GB1222130A - Cathode assembly for an x-ray tube - Google Patents

Abstract

1,222,130. X-ray tubes. PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd. 10 May, 1968 [13 May, 1967], No. 22282/68. Heading HID. An X-ray tube provided with a cathode structure including a cathode cap 3 is provided with at least two coaxially arranged hollow cylinders adapted to conduct heat away from the cathode cap. In Figs. 1 the cap 3 is joined to a plate Sa secured to one end of a nickel sleeve 4 the other end of which is welded to a cylindrical member 5 of an alloy having the same thermal expansion as glass. The member 5 is joined to the glass envelope portion 13 and also to a hard glass member 12 through which lead-in wires 9-11 extend to the filaments 7 and 8. A copper cylinder 6 is soldered to the member 5; when the cathode structure is sealed into the envelope, the cylinder 6 is directly gripped in the chuck of a sealing-in machine so that the cathode can be aligned accurately, and the heat generated during sealing is conducted away to the chuck through cylinder 6 thereby reducing the heating of the cathode sleeve 2 and of the cathode cap 3 In operation the cooling provided through cylinder 6 may be improved by circulating oil through the cylinder (Fig. 2, not shown), and the same cooling oil circuit may be used to cool the anode. In an alternative construction, Fig. 3 (not shown), the cylinder 5 is joined directly to the plate 3a, and the glass envelope is sealed to the periphery of cylinder 5. The cathode projects into the interior of an earthed metal screen to prevent electrons from impinging on a glass envelope portion, and the anode may be similarly arranged. The envelope may contain SF 6 to improve the heat conduction to the outside.