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951.
952.
利用新研制的紧凑型线性变压器驱动源(LTD)脉冲功率源二极管产生的电子束源,开展了S波段长脉冲相对论速调管放大器(RKA)的初步实验研究。采用无箔空心阴极和0.9 T恒流源引导磁场从LTD二极管引出了电压600 kV、束流6 kA、脉宽150 ns的环形电子束,该电子束经过1个同轴输入腔和2个同轴调制腔的调制后,产生了幅度5 kA、脉宽110 ns的基波调制束流,采用该调制束流驱动同轴微波提取腔,辐射输出了峰值功率820 MW/110 ns的辐射微波,效率28%,增益36 dB。同时,开展了重复脉冲RKA和相位特性的实验研究,重复频率10 Hz运行时,辐射微波达到800 MW/100 ns,相位抖动小于 20°。 相似文献
953.
954.
Low temperature quenching and high efficiency CaSc2O4:Ce3+ (CSO:Ce3+) phosphors co-doped with Tm3+, La3+ and Tb3+ ions were prepared by a solid state method and the phase-forming, morphology, luminescence and application properties of these phosphors were investigated. The results showed that co-doping of Tm3+, La3+ and Tb3+ ions can improve the luminescence properties and decrease temperature quenching of CSO:Ce3+ phosphor remarkably. High efficiency green-light-emitting diodes were fabricated with the prepared phosphors and InGaN blue-emitting (∼460 nm) chips. The good performances of the green-light-emitting LEDs made from co-doped CSO:Ce3+ phosphors confirm the luminescence enhancement and indicate that Tm3+, La3+ and Tb3+ co-doped CSO:Ce3+ phosphors are suitable candidates for the fabrication of high efficiency white LEDs. 相似文献
955.
Photoluminescence spectra of thenardite Na2SO4 activated with rare-earth ions, Ce, Sm, Tb, Dy and Tm
Five Na2SO4:RE3+ phosphors activated with rare-earth (RE) ions (RE3+=Ce3+, Sm3+, Tb3+, Dy3+ and Tm3+) were synthesized by heating natural thenardite Na2SO4 from Ai-Ding Salt Lake, Xinjiang, China with small amounts of rare-earth fluorides, CeF3, SmF3, TbF3, DyF3 and TmF3, at 920 °C in air. The photoluminescence (PL) and optical excitation spectra of the obtained phosphors were measured at 300 and 10 K. In the PL spectrum of Na2SO4:Ce3+ at 300 K, two overlapping bands with peaks at 335 and 356 nm due to Ce3+ were first observed. Narrow bands observed in PL and excitation spectra of Na2SO4:RE3+ (RE3+=Sm3+, Tb3+, Dy3+ and Tm3+) phosphors were well identified with the electronic transitions within the 4fn (n=5, 8, 9 and 12) configurations of RE3+. The existence of excitation bands with high luminescence efficiency at wavelengths shorter than 230 nm is characteristic of Na2SO4:RE3+ (RE3+=Sm3+, Tb3+, Dy3+ and Tm3+) phosphors. The obtained results suggest that these phosphors are unfavorable as the phosphor for usual fluorescence tubes, i.e., mercury discharge tubes, but may be favorable as the phosphor for UV-LED fluorescent tubes and as cathodoluminescence, X-ray luminescence and thermoluminescence phosphors. 相似文献
956.
The Fourier transform infrared (FTIR) absorption spectrum of the ν12 fundamental band of ethylene-d4 (C2D4) was recorded in the 1017-1137 cm−1 region with an unapodized resolution of 0.0063 cm−1. Upper state (v12 = 1) rovibrational constants consisting of three rotational and five quartic constants were improved by assigning and fitting 2103 infrared transitions using Watson’s A-reduced Hamiltonian in the Ir representation. The band centre of the A-type ν12 band is found to be 1076.98480 ± 0.00002 cm−1. The present analysis covering a wider wavenumber range and higher J and Kc values yielded upper state constants including the band centre which are more accurate than previously reported. The rms deviation of the upper state fit is 0.00045 cm−1. Improved ground state rovibrational constants were also determined from the fit of 1247 ground state combination differences (GSCD) from the presently-assigned infrared transitions of the ν12 band of C2D4. The rms deviation of the GSCD fit is 0.00049 cm−1. In the rovibrational analysis, local frequency perturbations were not detected even at high J and Ka values. The calculated inertial defect Δ12 is 0.32551 ± 0.00001 μÅ2. The line intensities of the individual transitions in the ν12 band were measured and the band strength of 39.8 ± 2.0 cm−2 atm−1 was derived for the ν12 band of C2D4. 相似文献
957.
We report a method for the measurement of nematic liquid crystal (NLC) cell parameters i.e., switching voltage, birefringence, retardation, dielectric anisotropy, average tilt angle and change in refractive index with applied DC voltage to LC material. The proposed method is based on optical interferometry and Fourier transform fringe analysis technique, in which we obtain 2-dimensional (2D) phase map of the interferograms as a function of applied voltage. Mach-Zehnder interferometer (MZI) was used for the study of cell parameters and interferograms were recorded at different applied DC voltages to NLC cell using CCD camera. From the phase map, 2D-refractive index distribution of the LC cell with applied voltage was reconstructed. Analytical equations are derived based on optical interferometry and then solved to obtain cell parameters. The present method is fast and can give 2D-cell parameters from only two quick interferograms. 相似文献
958.
959.
960.