GB912084A - Collimator for high energy radiation beams - Google Patents

Abstract

912,084. Collimators for high-energy radiation beams. AVIATION ELECTRIC Ltd. Feb. 6, 1961 [Feb. 8, 1960], No. 4333/61. Class 98 (1). A collimator for high-energy beams consists of an inner and an outer ring of leaves, each ring comprising at least three leaves, the leaves extending in a direction away from the source and of adjustable inclination thereto, and the rings being so arranged that gaps between leaves of the inner ring are covered by leaves of the outer ring. The form shown has four inner leaves 6 and four outer leaves 5 mounted on a base 1, the adjustment of the leaves being effected by a milled ring 2. Fig. 7 shows one form of mechanism by which the leaves can be moved. As ring 2 turns, rack teeth on it rotate a bevel gear 17 on a shaft 18. The other end of the shaft is threaded, as at 21, engaging in a threaded hole 20 in a housing 31 ending in a bar 11. As the threaded part 21 screws into and out of the housing 31, the bar portion 11 pushes against the leaf 6, causing it to swing about its pivot 25. A similar arrangement moves the leaf 5 about its pivot. Fig. 8 (not shown) is an alternative form of mechanism for linking the ring 2 with the leaves 5 and 6. The construction and shape of the individual leaves are shown in Figs. 5 and 6. The outer leaves 5 have extended edges 45, 46, and the inner leaves have extended edges 47, 48, so that they may overlap in all but the most open positions. At the end farthest from the radioactive source 40 the leaves 6 have an extended tongue portion 58, and the leaves 5 a relieved surface formation 71 into which this tongue portion may fit. The inner surface of the leaves may be plated with chromium or copper to minimize the production of secondary electrons.