2022, Volume 39, Issue 3
The nuclear low-lying excitation spectra are very important for understanding nuclear structure. The excitation energies of
The search for stable triaxial shapes in the ground states of even-even nuclei, with a maximum triaxial deformation of
The nuclear spectroscopic factor characterizes the properties and occupancy of single-particle orbits of nuclei and other information, which is also an essential physical quantity connecting nuclear structure, nuclear reactions, and astrophysics. The spectroscopic factor is sensitive to the many-body wave function obtained from the theoretical models, and the standard shell model is usually chosen. With the development of supercomputers and nuclear many-body methods, nuclear ab initio methods have been successfully employed to study the properties of atomic nuclei with great success. In the present paper, we study the nuclear spectroscopic factor of light nuclei with ab initio no-core shell model based on the realistic nucleon-nucleon interaction. Firstly, the energies of low-lying states in
Recently, Ref. [
Based on an equivparticle model incorporating both confinement and leading-order perturbative interactions, we fit the model parameters to the experimental masses of
Multi-sample high intensity Cs sputter ion source is one of the common ion sources in various accelerators, and has been widely used in scientific research and industrial production. However, the commercial products of this kind of ion source are monopolized by several European and American countries, and currently no domestic manufacturer can produce it. In order to enhance the independent innovation capability in accelerator operation and development, a multi-sample high intensity Cs sputter ion source was specially developed. The ion source mainly consists of ion source cavity, target replacement device, cooling system and control cabinet. According to the functional requirements, the key components of ion source were designed. A new servo motor-driven target method was adopted to provide fine-tuning of target position and remote control mode. And the Opera-3D software was used to simulate beam trajectory and optimize structural parameters. After testing, the ion source has been successfully used in a 400 kV compact accelerator mass spectrometer(AMS) independently developed by the China Institute of Atomic Energy. The sample is accurately positioned, and the beam current is stable. Beam parameters are as good as those of imported ion source, so the expected goal has been achieved.
One of the key tools for measuring the magnetic fields of accelerator magnets is the Hall sensor. Hall sensors must be frequently calibrated while in operation to guarantee that they can perform measurements with extreme accuracy. It is also of great practical importance to establish a standard Hall sensor calibration system with a broad span of magnetic field and temperature range because the current testing tasks of accelerator magnets have introduced new demands on the measurement range and operating temperature of Hall sensors. Dependent on this, a complete high-precision Hall sensor calibration system is built and the data acquisition part of the system is discussed here. Based on this system, a number of calibration attempts were made in the 0-2.0 T magnetic field region using Hall sensors like the HHP-NP, HPCS, DTM151, HE244T, etc. The calibration curves were fitted using both linear and polynomial methods, and the results show that the fitting results are good and the degree of linear deviation is better than 0.01%. The smaller the degree of linear deviation of the test results, the more accurate the measurements.
CAFe facility, located at Institute of Modern Physics, Chinese Academy of Sciences, is an experimental prototype of superconducting proton linac. The beam experiment research surrounding this facility can lay a foundation, and provide experience for the design and research of accelerator of Accelerator Driven Subcritical System(ADS) in the future. A special beam DUMP and a corresponding beam collimator before it are needed to achieve CAFe's 10-mA beam goal. In this paper, the systematic design and calculation of the beam collimator are carried out for the development of CAFe DUMP. To ensure that the residual radioactivity after beam bombardment is within a reasonable range, Material of Al6063 is used for the collimator inner element facing the beam. Based on Monte Carlo particle transport simulation, radionuclides and residual dose analysis were carried out. The results show that the peripheral dose of the collimator will be on the order of 100 μSv/h, which is acceptable during decommission. The temperature distribution and temperature raise of the collimator under various beam conditions are simulated with ANSYS code. It is demonstrated that the collimator can safely remove heat from beam power under normal conditions and protect the device under abnormal conditions effectively. The results show that the collimator meet the design requirements of beam halo removal. During the CAFe high power beam commissioning, the collimator and the DUMP were operated normally, with beam current monitoring value consistent with the designed parameters. It proved that the collimator realized the function of beam halo removal, beam parameters diagnostics and DUMP protection.
During the upgrade of ATLAS detector PHASE I, NSW detectors will be built to improve the detection efficiency of Muon trajectories, and this will further improve the L1 trigger efficiency. NSW is composed of 768 sTGC detector modules, with a total of about 330 000 channels. University of Science and Technology of China, on behalf of the Chinese cooperation group, has undertaken all the design and production tasks of the sTGC front-end readout electronics, and has developed sFEB for reading strip signals and pFEB for reading pad and wire signals. Analyzing the performance requirements of FEB on the NSW sTGC detector, a complete set of FEB test items and test procedures have been developed. In order to perform batch test on thousands of FEBs completed in production, a set of multi-parameter FEB batch test system was designed. The test system can test 704 channels at the same time and run in strict accordance with the requirements of the sTGC readout system. Using the FEB batch test system, all 850 pFEB and sFEB boards were tested and delivered to the ATLAS cooperation team for installation on the sTGC detector.
This paper designs a 20:1 Serializer for a 5 Gbps SerDes (Serializer/DESerializer) ASIC fabricated using China's domestic GSMC 130 nm CMOS process. This Serializer converts the 20-bit 250 Mbps parallel data into 1-bit 5Gbps serial data. It consists of one stage of 5:1 conversion module and two stages of 2:1 conversion module. The clocks are provided by a multi-phase clock generator and a frequency divider. Post-simulations with all process corners, the temperature is from −40 °C to 100 °C and supply voltage is from 1.08 to 1.32 Volt, show this Serializer functions correctly and can generate a clear eye diagram at 5 Gbps, which fulfills the design requirements. Mainly, simulation with the typical process corner, the temperature at 27 °C, and supply voltage at 1.2 Volt show that the total power dissipation is 39.12 mW, the total jitter is 8.34 ps, and the output voltage rail-to-rail is 800 mV.
Using the Monte Carlo simulation method, the virtual point source position of the volume source for different HPGe detectors can be quickly obtained. In the calculation, it is necessary to simulate the detection efficiency of the point source and the volume source. The effects of the size and type of HPGe crystals on their virtual point source positions were investigated through 241Am, 137Cs, 60Co point sources and volume sources. The simulation results show that the virtual point position of the 241Am source presents obvious differences. In the low energy range, the VPS calibration method is not valid in the measurement of small-volume samples of the surface of the detector. Finally, the semi-empirical formula for the height of the volume source and the position of the virtual point source is obtained by using the 137Cs and 60Co sources. In the test measurement, the detection efficiency of two types of HPGe detectors was calibrated using the standard soil source of the size of 70 mm×65 mm. Compared with the simulated detection efficiency curve and the calculation results of virtual point source efficiency, the validity of the semi-empirical formula was verified. In the gamma energy range of 300~2 000 keV, the relationship between the position of the volume source and the virtual point source can be established through a suitable radioactive source. This study provides a new approach in the radiation measurement to avoid the repeated detection efficiency calibration in detectors.
In-beam PET imaging provides an effective method to monitor the physical and biological dose distribution during carbon ion radiotherapy in real time. We investigate the dose distribution and In-beam PET image of a homogeneous water phantom and an abdominal tumor CT phantom by the Treatment Planning System(TPS) and Monte Carlo(MC) simulation. We compare the consistency of TPS dose distribution, the MC simulation dose distribution and the PET imaging profile at the tumor area. The relative biological effect values(RBE) were calculated using a linear quadratic model(LQ). Results show that the average error of the physical dose and RBE weighted dose in the water phantom and the abdominal tumor CT phantom were within 0.5% and 2% respectively. The carbon ion energy ranges from 120 to 400 MeV/u. The peak position difference between dose and PET imaging is within 8 mm. This paper proves the feasibility of using In-beam PET for dose monitoring during carbon ion radiotherapy.
Boron Neutron Capture Therapy (BNCT) based on accelerator neutron source is a new generation of radiation therapy. As an important part of the BNCT facility, Beam Shaping Assembly (BSA) aims to moderate the fast neutron beam in the neutron source to the epithermal neutron energy region (0.5 ev~10 keV), and to minimize the components of fast neutron, thermal neutron and
With the development of Magnetic Resonance Imaging(MRI) technology, the role and importance of image guided radiation therapy in radiation oncology are increasing rapidly. To develop the technique of MRI-guided heavy ion radiotherapy, the influence of uniform magnetic fields on the dose-averaged LET and nanodosimetric quantities of carbon-ion beams is analyzed. In this work, the GEANT4 kernel-based GATE Monte Carlo simulation platform was used to calculate the dose-averaged LET and nanodosimetric quantity distributions of carbon-ion beams with different energies under different magnetic fields. Compared to the cases without magnetic fields, it was found that the longitudinal uniform magnetic fields had little effect on the dose-averaged LET and nanodosimetric quantities of the carbon-ion beams. The influence of the lateral uniform magnetic fields on the dose-averaged LET and nanodosimetric quantities of the carbon ion beams mainly occurred in the Bragg peak regions, which was mainly caused by the lateral deflection of the carbon ion beams under the Lorentz forces in the magnetic fields, especially the lateral shift of the Bragg peak position of the carbon ion beams. These results provide a solid foundation for further study on how magnetic field affects the therapeutic performance of carbon ion beams.
In order to obtain high-yielding cellulase strains that can effectively degrade cellulose in plant cell walls, Aspergillus niger, which has the advantages of safety and reliability, non-toxicity, fast growth and short fermentation period, was used as the starting strain. The original strain, Aspergillus niger, was irradiated by heavy ion beam 12C6+ (irradiation doses: 40, 70, 100, 130, 160 and 190 Gy) , and two excellent strains were obtained after primary screening on the plate; 8 weeks of self-adaptive evolution, the strain has stable growth performance through 5 consecutive generations of fermentation; the obtained strains of each generation were compared for the molecular weight of intracellular proteins, and an optimal mutant strain CJH-JWSFZh-W122 was obtained, which was determined by shaking flask fermentation Cellulase activity, the filter paper activity(FPA) of cellulase production reached 223.5 U/mL, and the carboxymethyl cellulase activity(CMCase) reached 440.8 U/mL, which were 6.07% and 8.01% higher than the original strains, respectively. The excellent fermentation performance was still maintained after 5 consecutive generations; RAPD analysis and SDS-PAGE electrophoresis analysis were applied to compare the mutant strain CJH-JWSFZh-W122 and original strain, which confirmed the gene mutation of this strain.
We study the direct fragmentation channel of double ionization in the collision of relativistic ions and helium dimers from a theoretical point of view. Based on the symmetry eikonal approximation, two theoretical models have been established. In one model, the two atoms of the helium dimer are regarded as a whole system, while the other model completely ignores the interaction between the two helium atoms. The numerical calculation results of the model show that the total cross-section has a strong dependence on the spatial orientation of the helium dimer. When the helium dimer is parallel to the incident ion beam, the total cross section reaches the maximum, and when it is perpendicular, the total cross section reaches the minimum. Further research found that the results of the first model is more reasonable when the helium dimer nucleus distance is small, and the second model is more accurate when the nucleus distance becomes large.
In this paper, the energy spectrum and angular distribution data of neutron source of 9Be (d, xn) reaction accelerator with thick target are evaluated and calculated by using PHITS program. The applicability of JQMD, INCL and INCL/DWBA nuclear reaction physical models to calculate the neutron radiation field distribution of 9Be (d, xn) reaction with thick target is discussed. The results show that the energy spectrum and angular distribution data of the thick target 9Be(d, xn) reaction calculated by the PHITS program based on the INCL/DWBA nuclear reaction physical model are in good agreement with the experimental data, and can provide more accurate neutron radiation field data for the study and application of the characteristics of 9Be (d, xn) reaction neutron source with thick target. In addition, the scheme of water-cooled large-area rotating beryllium target is designed, and the simulation study of target surface temperature is carried out under the condition of 5~25 MeV/5 mA incident deuterium energy. The results show that the maximum temperature of target surface can be controlled below 100 ºC.
The evaluation of the half-life and emission rates of delayed neutrons is updated according to the reference library of nuclear science. For uncertain ground states in the fission products, spin designation is carried out using a combination of systematic and theoretical studies and improved data are obtained through corrections. For radionuclides with daughter nuclei in isomeric states, the branching fractions of ground and isomeric states are recalculated with the decay scheme and internal conversion coefficient. Then following a critical review of data in Nuclear Structure and Decay Data File, a special decay database for the design of fission product decay chain is developed. According to the decay law, the complete decay path and information of fission products are established. This work provides a convenient reference for fission product analysis and fission yield research.