## 2021 Vol. 38, No. 4

column
Display Method:
2021, 38(4): 1-2.
Abstract(125) HTML (32) PDF (325KB)(25)
Abstract:
2021, 38(4): 361-367. doi: 10.11804/NuclPhysRev.38.2021076
Abstract(299) HTML (62) PDF (3733KB)(84)
Abstract:
β-decay half-lives of r-process waiting-point nuclei are the crucial physical data for understanding the origin of heavy elements in the universe. Proton-neutron quasi-particle random phase approximation (pn-QRPA) is an important theoretical model to study nuclear β decays. In this work, we propose an improved pn-QRPA model to systematically study β decays from nuclei near closed shells. Compared with previous works, new forms of particle-particle and particle-hole interactions are adopted in the improved model, which depend on both the neutron number and the proton number. We first validate our new model by calculating β-decay half-lives and Gamow-Teller strength distributions of some known nuclei around closed shells. The theoretical results agree well with experimental data. We then predict the β-decay half-lives of various unknown waiting points nuclei near \begin{document}$N=50,~N=824$\end{document}, and \begin{document}$N=126$\end{document}, such as 124Mo, 126Ru, 128Pd, 186Nd, 188Sm, 192Dy, 194Er, 196Yb, 198Hf. The predictions are consistent with the previous model. These results are good references for the future physics research of r-process near the closed shell.
2021, 38(4): 368-372. doi: 10.11804/NuclPhysRev.38.2021059
Abstract(218) HTML (62) PDF (2870KB)(41)
Abstract:
With the robust shell-model foundation, the proton-neutron interacting boson model(IBM-2) is considered to be one of the standard models for the descriptions of heavy and intermediate-heavy nuclei. In this work, we demonstrate a new algorithm that is used to solve the IBM-2 Hamiltonian in the weak-coupling SU(3) basis in contrast to the original NPBOS algorithm in terms of the weak-coupling U(5) basis. Specifically, the SU(3) matrix element of a typical interactional term is given as an example to illustrate how to solve the IBM-2 Hamiltonian using the SU(3) group-algebra technique. With this algorithm, the consistent-Q Hamiltonian has been solved and applied to fit the low-lying experimental data for 152, 154Sm, which therefore provides an example for using the IBM-2 to describe the transitional nuclei and testing the validity of the SU(3) algorithm.
2021, 38(4): 373-379. doi: 10.11804/NuclPhysRev.38.2021074
Abstract(110) HTML (31) PDF (3089KB)(25)
Abstract:
We study the so-called magic mixing angles for doubly heavy baryons. Defining that a magic mixing angle rotates states with definite \begin{document}$^{2S+1}(l_\lambda)_J$\end{document} to make them heavy-quark symmetric states, we derive the magic mixing angle only in the case \begin{document}$L_\rho=0$\end{document} between the heavy quark symmetric states with quantum numbers \begin{document}$\left(J, j_\ell\right)$\end{document} and the states with \begin{document}$\left(J, s_{\rm q}+j_\rho\right)=\left(J, \{^4l_\lambda/^2l_\lambda\}\right)$\end{document} for a doubly heavy baryon in the standard \begin{document}$\rho-\lambda$\end{document} configuration, where \begin{document}${\boldsymbol{j}}_\ell={\boldsymbol{l}}_\lambda+{\boldsymbol{s}}_{\rm q}$\end{document}, \begin{document}${\boldsymbol{s}}_\rho={\boldsymbol{s}}_{\rm Q1}+{\boldsymbol{s}}_{\rm Q2}$\end{document}, and \begin{document}${\boldsymbol{j}}_\rho={\boldsymbol{s}}_\rho+{\boldsymbol{L}}_\rho$\end{document}. We point out that when we calculate decays of doubly heavy baryons, we need to consider decays of magically mixed states, such as \begin{document}$(1S1p)1/2^-$\end{document}, \begin{document}$(1S1p)3/2^-$\end{document} and so on.
2021, 38(4): 380-388. doi: 10.11804/NuclPhysRev.38.38.2021079
Abstract(184) HTML (51) PDF (5268KB)(28)
Abstract:
Quantum chromodynamics(QCD) allows the existence of exotic states, which beyond baryons and mesons in the quark model. The study of exotic states is one of the hot topics in high-energy experiments. X(3872) was the first candidate for an exotic particle observed experimentally. Experimental and theoretical study on X(3872) has never been stopped, which makes X(3872) also the best exotic state being understood. The Beijing Spectrometer(BESIII) Experiment at the Beijing Electron Positron Collider(BEPCII) collected large data samples for electron-positron collisions with center-of-mass energy from 3.87 to 4.70 GeV. The analysis of these data samples has resulted in a number of achievements on X(3872). In this paper, we will review the research on X(3872) at BESIII and a series of achievements and the latest progress made at BESIII. The study of X(3872) and other exotic states will help us understand the basic interactions of the nature, and it will also provide a strong support for the standard model theory.
2021, 38(4): 389-395. doi: 10.11804/NuclPhysRev.38.2021034
Abstract(129) HTML (42) PDF (4347KB)(17)
Abstract:
Extremum seeking algorithm with sliding mode is presented for design of automatic tuning control system of SSC-LINAC RFQ(Radio Frequency Quadrupole) based on the cavity reflected signal. Combined with the Lyapunov stability theory and the characteristics of SSC-LINAC RFQ radio frequency system, the control gain and reference signal of the sliding mode algorithm are improved. By solving the differential equation, the functions of the cavity reflected signal with respect to time and the position of the tuning rod are obtained. Through software simulation and hardware system design, the tuning process based on extremum seeking algorithm with slidig mode is simulated and tested. The results show that the designed frequency stabilization system can realize the automatic power feeding process of SSC-LINAC RFQ cavity in a short time, and the frequency stability meets the design index requirements, and has passed the long-time stability test. The feasibility of applying the extremum seeking algorithm with sliding mode to the tuning of high frequency resonator is proved.
2021, 38(4): 396-401. doi: 10.11804/NuclPhysRev.38.2021051
Abstract(144) HTML (41) PDF (8979KB)(14)
Abstract:
The China ADS Front-end demonstration facility(CAFe) is the prototype accelerator for the China Accelerator Driven Subcritical system(ADS), and exhibits extremely high requirement on operation stability. During the operation of CAFe, the field emission effect interferes with the pickup signal from the superconducting cavity, which is one of the most common causes for beam trips and other operation faults. Such interference seriously harmed the accelerator operation stability. The origin of the problem comes from the fact that field emission electrons cause discharge on the microwave transmission device, which interferes with the signal transmission and causes the low-level radio frequency system to control the superconducting cavity incorrectly, and finally leads to the superconducting cavity failure and accelerator shutdown. In this paper, the structure of the pick-up antenna was optimized to avoid the field emission electrons from entering the pick-up coupler, so as to solve the problem of abnormal signal. The optimized antenna showed desirable results during the online operation tests, the problem of abnormal signal extraction was solved, and the stability of accelerator operation was improved.
2021, 38(4): 402-409. doi: 10.11804/NuclPhysRev.38.2021020
Abstract(144) HTML (46) PDF (3573KB)(23)
Abstract:
In order to sample and process the signal of the Shanghai High Repetition Rate XFEL and Extreme Light Facility (SHINE) strip-line BPM system, a prototype of High-Repetition-Rate Beam Sampling Processor was developed. The processor has four channel input, 1 GSps maximum sampling rate and 16 bit resolution. It adopts Xilinx Zynq series FPGA with embedded ARM core, which can run Linux operating system and realize readout of high-speed sampled-data and data buffering. The processor adopts the structure of mother board and daughter board. The daughter board with ADC is for data sampling, and the mother board with FPGA is used to process the digital data. The daughter board and the mother board transmit data through the FMC interface. The ADC uses JESD204B protocol to transmit data, and the maximum total data rate is 80 Gbps through 16 pairs of differential channels. First the ADC data is transmitted to the digital motherboard. Then it is buffered by FIFO and DDR and finally transmitted to the upper computer for processing and analysis through the RJ45 interface with TCP/IP protocol. The data rate of RJ45 interface is about 900 Mbps. After testing, the bandwidth of ADC daughter board is higher than 480 MHz, and the ENOB(effective number of bits) is higher than 10-bit in 480 MHz bandwidth. The FPGA digital mother board runs Linux compiled by Petalinux, which can realize the data storage and transmission of 1 M sampling points of four channels in continuous or trigger mode. The processor can meet the design requirements.
2021, 38(4): 410-415. doi: 10.11804/NuclPhysRev.38.2021058
Abstract(254) HTML (104) PDF (4079KB)(47)
Abstract:
The 1.7 MV tandem accelerator at Peking University has been running for more than 30 years. The accelerator is equipped with a Radio Frequency(RF) charge exchange negative ion source and a cesium sputtering negative ion source, which can produce most of the ions from H to Au. It can accelerate the ions to energies from several hundreds of keV to several MeV. The accelerator is used for ion implantation and irradiation as well as for ion beam analysis, such as Rutherford Backscattering Spectroscopy(RBS) and channeling. Based on the experimental requirements, a high temperature irradiation system was established, with the highest temperature of 950 ℃. In order to achieve more accurate ion implantation, two Faraday cup structures, direct type and indirect type, are designed. The scanning area of the beam is controlled accurately. These designs can not only suppress the secondary electrons, the influence of secondary positive ions is also considered when measuring the beam intensity. The ion implantation experiments of Au ions with different energy on single crystal silicon were carried out. RBS analysis shows that the error between the measured fluence and the expected fluence is within 4%. In addition, the uniformity measurement shows that the relative standard deviation of the implant fluence is 2%.
2021, 38(4): 416-422. doi: 10.11804/NuclPhysRev.38.2021021
Abstract(106) HTML (73) PDF (3276KB)(17)
Abstract:
The Cooler-Storage-Ring External-target Experiment(CEE) is a spectrometer to study the properties of nuclear matter at high baryon density region. The CEE time projection chamber, which uses the state-of-the-art SAMPA electronics read-out chips is the key sub-detector of CEE. Neighboring signals in the same pad row are first grouped together to form a 2-dimensional cluster. Then a hit is created for each cluster at the ADC weighted average signal position. A cluster may also be divided into two or more hits, when the signal ADC vs. time bin has a peak-valley-peak structure, in order to obtain better two-track separation ability. The performance of the algorithm, including 0.100/0.043 cm of hit resolution and 1.1/2.8 cm of double-track resolution in the \begin{document}$x/y$\end{document} direction, is also presented.
2021, 38(4): 423-429. doi: 10.11804/NuclPhysRev.38.2021014
Abstract(153) HTML (33) PDF (5200KB)(28)
Abstract:
The gas-filled recoil nuclear separator SHANS(Spectrometer for Heavy Atoms and Nuclear Structure) is an important experimental device for synthesing new neutron-deficient actinide nuclides and studying α decay properties of heavy nuclides in China. In order to further improve the detective efficiency of the focal plane detector array for heavy nuclide α decay particles and \begin{document}$\gamma$\end{document} rays, we plan to upgrade the existing detection instrument. The main work of this paper is to simulate the existing detector array by using the GEANT4 software based on Monte Carlo method. In order to verify the accuracy of the program, the simulation was compared with the experimental data. The results show that the detective efficiency of the new detector system for α decay particles is about 88%, and the detective efficiency for \begin{document}$\gamma$\end{document} rays with an energy of 1 MeV is about 7%.
2021, 38(4): 430-437. doi: 10.11804/NuclPhysRev.38.2021018
Abstract(84) HTML (34) PDF (6539KB)(11)
Abstract:
A remote control system of data acquisition for the Schottky resonator at Experimental Cooler Storage Ring(CSRe) in Lanzhou has been assembled as a part of the experimental platform for nuclear mass and lifetime measurements. It is the combination of a data acquisition program and a data monitor program, both of which are exhibited in graphical user interface(GUI). It provides a number of key features to assist the users for adjusting the acquisition settings according to the experimental requirements. It is also characterized by the full utilization of a spectrum analyzer and an IQ recorder. The automatic acquisition of data files in both large size and large amount can be realized with the supplementation of an independent trigger system and a remote button pusher to overcome the intrinsic defect of the IQ recorder. It fulfills the requirements by the nuclear mass and lifetime measurements as well as other beam experiments using the Schottky resonator as the main detector at the CSRe.
2021, 38(4): 438-443. doi: 10.11804/NuclPhysRev.38.2021016
Abstract(909) HTML (68) PDF (3267KB)(25)
Abstract:
To study the effect of dose rate on irradiation hardening of the reactor pressure vessel steel (A508-3), the specimens of RPV steel were irradiated by 3.5 MeV Fe ions to four doses (0.1, 0.3, 1, 3 dpa) at three different dose rates (0.1, 0.5 and 1 dpa/h), respectively. Nano-indentation technique was used to characterize the change in hardness after irradiation. At high dose rate(1.0 dpa/h), the results indicated that irradiation hardening increases rapidly with dose and tends to saturation at the dose higher than 0.3 dpa. Compared to that with high dose rate, the hardness increment showed similar behavior at low dose rate(0.1 dpa/h) and medium dose rate(0.5 dpa/h), but it still increased gradually at dose higher than 0.3 dpa. When dose is lower than 0.3 dpa, a small difference showed in irradiation hardening under different dose rates irradiation, but the difference became significant when the dose was higher than 0.3 dpa. At present dose regime, the irradiation hardening was found to be inversely proportional to the dose rate.
2021, 38(4): 444-451. doi: 10.11804/NuclPhysRev.38.2021031
Abstract(73) HTML (28) PDF (3374KB)(15)
Abstract:
In this study, using K562 cells induced by hemin as erythroid differentiation models, the synergistic effects and mechanisms of radiation and simulated microgravity on erythroid differentiation were investigated. Results showed that the positive rates of benzidine staining and the expression of CD235a were down-regulated after treatment with X-ray radiation and simulated microgravity, meanwhile, cell proliferation was inhibited and the rates of apoptosis and necrosis were increased. The expressions of transcription factors related to erythroid differentiation EPOR and GATA-1 were down-regulated. The synergistic effects of X-ray irradiation and simulated microgravity were much stronger than those of the two alone. After irradiation and microgravity combined treatment, PIK3R2 gene expression was down-regulated. After adding PI3K inhibitor 3-MA, the apoptosis and necrosis rate of cells increased, and the erythroid differentiation rates decreased. These results indicate that X-ray irradiation and simulated microgravity treatment have synergistic inhibitory effects on erythroid differentiation, and the mechanism is related to erythroid related transcription factors EPOR, GATA-1 and damage repair pathway factor PI3K.
2021, 38(4): 452-457. doi: 10.11804/NuclPhysRev.38.2021024
Abstract(143) HTML (42) PDF (3200KB)(19)
Abstract:
By using cold target recoil ion momentum spectroscopy, we performed the single electron capture experiment between N6+ ion and Ne atom with energies of 6 and 8.6 keV/u. The n--resolved state-selective capture cross-sections and the scattering angular distributions were measured. The experimental results show the strong population of both n=3 and 4 states on the projectile, which is in good agreement with the results predicted by the reaction window calculated by the molecular coulomb over barrier model. However, the scattering angle distributions corresponding to capture to n=4 and 5 states, inconsistent with the interpretation of the classical model, the reason is mainly originated from the multi-channel coupling effect of the collision reaction process.
2021, 38(4): 458-469. doi: 10.11804/NuclPhysRev.38.2021026
Abstract(116) HTML (26) PDF (5146KB)(14)
Abstract:
Cross sections of radiative electron capture, non-radiative electron capture and target K-shell ionization by \begin{document}$300\sim 500$\end{document} MeV/u Ar18+, Kr36+ and Xe54+ ions in collisions with Ar, Kr and Xe atoms, were calculated by nonrelativistic dipole approximation, relativistic eikonal approximation, ECPSSR theory and the plane wave Born approximation, respectively. Combined with energy resolution of X-ray detectors and Doppler effect of transition spectra of the projectile ions, expected X-ray spectra of various collision systems, beam energies and different observation angles are produced for X-ray spectroscopy experiment on internal target of the Heavy Ion Research Facility at Lanzhou-Cooling Storage Ring(HIRFL-CSR). These expected spectra can help us to select and optimize experimental conditions such as collision system, beam energy, observation angle, type of detector, window and absorbing sheet of X-ray. In addition, these expected spectra can prevent weak reaction channels from overlap or disturbing with strong reaction channels and corresponding escape peaks. Therefore, accuracy of experimental data can be ensured, and utilization efficiency of beam is improved.
2021, 38(4): 470-478. doi: 10.11804/NuclPhysRev.38.2021004
Abstract(430) HTML (142) PDF (5686KB)(82)
Abstract:
Direct production of 99Mo and 99mTc with accelerator has a good development prospect in the field of nuclear medicine. Accurate and reliable nuclear reaction data is of great significance for isotope production. In this paper, the cross sections for natMo(p, x)96m+gTc, 100Mo(p, x)99Mo and 100Mo(p, 2n)99mTc reactions being taken from EXFOR database have been analyzed, and the experimental data were fitted by polynomial fit method. The excitation functions of natMo(p, x)96m+gTc、100Mo(p, x)99Mo and 100Mo(p, 2n)99mTc reactions were calculated up to 40 MeV by using TALYS-1.95 and EMPIRE-3.2.3 code with different energy level density and pre-equilibrium emission models. For the natMo(p, x)96m+gTc reaction, the calculation results predicted by preeqmode 1, 2 models are in good agreement with the experimental data when the input parameter ldmodel 6 of level density is used in TALYS-1.95 code. For the 100Mo(p, x)99Mo reaction, the calculation results predicted by preeqmode 4 models are in good agreement with the experimental data when the input parameter ldmodel 6 of level density is used in TALYS-1.95 code. For the 100Mo(p, 2n)99mTc reaction, the calculated results predicted by LEVDEN 2 in EMPIRE-3.2.3 code are in good agreement with the experimental data.
2021, 38(4): 479-486. doi: 10.11804/NuclPhysRev.38.2021043
Abstract(116) HTML (46) PDF (4379KB)(12)
Abstract:
The Steam Generator(SG) is an important connecting equipment between the primary and secondary loop of PWR nuclear power plant. The reliability of the Steam Generator Water Level Control System(SGWLCS) directly affects the safety and power generation efficiency of nuclear power plant. Based on the system structure and control logic of the steam generator water level control system, this paper adopts the Dynamic Fault Tree(DFT) method to model the reliability of SGWLCS. The fault tree model includes dynamic part and static part. The homogeneous Markov chain is used to calculate the hot standby dynamic gate about the control module of the processor and the feedwater valve, and then the whole fault tree model is analyzed according to the logical relationship. Finally, the reliability analysis results of the system and the importance analysis results of the equipment are obtained. The reliability analysis shows that the use of hot spare parts can effectively improve the reliability of the system, and the results of importance analysis can improve the design of the system and give suggestions for regular maintenance of the equipment.