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[en] The systematic investigation of the thermal and electrical properties of neutron transmutation doped (NTD) Ge at low temperatures and the development of a detector to search for weakly interacting massive particles (WIMP's), predicted by some theories to make up to 90 percent of the matter in the universe, is presented. We have fabricated NTD Ge phonon sensors operated on a dilution refrigerator near 20 mK. The thermal and electrical properties of NTD Ge were investigated first. The zero bias resistance was found to be governed by variable range hopping, but the nonlinearity of the current-voltage characteristics indicated significant hot electron effects near 20 mK. A detailed investigation of hot-electron effects in NTD Ge is described. NTD Ge sensors were found to be very sensitive to high energy phonons generated by interactions of Ge with alpha-particles and photons. The mean absorption length of the high energy phonons in NTD Ge was found to be about 500 microns. In order to use these phonon sensors in conjunction with a target crystal, we developed a bonding technique using a Au-Ge eutectic. The bonds were found to be mechanically strong, thermally cyclable, and more transparent to high energy phonons than conventional silver-filled epoxies. The eutectic bonding technique was also found to leave the thermal and electrical properties of NTD Ge unchanged. We describe ionization signals observed in pure Ge target crystals, generated by the interaction of Ge with alpha-particles and photons; these ionization signals were observed simultaneously with phonon signals from the NTD Ge sensors. Such simultaneous signals can be used to reject unwanted background events, which is an important requirement for a WIMP detector. Finally, we describe the design and testing of a 60 g Ge detector to which six phonon sensors were attached. Simultaneous phonon and ionization signals were observed when irradiating the crystal with photons from Am-241
[en] Effects of Ta substitution for Nb on the microwave dielectric properties of BiNbO4 ceramics have been investigated. BiNb(1-x)TaxO4 (x=0, 0.1, 0.2, 0.3, 0.4) with 0.3 wt.% CuO-V2O5 mixtures addition can be densified at very low sintering temperature below 860 deg. C. The dielectric constants (εr) of the Ta-modified BiNbO4 ceramics increase with increasing of Ta contents, but the Qxf values have no apparent changes. The temperature coefficient of resonant frequency (τf) changes from positive to negative with change of x values. The crystalline phase and microstructure of Ta-modified BiNbO4 ceramics have been characterized by X-ray diffraction and scanning electron microscopy respectively
[en] Experimental results show that spontaneous emission coefficients of argon ion Ar+ vary in instense light field. They are not constant parameters that do not depend on outside conditions. It is also found that their variance is related to change of total angular momentum ΔJ and orbital angular momentum ΔL of ion during transition
[en] Highlights: • A kinetics equation is proposed to predict the safety life of the cladding. • Lattice diffusion and grain boundary diffusion contribute to the columnar growth of Al–Mg intermetallic compounds. • The growth of γ was controlled by grain boundary diffusion and lattice diffusion. • Some micro-voids were observed due to the Kirkendall effect. - Abstract: A potential new research reactor fuel design proposes to use U–Mo fuel in a Mg matrix clad with Al. Interdiffusion between the Mg containing fuel core and Al cladding can result in the formation of intermetallic compounds that can be detrimental to fuel element performance. The kinetics of the reactive diffusion in the binary Al–Mg system was experimentally studied. Layers of the intermetallic compounds, β (Al3Mg2) and γ (Al12Mg17) phases, were formed between the Al alloy 1060 and Mg during annealing. The β layer was observed to grow faster than the γ phase. The thickness of each layer can be expressed by a power function of the annealing time with the exponent n close to 0.5 for the β phase and less than 0.5 for the γ phase. The results suggest that the growth of β phase is controlled by lattice diffusion and that of the γ phase by grain boundary and lattice diffusion. Metallographic examination showed the grain boundary diffusion in the form of columnar growth of γ phase during annealing. Based on the reactive diffusion equation developed in this work, in the absence of irradiation effects, it will take more than 110 h to consume a half thickness of 400 μm of the cladding
[en] Vanadium dioxide (VO2) has a great potential to be utilized as solar energy switching glazing, even though there exist some intrinsic problems of low luminous transmittance (Tlum) and poor oxidation resistance. Si–Al based anti-reflection (AR) sol–gel coatings processed at low temperature have been developed to tackle these issues assisted by adjusting ramping rate and annealing temperature. Si–Al based AR coating gives large relative enhancement on the transmittance (22% for Tlum, 14% for the whole solar spectrum Tsol,) and successfully maintains IR contrast at 2500 nm wavelength with 18% relative increase in solar modulation (ΔTsol). The optimized Si–Al based AR coating annealing conditions are recorded at 3 °C/min ramping rate and 100 °C annealing temperature. Fluorinated-Si based gel offers a new direction of multifunctional overcoat on thermochromic smart windows with hydrophobicity (contact angle 111°), averaged 14% relatively increased luminous transmittance and enhanced oxidation resistance.
[en] In recent years, China's nuclear power industry has been developing rapidly. Construction of a series of nuclear power plants were successively commenced. Most of these projects have applied with either the second generation plus or the third generation technologies imported from abroad. Since there is some inconsistence between the criteria of technology exporters and China's design criteria, it is required to make efforts to the gradual assimilation of the imported technology so as to improve its adaptability. This paper discusses on the electrical design of nuclear power plant for reference its adaptability projects afterwards. (author)
[en] The authors have studied the fusion reaction for 11Be + 208 Pb near barrier by applying QMD model, and find that in t he fusion reaction induced by halo nuclei there simultaneously exist two mechanisms competing with each other. On one hand, 11Be is a weakly bound nuclear system and is easily broke up caused by the interaction with target, when it approaches to target, so the fusion cross section is suppressed. On the other hand, several neutrons of 11Be transfer into 208Pb and interact with 208Pb to cause the local radius of 208Pb increase and result in an enhancement of fusion cross section. The fusion cross sections calculated show an enhancement near barrier, and the calculated results agree with the experimental data reasonably well
[en] We study in the framework of the Langevin model the influence of initial excitation energy (E"*) of Hg compound nuclei (CNs) on the sensitivity of the excitation energy at scission (E_s_c"*) to the nuclear friction strength (β). It is shown that the sensitivity is enhanced substantially with increasing E"*. Moreover, we find that the significant sensitivity of E_s_c"* to β at high E"* is little affected by a marked difference in the neutron-to-proton ratio of a CN and in its size and fissility. Our findings suggest that, on the experimental side, a measurement of E_s_c"* in energetic proton-induced spallation reactions can provide not only a sensitive but also a robust probe of nuclear dissipation in fission of highly excited nuclei. Further development of a suitable approach to spallation reaction is discussed. (authors)
[en] We discuss symmetry flows of noncommutative Kadomtsev-Petviashvili (NCKP) hierarchy. An operator-based formulation, alternative to the star-product approach of extended symmetry flows is presented. Noncommutative additional symmetry flows of the NCKP hierarchy are formulated. A rescaling symmetry flow which is associated with the rescaling of whole coordinates is introduced.