Design of a high-throughput grazing-incidence flat-field spectrometer

The optical design of a high-throughput grazing-incidence flat-field spectrometer is presented. The spectral focal curve is almost a straight line because of the flat-field focusing properties of spherical variable-line-spaced gratings. The angular acceptance in the direction perpendicular to the plane of dispersion is maximized by means of a focusing spherical mirror mounted with its tangential plane coincident with the sagittal plane of the grating. Analytical calculations for the determination of the optimum mirror parameters are presented. A spectrometer for high-throughput experiments in the 800-60-eV region is designed with an extreme-ultraviolet-enhanced CCD detector: when the available flux is compared with that of a spectrometer with the same kinds of grating and detector but without a focusing mirror, the increase is as much as a factor 3.     

Compact high-resolution soft-x-ray spectrograph design using two matched grazing-incidence gratings

A novel and simple soft-x-ray grating-spectrograph design for high-resolution plasma-spectroscopy applications is presented and analyzed. This design uses dual, matched, concave varied-groove-density gratings to provide high dispersion and slit magnification and can achieve a very high spectral resolution (λ/Δλ > 25,000) in an instrument that is less than 1 m in length while using detectors, such as microchannel plates, with relatively coarse spatial resolutions. The advantages of this design over other designs with a comparable spectral resolution include its simplicity and small size, whereas the disadvantages include a narrow useful spectral range (λ/Δλ ≈ 50). Potential applications include x-ray laser linewidth measurements.     

Fabrication and evaluation of a wideband multilayer laminar-type holographic grating for use with a soft-x-ray flat-field spectrograph in the region of 1.7 keV

A multilayer laminar-type holographic grating having an average groove density of 2400 lines/mm is designed and fabricated for use with a soft-x-ray flat-field spectrograph covering the 0.70-0.75 nm region. A varied-line-spaced groove pattern is generated by the use of an aspheric wavefront recording system, and laminar-type grooves are formed by a reactive ion-etching method. Mo/SiO2 multilayers optimized for the emission lines of Hf-M, Si-K, and W-M are deposited on one of the three designated areas on the grating surface in tandem. The measured first-order diffraction efficiencies at the respective centers of the areas are 18%-20%. The flat-field spectrograph equipped with the grating indicates a spectral linewidth of 8-14 eV for the emission spectra generated from electron-impact x-ray sources.     

Space-resolving flat-field extreme ultraviolet spectrograph system and its aberration analysis with wave-front aberration

The Nam aberration of a flat-field extreme ultraviolet spectrograph system, composed of a varied line-spacing concave grating and a toroidal mirror, was analyzed by calculating the wave-front aberration with respect to an astigmatic reference surface. The toroidal mirror was used to compensate for the astigmatism that was due to the grazing incidence of light at the concave grating. The spectrograph system could form a space-resolved spectrum along the sagittal direction. The spectral and spatial resolutions of the spectrograph system were estimated from the root-mean-square spot size. The actual spectral resolution of the spectrograph system was measured from extreme ultraviolet spectra obtained from plasmas produced by an iodine laser having an energy of 0.5 J in a 4-ns duration, and it was compared with the calculated value.     

Comparison of mechanically ruled versus holographically varied line-spacing gratings for a soft-x-ray flat-field spectrograph

Recent progress in the design of aspheric wave-front recording systems has permitted the manufacture of holographic gratings with highly variable groove densities that are suitable for flat-field spectrographs. A holographic grating thus recorded was processed to produce a laminar profile by use of reactive-ion etching. Measurements are reported of the absolute diffraction efficiency of this grating and of a comparable mechanically ruled grating. It is found that the holographic grating is much more effective in suppressing the higher orders. The spectral resolution was determined by use of a carbon Kalpha x-ray generator and a spectrograph with an imaging detector. The spectral resolution of the holographic grating was approximately 3 times worse than that of the ruled grating.     

High-resolution, flat-field, plane-grating, f/10 spectrograph with off-axis parabolic mirrors

A high-resolution, flat-field, plane-grating, f/10 spectrometer based on the novel design proposed by Gil and Simon [Appl. Opt. 22, 152 (1983)] is demonstrated. The spectrometer design employs off-axis parabolic collimation and camera mirrors in a configuration that eliminates spherical aberrations and minimizes astigmatism, coma, and field curvature in the image plane. In accordance with theoretical analysis, the performance of this spectrometer achieves a high spatial resolution over the large detection area, which is shown to be limited only by the quality of its optics and their proper alignment within the spatial resolution of a 13 microm x 13 microm pixelated CCD detector. With a 1500 lines/mm grating in first order, the measured spectral resolving power of lambda/Dlambda = 2.5(+/-0.5) x 10(4) allows the clear resolution of the violet Ar(I) doublet at 419.07 and 419.10 nm.     

Efficiency of a grazing-incidence off-plane grating in the soft-x-ray region

Efficiency measurements of a grazing-incidence diffraction grating in the off-plane mount were performed using polarized synchrotron radiation. The grating had 5000 grooves/mm, an effective blaze angle of 14 degrees, and was gold coated. The efficiencies in the two polarization orientations (TM and TE) were measured in the 1.5-5.0 nm wavelength range and were compared with the efficiencies calculated using the PCGrate-SX code. The TM and TE efficiencies differ, offering the possibility of performing unique science studies of astrophysical, solar, and laboratory sources by exploiting the polarization sensitivity of the off-plane grating.     

基于LabVIEW的定光栅摄谱仪的实现研究

为了实现对LED光谱特性参数的自动测量,利用虚拟仪器的设计思想及LabVIEW软件强大的信号处理功能,设计实现了基于LabVIEW的定光栅摄谱仪.系统以LabVIEW为软件平台,定光栅摄谱仪为硬件平台,获取信号通过PC机的控制和处理,实现了自动控制、测量信号、分析、显示等功能.实验表明,基于LabVIEW的定光栅摄谱仪具有界面友好、操作简单、测量精度高等特点,具有广阔的应用前景.     

High-resolution tunable spectrograph for x-ray laser linewidth measurements with a plane varied-line-spacing grating

We describe a spectrograph for x-ray laser linewidth measurements in the range 100-220 A. The design employs a plane varied-line-spacing grating operating in the convergent light produced by imaging of the entrance slit with a concave spherical mirror. By the appropriate choice of the linear term in the grating-spacing variation, two separate wavelengths can be focused at the same image distance. As a result all wavelengths within the range of interest are focused at or near the same distance. The spectrograph can be tuned by rotation of the grating to bring any wavelength within the range to the center of the focal plane, and the spectra are dispersed on a surface that is erect or practically flat and perpendicular to the principal ray. This allows the use of a planar detector. With a streak camera used as a detector, the instrument obtained time-resolved linewidth data on x-ray lasers with a resolving power of 1 x 10(4) to 2 x 10(4). This paper presents the design methods used to optimize the varied-line-spacing grating, the design of the tunable spectrograph, and the results from the instrument in operation.     

Ultraviolet groove efficiency of a holographic grating: implications for a dual-order spectrograph

The ultraviolet groove efficiency for a holographically ruled diffraction grating with a trapezoidal profile has been measured. The efficiencies for the +/-1 and the zero orders are in good agreement with those derived from scalar theory. The +/-1 orders have equal efficiency as a function of wavelength. The peak of the sum of fitted groove efficiency functions is 76%, a level that is competitive with the groove efficiency of a mechanically blazed grating. We suggest that a normal-incidence grating mount with detectors at both orders will offer a system with twice the efficiency and provide a built-in redundancy. We discuss design considerations for reducing astigmatism equally in both orders in such dual-order mountings.     

Stigmatic spectrometers for extended sources: design with toroidal varied-line-space gratings

Performances are presented of three classes of imaging slit spectrometers for extended sources with aberration-corrected gratings. A general analytical expression for minimizing off-axis grating aberrations is obtained, and it is demonstrated that these aberrations are minimized when the spectrometer is operated at a magnification higher than unity. Classical designs with toroidal uniform-line-spaced (TULS) or spherical varied-line-space (SVLS) gratings are compared with a new class of designs that utilize toroidal varied-line-space (TVLS) gratings. Although TULS and SVLS designs with two stigmatic points can be designed to operate at near-unity magnification with excellent on-axis spectral and spatial resolutions, they cannot be made to satisfy the general off-axis condition, and so their off-axis performances are not optimum. On the contrary TVLS designs with two stigmatic points can be operated at almost any magnification, thus satisfying the off-axis condition perfectly. Such designs are suitable for imaging spectrometer observations that require an extended field of view.     

Debye series analysis of scattering of a plane wave by a spherical Bragg grating

The Debye series decomposition of the partial-wave scattering amplitudes of a multilayer sphere is derived. The partial-wave transmission and reflection terms appearing in the Debye series are multiple-scattering amplitudes written in terms of four basic quantities and combined together layer by layer in an identical way. The resulting expressions are then used to calculate the scattered intensity of a spherical Bragg grating covering a dielectric core particle and to analyze a number of new structures appearing in the scattered intensity.     

Optimum structural design with stability constraints

This paper presents an optimization method based on optimality criterion for minimum weight of structures with stability requirements. A recurrence relation is derived and the method is explained in the context of the displacement method of finite element analysis. The incipient buckling of the structure is determined by a linear eigenvalue solution. The method is programmed for trusses and frames. Illustrative problems are given to show the applicability of the method of design of structures with a large number of design variables.     

正交设计在单分散球形SiO2制备中的研究

用正交试验,采用L9 (33)正交表,在醇水体系中采用氨作催化剂,正硅酸乙酯为硅源,研究了各原料浓度对单分散球形SiO2 粒度的影响。研究表明在其它条件不变的情况下,二氧化硅的粒度随着氨和水浓度的增加而明显增大,随TEOS 浓度的增加,二氧化硅的粒度也略有增大,但幅度较小。本文还详细研究了二氧化硅颗粒的形成机理。     

Optimum design of a cogeneration system in processes

Abstract

A systematic method is presented for the preliminary design of a cogeneration system with the desire of achieving minimum operating costs. The ratio of power to process heat is shown to be a critical factor in the preliminary selection of energy conversion systems. However, the final decision should be based on the operating costs and economical index, ROI. A fuel substitution factor is proposed to define theoretically the most economical power generation in plants. Two case studies are demonstrated to describe this approach.