Proceedings

of the Tomsk Polytechnic Institute named after S. M. Kirov,
holder of the Order of the October Revolution and the Order of the Red Banner of Labor

Volume 213　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　1972

On the Application of X-ray Vidicons with Various Types of FOS in Radiation Introscopes

V. I. Gorbunov, D. I. Sviryakin

The development of radiation television introscopy is continuously expanding the field of application of X-ray vidicons and is imposing increasingly stringent requirements on their technical characteristics. In order to make maximum use of the capabilities of an X-ray vidicon, it is necessary first of all to assess correctly the range of its application.

Like all electron-beam tubes, X-ray vidicons require electron-optical systems for forming and controlling the electron beam. The method of focusing and deflecting the beam largely determines such parameters of an X-ray vidicon as linear resolving power, or aperture characteristic, astigmatism, and aberration. The choice of the system for focusing and deflecting the beam is determined mainly by the dimensions of the X-ray vidicon target and by the purpose of the introscope. Without touching on the efficiency of conversion of X-ray radiation by the vidicon target, and without considering the properties of the materials from which it may be made, we shall determine the areas in which it is expedient to use X-ray vidicons with different systems for focusing and deflecting the beam.

Thus, X-ray vidicons with a small target diameter ($\varnothing 18$ mm) are most suitable for use in X-ray microscopes, since they possess a high signal-to-noise ratio and have magnetic focusing and beam deflection, owing to which they provide high resolving power (aperture 0.02 mm).

X-ray vidicons with a target diameter on the order of 100 mm may have electropotential beam deflection and electrostatic focusing of the latter. Such a system for focusing and deflecting the beam makes it possible to use comparatively simple circuits and, by combining the sweep generators of the transmitting and receiving tubes, to exclude (with progressive scanning) the sync block from the introscope system. An oscillographic tube may be used here as the receiving tube, making it possible, with a screen diameter of 110 mm, to obtain a definition of 300–350 lines, which in many cases is quite acceptable. The combination of an electrostatic focusing and deflecting system (FOS) with progressive scanning, which does not require rigid synchronization between lines and frames, will make it possible to create portable introscopes for detecting defective regions in materials and structures under field conditions. Such an introscope may have smooth or ste-

...printed sweep generators tunable in frequency, as well as a video channel with an adjustable passband, and to operate in different modes that are optimal from the standpoint of the specific conditions of operation and information processing. Magnetic beam-deflection systems lack this advantage because of the difficulty of matching, over a sufficiently wide frequency range, the output parameters of the sweep generators with the parameters of the deflecting coils. This, however, does not preclude the use of magnetic FOS for X-ray vidicons with a target diameter of 90 mm. In introscopes with standard resolution (625 lines, 50 fields) and non-tunable sweep frequencies, such an FOS is as yet irreplaceable. In this case, the greater complexity and higher cost of the introscope cannot be an obstacle to improving its quality characteristics.

X-ray vidicons with a target diameter of 100–200 mm will evidently become the principal type of transmitting tube in introscopes for broad application, since they provide an inspection area sufficiently convenient from the standpoint of observing and detecting defects, and a contrast sensitivity close to the requirements of the State Standard for radiographic inspection. With a further increase in the target diameter of X-ray-sensitive transmitting tubes, it becomes advisable to use electrostatic focusing and magnetic beam deflection, since the aperture requirements in this case remain the same, while increasing the beam-deflection angle with only a slight lengthening of the tube neck leads to a more complicated tube design and, with electrostatic beam deflection, to a significant increase in the voltages that provide the sweep. This, in turn, requires the use of powerful generator tubes, an increase in the voltages feeding the anodes and shielding grids of these tubes, and a complication of both the circuitry and the design of the entire introscope. In other words, for X-ray-sensitive transmitting tubes with large target areas, a magnetic beam-deflection system is more economical, more convenient, and causes less distortion. Such tubes may find broad application for diagnostic investigations in medicine and for visual detection of various inhomogeneities in large-size products, that is, where the dimensions and weight of the introscope do not play a significant role.