GB1328827A - Three-electrode arc lamps incorporating heat shielding means - Google Patents

Abstract

1328827 Discharge lamps VARIAN ASSOCIATES 17 Dec 1970 [19 Jan 1970] 60059/70 Heading H1D An are lamp has a sealed envelope filled with an ionizable gas and comprising three conductive members 34, 44 and 24 separated by and joined in a gas-tight manner to first and second insulative members 42 and 10, one of said members (24) having an optical window 26 sealed in a gas-tight manner within an aperture therein, each of said conductive members having a conductive electrode 32, 50, 28 connected thereto and extending within said envelope to form an arc gap, and thermal shielding means 54 mounted within said envelope between said arc gap and the joint between at least one of said conductive members and at least one of said insulative members. The envelope comprises a metallic cathode support plate 34, a metal reflector 44 brazed to metal spacer ring 46, and a metal anode support ring 20 connected to a metal window support 24, the metal parts being interconnected by cylindrical ceramic insulators 42, 10, e.g. of polycrystalline alumina. The connection between the spacer ring 46 and the insulator 42 is a brazed joint which is shielded from the arc by metallic heat sleeve 54 which is brazed to ring 46. A starter electrode 50 is joined by a tab 52 to the reflector 44 and is connected, e.g. to a 50 kV pulse source. The tungsten anode 28 connected to the anode support ring 20 by radial metal struts 30, e.g. of molybdenum, is connected, e.g. to a 12V, 12A D.C. supply and support 24 holds a window 26, e.g. of sapphire. A threaded mounting stud 36 is brazed to the cathode support plate 34 and has attached a tubulation 38 used to fill the envelope, e.g. with xenon and which is pinched off to form a cold-welded seal. The cathode 32 may be made of thoriated tungsten. Thermal stresses are relieved by ductile metallic rings 12, 18, 22, 48 which are brazed to the adjacent members.