. Electron microscopy; proceedings of the Stockholm Conference, September, 1956 . CRYSTAL SPECTROMETER 'MAY Be INSERTED AMPLIFIER PULSE ANALYSER Fig. 1. Block diagram of the scanning microscope. the lens aperture. The spot size is /< to 1 // and the area of scan about \ mm square at largest. Part of the emitted x-rays are collected through a window in the polepiece gap by a scintillation counter, or alternatively the phosphor of the counter may be pushed into the vacuum to record high energy scat- tered electrons. The amplified signal from the counter modulates the brightness of a catho
. Electron microscopy; proceedings of the Stockholm Conference, September, 1956 . CRYSTAL SPECTROMETER 'MAY Be INSERTED AMPLIFIER PULSE ANALYSER Fig. 1. Block diagram of the scanning microscope. the lens aperture. The spot size is /< to 1 // and the area of scan about \ mm square at largest. Part of the emitted x-rays are collected through a window in the polepiece gap by a scintillation counter, or alternatively the phosphor of the counter may be pushed into the vacuum to record high energy scat- tered electrons. The amplified signal from the counter modulates the brightness of a cathode ray tube scanned in synchronism with the microscope beam, so that an image is obtained of the variation of scattered electron intensity or of x-ray emission over the surface. The scan may then be stopped and the micro- scope beam accurately positioned on any feature in the specimen by observing the spot on the afterglow of the picture on the display tube. Through another window part of the emitted x-rays pass into a crystal spectrometer for analysis of the emission spectrum from that point, as in the method of microanalysis developed by Castaing (I, 2). Alternatively, the crystal can be removed from the spectrometer so that the x-rays pass straight into a proportional counter, which gives for each quan- tum a pulse of height approximately proportional to its energy. A single channel pulse analyser can be used to pass only pulses corresponding to a given characteristic line and, with the beam scanning, these can modulate the display tube so that the distribution of the element emitting that line is shown up. The second lens is shown in fig. 2. The electrons are focussed on to the specimen which is level with the lower pole face, and x-rays pass through a beryllium window into the phosphor of the scintilla- tion counter just outside the gap. The light generated is transmitted by a perspex rod to the photocathode of the multiplier outside the lens. The electrons scattered from
Size: 2809px × 1780px
Photo credit: © The Bookworm Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookcollectionameri, bookcollectionbiodiversity
