分类: 物理学 >> 核物理学 提交时间: 2016-09-13
摘要: An overview of neutrino electromagnetic properties, which open a door to the new physics beyond the Standard Model, is given. The effects of neutrino electromagnetic interactions both in terrestrial experiments and in astrophysical environments are discussed. The experimental bounds on neutrino electromagnetic characteristics are summarized. Future astrophysical probes of electromagnetic neutrinos are outlined.
分类: 物理学 >> 核物理学 提交时间: 2023-09-15
摘要: The Trojan horse method was employed to indirectly measure the bare-nucleus reaction cross-section and astrophysical S-factor of the 9Be(p,) 6Li reaction in the low-energy region , utilizing the three-body reaction 2H(9Be, 6Li)n. Comparing the two-body reaction data extracted from the Trojan horse method with that obtained through direct measurements, compatibility is observed in the energy region above approximately 100 keV. Additionally, the THM data successfully reproduces the expected low-energy resonance peak around 270 keV. The THM extraction of the astrophysical factor yields S(0) = 21.0 0.8 MeV b, which surpasses the extrapolation obtained from direct measurements. The 9Be(p,) 6Li reaction channel exhibits a subthreshold resonance with a width of 25 keV, positioned approximately -23 keV below the threshold. However, the strong electron shielding effect near the zero energy position in direct measurements often masks the influence of the subthreshold resonance on the low-energy region. In contrast, the THM method allows us to neglect the electron shielding effect. The THM experimental data were subjected to fitting using the Breit-Wigner function and subsequently compared with directly measured data. Following a comprehensive comparative analysis, it was discerned that the S(0) value obtained through THM exceeded the extrapolated value derived from direct measurements. This disparity was primarily attributed to the influence of the subthreshold resonance.
分类: 物理学 >> 核物理学 提交时间: 2024-04-28
摘要: The Shanghai Laser Electron Gamma Source (SLEGS, located in BL03SSID) beamline at the Shanghai Synchrotron Radiation Facility (SSRF) is a laser Compton scattering (LCS) gamma source used for the investigation of nuclear structure, which is in extensive demand in fields such as nuclear astrophysics, nuclear cluster structure, polarization physics, and nuclear energy. The beamline is based on the inverse Compton scattering of 10640 nm photons on 3.5 GeV electrons and a gamma source with variable energy by changing the scattering angle from 20° to 160°. γ-rays of 0.25–21.1 MeV can be extracted by the scheme consisting of the interaction chamber, coarse collimator, fine collimator, and attenuator. The maximum photon flux for 180° is approximately 10^7 photons/s at the target at 21.7 MeV, with a 3-mm diameter beam. The beamline was equipped with four types of spectrometers for experiments in (γ,γ’), (γ,n), and (γ,p α). At present, nuclear resonance fluorescence (NRF) spectrometry, flat efficiency neutron detector (FED) spectrometry, neutron time-of-flight (TOF) spectrometry, and light-charged particle (LCP) spectrometry methods have been developed.
分类: 天文学 >> 天文仪器与技术 提交时间: 2024-12-27 合作期刊: 《Astronomical Techniques and Instruments》
摘要: We present preliminary investigations of a potential optics system for wideband X-ray telescopes. The optical design adopts the conical approximation of the Wolter-I configuration and a combination of multilayer coatings and silicon pore optics. The total number of mirror modules is 79, distributed in 8 rows with the radii at the intersection plane between 250 mm and 500 mm. The optimization of the total effective area using the figure of merits method suggests that the focal length is 30 m and the mirror coating is a combination of the W/Si and Pt/C multilayers. This fulfills the on-axis effective area requirements of 2 000 cm2 at 10 keV and 300 cm2 at 60 keV and provides a broad energy response between 3 keV and 78.4 keV. With the current geometry and coating compositions, we implement a mass modeling of the telescope in Geant4 to predict mirror performances via the ray-tracing algorithm, including the angular resolution and effective area. With the presumed metrological data as input, this can provide precision and finishing requirements for the manufacture of optics. This work demonstrates the feasibility of combining multilayer coatings and silicon pore optics for potential use in wideband X-ray telescopes and advances the development and progress of such missions.
分类: 物理学 >> 核物理学 提交时间: 2024-09-03
摘要: The 12C + 12C fusion is one of the most important reactions in modern nuclear astrophysics. The trend and magnitude of the reaction rate within the Gamow window strongly influence various astrophysical processes. However, direct measurement of this reaction is extremely difficult, which makes it necessary to develop indirect methods. In this study, the 23Na + p reaction system was used to study the compound nucleus 24Mg. We employed a thick-target inverse kinematics method combined with theγ-charged-particle coincidence technique to measure the proton and ɑexit channels of 24Mg. Technical details of the 23Na + p thick-target inverse kinematics experiment and analysis are presented herein.