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1. chinaXiv:201703.00562 [pdf]

Temperature dependent defects evolution and hardening of tungsten induced by 200 keV He-ions

M. H. Cui; Z. G. Wang; L. L. Pang; T. L. Shen; C. F. Yao; B. S. Li; J. Y. Li; X. Z. Cao; P. Zhang; J. R. Sun; Y. B. Zhu; Y. F. Li; Y. B. Sheng
Subjects: Physics >> Condensed Matter: Structural, Mechanical and Thermal Properties

Tungsten has been selected as one of the potential candidate materials to cover some parts of the divertor in the future International Thermonuclear Experimental Reactor (ITER). The accumulation of defects and He induced by neutron irradiation and their impact on the mechanical properties of tungsten are of very importance. In this work, the high pure polycrystalline tungsten samples were implanted by 200 keV He+ with a fluence of 5016 He+/cm2 at temperatures of room temperature(RT), 200, 400 and 800oC. Vacancy-type defects were detected in all implanted samples by means of positron annihilation spectroscopy. Vacancy-type defects produced by He implantation exist in the damaged layer and are decorated by He atoms. With increasing implantation temperature, more He atoms fill in the vacancy-type defects and make for the formation of larger defects. The nano-hardness values were measured by nano-indentation technique. It is observed that implantation hardening occurred for all the implanted samples. With increasing implantation temperature from 200 to 800 oC, the change of the average hardness values which are lower than the value at RT has a tendency of enhancement for the shallower layer and degradation for the deeper layer. The hardness variations are discussed to be the pinning effects of the defects with different density or size.

submitted time 2017-03-26 Hits1312Downloads754 Comment 0

2. chinaXiv:201609.01019 [pdf]

Neutral hidden charm pentaquark states $P_c^0(4380)$ and $P_c^0(4450)$ in $\pi^-p \to J/\psi n$ reaction

Qi-Fang L╱; Xiao-Yun Wang; Ju-Jun Xie; Xu-Rong Chen; Yu-Bing Dong
Subjects: Physics >> Nuclear Physics

We investigate the neutral hidden charm pentaquark states?P0c(4380)?and?P0c(4450)?in?π?p→J/ψnreaction within an effective Lagrangian approach. The background contributions for the process mainly come from?t-channel?π?and?ρ?meson exchanges. The contributions of?P0c(4380)?and?P0c(4450)?states give clear peak structures in the magnitude of 1?μb at center of mass energy 4.38 GeV and 4.45 GeV in the total cross sections. Hence, this reaction may provide a new good platform to search for neutral?Pc?states. It is expected that our estimated total cross sections together with the angular distributions can be tested by future experiments at J-PARC.

submitted time 2016-09-14 Hits1094Downloads659 Comment 0

3. chinaXiv:201609.00950 [pdf]

Role of the $\Lambda^+_c(2940)$ in the $\pi^- p \to D^- D^0 p$ reaction close to threshold

Ju-Jun Xie; Yu-Bing Dong; Xu Cao
Subjects: Physics >> Nuclear Physics

We report on a theoretical study of the?π?p→D?D0p?reaction near threshold within an effective Lagrangian approach. The production process is described by?t?channel?D?0?meson exchange,?s-channel nucleon pole, and?u?channel?Σ++c?exchange. In our work, the final?D0p?results from the ground?Λ+c(2286)?state and also dominantly from the excited?Λ+c(2940)?state which is assumed as a?D?0p?molecular state with spin parity?JP=12+?or?12?. We calculate the total cross section of the?π?p→D?D0p?reaction. It is shown that the spin parity assignment of?12??for?Λ+c(2940)?gives a sizable enhancement for the total cross section in comparison with a choice of?Jp=12+. However, our theoretical result of the total cross section is sensitive to the value of the cutoff parameter involved in the form factor of the exchanged off-shell particles. Moreover, we also calculate the second order differential cross section and find it can be used to determine the parity of the?Λ+c(2940). It is expected that our model calculations can be tested by future experiments at J-PARC in Japan.

submitted time 2016-09-13 Hits1061Downloads610 Comment 0

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