分类: 物理学 >> 核物理学 提交时间: 2024-05-20
摘要: Tritium, a radioactive nuclide discharged by nuclear power plants, poses challenges for removal. Continuous online monitoring of tritium in water is crucial for real-time radiation data, given its predominant existence in the environment as water. This paper presents the design, simulation, and development of a tritium monitoring device utilizing a plastic scintillation fiber (PSF) array. Experimental validation confirmed the device’s detection efficiency and minimum detectable activity. The recorded detection efficiency of the device is 1.6 × 10−3 , which exceeds the theoretically simulated value of 4 × 10−4 by four times. Without shielding, the device can achieve a minimum detectable activity of 3165 Bq L−1 over a 1600-second measurement duration. According to simulation and experimental results, enhancing detection efficiency is possible by increasing the number and length of PSFs and implementing rigorous shielding measures. Additionally, reducing the diameter of PSFs can also improve detection efficiency. The minimum detectable activity of the device can be further reduced using the aforementioned methods.
分类: 核科学技术 >> 辐射物理与技术 提交时间: 2024-05-11
摘要: Carbon-based nanomaterials have important research significance in various disciplines, such as compositematerials, nanoelectronic devices, biosensors, biological imaging, and drug delivery. Recently, the human andecological risks associated with carbon-based nanomaterials have received increasing attention. However, thebiosafety of carbon-based nanomaterials has not been investigated extensively. In this study, we used differenttypes of carbon materials, namely, graphene oxide (GO), single-walled carbon nanotubes (SWCNTs), and multiwalledcarbon nanotubes (MWCNTs), as models to observe their distribution and oxidative damage in vivo.The results of Histopathological and ultrastructural examinations indicated that the liver and lungs were the mainaccumulation targets of these nanomaterials. SR-μ-XRF analysis revealed that SWCNTs and MWCNTs mightbe present in the brain. This shows that the three types of carbon-based nanomaterials could cross the gas–bloodbarrier and eventually reach the liver tissue. In addition, SWCNTs and MWCNTs could cross the blood–brainbarrier and accumulate in the cerebral cortex. The increase in ROS and MDA levels and the decrease in GSH,SOD, and CAT levels indicated that the three types of nanomaterials might cause oxidative stress in the liver.This suggests that direct instillation of these carbon-based nanomaterials into rats could induce ROS generation.In addition, iron (Fe) contaminants in these nanomaterials were a definite source of free radicals. However,these nanomaterials did not cause obvious damage to the rat brain tissue. The deposition of selenoprotein inthe rat brain was found to be related to oxidative stress and Fe deficiency. This information may support thedevelopment of secure and reasonable applications of the studied carbon-based nanomaterials.
分类: 核科学技术 >> 核科学与技术 提交时间: 2024-03-08
摘要: 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 measure#2;ments. 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 experi#2;mental 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 qual#2;ity are analyzed and discussed, including the depth of the sampled data, quantization noise of analog-to-digital converter (ADC), beam transverse oscillation, and longitudinal oscillation. The results of the beam experiments show that under the user operation conditions of the Shanghai Synchrotron Radiation Facility (SSRF), a beam excitation signal with an amplitude uncertainty of 2% can be reconstructed.
分类: 物理学 >> 核物理学 提交时间: 2024-02-28
摘要: 上海激光电子伽马源(Shanghai Laser Electron Gamma Source,SLEGS)是通过激光与电子逆康普顿散射产生准单能、能量连续可调的兆电子伏伽马束,是目前国际上唯一一台可连续变换碰撞角度的激光康普顿散射(Laser Compton Scattering,LCS)伽马源装置。伽马活化是研究材料特性的有效手段之一,本文介绍了上海激光电子伽马源的伽马活化平台情况、包括在线活化过程,离线低本底测量,高纯锗(High Purity Germanium,HPGe)探测器的能量效率刻度等。目前的简易低本底屏蔽使得测量系统本底计数率降低到约 5.2cps/(60 keV-3 MeV 能区)。SLEGS 伽马源的活化平台为开展伽马活化测量研究提供了有利条件,未来在核物理、核天体物理、医学应用、材料科学和环境科学等领域的研究将会发挥重要的作用。
分类: 物理学 >> 核物理学 提交时间: 2024-02-16
摘要: The Shanghai Laser Electron Gamma Source(SLEGS) has delivered a quasi-monochromatic, continuously energy-tunable gamma-ray beam. Based on the photon activation analysis(PAA) method, SLEGS has built and developed a photon activation analysis platform, including online activation and offline low-background HPGe detector measurement systems, as an alternative to direct measurement methods and a cross-tests at low throughput. Due to the short half-lives spanning from minutes to days and characteristics such as ease of fabrication, cost-effectiveness, and stability, gold (197Au) and zinc (64Zn) emerge as favorable activation targets in the gamma-ray beam flux monitor. Notably, their utility shows a multitude of advantages in monitoring the gamma-ray beam flux typically 105 photons/s with the energy of 13.16 to 19.08 MeV under the condition of the 3 mm coarse collimator. Especially in high-flux $\gamma$-ray beam experiments can be well applied.
分类: 物理学 >> 核物理学 分类: 物理学 >> 交叉学科物理及相关领域的科学与技术 提交时间: 2024-01-10
摘要: Traditional particle identification methods are time consuming, experience-dependent, and poor repeatability challenges in heavy-ion collisions at low and intermediate energies. Researchers urgently need solutions to the dilemma of traditional particle identification methods. This study explores the possibility of applying intelligent learning algorithms to the particle identification of heavy-ion collisions at low and intermediate energies. Multiple intelligence algorithms, including XgBoost and TabNet, were selected to test datasets from the neutron ion multi-detector for reaction-oriented dynamics (NIMRODISiS) and Geant4 simulation. Machine learning algorithms based on tree structures and deep learning algorithms e.g. TabNet show excellent performance and generalization ability. Adding additional data features besides energy deposition can improve the algorithm's identification ability when the data distribution is nonuniform. Intelligent learning algorithms can be applied to solve the particle identification problem in heavy-ion collisions at low and intermediate energies.
分类: 物理学 >> 核物理学 提交时间: 2023-11-16
摘要: The corrosion behavior of 316H stainless steel (SS) in the impure and purified NaCl-KCl-MgCl2 salt was investigated at 700 C . Results indicate that the main deleterious impurity induced corrosion in the impure salt was the absorbed moisture, present in the form of MgCl26H2O. 316H SS occurred severe intergranular corrosion with a corrosion depth of 130 m for 1000 h in the impure NaCl-KCl-MgCl2 salt. In contrast, the purification treatment of molten chloride salt by the dissolved Mg metal can remove the absorbed moisture, and the corresponding reactions were also discussed. As a result, the corrosiveness of NaCl-KCl-MgCl2 salt is reduced significantly. 316H SS occurred slight uniform corrosion with a depth of less than 5 m for 3000 h in the purified NaCl-KCl-MgCl2 salt.
分类: 物理学 >> 核物理学 分类: 物理学 >> 地球物理学、天文学和天体物理学 提交时间: 2023-09-12
摘要: The neutron capture cross sections (${n, upgamma}$) of Bromine was performed with the time-of-flight (TOF) technique at the Back-n facility of the China Spallation Neutron Source (CSNS). Prompt $ upgamma$-rays originating from neutron-induced capture events were detected by four C${}_6$D${}_6$ detectors. The pulse height weighting technique (PHWT) and the double-bunch unfolding method based on the Bayesian theory were used in the data analysis. To obtain reliable measurement results, background deductions, normalization, and corrections were carefully considered. The multilevel R-matrix Bayesian code SAMMY was used to extract the resonance parameters in the resolved resonance region (RRR). The average cross sections in unresolved resonance region the was obtained from 10 to 400 keV. The experimental results were compared with the data of several evaluated libraries and previous experiments in the resolved and unresolved resonance region. The TALYS code was used to describe the average cross sections in the unresolved resonance region. Astrophysical Maxwell average cross sections (MACSs) of ${}^{79,81}$Br from $ kT $ = 5 to 100 keV was calculated over a sufficiently wide range of neutron energies. At a thermal energy of $kT=30$ keV, the MACS value for ${}^{79}$Br 638$ pm$64 mb is in good agreement with the KADoNiS recommended value. By contrast, the value of 293$ pm$29 mb for ${}^{81}$Br is substantially higher than those of the evaluated database and the KADoNiS recommended value.
分类: 物理学 >> 核物理学 提交时间: 2023-09-11
摘要: The NaI:Tl scintillator is an innovative material for dual-gamma-ray and neutron detection with a low 6Li concentration. To achieve real-time n/ discrimination, a zero-crossing time comparison algorithm based on trapezoidal pulse shaping was developed. The algorithm can operate efficiently at low sampling rates and was implemented on a single-probe portable digital n/ discriminator based on a feld-programmable gate array (FPGA). The discriminator and NaI:Tl,6Li detector were tested in a neutron-gamma mixed field produced by an 241Am-Be neutron source to evaluate the performance of the algorithm. The Figure of Merits (FoM) was measured as 2.88 at a sampling rate of 50 MHz, indicating that the discriminator with its embedded algorithm has a promising n/ discrimination capability. Efficient discrimination at sampling rates of 40 and 25 MHz demonstrates that the capability of this method is not limited by low sampling rates.
分类: 物理学 >> 核物理学 提交时间: 2023-06-09
摘要: A diffraction-limited storage ring with a multi-bend achromat lattice suffers from a small dynamic aperture for conventional off-axis injection. Thus, a longitudinal on-axis injection scheme based on a new type of crab cavity is proposed in this paper. Particle tracking simulations were performed to study the disturbance of the stored beam and the motion of the injected beam during the injection process. The possibility of multi-bunch injections was discussed. In addition, the effect of the long-range wake field induced by the stored beam was analyzed. A C-band standing-wave crab cavity was designed and produced as requested, and its field distribution was measured. The corresponding results are consistent with the simulation results.