双道X射线分光光谱仪及其与扫描电子显微镜的匹配

A Dual X-ray Dispersive Crystal Spectrometer and its Fitting to a Scanning Electron Microscope

本X光谱仪是一种线性全聚焦弯晶谱仪。装备在扫描电镜上后,可使之兼具电子探针X光微区分析仪的功能。本文重点讨论了X光光谱仪的几何精度、分光晶体的制备、光谱仪与电子光学镜筒的匹配衍射峰值强度的提高、本底噪音的减低以及同轴光学显微镜的匹配等问题。X光谱仪的总几何精度应为±1′,重复精度为6″。实际结果表明,元素分析范围为B^5(Be^4)～U^(92);波长分辨率△λ/λ为1～5×10^(-3)(Na^(11)～U^(92))及1～5×10^(-2)(B^5～F^9),可分开Cu,Fe,Ti等元素的K_(α1,α2)谱线,Ti-6A1-4V合金中VK_(α1),VK_(α2)及TiK_β谱线;波长重复性为0.00014A;探测限对Na^(11)～U^(92)为10^(-3)％量级,B^5～F^9为10^(-2)％量级。

This dual X-ray spectrometer consists of two linear-type full fo-cus dispersive spectrometer for analyzing elements. Each contains two Johann typecrystals, i. e. LiF, PET or TAP, STE (CER). The take off angle of X ray is30°, radius of Rowland circle is 140mm. Bragg angle (2θ) ranges from 25° to 120°.These spectrometers can be equipped on the Chinese DX-3 SEM and turn itinto a high grade EPMA-SEM. In this paper the geometric tolerances of the lineartype curved crystal fully focusing X-ray wavelength spectrometer have been calcu-lated. The preparation of analyzing crystals, fitting the spectrometer to a SEM,increasing peak intensity of diffraction lines, reduction of background and providinga coaxial optical microscope on the specimen chamber are discussed. The overall geo-metric accuracy and reproductibility of the spectrometer should be 1′and 6″respectively. In result, the performances are as follows: range of detectable ele-ments is from B^5 (Be^4) to U^(92). Wavelength resolving power Δλ/λ is 1～5×10^(-3) (Na^(11)～U^(92)) or 1～5×10(-2) (B^5～F^9), spectra of K_(α1), K(α2) of Cu, Fe, Ti; VK_(α1), VK_(α2) andTiK_β of Ti-6Al-4V alloy can be discriminated, and the limit of detectability is10^(-3)％ (Na^(11)～U(~92)) to 10^(-2)％ (B^5～F^9) order.