Shi Liu

Technical Issues for the Fabrication of a CN-HCCB-TBM Based on RAFM Steel CLF-1

Reduced activation ferritic/martensitic steel (RAFM) is recognized as the primary candidate structural material for ITERs test blanket module (TBM). To provide a material and property database for the design and fabrication of the Chinese helium cooled ceramic breeding TBM (CN HCCB TBM), a type of RAFM steel named CLF-1 was developed and characterized at the Southwestern Institute of Physics (SWIP), China. In this paper, the R&D status of CLF-1 steel and the technical issues in using CLF-1 steel to manufacture CN HCCB TBM were reviewed, including the steel manufacture and different welding technologies. Several kinds of property data have been obtained for its application to the design of the ITER TBM.

Nonlinear free-carrier absorption of intense THz radiation in semiconductors

We calculate the nonlinear free-carrier absorption coefficient of an intense terahertz (THz) electromagnetic wave propagating in a bulk semiconductor and the absorption percentage when an intense THz radiation passes through a quasi-two-dimensional (2D) sheet, with the help of the balance-equation approach to hot-electron transport in semiconductors subject to an intense high-frequency field. We find that at frequency around 1 THz, the absorption coefficient in a bulk GaAs system increases with increasing amplitude of the radiation field from zero and reaches a maximum at around 8 kV cm-1 before decreasing quickly with further increase of the field strength. The absorption percentage of a quasi-2D system exhibits an even stronger nonlinearity than that of a three-dimensional bulk. It is shown that high-order multiphoton processes play a major role in determining the absorption of an intense THz field.

A first principles study of the thermal stability of A(m)(MH(4))(n) light complex hydrides.

From the physical point of view, the cohesive energy of a reactant is preferable to its formation energy for characterizing its influence on the reaction processes from the reactants to the products. In fact it has been found that there is a certain correlation between the experimental hydrogen desorption temperature and the cohesive energy calculated by a first principles method for a series of A(m)(MH(4))(n) (A = Li, Na, Mg; M = Be, B, Al) light complex hydrides (including Na(2)BeH(4), Li(2)BeH(4), NaAlH(4), LiAlH(4), Mg(AlH(4))(2), LiBH(4) and NaBH(4)), which suggests that cohesive energy may be a useful physical quantity for evaluating the hydrogen desorption ability of complex hydrides, especially in cases when dehydrogenation products have unknown crystal structures, or may even be unknown. To understand this correlation more deeply, the ionic interaction between A and the MH(4) complex and the covalent interaction between M and H were calculated and their contributions to the cohesive energy evaluated quantitatively. The calculated results show that the covalent M-H interaction in the MH(4) complex is the dominant part of the cohesive energy E(coh) (up to more than 75%) and hardly changes during high-pressure structural transitions of A(m)(MH(4))(n). It was also found that low electronegativity of M or high electronegativity of A is responsible for the weak covalent M-H interaction and finally leads to the low thermodynamic stability of A(m)(MH(4))(n), suggesting that complex hydrides A(m)(MH(4))(n) can be destabilized by partial substitution of M (A) with an element with electronegativity lower (higher) than Ms (As). This conclusion has been confirmed by lots of experimental results and may be a useful guideline for the future design of new complex hydrides of the type A(m)(MH(4))(n).

MgO SECONDARY ELECTRON EMISSION FILM PREPARED BY RADIO-FREQUENCY REACTIVE SPUTERRING

High, stable and durable secondary electron emission is an essential property for the application of dynodes of electron multipliers and photomultiplier tubes. The MgO film have been widely used as dynode materials for the applications owing to its good secondary electron emission properties. In this work, MgO and CoO doped MgO films, as secondary electron emission films, were prepared by radio-frequency reactive sputtering deposition on the stainless steel substrate, and also another MgO film at the surface of activated AgMg alloy was prepared. The effect of preparation processes on the secondary electron emission properties of the films was focused. It was found that the film thickness significantly affected the resistance to electron beam bombardment. With the increase of film thickness, the resistance to electron beam bombardment was significantly enhanced. Radio-frequency reactive sputtering deposition could control the film thickness by varying deposition time. The surface quality of MgO film is quite sensitive to the oxygen partial pressure of the deposition atmosphere. Higher oxygen partial pressure caused higher surface roughness, which was harmful to the secondary electron emission. After doping with CoO, the surface of MgO films were much flatter and smoother, resulting in the improvement of the secondary electron emission coefficient. The CoO doping also reduced of the sensitivity of film surface quality to the oxygen partial pressure. The secondary electron emission coefficient of CoO doped MgO film sharply decreased after heated at 550 °C for 1 h due to the surface quality degrading and the thermal decomposition induced loss of oxygen. Ele*收到初稿日期: 2015-04-02,收到修改稿日期: 2015-07-20 作者简介:王彬,男, 1988年生,博士生 DOI: 10.11900/0412.1961.2015.00189 第10-16页 pp.10-16 第 1期 王 彬等:射频反应溅射制备MgO二次电子发射薄膜 vating the substrate temperature or oxygen partial pressure during deposition accounted for the presence of metallic Mg in film and the degrading of surface quality, which finally lead to lower secondary electron emission coefficient.