Nuclear Science and Techniques最新文献

One-neutron stripping process between (^{6})Li and (^{209})Bi was studied at 28, 30, and 34 MeV using the in-beam (gamma )-ray spectroscopy method. The (gamma )–(gamma ) coincident analysis clearly identified two (gamma )-rays feeding the ground and long-lived isomeric states, which were employed to determine the cross section. The one-neutron stripping cross sections were similar to the cross sections of complete fusion in the (^6)Li+(^{209})Bi system, but the one-neutron stripping cross sections decreased more gradually at the sub-barrier region. A coupled-reaction-channel calculation was performed to study the detailed reaction mechanism of the one-neutron stripping process in (^6)Li. The calculations indicated that the first excited state of (^5)Li is critical in the actual one-neutron transfer mechanism, and the valence proton of (^{209}textrm{Bi}) can be excited to the low-lying excited state in ((^{6}textrm{Li}),(^{5}textrm{Li})) reaction, unlike in the (d,p) reaction.

Transverse mode-coupling instability (TMCI) is a dangerous transverse single-bunch instability that can lead to severe particle loss. The mechanism of TMCI can be explained by the coupling of transverse coherent oscillation modes owing to the transverse short-range wakefield (i.e., the transverse broadband impedance). Recent studies on future circular colliders, e.g., FCC-ee, showed that the threshold of TMCI decreased significantly when both longitudinal and transverse impedances were included. We performed computations for the circular electron–positron collider (CEPC) and observed a similar phenomenon. Systematic studies on the influence of longitudinal impedance on the TMCI threshold were conducted. We concluded that the imaginary part of the longitudinal impedance, which caused a reduction in the incoherent synchrotron tune, was the primary reason for the reduction in the TMCI threshold. Additionally, the real part of the longitudinal impedance assists in increasing the TMCI threshold.

We investigated (^{50,52-54})Cr-induced fusion reactions for the synthesis of the superheavy element in the (104le Zle 122) range. The cross sections produced in this investigation using (^{54})Cr projectiles were compared with those obtained in prior experiments. The estimated cross sections from this analysis are consistent with the findings of prior studies. From the current study, the predicted cross section was found to be 42fb at 236 MeV for (^{53})Cr+(^{243})Am, 23.2 fb at 236 MeV for (^{54})Cr+(^{247})Cm, 95.6 fb at 240 MeV for (^{53})Cr+(^{248})Bk, and 1.33 fb at 242 MeV for (^{53})Cr+(^{250})Cf. Consequently, these projected cross sections with excitation energy and beam energy will be useful in future Cr-induced fusion reaction investigations.

Nuclear mass is a fundamental property of nuclear physics and a necessary input in nuclear astrophysics. Owing to the complexity of atomic nuclei and nonperturbative strong interactions, conventional physical models cannot completely describe nuclear binding energies. In this study, the mass formula was improved by considering an additional term from the Fermi gas model. All nuclear masses in the Atomic Mass Evaluation Database were reproduced with a root-mean-square deviation (RMSD) of (sim)1.86 MeV (1.92 MeV). The new mass formula exhibits good performance in the neutron-rich nuclear region. The RMSD decreases to 0.393 MeV when the ratio of the neutron number to the proton number is (ge)1.6.

Various electromagnetic signals are excited by the beam in the acceleration and beam-diagnostic elements of a particle accelerator. It is important to obtain time-domain waveforms of these signals with high temporal resolution for research, such as the study of beam–cavity interactions and bunch-by-bunch parameter measurements. Therefore, a signal reconstruction algorithm with ultrahigh spatiotemporal resolution and bunch phase compensation based on equivalent sampling is proposed in this paper. Compared with traditional equivalent sampling, the use of phase compensation and setting the bunch signal zero-crossing point as the time reference can construct a more accurate reconstructed signal. The basic principles of the method, simulation, and experimental comparison are also introduced. Based on the beam test platform of the Shanghai Synchrotron Radiation Facility (SSRF) and the method of experimental verification, the factors that affect the reconstructed signal quality are analyzed and discussed, including the depth of the sampled data, quantization noise of analog-to-digital converter, beam transverse oscillation, and longitudinal oscillation. The results of the beam experiments show that under the user operation conditions of the SSRF, a beam excitation signal with an amplitude uncertainty of 2% can be reconstructed.

We proposed and compared three methods (filter burnup, single energy burnup, and burnup extremum analysis) to build a high-resolution neutronics model for 238Pu production in high-flux reactors. The filter burnup and single energy burnup methods have no theoretical approximation and can achieve a spectrum resolution of up to ~ 1 eV, thereby constructing the importance curve and yield curve of the full energy range. The burnup extreme analysis method combines the importance and yield curves to consider the influence of irradiation time on production efficiency, thereby constructing extreme curves. The three curves, which quantify the transmutation rate of the nuclei in each energy region, are of physical significance because they have similar distributions. A high-resolution neutronics model for ²³⁸Pu production was established based on these three curves, and its universality and feasibility were proven. The neutronics model can guide the neutron spectrum optimization and improve the yield of ²³⁸Pu by up to 18.81%. The neutronics model revealed the law of nuclei transmutation in all energy regions with high spectrum resolution, thus providing theoretical support for high-flux reactor design and irradiation production of ²³⁸Pu.

Global variance reduction is a bottleneck in Monte Carlo shielding calculations. The global variance reduction problem requires that the statistical error of the entire space is uniform. This study proposed a grid-AIS method for the global variance reduction problem based on the AIS method, which was implemented in the Monte Carlo program MCShield. The proposed method was validated using the VENUS-III international benchmark problem and a self-shielding calculation example. The results from the VENUS-III benchmark problem showed that the grid-AIS method achieved a significant reduction in the variance of the statistical errors of the MESH grids, decreasing from 1.08 × 10^–2 to 3.84 × 10^–3, representing a 64.00% reduction. This demonstrates that the grid-AIS method is effective in addressing global issues. The results of the self-shielding calculation demonstrate that the grid-AIS method produced accurate computational results. Moreover, the grid-AIS method exhibited a computational efficiency approximately one order of magnitude higher than that of the AIS method and approximately two orders of magnitude higher than that of the conventional Monte Carlo method.

Herein, we employ the threshold energy neutron analysis (TENA) technique to introduce the world's first active interrogation system to detect special nuclear materials (SNMs), including U-235 and Pu-239. The system utilizes a DD neutron generator based on inertial electrostatic confinement (IEC) to interrogate suspicious objects. To detect secondary neutrons produced during fission reactions induced in SNMs, a tensioned metastable fluid detector (TMFD) is employed. The current status of the system's development is reported in this paper, accompanied by the results from experiments conducted to detect 10 g of highly enriched uranium (HEU). Notably, the experimental findings demonstrate a distinct difference in the count rates of measurements with and without HEU. This difference in count rates surpasses two times the standard deviation, indicating a confidence level of more than 96% for identifying the presence of HEU. The paper presents and extensively discusses the proof-of-principle experimental results, along with the system's planned trajectory.

The 28 nm process has a high cost-performance ratio and has gradually become the standard for the field of radiation-hardened devices. However, owing to the minimum physical gate length of only 35 nm, the physical area of a standard 6T SRAM unit is approximately (0.16,upmu hbox{m}^{2}), resulting in a significant enhancement of multi-cell charge-sharing effects. Multiple-cell upsets (MCUs) have become the primary physical mechanism behind single-event upsets (SEUs) in advanced nanometer node devices. The range of ionization track effects increases with higher ion energies, and spacecraft in orbit primarily experience SEUs caused by high-energy ions. However, ground accelerator experiments have mainly obtained low-energy ion irradiation data. Therefore, the impact of ion energy on the SEU cross section, charge collection mechanisms, and MCU patterns and quantities in advanced nanometer devices remains unclear. In this study, based on the experimental platform of the Heavy Ion Research Facility in Lanzhou, low- and high-energy heavy-ion beams were used to study the SEUs of 28 nm SRAM devices. The influence of ion energy on the charge collection processes of small-sensitive-volume devices, MCU patterns, and upset cross sections was obtained, and the applicable range of the inverse cosine law was clarified. The findings of this study are an important guide for the accurate evaluation of SEUs in advanced nanometer devices and for the development of radiation-hardening techniques.

In this study, to efficiently remove Pb(II) from aqueous environments, a novel L-serine-modified polyethylene/polypropylene nonwoven fabric sorbent (NWF-serine) was fabricated through the radiation grafting of glycidyl methacrylate and subsequent L-serine modification. The effect of the absorbed dose was investigated in the range of 5–50 kGy. NWF-serine was characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, and scanning electron microscopy. Batch adsorption tests were conducted to investigate the influences of pH, adsorption time, temperature, initial concentration, and sorbent dosage on the Pb(II) adsorption performance of NWF-serine. The results indicated that Pb(II) adsorption onto NWF-serine was an endothermic process, following the pseudo-second-order kinetic model and Langmuir isotherm model. The saturated adsorption capacity was 198.1 mg/g. NWF-serine exhibited Pb(II) removal rates of 99.8% for aqueous solutions with initial concentrations of 100 mg/L and 82.1% for landfill leachate containing competitive metal ions such as Cd, Cu, Ni, Mn, and Zn. Furthermore, NWF-serine maintained 86% of its Pb(II) uptake after five use cycles. The coordination of the carboxyl and amino groups with Pb(II) was confirmed using X-ray photoelectron spectroscopy and extended X-ray absorption fine structure analysis.