Measurement and model analysis of(n,xα)cross sections for Cr, Fe,59Co, and

Abstract

Neutron reactions that produce alpha-particles have been investigated experimentally and analyzed by reaction model calculations for incident neutron energies from threshold to 150 MeV on elemental chromium and iron. The cross sections were measured at the Los Alamos Neutron Science Center by direct observation of alpha-particles. Previous data on isotopes 59 Co and 58,60 Ni were also included in the analysis. The model calculations are made for both statistical decay and pre-equilibrium processes. This study particularly focuses on the pre-equilibrium cluster emission, which is described by the clustering exciton model of Iwamoto and Harada. We calculate the alphaparticle formation factors numerically without any approximations that appeared in the original model. The model parameter ∆R, the nuclear surface area where the pickup reaction may occur, is determined by fitting the calculated alpha-particle energy spectra to experimental data. The calculated alpha-particle production cross sections agree well with the measured data, except for the Cr case. With a simple sensitivity study for the level density parameters, it is reported that relatively small changes in the level density parameters improve reproduction of experimental data significantly. Our realistic model calculations for the pre-equilibrium process shed light on uncertainties in the nuclear level densities in the statistical decay calculation.

Progress of experimental researches on neutron induced light charged-particle emission nuclear reactions

“…采用3×3排列的9个sCVD金刚石探测器作为带电 粒子探测器, 每个探测器的面积为4 mm×4 mm [15] . 6 Li(n,t) 4 He等核反 应开展了实验测量 [16][17][18][19] . [20] , 包括 14 N(n,p) (1989), 17 O(n,α) (1991), 36 Cl(n,p) (1993), 26 Al(n,p), (n,α) (1997)反应等 [21][22][23][24] .…”

“…平均每个电子产生约0.05个中子 [7] . 在这两个中子源 上开展的中子核反应截面测量, 其中与(n,lcp)反应有 关的主要是共振能区核天体物理方面的工作 [20] , 比 如 147 Sm(n,α) (2000, 2004), 95 Mo(n,α) (2003), 17 O(n,α) (2002), 26 Al(n,α) (2007), 36 Cl(n,p), (n,α) (2007), 35 Cl(n,p) (1994), 37 Ar(n,p), (n,α), 39 Ar(n,α) (2001)等反…”

“…反应堆中子源, 典型的是法国Grenoble的ILL, 它 是世界上最强的反应堆中子源, 可以提供热中子束与 冷中子束. 依托该中子源, 开展了热中子诱发的 35 Cl(n,p) (1994), 50 V(n,p) (1994), 17 O(n,α) (1995), 36 Cl (n,p)和(n,α) (1996), 41 Ca(n,p)和(n,α) (1998), 37 Ar(n,p)和 (n,α) (1999,2001), 14 N(n,p) (2000), 26 Al(n,p i ) (n,α i ) (2001)等一系列带电粒子出射核反应截面测量 [2][3][4] . 采 用极化的冷中子束, 分别在2011和2017年, 得到了 6 Li (n,t) 4 He反应中的t粒子和 10 B(n,α) 7 Li*→ 7 Li+γ反应中的 γ射线及α粒子的所谓P-odd asymmetry实验结果 [5,6] .…”

Implementation and validation of realistic (n,x) reaction yields in GEANT4 utilizing a detailed evaluated nuclear reaction library below 20 MeV

“…The Low Energy Neutron-induced charged-particle (Z) chamber (LENZ) [22] was developed at Los Alamos Neutron Science Center (LANSCE) to provide the high-quality nuclear data needed for modern applications. It is designed for the study of neutroninduced charged particle reactions with neutrons in the energy range from thermal to several tens of MeV, and is optimized for measurements of differential cross-sections and angular distributions with a small energy step over the broad-energy neutron beam at LANSCE, and with a total geometrical efficiency surpassing previous systems in operation [23][24][25][26].…”

16O(n,α) cross section investigation using LENZ instrument at LANSCE

“…The in-beam commissioning of the LENZ instrument at LANSCE was performed by repeating the 59 Co(n,p) and (n,α) reaction, which were measured previously using the NZ chamber [20]. This is in particular to investigate the beam-induced background reactions on gas elements and to determine the timing resolution of detectors relative to the incoming neutron time stamp.…”