分类: 核科学技术 >> 辐射物理与技术 提交时间: 2024-07-12
摘要: 研究了在 700 ◦C 高温下暴露的 UNS N10003 合金激光焊缝的微观组织和拉伸断裂机制的演变。暴露 100 小时后,熔合区中初生共晶 M6C-γ 碳化物周围析出了细小的 M6C 碳化物。在长期热暴露过程中,细小的 M6C 碳化物的尺寸增大。当暴露时间延长至 10 000 小时时,焊态熔合区中的共晶 M6C-γ 碳化物转变为球形 M6C 碳化物。此外,随着暴露时间的增加,球形 M6C 颗粒的尺寸出现粗化。共晶 M6C-γ 碳化物的演变和 M6C 碳化物的粗化不会对焊接接头的拉伸性能产生不利影响。
分类: 核科学技术 >> 辐射物理与技术 提交时间: 2024-06-07
摘要: 本文介绍了一种超疏水性三聚氰胺(ME)海绵(ME-g-PLMA),该海绵通过高能辐射诱导的原位共价接枝长烷基十二烷基甲基丙烯酸酯(LMA)到ME海绵上,以实现高效的油水分离。所得的ME-g-PLMA海绵具有优良的孔隙结构,具有超疏水性(水接触角为154°)和超亲油性,可吸收高达自身重量66-168倍的各类油脂。所得到的ME-g-PLMA海绵可以通过连接泵连续分离水面上的浮油,或者通过重力驱动装置分离水下的浮油。ME-g-PLMA海绵在长期浸泡在不同的腐蚀性溶液中,多次反复吸油后,也能保持其高疏水性。所得改性ME-g-PLMA海绵具有优异的分离性能,在溢油清理方面具有巨大的潜力。
分类: 核科学技术 >> 辐射物理与技术 提交时间: 2024-05-30
摘要: Cone-beam computed tomography (CBCT) is mostly used for position verification during the treatment pro#2;cess. However, severe image artifacts in CBCT hinder its direct use in dose calculation and adaptive radiationtherapy re-planning for proton therapy. In this study, an improved U-Net neural network named CBAM-U-Netwas proposed for CBCT noise reduction in proton therapy, which is a CBCT denoised U-Net network with con#2;volutional block attention modules. The datasets contained 20 groups of head and neck images. The CT imageswere registered to CBCT images as ground truth. The original CBCT denoised U-Net network, sCTU-Net, wastrained for model performance comparison. The synthetic CT(SCT) images generated by CBAM-U-Net and theoriginal sCTU-Net are called CBAM-SCT and U-Net-SCT images, respectively. The HU accuracies of the CT,CBCT, and SCT images were compared using four metrics: mean absolute error (MAE), root mean square error(RMSE), peak signal-to-noise ratio (PSNR), and structure similarity index measure (SSIM). The mean values ofthe MAE, RMSE, PSNR, and SSIM of CBAM-SCT images were 23.80 HU, 64.63 HU, 52.27 dB, and 0.9919,respectively, which were superior to those of the U-Net-SCT images. To evaluate dosimetric accuracy, the rangeaccuracy was compared for a single-energy proton beam. The γ-index pass rates of a 4 cm × 4 cm scannedfield and simple plan were calculated to compare the effects of the noise reduction capabilities of the originalU-Net and CBAM-U-Net on the dose calculation results. CBAM-U-Net reduced noise more effectively thansCTU-Net, particularly in high-density tissues. We proposed a CBAM-U-Net model for CBCT noise reductionin proton therapy. Owing to the excellent noise reduction capabilities of CBAM-U-Net, the proposed modelprovided relatively explicit information regarding patient tissues. Moreover, it can be used in dose calculationand adaptive treatment planning in the future.
分类: 核科学技术 >> 核科学技术其他学科 提交时间: 2024-05-08
摘要: 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.
分类: 物理学 >> 核物理学 提交时间: 2024-03-19
摘要: The exploration of exotic shapes and properties of atomic nuclei, e.g., α cluster and toroidal shape, is afascinating field in nuclear physics. To study the decay of these nuclei, a novel detector aimed at detectingmultiple alpha-particle events was designed and constructed. The detector comprises two layers of double-sidedsilicon strip detectors (DSSD) and a cesium iodide scintillator array coupled with silicon photomultipliers arrayas light sensors, which has the advantages of their small size, fast response, and large dynamic range. DSSDscouple with cesium iodide crystal arrays are used to distinguish multiple alpha hits. The detector array has acompact and integrated design that can be adapted to different experimental conditions. The detector array wassimulated using Geant4, and the excitation energy spectra of some alpha-clustering nuclei were reconstructedto demonstrate the performance. The simulation results show that the detector array has excellent angularand energy resolutions, enabling effective reconstruction of the nuclear excited state by multiple alpha particleevents. This detector offers a new and powerful tool for nuclear physics experiments and has the potential todiscover interesting physical phenomena related to exotic nuclear structures and their decay mechanisms
分类: 物理学 >> 核物理学 提交时间: 2024-03-19
摘要: In recent years, the gap between the supply and demand of medical radioisotopes has increased, necessitating new methods for producing medical radioisotopes. Photonuclear reactions based on gamma sources have unique advantages in terms of producing high specific activity and innovative medical radioisotopes. However, the lack of experimental data on reaction cross sections for photonuclear reactions of medical radioisotopes of interest has severely limited the development and production of photonuclear transmutation medical radioisotopes. In this study, the entire process of the generation, decay, and measurement of medical radioisotopes was simulated using online gamma activation and offline gamma measurements combined with a shielding gammaray spectrometer. Based on a quasi-monochromatic gamma beam from the Shanghai Laser Electron Gamma Source (SLEGS), the feasibility of the measurement of production cross section for surveyed medical isotopes was simulated, and specific solutions for measuring medical radioisotopes with low production cross sections were provided. The feasibility of this method for high precision measurements of the reaction cross section of medical radioisotopes was demonstrated.
分类: 核科学技术 >> 核科学与技术 提交时间: 2024-03-12
摘要: This paper presents a new technique for measuring the bunch length of a high-energy electron beam at a bunch-by-bunch rate in storage rings. This technique uses the time–frequency-domain joint analysis of the bunch signal to obtain bunch-by-bunch and turn-by-turn longitudinal parameters, such as bunch length and synchronous phase. The bunch signal is obtained using a button electrode with a bandwidth of several gigahertz. The data acquisition device was a high-speed digital oscilloscope with a sampling rate of more than 10 GS/s, and the single-shot sampling data buffer covered thousands of turns. The bunch length and synchronous phase information were extracted via offline calculations using Python scripts. The calibration coefficient of the system was determined using a commercial streak camera. Moreover, this technique was tested on two different storage rings and successfully captured various longitudinal transient processes during the harmonic cavity debugging process at the Shanghai Synchrotron Radiation Facility (SSRF), and longitudinal instabilities were observed during the single bunch accumulation process at Hefei Light Source (HLS). For Gaussian-distribution bunches, the uncertainty of the bunch phase obtained using this technique was better than 0.2 ps, and the bunch length uncertainty was better than 1 ps. The dynamic range exceeded 10 ms. This technology is a powerful and versatile beam diagnostic tool that can be conveniently deployed in high-energy electron storage rings.
分类: 物理学 >> 核物理学 提交时间: 2024-02-07
摘要: We report on using synthetic silicon for a high-precision X-ray polarimeter comprising a polarizer and an analyzer, each based on a monolithic channel-cut crystal used at multiple Brewster reflections with a Bragg angle very close to 45. Experiments were performed at the BL09B bending magnet beamline of the Shanghai Synchrotron Radiation Facility using a Si(800) crystal at an X-ray energy of 12.914 keV. A polarization purity of 8.410-9was measured. This result is encouraging, as the measured polarization purity is the best-reported value for the bending magnet source. Notably, this is the firstly systematic study on the hard X-ray polarimeter in China, which is crucial for exploring new physics, such as verifying vacuum birefringence.
分类: 核科学技术 >> 核科学与技术 提交时间: 2023-12-10
摘要: X-ray photon correlation spectroscopy (XPCS) has emerged as a powerful tool for probing nanoscale dynamics of soft condensed matter and strongly correlated materials, offering high spatial resolution and high penetration capability. This technique requires high brilliance and beam coherence, which are not directly available at modern synchrotron beamlines in China. To pave the way for future XPCS experiments, we first modified the optical setup of the newly commissioned BL10U1 USAXS beamline at the Shanghai Synchrotron Radiation Facility (SSRF). Subsequently, we carried out XPCS measurements on silica suspensions of glycerol, which were opaque in appearance due to high concentrations. Image series were collected by a high frame-rate area detector. Comprehensive analysis was carried out, yielding the correlation functions and several key dynamic parameters. All results agree well with the theory of Brownian motion, demonstrating the feasibility of XPCS at SSRF. Eventually, by carefully optimizing the setup and analyzing algorithms, we achieved a time resolution of 2 ms, enabling characterization of millisecond dynamics in opaque systems.
分类: 核科学技术 >> 辐射物理与技术 提交时间: 2023-11-24
摘要: Evaluating the comprehensive characteristics of extreme ultraviolet (EUV) photoresists is crucial for their application in EUV lithography, a key process in modern technology. This paper highlights the capabilities of the Shanghai Synchrotron Radiation Facility (SSRF) 08U1B beamline in advancing this field. Specifically, it demonstrates how this beamline can create fringe patterns with a 15-nm half-pitch (HP) on a resist using synchrotron-based EUV lithography (EUV-IL). This achievement is vital for evaluating EUV photoresists at the advanced 5-nm node. We provide a detailed introduction to the methods and experimental setup used at the SSRF 08U1B beamline to assess an EUV photoresist. A significant part of this research involved the fabrication of high-resolution hydrogen silsesquioxane (HSQ) mask gratings. These gratings, with an aspect ratio of approximately 3, were created using electron beam lithography (EBL) on an innovative mask framework. This framework was crucial in eliminating the impact of zeroth-order light on interference patterns. The proposed framework offers a new approach to mask fabrication, particularly beneficial for achromatic Talbot lithography and multicoherent-beam interference applications.
分类: 物理学 >> 核物理学 提交时间: 2023-10-12
摘要: Thispaper introducesthe proposed Insertion Device (ID) scheme for the Shanghai Synchrotron Radiation Facility Upgrade (SSRF-U). Based on this scheme, the influences of the ID radiation on the Intra-Beam Scattering (IBS) emittance and energy spread were evaluated. Optical distortion caused by the IDs was comprehensively examined and compensated using both local and global corrections. Subsequently, a Frequency Map Analysis (FMA) method was used to identify potentially dangerous resonance lines. In addition, the dynamic aperture, energy acceptance, and Touschek lifetime were calculated after considering high-order magnetic field errors to ensure that the ID effect did not affect the operation of the storage ring.
分类: 核科学技术 >> 粒子加速器 提交时间: 2023-08-21
摘要: The purpose of this study was to design a rapid cycling synchrotron, making it capable of proton beam ultra-high dose rate irradiation, inspired by laser accelerators. The design had to be cheap and simple. We consider our design from six aspects: the lattice, injection, extraction, space charge effects, eddy current effects and energy switching. Efficiency and particle quantity must be addressed when injected. The space charge effects at the injection could affect particles number. The eddy current effects in the vacuum chambers would affect the magnetic field itself and generate heat, all of which need to be taken into account. Fast extraction can obtain 1010 protons/pulse, equal to instantaneous dose rate up to 107 Gy/s in a very short time, while changing various extraction energies rapidly and easily to various deposition depths. In the further research we expect to combine a delivery system with this accelerator to realize the FLASH irradiation.
分类: 物理学 >> 核物理学 提交时间: 2023-07-06
摘要: Proton computed tomography (CT) has a distinct practical significance in clinical applications. It eliminates 35% errors caused by the transformation of Hounsfield unit (HU) to relative stopping power (RSP) valueswhen using X-ray CT for positioning andtreatment planning systems (TPSs). Following the development of FLASH proton therapy, there are increased requirements for accurate and rapid positioning in TPSs. Thus, anewrapid proton CT imaging mode is proposed based on sparsely sampled projections. The proton beam wasboosted to 350 MeV by a compact proton linear accelerator (linac). In this study,thecomparisons of the proton scattering with the energyof 350 MeV and 230 MeV are conducted based on GEANT4simulations.Asthe sparsely sampledinformation associated with beam acquisitions at 12angles is not enough for reconstruction, X-ray CT is used as a prior image. The RSP map generated by converting the X-ray CT was constructed based onMonte Carlo simulations. Consideringtheestimationof the most likely path (MLP), the prior image-constrained compressed sensing (PICCS) algorithm isused to reconstruct images from twodifferent phantoms using sparse protonprojections of 350 MeV parallel proton beam. The results show that it is feasible to realize the proton image reconstruction with the rapid protonCT imaging proposed in this paper. It can produce RSP maps withmuchhigher accuracy for TPSs and fast positioning to achieve ultra-fast imaging for real-time image-guided radiotherapy(IGRT) in clinical proton therapyapplications.
分类: 物理学 >> 核物理学 提交时间: 2023-06-20
摘要: The number of nucleon (NN) scaling of the directed ow v1 and elliptic ow (v2) as well as thenuclear modi#12;cation factor (Rcp) are tested for light nuclei which are produced in 0.4A GeVAu +Au collisions at di#11;erent impact parameters with two di#11;erent in-medium nucleon-nucleon cross sections in aframework of an isospin-dependent quantum molecular dynamics (IQMD) model. In that energy domain,the emission of light nuclei can be well described by the squeeze-out phenonomenon. The results show anice NN scaling behavior for ow parameters v1, v2 and Rcp. These results demonstrate that the nucleoncoalescence mechanism is responsible for nucleon-number scaling of above physical observables in squeezeout region in heavy-ion collisions at intermediate energy.
分类: 物理学 >> 核物理学 提交时间: 2023-06-20
摘要: Two-nucleon momentum correlation functions are investigated for different single thermal sourcesat given initial temperature (T ) and density (). To this end, the evolutions of various singleexcited nuclei at T = 1 20 MeV and = 0.2 - 1.2 0 are simulated using the thermal isospindependent quantum molecular dynamics (T hIQMD) model. Momentum correlation functions ofidentical proton-pairs (Cpp(q)) or neutron-pairs (Cnn(q)) at small relative momenta are calculatedby Lednick y and Lyuboshitz analytical method. The results illustrate that Cpp(q) and Cnn(q) keepsensitivities to the source size (A) at lower T or higher , but almost not at higher T or lower . Andthe sensitivities become stronger for smaller source. Moreover, the T , and A dependencies of theGaussian source radii are also extracted by fitting the two-proton momentum correlation functions,and the results are consistent with the above conclusions.
分类: 核科学技术 >> 裂变堆工程技术 提交时间: 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要: Molecular dynamics method is used to investigate the displacement cascades in Ni-Mo binary alloy. Effects of the irradiation temperature, energy of the primary knock-on atoms and concentration of solute Mo atoms are taken into consideration on radiation damage to the Ni-Mo alloy. It is found that Mo atoms reduce production of the Frenkel pairs at 100 K, while they enhance defect production at 300 K and 600 K. Size of the largest defect clusters decreases with increasing concentrations of Mo atoms (CMo) at 100 K, but it increases with CMo at 300 K and 600 K. Most of the point defects get clustered in cascades leaving only a few vacancies and interstitials isolated.
分类: 核科学技术 >> 裂变堆工程技术 提交时间: 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要: To investigate the corrosion products of Cr in molten FLiNaK salt (46.5 mol% LiF11.5 mol% NaF42 mol% KF), the corrosion test of the pure metal Cr was performed in molten FLiNaK salt at 700 ℃ for 200 h. The FLiNaK salt after the corrosion test was thoroughly investigated by X-ray absorption near-edge structure spectroscopy, a transmission electron microscope, and X-ray diffraction. The results demonstrate that the predominant oxidation state of Cr in FLiNaK salt is Cr3+, and the main corrosion product in cooled FLiNaK salt is K2NaCrF6.
分类: 物理学 >> 核物理学 提交时间: 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要: In this paper, a novel method for selectively detection of dopamine (DA) in the interference of ascorbic acid (AA) is described. A nanometer-sized gold flower microelectrode (NGFME) is prepared by flame-etching and electrochemical deposition. The electrode tip was characterized by scanning electron microscope (SEM). The NGFME is sized at about 100 m and dimensions of thorns of the electrode were in nanometers. By modifying with DA aptamer on the surface, the prepared aptasensor can selectively detect DA even in the presence of high concentration AA. Experimental results show that this NGFME has no response to AA. As a comparison, the carbon fiber electrode without DA aptamer modification is unable to effectively detect DA in the presence of AA. The NGFME is easy-to-prepare, selective and sensitive for DA detection down to 25 m. The electrode can be expected to detect DA in vivo and in real biological samples.