Backscattered electron detector

Backscattered Electron Detectors and Applications, Amray Technical Bulletin 122-685, Amray, Bedford, Mass., 1986, pp. 89-106. 

At the start of 1978 the particle analysis method183 replaced the flameless atomic absorption bulk elemental method184 as the firearm residue detection method in the NIFSL. Since then the particle analysis method has been substantially improved by the use of a sample concentration/cleanup procedure,185 the addition of a backscattered electron detector, and the development of an automated residue detection system.186 187 Despite these improvements the technique remains costly and labor intensive. Certain aspects of the system required further work, in particular, the particle classification scheme discharge particles from mercury fulminate-primed ammunition and discharge particles from new primer types (Sintox). 

A scanning electron microscope (Philips 505) equipped with four scintillator-type backscattered electron detectors and an energy-dispersive X-ray microanalysis system (Tracor Northern 5500) were used to analyze the specimens. 

In its basic form, a scanning electron microscope is an electron column fitted with a secondary electron detector. X-ray and backscattered electron detectors are increasingly frequently added for local chemical analysis. 

The column is generally fitted with secondary and backscattered electron detectors in order to obtain the images required for identifying the areas to be analysed. 

Scanning Electron Microscope PHILIPS SEM 505 equipped with LaB6-Cathode, Specimen Current Detector, Backscattered Electron Detector, Signals Mixing Unit, Computer-Interface, SDR-Unit and EDAX PV 9100 Energy Dispersive X-Ray Analyzer. 

Fig. 22 PAEMA-coated PU-capsules with physically adsorbed gold-IgG antibodies. Gold is visualized with the backscattered electron detector red) in the HR-SEM [190]...

SEM can be equipped with various detector systems like scintillator detectors (e.g., Everhart-Thomley detector) and solid state detectors. The standard setup contains a backscattered electron detector and a secondary electron detector. Since BSEs are deflected out of the specimen, the detector is mounted at the exit point of the electron beam. The collector system for SE and BSE are shown in Fig. 1. 

The method relies on the ability to provide a vacuum differential across the objective aperture in the electron optical column. This is in principle possible in all SEMs, but in practice easier to achieve in some microscopes than others. Image formation requires a BSE detector rather than the more commonly used SE detector. While any backscattered electron detector can be used, the high resolution potential of the SEM can only be maintained by employing a high efficiency detector, such as the Robinson detector used here. 

Specimen chatnber j Backscattered electron detector Specimen holder... 

Fig. 10. Diagram showing the relative position of the secondary and backscattered electron detectors in SEM.

FIGURE 13.5 (a) Aluminum stub viewed by a secondary electron detector (left panel) and a backscatter electron detector (right panel). (b) Carbon-gold composite electrode viewed by a secondary electron detector and a backscatter electron detector (inset). (Reproduced with permission from Ref [11]. Copyright 2012, Wiley-VCH Verlag GmbH.) ( All unattributed images taken by author KEF.)... 

XRD (X-ray diffraction) and SEM with a backscattered electron detector. The most important parameters affecting the CVD process were reaction temperature, reactant concentrations, and top layer quality. Deposition of Pd in the y-AljOj top layer resulted in a 100- to 1000-fold reduction in He permeance of the porous substrate. The permeation flux of these membranes was in the range 0.5-1.0 x 10 mol m s Pa" at 350-450°C. The Hj permeation data suggest that surface reaction steps are rate-limiting for Hj transport through such thin membranes in the temperature range studied. 

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