A neutron polarization analysis study of Ce2Fe17 in its paramagnetic phase

Spin-flip (paramagnetic) scattering and neutron depolarization studies were performed on Ce₂Fe₁₇ in its paramagnetic phase on the Dhruva neutron polarization analysis spectrometer. The absence of normalQ dependence of the scattered spin flip intensity shows that Ce₂Fe₁₇ is not a normal paramagnetic and there exist superparamagnetic clusters of sufficiently large dimensions (～100Å). The observed neutron depolarization gives an indication of the dynamics of these Ce₂Fe₁₇ superparamagnetic clusters.     

多缝衍射光谱技术

本文从重叠干涉强度分布和重叠光谱强度分布的概念出发,论证和推导了多缝衍射光谱技术中复原光谱的极限理论分辨率的公式。讨论了稳定求解的条件。并对多缝衍射光谱技术和经典的衍射光谱技术两者的光谱分辨本领作了比较,同时给出了几个计算机实验的结果。     

Improvement of real time diffraction efficiency of NGD holograms by introducing electron donors

Nongelatin dichromated holographic film(NGD) is a new holographic recordingmaterial.Holograms recorded on this material have better environmental stability, higherdiffraction efficiency and stronger real time effect, etc..An experimental study to ascertainthe influence of two electron donors, namely,N,N-dimethylformamide(DMF) and dimethyl-sulfoxide(DMSO),on the real time diffraction efficiency(RTDE) of NGD holograms is car-ried out.The pressence of electron donors not only improves the sensitivity,but also enhancesthe real time effect greatly.RTDE of above 60% at±1 orders of NGD plane transimissiongrating is achieved by introducing electron donors.     

计算凹面闪耀光栅衍射效率的通用方法

为使凹面光栅的衍射能量更多地集中在所需要的级次上,提出了利用机械刻划的方法在凹面基底上制作变刻槽角度的凹面闪耀光栅,并利用菲涅耳-基尔霍夫衍射公式推导了同时在主截面和非主截面内计算凹面闪耀光栅衍射效率的理论方法,弥补了以往只在主截面内考虑衍射效率的不足,最后利用Matlab仿真软件模拟了衍射效率随波长的变化曲线,并对比了在不同制作和使用参数下衍射效率峰值的变化规律,为今后凹面光栅的设计和制作提供了参考价值。     

An optical study of the D-D neutron irradiation-induced defects in Co-and Cu-doped ZnO wafers

Room-temperature photoluminescence and optical transmittance spectroscopy of Co-doped(1×1014,5×1016,and 1×1017cm-2) and Cu-doped(5×1016cm-2) ZnO wafers irradiated by D-D neutrons(fluence of 2.9×1010 cm-2) have been investigated.After irradiation,the Co or Cu metal and oxide clusters in doped ZnO wafers are dissolved,and the wu¨rtzite structure of ZnO substrate for each sample remains unchanged and keeps in high c-axis preferential orientation.The degree of irradiation-induced crystal disorder reflected from the absorption band tail parameter(E0) is far greater for doped ZnO than the undoped one.Under the same doping concentration,the Cu-doped ZnO wafer has much higher irradiation-induced disorder than the Co-doped one.Photoluminescence measurements indicate that the introduction rate of both the zinc vacancy and the zinc interstitial is much higher for the doped ZnO wafer with a high doping level than the undoped one.In addition,both crystal lattice distortion and defect complexes are suggested to be formed in doped ZnO wafers.Consequently,the Co-or Cu-doped ZnO wafer(especially with a high doping level) exhibits very low radiation hardness compared with the undoped one,and the Cu-doped ZnO wafer is much less radiation-hard than the Co-doped one.     

含多层衍射光学元件的折/衍射混合头盔目镜

基于对多层衍射元件的衍射效率的理论分析,设计了用于头盔显示器的含有多层衍射元件的60视场折/衍射混合目镜系统。系统在设计波段和整个视场范围内衍射效率均在90 %以上,提高了光能利用率和像面对比度。目镜的出瞳距离为22 mm,出瞳直径为8 mm。调制传递函数（MTF）在25 lp/mm时全视场均在0.38以上,满足VGA分辨率要求。目镜中畸变为4.8%,垂轴色差最大为10 m。整个系统结构紧凑,镜头总长26.8 mm,最大直径16 mm,全系统质量仅8 g,实现了光学系统的轻小型化     

平面透射光栅的菲涅耳衍射

从标量场的菲涅耳衍射理论出发,研究了球面波入射平面透射光栅的衍射场,导出菲涅耳衍射场的复振幅分布,并得到光栅菲涅耳衍射角的计算公式．结果表明,在理想情况下菲涅耳衍射的每一级衍射波都是一个球面波;在对菲涅耳衍射角进行新的定义后,衍射角的计算仍然可以采用夫琅禾费衍射的光栅方程．     

Radiation damage in Si photodiodes by high-temperature irradiation

Results are presented of a detailed study of the effects of high-temperature 4-MeV neutron irradiation on the performance degradation of Si pin photodiodes together with the radiation-induced defects, observed by deep level transient spectroscopy. The degradation of the device performance and the introduction rate of the lattice defects decrease with increasing sample temperature during irradiation. For a 250°C irradiation, the reduction of the reverse current is only 20% of the starting value. This result suggests that the creation and recovery of the radiation damage proceeds simultaneously at high temperatures. Carbon-related complex as hole capture levels is also mainly responsible for the device degradation for high-temperature neutron irradiation.     

具有存储功能的衍射图像光刻系统的研制

研制了一种在衍射光变图像器件上进行信息存储的新型数字化激光光刻系统。采用空间光调制器作图形自动输入,双远心投影成像系统在光刻记录面上缩微图形。通过光栅干涉光学头对记录面上的微图形进行干涉调制,使微图形上产生干涉条纹,条纹空间频率范围为500-1200lp／mm。在光刻胶干版上的存储实验表明,在衍射光变图像上的单角度存储信息密度大于3．7Mbit／cm^2。改变干涉条纹取向、条纹间隔和需要存储的图形,光刻系统可实现信息的旋转复用存储。上述光刻系统将会在防伪和衍射光变图像器件制造领域有良好应用。     

Experimental confirmation by galvanomagnetic methods of a complex transport model in In0.53Ga0.47As layers deposited by MBE on SI-InP

At low temperatures In_0.53Ga_0.47As samples show an increase of carrier concentration, which can be explained in terms of a two carriers transport model. This type of problem exists since the beginning of the semiconductor era, dating back to monocrystalline germanium.We propose that in all the investigated layers, there are X atoms or charged dislocations in the region of the first monolayers, which are built in during epitaxial growth. The layers were intentionally undoped. They form an impurity band in which low mobility carriers dominate over the localised electron scattering due to the s-d exchange interaction. These carriers do not freeze out at liquid helium temperature and give rise to two transport media for electrons; a conduction band at higher temperatures and an impurity band at lower temperatures. The electron which fall down onto the previously ionised X atoms, then move by thermally activated hopping. We show that the two carriers model for In_0.53Ga_0.47As epitaxial layers are confirmed by the carrier concentration-temperature, carrier concentration-magnetic field, resistivity-magnetic field behaviour, and also by YKA theory also. The differences between the two transport models are so distinctive that observed phenomena may exist. This paper presents experimental results, which constitute comprehensive evidence for the complicated structure of the semiconductor epitaxial layers on the sample of n-type In_0.53Ga_0.47As/InP layer with n=2.2×10¹⁵/cm³.