## Current Articles 2022, Volume 39,  Issue 1

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2022, 39(1): 1-2.
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2022, 39(1): 1-15. doi: 10.11804/NuclPhysRev.39.2021075
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Within the framework of Lanzhou quantum molecular dynamics(LQMD) transport model, the isospin and in-medium effects on the hyperon production and kinetic energy spectra in the reaction of different heavy-ion reaction are investigated thoroughly. A repulsive hyperon-nucleon potential which is related to the hyperon momentum and baryon density from the chiral effective field theory is implemented into the model. The correction on threshold energy of the elementary hyperon cross section is taken into account. It is found that the \begin{document}$\varSigma$\end{document}yields are suppressed in the domain of midrapidity and domain of kinetic energy spectra with the potential. The emission behavior of the hyperons is also affected by the repulsive hyperon-nucleon potential. The hyperons tend to move along the direction of the beam and along the direction perpendicular to the reaction plane. Finally, we found that \begin{document}$\varSigma^{-}$\end{document}/\begin{document}$\varSigma^{+}$\end{document} yield ratio depends on the stiffness of nuclear symmetry energy in the high-energy region. The \begin{document}$\varSigma^{-}$\end{document}/\begin{document}$\varSigma^{+}$\end{document} yield ratio with a hard symmetry energy is increased by the repulsive hyperon-nucleon potential. And it is found that the compressibility of nuclear matter will affect the hyperon production obviously.
2022, 39(1): 16-22. doi: 10.11804/NuclPhysRev.39.2021071
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The effect of the two forms of momentum-dependence potential on the directed flow and elliptic flow of neutron, proton, hydrogen isotopes, and charged particles are explored with the ultrarelativistic quantum molecular dynamics(UrQMD) model. The results show that the directed flow is almost insensitive to the momentum-dependence potential for the given incompressibility \begin{document}$K_0$\end{document}. But the elliptic flow of the above four particle species are sensitive to the strength and momentum dependence of the momentum- dependence potential, especially at high transverse momentum. The stronger momentum-dependence potential leads to a stronger elliptic flow. By comparing with the ASY-EOS experimental data, the calculation with a stronger momentum-dependence potential is favored.
2022, 39(1): 23-29. doi: 10.11804/NuclPhysRev.39.2021081
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Neutron-rich nuclei which are far away from the “ valley of stability ” on the chart of nuclides have always been a hotspot of nuclear physics. As a special kind of metastable excited states of deformed neutron-rich nuclei, high-K isomers usually are prolate, while oblate high-K isomers are rare. A recent experiment suggested that the \begin{document}${K}^{\mathrm{\pi }}={7}^{-}$\end{document} two-quasiparticle state of neutron-rich 94Se is oblate. This is the first experimental evidence that oblate high-K isomers exist in deformed nuclei. In combination with relevant experiments, we made an assumption that there are other unobserved oblate high-K isomers in the neutron-rich A~100 region. Theoretical investigations of \begin{document}${K}^{\mathrm{\pi }}={9}^{-}$\end{document} and \begin{document}${K}^{\mathrm{\pi }}={7}^{-}$\end{document} two-quasiparticle states in the neutron-rich A~100 region have been performed with the configuration-constrained potential energy calculation method, possible positions of oblate high-K isomers in this region have been predicted. According to Nilsson model, the existence of oblate high-K isomers relies on high-Ω single particle orbitals around the Fermi level. These high-Ω single particle orbitals origin from the breaking of degeneracy of high-j intruder states when the nuclei are oblate. Oblate high-K isomers are ideal subjects for the research of deformation parameters and excited energies of neutron-rich nuclei, and contribute to a better understanding of energy level structures of deformed nuclei.
2022, 39(1): 30-36. doi: 10.11804/NuclPhysRev.39.2022001
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We apply linear Regge trajectory and relatived quark model to revisit the low-lying excited singly-heavy mesons and explain the narrow mass splitting of these excited states to arise mainly from relativistic effect of the light quarks. The P-wave masses of the singly heavy mesons (D, \begin{document}${D_s}$\end{document}, B, \begin{document}${B_s}$\end{document}) with spin-parity \begin{document}${J^ + }$\end{document}(\begin{document}$J = 0$\end{document}, \begin{document}$1$\end{document}, \begin{document}$2$\end{document}) have been computed, suggesting the unseen states of the mesons B and \begin{document}${B_s}$\end{document} to be the \begin{document}${0^ + }$\end{document} state with mass 5 659 and 5 788 MeV, respectively. Our calculations show that \begin{document}${D_{s{\text{0}}}}\left( {{\text{2\;317}}} \right)$\end{document} contains a mass downshift of around 70 MeV while \begin{document}${D_{s{\text{1}}}}\left( {{\text{2\;460}}} \right)$\end{document} has no significant mass shift.
2022, 39(1): 37-44. doi: 10.11804/NuclPhysRev.39.2021045
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Long-term stable operation is one of difficult and frontier topics in the field of high-current linear accelerators. In this article, taking the China initiative Accelerator Driven System(CiADS) accelerator as an example, of whose virtual model implemented with TraceWin software by using simulation data, a segmented failure compensation method of superconducting(SC) cavity by artificial intelligence algorithm has been proposed. The neighboring elements of the failure cavities are used to rematch the beam envelope, while all the downstream cavities are used to compensate the beam energy. Compared with traditional optimization methods, this research can realize the failure compensation of low energy SC section, and has the advantages of fast calculation speed and strong versatility. It provides new feasibility for the practical application of component failure compensation.
2022, 39(1): 45-53. doi: 10.11804/NuclPhysRev.39.2021049
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The low-level radio frequency control system(LLRF) is mainly used to control the electric field and resonate frequency of the accelerating cavity to ensure the stable operation of the accelerator and output high-quality beam. The LLRF software provides a graphical user interface, and realize the functions such as data display and storage, as well as some algorithm like automatic logic and so on. A well-designed LLRF software improves the operability of the LLRF and reduces the amount of manual work and failure rate. This paper introduces the development and design of LLRF software for China spallation neutron source(CSNS) linac, mainly including feedforward automatic calculation, automatic frequency control of acceleration cavity, frequency detuning algorithm, automatic RF power up and so on. Finally, the amplitude and phase stability index of the system is better than the required design index, and meets the requirements of long-term stable operation.
2022, 39(1): 54-64. doi: 10.11804/NuclPhysRev.39.2021011
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Accelerator mass spectrometry(AMS) is the most sensitivity measurement technique for the long-lived radioisotopes up to now and has been widely used in archaeology, geology, environment, physics and other fields. With the development of technology, the AMS devices are developing towards the miniaturization. The miniaturization of AMS device has been well applied. In this paper, the key technologies of AMS for long-life radionuclide high-sensitivity analysis are comprehensively discussed, and the characteristic technologies used in the miniaturized AMS system are systematically introduced. Finally, the devices and performances of two miniaturization AMS system developed by China Institute of Atomic Energy are discussed.
2022, 39(1): 65-72. doi: 10.11804/NuclPhysRev.39.2021035
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To improve the ability of particle identification of the RIBLL2 separator at the HIRFL-CSR complex, a new high-performance detector for measuring fragment starting time and position at the F1 dispersive plane has been constructed and installed, and a method for achieving precise Bρ determination has been developed using the experimentally derived ion-optical transfer matrix elements from the measured position and ToF information. Using the high-performance detectors and the precise determination method, the fragments produced by the fragmentation of 78Kr at 300 MeV/nucleon were identified clearly at the RIBLL2-ETF under full momentum acceptance. The atomic number Z resolution of σZ~0.19 and the mass-to-charge ratio A/Q resolution of σA/Q~5.8×10−3 were obtained for the 75As33+ fragment. This great improvement will increase the collection efficiency of exotic nuclei, extend the range of nuclei of interest from the A<40 mass region up to the A~80 mass region, and promote the development of radioactive nuclear beam experiments at the RIBLL2 separator.
2022, 39(1): 73-80. doi: 10.11804/NuclPhysRev.39.2021039
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A statistical correction method is proposed to suppress the pile-up background events in data analysis. This method is verified by a cosmic muon lifetime measurement experiment, achieved by a plastic scintillator detector using the timing coincidence method, where dominant background events originate from pile up muons and electronic noise. To complement the intrinsic shortcoming of relatively rare decay events from registered cosmic muon events in the local laboratory, Monte Carlo simulation is applied to generate large samples in order to cross check the new method. The measurement of the muon lifetime in our setup gives a result of \begin{document}$\tau_\mu^{\rm exp} = 2.19 \pm 0.07 \ \mu \text{s}$\end{document} at 95% confidence level, while the result before applying the correction is \begin{document}$\tau_{\mu}' = 2.27 \pm 0.07 ~\mu \text{s}$\end{document} (95% C.L.). The treatment of pile-up events by a statistical correction equation in this study might be adapted to improve data analysis in the general coincident background dominating experiments.
2022, 39(1): 81-87. doi: 10.11804/NuclPhysRev.39.2021023
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As one of the key components in high precision time measurement based on discrimination and time digitization, the time-to-digital converter(TDC) is widely used in many fields. This paper presents the design and testing of a DLL based TDC prototype ASIC named DHR TDC with a large detectable range and high resolution in 180 nm CMOS technology. A test module was designed and the test platform was set up for the TDC performance evaluation. Test results indicate that this TDC achieves a time resolution of better than 60 ps RMS with an averaged bin size of around 156 ps, as well as a measurement dynamic range of up to 20 µs, and its differential nonlinearity(DNL) and integral nonlinearity(INL) are better than 0.13 LSB and 0.15 LSB, respectively.
2022, 39(1): 88-94. doi: 10.11804/NuclPhysRev.39.2021040
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To monitor the irradiation dose and position of heavy ion beam with the imaging methods in the treatment of the heavy ion tumor radiotherapy, an In-Beam Positron Emission Tomography(In-beam PET) will be mounted in Heavy-Ion Medical Machine(HIMM) in China. In In-beam PET, the event data is collected by the detector array and digitized by front-end Data Acquisition Units(DAQU). Then digitized data will be sent to the Central Processing Module (CPM) through the optical fiber link, and finally transmitted to the host sever via the PCIe interface. A single DAQU can obtain a maximum data rate of 2.2 Gbit/s, which imposes high requirements on the transmission bandwidth of the optical fiber link accordingly. As the core of DAQU is Cyclone V FPGA and the core of CPM is Kintex-7 FPGA, the realization of reliable real-time communication between FPGAs of different companies is a challenge. This paper presents a new design and the implementation of the optical fiber link for In-beam PET, aiming to realize the stable communication between Cyclone V FPGA and Kintex-7 FPGA. The performance of the design shows that it can meet the demand of high stability and high accuracy in real-time.
2022, 39(1): 95-100. doi: 10.11804/NuclPhysRev.39.2021029
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Simulation programmes which combine the quantum model and Monte Carlo method by Schulz et al. are developed to reconstruct the experimental spectra of the single ionization in collisions between 100 MeV/u \begin{document}${\rm{C}}^{6+}$\end{document} and He (Nature, 2003, 422(6927): 48.). By introducing the uncertainty of the experimental set-ups the discrepancy between the theory and the experimental data can be studied. The simulation results show that the position resolution of the detector, target temperature and the small fluctuation of the extraction DC voltage applied to the spectrometer can have a significant influence on the final experimental results. The experimental fully differential cross sections can be reproduced when the target temperature reaches 16 K, or the voltage fluctuation reaches 0.05 V, which provides an alternative perspective for the long-term \begin{document}${\rm{C}}^{6+}$\end{document} puzzle. The simulation also provides a practical method for fast discrimination of influences from different set-up aspects in real few-body quantum dynamics experiments.
2022, 39(1): 101-107. doi: 10.11804/NuclPhysRev.39.2021030
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A new type of F/M steel (SIMP steel) and two kinds of ODS steels (MA956 and Eurofer-ODS steels) were irradiated by 2 MeV He ions to fluence of 1×1017 ions/cm2 at 500 and 600 °C. After irradiation, swelling behaviors and effect of nanostructures (such as grain boundaries, precipitates and nano-oxide particles) on the nucleation and growth of He bubbles were studied by transmission electron microscope. The results show that both SIMP and Eurofer-ODS steels exhibit better swelling resistance than MA956 ODS steel at 500 °C, because the grain boundaries or precipitates pronouncedly inhibit the growth of He bubbles. The Eurofer-ODS steel shows best swelling resistance due to the inhibition of He bubbles growth by the grain boundary and oxide interface at 600 °C. The present work shows that nanostructures in materials inhibit the process of He bubble growth under high He fluence conditions, but the degree of inhibition varies with different materials.
2022, 39(1): 108-113. doi: 10.11804/NuclPhysRev.39.2021032
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Molecular dynamics(MD) simulations were performed to investigate the effects of grain size on the mechanical properties of nano-polycrystalline iron doped with helium(He). Simulated X-ray diffraction(XRD) was used to explore the relationship between the generation of cracks and the distortion of crystal structural in nano-polycrystalline iron during tensile deformation. The simulation results show that the peak stresses are obviously decreased due to the introduction of He atoms into the grain boundaries of nano-polycrystalline iron. In addition, it is observed that the generation and growth of intergranular cracks are significantly enhanced by He atoms which are distributed at grain boundary(GB) regions during tensile simulation. The results suggest that the intergranular cracks are promoted by GB He atoms, and the size and number of cracks increase with the increasing grain size of nano-polycrystalline iron. The separation of peak {200} and {211} are significantly observed in the XRD patterns during loading. The diffraction angle of subpeaks is higher in the XRD patterns of nano-polycrystalline iron with GB He than in that without He during the strain range from 6% to 10%, and the diffraction angle of subpeaks and the growth of cracks increase with the increasing grain size. It is demonstrated that the degradation of mechanical property caused by intergranular cracks has close relationship with the change of structural distortion obtained by simulated XRD patterns in nano-polycrystalline iron.
2022, 39(1): 114-120. doi: 10.11804/NuclPhysRev.39.2021033
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In carbon-ion radiotherapy, a variety of secondary particles are produced when carbon-ion beams pass through beam-line components during the dose delivery process and form an external radiation field. The predominant part of external radiation is from neutrons. As high LET radiation, low-dose neutron exposures have high relative biological effectiveness. Reducing the secondary neutrons can help to curb the risks of normal tissue complications and secondary cancers. The fluence and dose equivalent spectrums of exogenous neutrons induced by the passive beam delivery system of carbon ion therapy at different locations around the isocenter were simulated using the Monte Carlo method to evaluate the dose equivalent contribution of neutron radiation; The influence of the different collimating aperture sizes on the secondary neutron dose equivalent was also investigated. The simulation results show that high-energy neutrons had a certain contribution to the total neutron dose equivalent of the simulated locations, which account for up to 26%. Under real treatment conditions, as the collimating aperture size increased from closed to 15 cm×15 cm, the neutron dose equivalent decreased by approximately 85% at the isocenter and laterally distal locations, and about 70% at the distal locations in the beam direction. These results can be used to guide the study of secondary neutrons under different treatment conditions, and provide a basis for assessing non-therapeutic radiation received by patients under treatment conditions.
2022, 39(1): 121-126. doi: 10.11804/NuclPhysRev.39.2021064
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The control method for the reactor power by adjusting the beam intensity has been studied for the China initiative Accelerator Driven System(CiADS) facility. In the proposed control method, the beam intensity can be adjusted continuously by changing the aperture size. The aperture size is adjusted automatically based on the PID controllers by comparing the setting power with the measured value. To evaluate the proposed method, a CiADS core model is built based on the point reactor kinetics equation. The simulations based on the CiADS core model have indicated that the reactor power varies with the beam intensity and that the reactor power can be controlled effectively by adjusting the aperture size. Finally, the automatic and manual control functions for the reactor power have been implemented in a Distributed Control System(DCS). In the automatic control function, the measured value of the reactor power is sent to the input-output model of DCS system and is compared with the setting value. Then, the new value of the aperture size is calculated with the PID controller and is sent the drive motor system of the aperture. In addition, the reactor power can also be adjusted by setting manually the aperture size in the control room.
2022, 39(1): 127-133. doi: 10.11804/NuclPhysRev.39.2021077
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Pulsed neutron source method(PNS) is an important technique for the reactivity measurement of accelerator driven sub-critical systems. The CiADS sub-critical reactor model is established using Monte Carlo code to simulate the neutron transport process bombarded by pulsed proton beam, and the time spectrum of neutron flux is obtained. A code is developed by Python programming language to finish the pulsed neutron superposition process. It can obtain a stable delayed neutron background and the variation of neutron flux at different positions of the core under the continuously pulsed period proton injection. The reactivity measurement simulation of the sub-critical reactor by PNS method come true. Subsequently, the PNS method is used to simulate the reactivity of the CiADS core under different sub-criticalities and detection positions, and the results is compared with the reference values. It shows that this method can accurately predict the reactivity of sub-critical reactor at high effective multiplication factor (\begin{document}$k_{\mathrm{eff}} >0.94$\end{document}). The result nearby the spallation target shows a strong spatial effect. It needs to do experiments to figure it out.While, the outer fuel zone and the reflector assembly positions are more suitable for detector placement. Those conclusions can be used as a reference for the reactivity measurement of CiADS in the future.