The accurate alignment of energy-dispersive X-ray detectors for quantitative microanalysis

Modern collimator design for energy-dispersive X-ray detectors requires very accurate positioning of the crystal/collimator assembly in order to achieve the maximum solid angle of collection for the irradiated volume on the specimen. Thus it is important to have a method of checking the alignment of the detector when mounted on the microscope and under vacuum. This paper describes a number of techniques, principally X-ray mapping, for performing such an alignment check. These techniques are applicable to windowless detectors as well as to those with integral windows which will support atmospheric pressure. Methods of obtaining the non-standard modes of microscope operation suitable for this task are described, and some suggestions are made for ways of moving the crystal/collimator assembly and monitoring this movement while it is in progress.