2021, Volume 38, Issue 3
As one type of single nucleon transfer reactions, deuteron stripping reaction has been playing an important role in the study of the single particle structure of atomic nuclei. Also, as a typical three-body nuclear reaction, deuteron stripping reaction is also an important subject in the development of direct nuclear reaction theories. We briefly review the history of the study of deuteron stripping reactions, focusing on the evolution of its theoretical descriptions, and the differences and the relations of the Plane Wave Born Approximation(PWBA), the distorted wave Born approximation(DWBA), the Continuum Discretized Coupled Channel method(CDCC), the Adiabatic Wave Approximation(ADWA), and the approach based on the Faddeev equations. Some important problems being currently addressed in deuteron stripping reaction theories and those should be addressed in near future are also discussed, including deuteron strippings at intermediate and high energies, theory for transfer to continuum states of the residue nuclei, applications of dispersive optical model potentials and non-local potentials, etc. Some preliminary results of our theoretical calculations for deuteron stripping at intermediate and high energies are presented.
The multinucleon transfer reaction processes of
Energy level density plays an important role in the study of kinetic and thermodynamic properties of nuclear physics. In this paper, shell model and the truncation algorithm are used to calculate the lowest 10 000 states of Sn isotopes. The number of holes and the number of particles in the
π0→γγ decay is dominated by chiral anomaly in quantum chromodynamics(QCD). Based on this anomaly and corrections of chiral perturbation theory(ChPT), π0 lifetime is predicted in high precision and the estimated uncertainty is on the level of 1%. The experimental measurement of π0 lifetime in a comparable precision is critical to test the QCD and ChPT at confinement scale energy. The methods of π0 lifetime measurement and experiments included in PDG of 2018 version for π0 lifetime average are reviewed, in which PrimEx-I performed in JLab in 2004 is the most precise experiment and has a total uncertainty of 2.8%. Even though those experimental results are in agreement with theoretical prediction in the range of experimental errors, the precision is not yet sufficient totri sngently test the theoretical prediction. In order to get more precise measurement of π0 lifetime, PrimEx-II was performed in JLab in 2010 with the precision of 1.57%. The weighted average of PrimEx-I and PrimEx-II results has a total uncertainty of 1.50% and confirms the prediction based on the chiral anomaly in QCD. Moreover, the experiment setup and data analysis approach of PrimEx-II are also reviewed in this article.
Most of the existing methods for beam control using magnet field use the open-loop mode, which is to directly set the value of current and voltage of the magnet power supply output based on the demand of magnetic field intensity. However, magnetic fields in the open-loop state are easy to be deflected due to the field noise and the eddy current effect of the magnet. To solve this problem, the closed-loop control system of the magnetic field based on the PID algorithm is developed in this article. This system takes the deflection magnet as the control object, uses the Hall sensor to obtain the magnetic field intensity as the feedback, and utilizes the output of the excitation current of the magnet power supply as the input of the control system. The controller uses the PID algorithm to automatically tune the output of the magnet power supply to achieve the closed-loop control of the magnetic field. The result shows that when the PID parameters are properly set, the magnetic field offset can be significantly reduced by the closed-loop control method which takes the online measured value of the magnetic field as the feedback signal to simultaneously tune the excitation current value of the magnet power supply.
Laser ablation plasma(LAP) can be used as an ion source for particle accelerators and for ion implantation. Although the too intensive current intensity of laser ion sources give them advantages over other ion sources, yet the minute duration of laser produced ion pulses limits their applications in accelerators. By introducing a solenoid into the plasma expansion region, the modulation of the plasma temporal structure had been achieved[
The atmospheric cosmogenic nuclides of 10Be, 7Be, 22Na are of great significance to research on global climate change and atmospheric environmental governance, as the sensitivity tracer of the Stratosphere-Troposphere Exchange(STE) dynamic processes. The current status of the international research on the application of these nuclides in STE and the difficulties are introduced. The advantages and research basis of Accelerator Mass Spectrometry(AMS) in this respect are summarized. Feasibility analysis and exploration of the key technologies faced by AMS measurement of 7Be and 22Na are presented based on the compact low energy AMS system and the established 10Be measurement method of Tianjin University.
The current intensive storage method of spent fuel based on fuel consumption trust system has put forward higher requirements for the reliability and effectiveness of neutron absorbing materials in the spent fuel pool grid. Non-destructive testing and monitoring of neutron absorption performance (boron content) is required during the production and use of grid materials. In response to these two requirements, a nuclear power plant spent fuel pool grid B4C_Al neutron absorption material testing equipment has been successfully developed. The detection equipment is mainly composed of the neutron source (3 252Cf radiation sources), the neutron detection array (a detection array composed of 10 lithium glass detectors), the neutron shielding collimation and slowing system, etc., and then the 10B surface density of each measuring point on the sample plate would be calculated by measuring the neutron transmittance, and the method of non-destructive testing of the B4C_Al alloy boron content of the spent fuel pool storage grid material would be accomplished. The equipment has been successfully used to complete the 20 cm×30 cm hanging sample test, and the results were reliable. The detection equipment is the first one designed for B4C_Al material neutron absorption performance testing, which promotes the non-destructive testing of boron-containing neutron absorption materials of China, and provides a strong guarantee for the criticality safety monitoring of the spent fuel pool of nuclear power plants.
The Heavy Ion Research Facility in Lanzhou(HIRFL) is the largest heavy ion research facility in China, which has the most kinds of accelerated ions and the highest energy. Radiation will be generated in the accelerator tunnel during the operation of HIRFL, so it is necessary to establish a radiation safety interlock system to ensure the radiation safety of the workers. The system folows the design principles of zone partition interlocking, reliable hardware, failure protection, redundancy and independence, self-locking, etc. Redundant PLCs with high reliability are used as the central controller and interlocking components with high safety are selected. The successful establishment of the radiation safety interlock system is of great significance to the radiation safety of the staff at HIRFL, and it can also provide a reference for the design of interlock systems of other accelerators.
The CSR External-target Experiment(CEE) system under development may reach an average data rate of 2 GB/s after being triggered. In response to the design requirements of the entire spectrometer, a generic stream processing data acquisition architecture D-Matrix is put forward in the article, and a specific scheme of D-Matrix in the Time-of-Flight detector(TOF) subsystem is proposed. The DAQ of the TOF system uses high-speed serial communication methods such as optical fiber and PCIe bus to complete data transmission from Front-End Electronics(FEE) to the servers, and deploys and cascades stream processing nodes with a unified interface to complete event building, command routing, Real-time status monitoring and displaying and data storage tasks. In addition, the DAQ of the TOF system has strong versatility in hardware and logic design, it also can be compatible with other sub-detector systems, and can be further applied to the global system of CEE experiments.
In modified uniformly redundant arrays code imaging of gamma radiation internal contamination, in order to further decrease reconstruction artifacts with Maximum Likelihood Expectation Maximisation(MLEM) algorithm and to improve the efficiency of reconstruction, this paper proposed an anisotropic diffusion wavelet image denoising algorithm based on differential curvature (ADWIDDC algorithm), and combining with MLEM algorithm, a modified code imaging MLEM-ADWIDDC algorithm was obtained. Firstly, the reconstruction of the projection data obtained from the detector was conducted with MLEM algorithm. Secondly, the near-field artifacts were decreased with complementary imaging method. Finally, the image artifacts were further reduced by ADWIDDC algorithm. The simulation results show that the MLEM-ADWIDDC algorithm can better remove the artifacts and the texture of the reconstructed gamma source image is clearer when 131I source is designed as circular distribution, with the cut-off time of 195 s for the reconstruction algorithm to run. When 131I source is designed as “CDUT” distribution and the signal-to-noise ratio is set 5.10 dB as cut-off condition of code imaging reconstruction, the real reconstruction time of the MLEM-ADWIDDC algorithm is 98.36 s, which is 49% shorter than that of MLEM algorithm alone.
Vanadium alloys (V-5Cr-5Ti) have been considered as the candidate materials for the first wall and the blanket of fusion reactors. Different fabrication process will affect the performance of vanadium alloy in fusion reactors. In this study, the response of hardening of V-5Cr-5Ti vanadium alloys with different cold deformation (40%, 60% and 80%) followed by annealing treatment (1 273 K for 1 h) under irradiation with 337 MeV Fe ions was investigated. The irradiation experiment was performed at a terminal of the Sector-Focused Cyclotron(SFC) at HIRFL(Heavy Ion Research Facility in Lanzhou). The results of electron backscattering diffraction(EBSD) indicated that the proportion of fine broken grains in the sample increased and the average grain size decreased with the increase of cold deformation amount. After annealing, the distribution of grains become more uniform with the fine broken grains growing up and the large grains almost disappeared. The results of the Vickers hardness test show that the hardness increases with the increase of cold deformation amount and decreases after annealing treatment. After irradiation, the hardness of all samples increased significantly, which suggested the occurrence of irradiation hardening. In both cold rolling samples and annealing samples, the irradiation hardening effect decreased with the increase of cold deformation amount, which indicated that cold rolling can significantly improve the irradiation hardening resistance property. Based on the EBSD and hardness results, the mechanism of the effect of cold rolling and annealing on irradiation hardening resistance property of V-5Cr-5Ti was discussed. The increase of the cold deformation amount results in the increase of the sink strength, which suppressed the occurrence of irradiation hardening. The annealing treatment results in the decrease of the density of grain boundary and dislocation and the decrease of the total sink strength, which caused more significant irradiation hardening in the sample with annealing treatment.
The characteristic of single-event upset(SEU) in a 14-nm bulk fin field-effect transistor (FinFET) static random access memory(SRAM) is investigated by heavy-ion experiments. The linear energy transfer(LET) threshold 0.1 MeV/(mg/cm2) is obtained by fitting the SEU cross-section using the Weibull function. The contribution of multiple-bit upset(MBU) is investigated. The results show that when the LET is equal to 40.3 MeV/(mg/cm2), greater than 95% of SEU comes from the MBU. Additionally, the SEU cross-section of the FinFET SRAM presents anisotropies for incident angles associated with the fin direction. This research has a certain kind of guiding role in designing of radiation-hardened complementary metal-oxide semiconductor(CMOS) integrated circuits(ICs) based on FinFET technology.
Nanodosimetric quantities are becoming new measures to characterize radiation quality, which provide basic data for calculating Relative Biological Effectiveness(RBE). The biological effects under mixed ion-beam irradiation fields with the same dose-averaged Linear Energy Transfer(LET) value may not be the same. To study the distributions of key nanodosimetric indexes [the first moment of the conditional cluster size distribution with ionization cluster size (NICS)
Methods and criteria for the identification of male individual radiosensitivity are investigated. The peripheral blood of 50 male volunteers was irradiated with different doses of X-ray, the micronucleus frequency(MNF) was measured by cytokinesis-B block micronucleus assay, and the central standard curve of micronucleus dose effect was drawn by second-order multinomial fitting method so that the individual dose-response curve of micronucleus was compared with the standard curve to judge individual radiosensitivity. In the dose range of 0.0~2.5 Gy, the central equation of second-order polynomial fit for dose effect is (MNF=0.014 7+0.036 2D+0.023 1D 2, R=0.726). Among the 50 male volunteers, 13 were sensitive to radiation (26.0%) and 14 were resistant (28.0%), which basically fits the normal distribution. Spearman rank correlation analysis showed that the MNF increased with the dose and there was a positive correlation between the background MNF and the radiosensitivity of each dose, but negative correlation with the radioresistance. In conclusion, a "curve-instead-of-dose" male individual radiosensitivity identification method was established. Moreover, it was found that the background of micronuclei in peripheral blood lymphocytes was positively correlated with individual radiosensitivity.
Lead-bismuth eutectic(LBE) is the candidate material of spallation target for China initiative Accelerator Driven System(CiADS). Long-term irradiation makes the LBE highly radioactive. Most of the spallation target radionuclide studies focused on the effects of the proton beam and ignored fission neutrons from the reactor. In this paper, both the fission neutrons and the high-energy protons have been taken into account in the radionuclide calculations of LBE and spallation target structural parts by coupling codes FLUKA and MCNP. Contributions from the fission neutron and the high-energy proton have been compared in the aspects of the activity, main radionuclides, toxicity, and the decay photon of radioactive products. The main shell, guide tube, and beam tube are significantly affected by the fission neutron activation. When the reactor tends to be critical, the fission neutron-induced LBE target activations are even greater than that induced by the proton beam. In the LBE itself, 96.66% of 210Po is induced by the fission neutrons. These results illustrate that fission neutrons are also essential for the radionuclides calculation of LBE and its structural parts. In addition, this study provides reference data for the radiation protection of CiADS and a more accurate method for the radionuclides study of the spallation target in ADS systems.
Distributed Control System(DCS) is being applied increasingly in nuclear power plants due to its safety and reliability operation. In this paper, a new method for optimizing the reliability of the DCS design based on the sensitivity analysis is proposed. Within this method, the accident sequences after the DCS fault was firstly analyzed, and the corresponding event tree model was built. Subsequently, a sensitivity analysis model was developed to guide the DCS reliability design. Finally, a case study was performed to validate the effectiveness of the proposed method. Results indicate that the proposed DCS reliability design method exhibited superior ability in decreasing the core damage in a nuclear power plant.