GB1219042A - Target electrodes for x-ray tubes - Google Patents

Abstract

1,219,042. X-ray tubes. SIEMENS A.G. 29 Sept., 1969 [27 Sept., 1968], No. 47862/69. Heading H1D. [Also in Division C7] A rotatable target for an X-ray tube comprises a central graphite disc 10, Fig. 1, and an annular outer metal member 13 which is preferably heat shrunk on to the disc. In Fig. 1 the member 13 is of tungsten and has surfaces 19 and 20 inclined at 17À5 degrees and 10 degrees respectively to the plane of the disc and either or both of which may be bombarded with electrons according to how the cathode is energized. The disc 10 is stepped at 14 to improve the adhesion of the member 13, and the disc is clamped by a nut 11 against an abutment 12 on the rotor shaft 8. In a modification, Fig. 2 (not shown), the graphite disc 10 is extended beneath the lower face of the outer metal member which comprises a molybdenum alloy containing 5% tungsten and has a flat surface facing the cathode coated with a 1 mm. layer of a 90% tungsten 10% rhenium alloy. In a further modification, Fig. 4 (not shown), the extension folds round the outer edge of the outer metal member and may be additionally secured to it by bolts (Fig. 4a, not shown). In another construction, Fig. 7, the graphite disc 41 ends in a flange 47 and is surrounded by a 95% Mo-5% W alloy ring 45 provided with a 1À5 mm. thick layer 52 of an alloy comprising 0À3% iridium, 0À3% rhenium and the balance tungsten; the assembly is arranged adjacent a cup-shaped graphite member 50 to which it is clamped when mounted on the rotor shaft. With this construction the axial projections 43 and 47 prevent the escape of stray electrons produced when the surface 52 is bombarded by electrons. In a modification, Fig. 6 (not shown), the graphite members 41 and 50 are integral. In another arrangement, Fig. 8, the metal ring 56 is heat shrunk on to a graphite ring 55 which is threaded on to the graphite member 54; the outer part of ring 55 is conical and a flange 57 on to ring 56 extends round a tapering lower edge of the ring 55. In a similar construction, Fig. 5 (not shown), the graphite members are integral, leaving a sector-shaped groove in which the metal ring is inserted. The ring is of molybdenum with a 2 mm. layer of an alloy of 12% rhenium-88% tungsten. A further construction, Fig. 3 (not shown), comprises a graphite ring of rectangular section surrounded by a molybdenum ring surrounded by a 2 mm. layer of 99À9% tungsten-0À1% rhenium. This electrode is suitable for use when the electron beam is directed towards the radially outer edge of the target.