International
Tables for
Crystallography
Volume C
Mathematical, physical and chemical tables
Edited by E. Prince

International Tables for Crystallography (2006). Vol. C, ch. 7.1, p. 632

Section 7.1.6.5.3. Image intensifiers

U. W. Arndtb

7.1.6.5.3. Image intensifiers

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In an image intensifier, the photoelectrons from a photocathode are made to produce a visible intensified image on an output phosphor. In so-called first-generation tubes, the intensification is produced by subjecting the electrons to accelerating voltages of up to about 15 keV: the number of visible-light photons at the output per keV of electron energy is about 80. The photon gain of the devices is typically about 100; there may be a brightness gain factor of M2 if the electrostatic electron-optical system produces a demagnification of M. Standard first-generation image intensifiers of this type are made with input field diameters up to 80 mm, they always have fibre-optics input face plates on which X-ray phosphor may be deposited, they are stable and robust, and have a good resolution of better than 100 µm at the input. Their low gain requires the use of a low-light-level TV camera tube in the next stage (Arndt & Gilmore, 1979[link]) or of two or more intensifiers of this type in tandem (Kalata, 1982[link]) or of an intrinsically more sensitive slow-scan read out (Eikenberry, Gruner & Lowrance, 1986[link]).

For military and civilian night-vision applications, first-generation image intensifiers have largely been replaced by devices embodying one or two microchannel plates (MCP's) that produce an electron gain of up to 1000 per stage (see, for example, Emberson & Holmshaw, 1972[link]; Garfield, Wilson, Goodson & Butler, 1976[link]). Commercial second- and third-generation intensifiers (Pollehn, 1985[link]) are less suitable for quantitative scientific purposes than the first-generation devices: their GaAs photocathodes are less well matched to most X-ray phosphors, the gain of MCP's decreases with time, and the tubes have a slightly lower resolution than diode types of comparable diameter. Most third-generation intensifiers have plain rather than fibre-optics face plates and none appear to be available with a diameter greater than 50 mm (Airey & Morgan, 1985[link]). Nevertheless, these high-gain intensifiers do make it possible to construct relatively cheap moderate-performance X-ray detectors using standard-sensitivity TV pick-up devices, including CCD's (Dalglish, James & Tubbenhauer, 1984[link]), instead of the low-light-level camera tubes necessary with a lower pre-amplification.

An intensifier can, in principle, employ a variety of read-out methods, e.g. by substituting a resistive disc anode, a coded anode or a CCD for the output phosphor. However, the only way of employing standard modules is to couple them to a TV pick-up device.

References

Airey, R. W. & Morgan, B. L. (1985). A microchannel plate image intensifier for detection of photon-noise-limited images. IEE Conf. Publ. (London), 253, 5–7.
Arndt, U. W. & Gilmore, D. J. (1979). X-ray television area detectors for macromolecular structural studes with synchrotron radiation sources. J. Appl. Cryst. 12, 1–9.
Dalglish, R. L., James, V. J. & Tubbenhauer, G. A. (1984). A 2-D X-ray diffraction pattern sensor using a solid-state area-sensitive detector. Nucl. Instrum. Methods, 227, 521–525.
Eikenberry, E. F., Gruner, S. M. & Lowrance, J. L. (1986). A two-dimensional X-ray detector with a slow-scan charge-coupled device readout. IEEE Trans. Nucl. Sci. 33, 542–545.
Emberson, D. L. & Holmshaw, R. T. (1972). Some aspects of the design and performance of a small high-contrast channel image intensifier. Adv. Electron. Electron Phys. 33A, 133–144.
Garfield, B. R. C., Wilson, R. J. F., Goodson, J. H. & Butler, D. J. (1976). Developments in proximity-focused diode image intensifiers. Adv. Electron. Electron Phys. 40A, 11–20.
Kalata, K. (1982). A versatile television X-ray detector and image processing system. Nucl. Instrum. Methods, 201, 35–41.
Pollehn, H. K. (1985). Performance and reliability of third-generation image intensifiers. Adv. Electron. Electron Phys. 64A, 61–69.








































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