Rutherford Appleton Laboratory, Chillon, Didcot, Oxfordshire, United Kingdom.
J Xray Sci Technol. 1995 Jan 1;5(1):88-104. doi: 10.3233/XST-1995-5108.
Using an x-ray spectrometer with an elliptically curved crystal it is possible to study absorption spectra from a target placed at one focus of the ellipse using a backlighting source placed at the other focus. This principle has been used to develop a spectrometer for EXAFS studies of laser compressed materials. The backlighting source is placed at one focus of the ellipse and the laser compressed EXAFS sample at the other. Using this technique a small area of the EXAFS target can be probed, thereby minimizing any spatial variations in the compressed plasma due to nonuniformities in the laser beams. Also, the dispersive nature of the crystal ensures that it acts as a bandpass filter, so that the EXAFS sample is not probed by other x-ray wavelengths which may cause unwanted heating. Another advantage is that compressed and uncompressed EXAFS spectra can be compared on a single shot. The optical properties of the spectrometer are discussed analytically and using a computer ray-tracing program. The development and alignment of the elliptical spectrometer are discussed, and its performance using both x-ray film and a CCD detector is evaluated. The use of the elliptical spectrometer as a high-resolution x-ray instrument is presented.
使用具有椭圆形晶体的 X 射线分光计，可以使用放置在椭圆另一个焦点处的背光源来研究放置在椭圆一个焦点处的目标的吸收光谱。这一原理已被用于开发用于激光压缩材料 EXAFS 研究的分光计。背光源放置在椭圆的一个焦点处，而激光压缩 EXAFS 样品则放置在另一个焦点处。使用这种技术，可以探测 EXAFS 靶的一小部分区域，从而最大程度地减少由于激光束不均匀而导致的压缩等离子体中的任何空间变化。此外，晶体的色散性质确保它充当带通滤波器，因此不会探测到可能引起不必要加热的其他 X 射线波长的 EXAFS 样品。另一个优点是可以在单次拍摄中比较压缩和未压缩的 EXAFS 光谱。还分析和使用计算机射线追踪程序讨论了分光计的光学性质。讨论了椭圆形分光计的开发和对准，并评估了其使用 X 射线胶片和 CCD 探测器的性能。介绍了椭圆形分光计作为高分辨率 X 射线仪器的用途。
