the Ministry of Science and Technology of China(Grant No.2016YFA0400301)+4 种基金the Office of Science and Technology,Shanghai Municipal Government(Grant Nos.11DZ2260700,16DZ2260200,and 18JC1410200)the Key Laboratory for Particle Physics,Astrophysics and Cosmology,Ministry of Education,for important supportthe Chinese Academy of Sciences Center for Excellence in Particle Physics(CCEPP)Hongwen Foundation in Hong Kongwe thank the CJPL administration and the Yalong River Hydropower Development Company Ltd.for indispensable logistical support and other help.
文摘In dark matter direct detection experiments,neutron is a serious source of background,which can mimic the dark matter-nucleus scattering signals.In this paper,we present an improved evaluation of the neutron background in the PandaX-II dark matter experiment by a novel approach.Instead of fully relying on the Monte Carlo simulation,the overall neutron background is determined from the neutron-induced high energy signals in the data.In addition,the probability of producing a dark-matter-like background per neutron is evaluated with a complete Monte Carlo generator,where the correlated emission of neutron(s)andγ(s)in the(α,n)reactions and spontaneous fissions is taken into consideration.With this method,the neutron backgrounds in the Run 9(26-ton-day)and Run 10(28-ton-day)data sets of PandaX-II are estimated to be(0.66±0.24)and(0.47±0.25)events,respectively.
基金Supported by a grant from the Ministry of Science and Technology of China(2016YFA0400301)National Science Foundation of China(12090060,11525522,11775141,11755001)Office of Science and Technology,Shanghai Municipal Government(18JC1410200)。
文摘We present a systematic determination of the responses of PandaX-Ⅱ,a dual phase xenon time projection chamber detector,to low energy recoils.The electron recoil(ER) and nuclear recoil(NR) responses are calibrated,respectively,with injected tritiated methane or 220Rn source,and with 241Am-Be neutron source,in an energy range from 1-25 keV(ER) and 4-80 keV(NR),under the two drift fields,400 and 317 V/cm.An empirical model is used to fit the light yield and charge yield for both types of recoils.The best fit models can describe the calibration data significantly.The systematic uncertainties of the fitted models are obtained via statistical comparison to the data.
基金Supported in part by a grant from the Ministry of Science and Technology of China(2016YFA0400301)National Science Foundation of China(12090060,12005131,11905128,11925502,11775141)Office of Science and Technology,Shanghai Municipal Government(18JC1410200)。
文摘Ⅰ.INTRODUCTION The direct detection of dark matter particles,especially the weakly interacting massive particles(WIMPs),is being actively carried out by a couple of experiments worldwide[1].In recent years,the PandaX-Ⅱ experiment located in the China Jinping Underground Laboratory(CJPL)[1-3],which uses the technology of dual phase liquid xenon time projection chambers(TPCs),has pushed the limits of the cross section between WIMPs and nucleons to a new level for most of the possible WIMP masses;other experiments of the same type are also being performed[4–10].
基金Supported by the National Nature Science Foundation of China(11875191,11775140)the Strategic Priority Research Program(CAS XDB1602)。
文摘The dark matter puzzle is one of the most important fundamental physics questions in the 21st century.There is no doubt that solving the puzzle will be a new milestone for human beings in achieving a deeper understanding of nature.Herein,we propose the use of the Shanghai laser electron gamma source(SLEGS)to search for dark matter candidate particles,including dark pseudoscalar particles,dark scalar particles,and dark photons.Our simulations indicate that,with some upgrading,electron facilities such as SLEGS could be competitive platforms in the search for light dark matter particles with a mass below tens of keV.
基金Supported in part by grants from National Science Foundation of China(12090061,12005131,11905128,11925502)the Ministry of Science and Technology of China(2016YFA0400301)the Office of Science and Technology,Shanghai Municipal Government(18JC1410200)。
文摘Neutron-induced nuclear recoil background is critical to dark matter searches in the PandaX-4T liquid xenon experiment.In this study,we investigate the features of neutron background in liquid xenon and evaluate its contribution in single scattering nuclear recoil events using three methods.The first method is fully based on Monte Carlo simulations.The last two are data-driven methods that also use multiple scattering signals and high energy signals in the data.In the PandaX-4T commissioning data with an exposure of 0.63 tonne-year,all these methods give a consistent result,i.e.,there are 1.15±0.57 neutron-induced backgrounds in the dark matter signal region within an approximated nuclear recoil energy window between 5 and 100 keV.
基金supported by the Science Challenge Project (No. TZ2016005)the National Basic Program of China (No. 2013CBA01501/03)+2 种基金the National Natural Science Foundation of China (Nos. 11503041, 11522326, 11622323, and 11573040)the Strategic Priority Research Program of the Chinese Academy of Sciences (Nos. XDB16010200 and XDB07030300)the Project Funded by China Postdoctoral Science Foundation (No. 2015M571124)
文摘Astrophysical collisionless shocks are amazing phenomena in space and astrophysical plasmas, where supersonic flows generate electromagnetic fields through instabilities and particles can be accelerated to high energy cosmic rays. Until now, understanding these micro-processes is still a challenge despite rich astrophysical observation data have been obtained. Laboratory astrophysics, a new route to study the astrophysics, allows us to investigate them at similar extreme physical conditions in laboratory. Here we will review the recent progress of the collisionless shock experiments performed at SG-Ⅱ laser facility in China. The evolution of the electrostatic shocks and Weibel-type/filamentation instabilities are observed. Inspired by the configurations of the counter-streaming plasma flows, we also carry out a novel plasma collider to generate energetic neutrons relevant to the astrophysical nuclear reactions.
基金supported by the National Natural Science Foundation of China(11875191)the Strategic Priority Research Program of the Chinese Academy of Sciences(XDB16)。
文摘Over one hundred years have passed since the nuclear isomer was first introduced,in analogy with chemical isomers to describe long-lived excited nuclear states.In 1921,Otto Hahn discovered the first nuclear isomerPa.After that,step by step,it was realized that different types of nuclear isomers exist,including spin isomer,K isomer,seniority isomers,and"shape and fission"isomer[1,2].