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A statistical description of scattering at the quantum level
摘要： Quantum physics is undoubtedly the most successful theory of the microscopic world, yet the complexities which arise in applying it even to simple atomic and molecular systems render the description of basic collision probabilities a formidable task. For this reason, approximations are often employed, the validity of which may be restricted to given energy regimes and/or targets and/or projectiles. Now we have found that the lognormal function, widely used for the probability distribution of macroscopic stochastic events (as diverse as periods of incubation of and recovery from diseases, size of grains, abundance of species, fluctuations in economic quantities, etc.) may also be employed to describe the energy dependence of inelastic collisions at the quantum level (including ionization, electron capture and excitation by electrons, positrons, protons, antiprotons, etc.), by allowing for the relevant threshold energy. A physical interpretation is discussed in this article by analogy with the heat capacity of few-level systems in solid state physics. We find the generality of the analysis to extend also to nuclear reactions. As well as aiding the description of collision probabilities for quantum systems, this finding is expected to impact also on the fundamental understanding of the interface between the classical and quantum domains.
关键词： ionization,electron capture,nuclear reactions,lognormal distribution,excitation,inelastic collisions,quantum physics
更新于2025-09-23 15:21:21
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Calibration of CR-39 solid-state track detectors for study of laser-driven nuclear reactions
摘要： It is of particular interest to investigate nuclear fusion reactions generated by high-intensity lasers in plasma environments that are similar to real astrophysical conditions. We have experimentally investigated 2Hed; pT3H, one of the most crucial reactions in big bang nucleosynthesis models, at the Shenguang-II laser facility. In this work, we present a new calibration of CR-39 solid-state track detectors, which are widely employed as the main diagnostics in this type of fusion reaction experiment. We measure the dependence of the track diameter on the proton energy. It is found that the track diameters of protons with different energies are likely to be identical. We propose that in this case, the energy of the reaction products can be obtained by considering both the diameters and gray levels of these tracks. The present results would be very helpful for analyzing the 2Hed; pT3H reaction products recorded with the same batch of CR-39 solid-state track detectors.
关键词： Gray levels,Laser-driven nuclear reactions,CR-39 detectors,Big bang nucleosynthesis
更新于2025-09-23 15:21:01
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The Tvs of Tomorrow: How RCA's Flat-Screen Dreams Led to the First Lcds
摘要： The Optimized Energy Degrading Optics (OEDO) beamline is an upgrade of the High-resolution beamline at the RI Beam Factory at RIKEN. Its purpose is to measure nuclear reactions induced by radioactive ions at 10–50 MeV/u. The main components of the OEDO beamline are two superconducting quadrupole triplet magnets and one radio-frequency deflector, which were recently installed. This setup produces slowed-down, well-focused radioactive-isotope beams by using a degree of freedom in the longitudinal phase space of the beam. This paper describes the OEDO beamline in detail, discusses the unique concept of its ion optics, and demonstrates its feasibility by conducting measurements with medium-mass radioactive-isotope beams.
关键词： RI Beam Factory,radioactive ions,superconducting quadrupole triplet magnets,OEDO,nuclear reactions,radio-frequency deflector
更新于2025-09-23 15:19:57
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Study of Lithium Rich Giants with the GALAH Spectroscopic Survey
摘要： In this article, we speculate on the possible mechanisms for Li enhancement origin in RGB stars based on a large data set of around 340 299 stars collected from the GALAH survey combined with the Gaia astrometry. Data has 51 982 low mass (M ≤ 2 M(cid:3)) RGB stars with reliable atmospheric parameters. The data set shows a well-populated RGB with well-defined luminosity bump and red clump with significant number of stars at each of these two key phases. We found 335 new Li-rich RGB stars with Li abundance, A(Li) ≥ 1.80 ± 0.14 dex, of which 20 are super Li-rich with A(Li) ≥ 3.20 dex. Most of them appear to be in the red clump region which, when combined with stellar evolutionary time-scales on RGB, indicates that the Li enhancement origin may lie at RGB tip during He-flash rather than by external source of merging of sub-stellar objects or during luminosity bump evolution. Kinematic properties of sample stars suggest that Li-rich giants are relatively more prevalent among giants of thin disc compared to thick disc and halo.
关键词： stars: abundances,surveys,abundances,nucleosynthesis,Hertzsprung-Russell and colour-magnitude diagrams,stars: kinematics and dynamics,stars: evolution,nuclear reactions
更新于2025-09-19 17:15:36
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Experimental investigation on nuclear reactions using a laser-accelerated proton and deuteron beam
摘要： We report an experimental investigation on nuclear reactions using an intense, ultra-short laser-accelerated proton and deuteron beam generated by the interaction of 25 fs, 150 TW Ti: sapphire laser pulse with normal thin foils and foils containing deuterium atoms. The production of a positron-emitting short-lived 11C radio-isotope from the interaction of protons and deuterium ions with a solid boron palette by means of 11B (p, n)11C and 10B (d, n)11C nuclear reactions was studied. The maximum radioactivity in the optimized laser irradiation condition was found to be 5.2 kBq per laser shot, which corresponds to ～9 × 106 atoms of 11C isotopes using the 11B (p, n)11C reaction. The relative ef?ciency of 11C production using a proton and deuteron beam was also explored experimentally. About 30 % enhancement in 11C activity was observed with CD2 coated targets. It was also found that because of the relatively low deuteron energy threshold of the reaction 10B (d, n)11C, even the low energy part of the accelerated deuterons in the spectrum can be used for ef?cient 11C production. In the same setup, the proton-induced fusion reaction in the boron target (p + 5B11 ? 3α + 8.7 MeV) was also studied. The resultant fusion yield and alpha particle energy spectrum was measured.
关键词： p?11B fusion,laser particle acceleration,positron emission tomography (PET) isotopes,laser driven ion acceleration,laser plasma interaction,laser induced nuclear reactions,high intensity lasers
更新于2025-09-19 17:13:59