Study of normal incidence of three-component multilayer mirrors in the range 20-40 nm

We study theoretically and experimentally the increase of normal incidence reflectivity generated by addition of a third material in the period of a standard periodic multilayer, for wavelengths in the range 20 to 40 nm. The nature and thickness of the three materials has been optimized to provide the best enhancement of reflectivity. Theoretical reflectivity of an optimized B4C/Mo/Si multilayer reaches 42% at 32 nm. B4C/Mo/Si multilayers have been deposited with a magnetron sputtering system and a reflectivity of 34% at 32 nm has been measured on a synchrotron radiation source.     

梯度反射率镜的设计及镀制

针对所设计的单横模Nd：YAG激光器谐振腔对梯度反射率镜的设计要求，以及遮蔽挡板是实现梯度反射率镜的重要内容，论文建立了精确设计遮蔽挡板的数学模型，提出了设计遮蔽挡板的算法，编程计算出具体的遮蔽挡板的孔径尺寸及安放位置，并分析模拟了遮蔽挡板的位置误差对反射率分布的影响。最后，根据遮蔽档板的设计与模拟分析，实际镀制出与设计目标相吻合的梯度反射率镜。     

Frequency-dependent graded reflectivity mirror: characterization and laser implementation

We present a theoretical and experimental investigation of a new family of variable reflectivity mirrors, based on frustrated total internal reflection and interference effects. These mirrors are sensitive to frequency in the sense that their transverse reflectivity distribution changes significantly as a function of the frequency of light. The mirror reported here shows total power reflectivity changes of 50% within 8.0 GHz. The mirror was tested as the output coupler of an unstable resonator in a Nd:YAG laser working in the free-running regime. This configuration was compared with the standard stable multimode resonator configuration. The beam divergence was reduced by more than 1 order of magnitude and the output power was reduced by only 10%. The laser resonator mode competition that is due to the frequency-dependent mirror reflectivity distribution is discussed.     

Variational asymptotic modeling of the multilayer functionally graded cylindrical shells

An efficient high-fidelity shell model is developed for heterogeneous multilayer cylindrical shells made of functionally graded material by using the variational asymptotic method (VAM). Taking advantage of the smallness parameters inherent in the shell structure, the VAM is applied to rigorously decouple the 3-D, anisotropic elasticity problem into a 1-D through-the-thickness analysis and a 2-D shell analysis. The through-the-thickness analysis servers as a link between the original 3-D analysis and the shell analysis by providing a constitutive model for the shell analysis and recovering the 3-D field variables in terms of global responses calculated by the shell analysis. The present model is valid for large displacements and global rotations and can capture all the geometric nonlinearity of a shell when the strains are small. A cylindrical bending example of a homogeneous substrate with a thin SiC-Al functionally graded coating under sinusoidal pressure on the top surface is used to validate this model.     

Preparation of graded multilayer materials and evaluation of residual stresses

It is generally difficult to join ceramics to alloys by conventional welding technologies to fabricate graded multilayer materials with various excellent engineering properties. In this study, MoSi₂ and 316L stainless steel are chosen a typical example and are joined together using the spark plasma sintering technique. To evaluate the joint quality, the interlayer system of the graded material is characterized using analysis of the residual stress by the finite element ANSYS code. The results show that dense uniformed joints can be achieved with such graded inter-layers because the coefficient of thermal expansion (CTE) of each interlayer closely matched over a wide temperature range. Such a compatibility between the graded inter-layers prevents MoSi₂ with low toughness from the occurrence of microcracks resulted from the residual stresses formed during cooling of the joint. Further theoretical analysis indicates that with the increase in the compositional distribution exponent (P), maximum radial and axial residual tensile stress first increases and then decreases. In addition, with the increase in the number (n) of graded layer, maximum radial and axial residual tensile stress decreases gradually.     

Optimization of graded multilayer designs for astronomical X-ray telescopes

We developed a systematic method for optimizing the design of depth-graded multilayers for astronomical hard-x-ray and soft-gamma-ray telescopes based on the instrument's bandpass and the field of view. We apply these methods to the design of the conical-approximation Wolter I optics employed by the balloon-borne High Energy Focusing Telescope, using W/Si as the multilayer materials. In addition, we present optimized performance calculations of mirrors, using other material pairs that are capable of extending performance to photon energies above the W K-absorption edge (69.5 keV), including Pt/C, Ni/C, Cu/Si, and Mo/Si.     

Reflectance of a wideband multilayer x-ray mirror at normal and grazing incidences

The reflectance of a W-B(4)C multilayer mirror, with a period thickness that increased with depth into the multilayer, was measured at near-normal incidence with synchrotron radiation and at grazing incidence with Cu Kα radiation. The period thickness increased linearly from 17.9 ? at the top of the multilayer structure to 21.9 ? at the substrate while the same ratio of nodal layer to period thickness was maintained. For a grazing angle of 80° (10° from normal incidence), the peak reflectance was 1.1% at a wavelength of 36 ?, and the reflectance profile was 1 ? wide. For Cu Kα radiation the reflectance peaked at a grazing angle of 2.4° and was 0.4° wide. Compared with a W-B(4)C multilayer mirror with a constant period thickness, the depth-graded multilayer mirror has wider reflectance profiles at near-normal and grazing incidences, resulting in larger integrated reflectances and wider fields of view.     

Characterization of a multilayer highly reflecting mirror by spectroscopic phase-modulated ellipsometry

The characterization of optical multilayer coatings has been a challenging task for thin-film scientists and engineers because of the various complex, interdependent layer parameters that exist in the system. Spectroscopic phase-modulated ellipsometry has some advantages in the postanalysis of the layer parameters of such multilayer coatings because it suitably models the layer structure with respect to the ellipsometric measurements. An algorithm to characterize multilayer optical coatings with large numbers of layers has been described by spectroscopic ellipsometry by use of a discrete spectral zone fitting approach. A 23-layer multilayer highly reflecting mirror has been characterized by this technique in the wavelength range 280-1000 nm. The ellipsometric spectra (? and D versus wavelength) have been fitted separately in three wavelength regimes. Fitting the ellipsometric spectra in the wavelength regime of 700-1000 nm permitted the sample structure to be determined. The data were then fitted in the wavelength range 280-340 nm, i.e., near the fundamental absorption edge of TiO(2), to yield the dispersion relation for the optical constants of TiO(2). Finally, the data were fitted in the wavelength range 340-700 nm, and the true dispersion of the refractive index of TiO(2), along with the best-fitting sample structure, was obtained.     

Optical constants of in situ-deposited films of important extreme-ultraviolet multilayer mirror materials

We have performed angle-dependent reflectance measurements of in situ magnetron sputtered films of B(4)C, C, Mo, Si, and W. The Fresnel relations were used to determine the complex index of refraction from the reflectance data in the region of approximately 35-150 eV. In the cases of Si, C, and B(4)C we found excellent agreement with published data. However, for Mo and W we found that the optical properties from 35 to 60 eV differed significantly from those in the literature.     

Surface crystallization of melt-spun Pd40Ni40P20 glass

The crystallization of Pd₄₀Ni₄₀P₂₀ glass, produced by melt-spinning in air, has been studied by optical metallography. Crystallization is predominantly from the surface and is more prevalent on the wheel-side. The non-uniformity is attributed to variation in quench rate during production. A three-stage anneal permits crystals which have nucleated at the surface to be identified and their size distribution to be analysed. The surface nucleation is heterogeneous and appears to be hindered by mild oxidation. The annealing atmosphere markedly affects the surface crystallization behaviour, as does removal of the original ribbon surface. When nucleation is sparse, partial crystallization causes the development of noticeable relief on the sample surfaces.     

Design and performance of capping layers for extreme-ultraviolet multilayer mirrors

Multilayer lifetime has emerged as one of the major issues for the commercialization of extreme-ultraviolet lithography (EUVL). We describe the performance of an oxidation-resistant capping layer of Ru atop multilayers that results in a reflectivity above 69% at 13.2 nm, which is suitable for EUVL projection optics and has been tested with accelerated electron-beam and extreme-ultraviolet (EUV) light in a water-vapor environment. Based on accelerated exposure results, we calculated multilayer lifetimes for all reflective mirrors in a typical commercial EUVL tool and concluded that Ru-capped multilayers have approximately 40x longer lifetimes than Si-capped multilayers, which translates to 3 months to many years, depending on the mirror dose.     

Investigations into the thermal performance of multilayer insulation (300-77 K) Part 2: Thermal analysis

Simple analytical methods have been employed for heat transfer analysis of experimental data obtained through calorimetric investigations on multilayer insulation (MLI). Sectional heat transfer analysis has shown that the effective thermal conductivity of the MLI varies from section to section of the insulation structure and it has a peak which lies between the middle and warm boundary regions of the MLI. This could be attributed to a peak in residual gas conduction in this region. The theoretical estimation of heat flux through MLI, using a simple analytical model, is also discussed in this paper. This model takes into consideration the non-linear temperature profile of the insulation. The computed heat flux using this model gives a lower (2 to 4 times) value in comparison with the heat flux estimated from calorimetric measurements. A refined model has been suggested which includes the residual gas conduction also in MLI.     

EL20-1型装药机在连续乳化炸药生产线中的应用

文章首先分析了国内工业乳化炸药生产中装药机技术现状,然后介绍了EL20-1型装药机的机械、液压和自动控制系统的组成及工作原理.主要从运行稳定性、装药速度和药卷合格率三个方面叙述了该装药机的工作性能,同时对EL20-1型装药机在实际使用中应注意的问题进行了探讨.     

Measurements of the photocurrent enhancement of reverse-biased silicon photodiodes in the 0.05-1.5-keV photon-energy range

The measured photocurrents from two different p-n-junction silicon photodiodes at 170-? (73-eV) and at 8.34-? (1480-eV) light are presented. One is a standard extreme-UV photodiode fabricated on low resistivity silicon (70-100 Ω cm), and the other is fabricated on high-resistivity silicon (> 2 × 10(4) Ω cm). The photocurrents from the diode on high-resistivity silicon are at least an order of magnitude greater than the photocurrents from the diode on low-resistivity silicon when a reverse bias of 40 V is applied to each. This photocurrent enhancement is 15.4 ± 4 at 8.34 ? and 12.5 ± 2 at 170 ?.     

TiOx/Ag/TiOx multilayer for application as a transparent conductive electrode and heat mirror

Amorphous TiO_x films and Ag layer were deposited by electron-beam evaporation on soda-lime glass at room temperature. The details regarding the structure, surface morphology, and optical properties of the as-prepared TiO_x films were examined by X-ray diffraction, scanning electron microscopy, and ultra-violet (UV) -visible-near-infrared (NIR) spectrometry. The TiO_x films exhibit amorphous phase with an optical band gap of 3.35 eV. The polygrains oriented along the (111) and (200) directions in the Ag films were adopted to supply carriers into the TiO_x film and lower the sheet resistance of the stacked layer. The multilayer exhibited a sufficiently large Ag thickness (>15 nm), low resistance, high UV transmittance, visible transmittance, and high NIR reflection. Dependence of Ag thickness, TiO_x bottom-layer, and TiO_x overlayer on the optical and electrical properties of TiO_x/Ag/TiO_x were explored. A figure of merit (FOM) was used to find an optimal structure for a multilayer with superior conductivity and visible transparency. An FOM of 9.8 × 10^?2 (Ω^?1) at the visible wavelength of 550 nm for a TiO_x/Ag/TiO_x stacked layer with an 18-nm-thick Ag and a 20-nm-thick TiO_x was achieved. The TiO_x/Ag/TiO_x sample annealed at 500 °C 10 min also shows a good thermal stability.     

X-ray photoemission study of Fe40Ni40B20 metallic glass

X-ray photoelectron spectroscopic (XPS) study of the valence band and the core levels of amorphous Fe₄₀Ni₄₀B₂₀ are presented. The oxides which formed at the surface of as-received sample are due to oxidation of iron and boron. For etched samples, the presence of oxide is not discernible, and the chemical environment is predominantly iron-boron-like, while nickel remains unassociated. The valence band has a high density of states at Fermi levels of amorphous Fe₄₀Ni₄₀B₂₀ are presented. The oxides which formed at the surface of B2s and Fe3d states, and metalloids-states respectively.