Subjects: Nuclear Science and Technology >> Nuclear Materials and Techniques submitted time 2024-03-20
Abstract： Background Within GEN-IV reactors, nuclear graphite plays a crucial role as both a moderator and reflector in an environment characterized by high temperatures and intense fast neutron irradiation. The exposure to fast neutron irradiation induces the formation of numerous Frankel defects in the nuclear graphite. These defects undergo processes of annihilation and diffusion, ultimately giving rise to larger defect clusters. This transformation in the microstructure of nuclear graphite directly impacts its macroscopic properties, necessitating a thorough investigation. Purpose The paramount significance lies in comprehensively studying the evolution of defects in nuclear graphite under conditions of high-temperature irradiation. This research is essential for advancing reactor safety. Methods This study employed 30 MeV 107Ag5+ ions to irradiate IG-110 nuclear graphite at 420 ℃ to simulate the defect evolution behavior during fast neutron irradiation of nuclear graphite. The energy loss, defect distribution, and ion implantation profiles of 30 MeV 58Ni5+ and 107Ag5+ ion beams bombarding standard nuclear graphite ICRU-906 (density of 2.26 g/cm3, displacement energy of 28 eV) were calculated using the full cascade damage model in the SRIM (Stopping and Range of Ions in Matter) software. The cross-sectional structure of IG-110 nuclear graphite was characterized using micro-Raman spectroscopy. The relationship between the Raman spectroscopic features at various depths of IG-110 nuclear graphite and the irradiation damage dose was compared to investigate the evolution of IG-110 nuclear graphite microstructure with increasing irradiation damage dose (DPA, Displacements Per Atom). Results With the increase in particle fluence, the characteristic parameters of the Raman spectra of nuclear graphite, including the ID/IG ratio (the ratio of the D peak height to the G peak height), the Full Width at Half Maximum of the G peak (FWHM(G)), and the shift of the G peak, all show significant increments. When compared to samples irradiated with 58Ni5+ at the same irradiation damage dose, the graphite Raman spectra irradiated with 107Ag5+ demonstrate higher ID/IG ratios and FWHM(G). At the same FWHM(G) level, the ID/IG ratio of the graphite Raman spectra irradiated with 107Ag5+ is greater than that of the samples irradiated with 58Ni5+. Conclusion The results suggest that irradiation with heavier ions induces a higher rate of defect accumulation in nuclear graphite, leading to a more rapid reduction in graphite grain size and promoting the progression towards nanocrystallization.
Subjects: Physics >> Nuclear Physics submitted time 2024-02-28
Xu Hanghua
Liu Longxiang
Zhang Yue
Hao Zirui
Yang Yuxuang
Jin Sheng
Chen Kaijie
Li Zhicai
Jiao Pu
Zhou Mengdie
Wang Zhenwei
Wang Hongwei
Fan Gongtao
Abstract： : Introduces the construction and trial operation of Shanghai Laser Electron Gamma Source (SLEGS) beamline station, one
of the Shanghai light source(SSRF) projects II, which can carry out basic research on nuclear physics and nuclear astrophysics, and
carry out applied research such as gamma irradiation, gamma imaging and gamma activation at SLEGS gamma source. The SLEGS
beamline station passed the process acceptance in December 2021, entered the trial operation stage in October 2022, and have open
to users in September 2023. SLEGS is the first in the world to use the continuous collision angle mode to change the energy of the
gamma beam, with the best energy scanning accuracy, flow intensity density and efficient energy regulation ability. In the trial
operation stage, the SLEGS beamline station focused on solving the problem of online monitoring of gamma beam energy spectrum
and flow intensity, mainly completed the experimental methodology research of optical neutron cross-section measurement by flat
efficiency spectrometer (FED), and carried out the expansion and research of application platforms such as gamma imaging, gamma
activation, and positron source generation. With the development of inverse Compton scattering techniques, short-pulse,
high-polarization, high-throughput, and miniaturized laser Compton scattering light sources will usher in better development
opportunities in the future, and will play an important role in nuclear physics, astrophysics, particle physics, polarization physics, as
well as aerospace, medical testing, energy development and other gamma source application research fields.
Subjects: Physics >> Nuclear Physics submitted time 2023-06-12 Cooperative journals: 《核技术》
Abstract： The RHIC-STAR (Relativistic Heavy Ion Collider-Solenoid Tracker at RHIC) experiments have measured the cumulants of net-proton (a proxy for net-baryon), net-charge, and net-kaon (proxy of net-strangeness) multiplicity distributions in Au+Au collisions at different centers of mass with energies ranging from 7.7 GeV to 200 GeV. Recent results have shown that the ratio of the fourth-order net-proton cumulant over the second-order one (κσ 2) exhibits a nonmonotonic energy dependence. In relativistic heavy-ion collision experiments, only information about the final state particles can be measured. Therefore, we investigated the fluctuations of the conserved charges (baryon, electric charge, and strangeness) in Au+Au collisions using a multiphase transport (AMPT) model. This model can basically describe the results measured by the RHIC-STAR experiment. More importantly, the AMPT model is used to understand the key impacts of the dynamical evolution of relativistic heavy-ion collisions on fluctuations and correlation functions, including the creation and diffusion of conserved charges, hadronization, hadronic rescatterings, and weak decays. It was discovered that the correlation between positive and negative charges may originate from the string melting mechanism. Baryon (proton) correlation functions are consistent with the expectation of baryon number conservation. Net-strangeness (net-kaon) originates from pair production. We studied the correspondence between representative quantities and their conserved charges and found that their behaviors are qualitatively consistent yet quantitatively different. Although the physics of quantum chromodynamics (QCD) critical fluctuations is not included in the AMPT model, our results are expected to provide a baseline for the search of possible critical behavior at the QCD critical end point in relativistic heavy-ion collisions. We incorporated critical density fluctuations into the model and found that they play a role.
Hits
Hits
Downloads
Comment
YES