A Compact Pressure-Insulated Electrostatic X-Ray Generator

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Abstract
A compact, pressure-insulated, electrostatic x-ray generator has been developed for scientific and medical purposes. A major object of the work was the investigation, with a small and thus flexible machine, of the principles and design factors involved in pressure-insulated electrostatic generators with a view to the subsequent development of higher voltages in compact apparatus. The generator is housed in a steel tank 34 in. in diameter and 100 in. high. At air pressures of 11 atmospheres absolute, 1250-kv x-rays are obtained with target currents of over one milliampere supplied by the single 14-in. belt. With Freon gas the same voltages and currents can be obtained at one-third the pressure required with air. The problem of belt charge is analyzed and a method is described for controlling the electrostatic fields within the column in order to realize the high charge densities possible at high pressure. The construction of a supporting column of high breakdown strength, and other features of the design are described. At 1250 kv the x-ray intensity per milliampere of target current is about 340 roentgens per minute at 50 cm from the target in the direction of the electron beam with five mm of lead equivalent filtration.