Subjects: Physics >> Nuclear Physics submitted time 2024-03-28
Abstract: Charge exchange reactions with the intermediate energy can be used to study the complex structure of atomic nuclei from the respect of spin-isospin excitation. By utilizing the radioactive beam line at the Institute of Modern Physics, Chinese Academy of Sciences, charge exchange reaction experiments in inverse kinematics can expand the target nuclides to be studied to neutron-rich nuclei and even unstable nuclei. Based on this, a detector system for charge exchange reaction experiments has been designed, which mainly consists of a 3He gas target, TPC and CsI(Tl) arrays, where the TPC and CsI(Tl) arrays form a ΔE-E system. Using simulation software such as Geant4 and Garfield++, the operating conditions of the TPC were optimized, the kinematic intervals and the basic design of the detector for the experimental study were determined, and the particle discrimination ability of the detection system was investigated. Based on the simulation, the detection system was built.
Subjects: Physics >> Nuclear Physics submitted time 2024-02-16
Abstract: The basic properties of atomic nuclei including spins, magnetic moments, electric quadrupole moments and charge radii, are sensitive probes to different aspects of exotic nuclear structure, and are also important to investigate the unrevealed nature of interaction between nucleons. Based on multidiscipline, laser spectroscopy is a unique tool to precisely measure the basic nuclear properties mentioned above in a nuclear-model independent way by measuring the hyperfine structure of atoms, ions, or molecules, which has played an important role in the study of exotic nuclear structures across the different regions of the nuclear chart. Basic principles of laser spectroscopy and various types of experimental devices are expounded after the brief history of the hyperfine structure. Furthermore, advantages of utilizing laser spectroscopy in the study of nuclear structure are briefly introduced by taking the radioactive neutron-deficient Pb region as an illustration. In addition, current condition of collinear laser spectroscopy setup has been systematically reviewed, together with the latest progress on collinear resonance ionization spectroscopy offline devices at Peking University. Finally, the developing status and ongoing plan of laser spectroscopy devices for current and future radioactive ion beam facilities in China have been put forward, and the broad prospects of laser spectroscopy in unstable nuclear properties and the fundamental symmetries based on molecular spectroscopy are interpreted.
Subjects: Physics >> Nuclear Physics submitted time 2024-01-17
Abstract: The research in hypernuclear physics provides crucial information for uncovering the characteristics of baryon-baryon interactions in the nuclear medium and understanding the internal structure of atomic nuclei and neutron stars. Based on the density-dependent relativistic Hartree-Fock (RHF) theory, the $ Lambda N$ effective interaction in the model is obtained by fitting experimental data of hyperon separation energies for single-$ Lambda$ hypernuclei. The inclusion of the Fock term alters the dynamic equilibrium of the effective nuclear force in the hyperon channel, resulting in a meson-hyperon coupling strength that differs from the relativistic mean-field model and influences the description of hyperon spin-orbit splitting. Considering the uncertainty in the values of the effective nuclear force within the model, further research is conducted to explore the dependence of hypernuclear bulk and single-particle properties on the hyperon coupling strength, aiming to identify possible ways to constrain its range of values. Taking the $^{16}_{ Lambda}$O hypernucleus as an example, the effects of the nuclear medium and Fock terms are systematically analyzed by adjusting the hyperon coupling strength in the isoscalar channel within the hypernuclear energy functional. The results suggest a possible linear relationship between the ratio of hyperon coupling strength and quantities such as hyperon spin-orbit splitting, Dirac effective mass, and hypernuclear characteristic radius. Therefore, by constraining these quantities through experimental or theoretical means, it is possible to impose stronger limitations on the effective nuclear force associated with hyperons in the nuclear medium.
Subjects: Nuclear Science and Technology >> Nuclear Instrument and Meter submitted time 2024-01-15
Abstract: With the development of domestic semiconductor enterprise technology, some domestic components performance indicators have been comparable to imported components, to meet the performance needs of nuclear radiation monitoring instrumentation. A fully localized 𝛾 energy spectrometer based on a 1.5-inch LaBr3 scintillator, including scintillators, photomultiplier tubes, and electronic components, has been designed by using products of domestic manufacturers.The test results show that the resolution of the spectrometer can reach 2.8%@662keV at room temperature, the working temperature range can reach -40℃ to 50℃ , and the energy resolution is better than 3.0% in the whole temperature range, and the change rate of the all-around peak channel address of 137Cs with temperature is about -0.67/℃
, and the linearity is good. The high-voltage adjustment rate is 0.02V, which meets the requirement of 0.2V /℃ for the stable spectrum. The energy nonlinearity of the spectrometer is better than 0.01%. The experimental data show that the domestic LaBr3 scintillator, photomultiplier tube and electronic components can meet the design requirements of 𝛾 energy spectrometer.
Subjects: Nuclear Science and Technology >> Nuclear Detection Technology and Nuclear Electronics submitted time 2023-11-01
Abstract: In the field of nuclear industry, α surface contamination exists in many places. In the case of emergency conditions, it is generally necessary to carry out remote detection of abnormal areas firstly, and then make a plan scientifically based on the measurement results. In view of this situation, technology for remote detection of α particles based on air fluorescence has been proposed internationally. The principle is that nitrogen in the air will emit a specific wavelength of ultraviolet fluorescence through the excitation and deexcitation process under the action of α radiation, allowing the ultraviolet camera to detect α radiation remotely. In China, there are few reports on remote detection of α surface contamination, the research has been pioneered by the 404 Company Limited and Lanzhou University. In this paper, the international development of remote α contamination detecting technology based on nitrogen fluorescence is reviewed, and the latest research work of our team is briefly described, in order to provide reference for promoting research on remote detection of α contamination.
Subjects: Physics >> Nuclear Physics submitted time 2023-10-07
Abstract: The measurement of the muonic hydrogen atom Lamb shift is one of the most fundamental ways to obtain the proton charge radius experimentally. The theoretical calculation of the muonic hydrogen atom Lamb shift is necessary to extract the proton charge radius from the Lamb shift. In this work, we calculate the muonic hydrogen atom Lamb shift within the relativistic framework. The relativistic effect is described with the Breit-Pauli hamiltonian. The vacuum polarization effect is realized with the effective Uehling potential. With a high precision calculational method, Gaussian expansion method, we calculate the 2S1/2 and 2P1/2 levels of the muonic hydrogen atom. We find that the muonic hydrogen atom Lamb shift with considering the relativistic effect is about 0.09 meV larger than the one without considering the relativistic effect and the former one is closer to the experimental value.
Subjects: Physics >> Nuclear Physics submitted time 2021-12-25
Abstract: We report the reconstruction method of the fast fission events in 25 MeV/u $^{86}$Kr +$^{208}$Pb reactions at the Compact Spectrometer for Heavy IoN Experiment (CSHINE). The fission fragments are measured by three large-area parallel plate avalanche counters, which can deliver the position and the arrival timing information of the fragments. The start timing information is given by the radio frequency of the cyclotron. Using the velocities of the two fission fragments, the fission events are reconstructed. The broadening of both the velocity distribution and the azimuthal difference of the fission fragments decrease with the folding angle, in accordance with the picture that fast fission occurs. The anisotropic angular distribution of the fission axis also reveals consistently the dynamic feature the fission events.
Peer Review Status:Awaiting Review