GAS DISCHARGE TUBE FOR A LASER

1283877 Lasers TURLABOR AG 19 April 1971 [13 April 1970] 26797/71 Heading HlC A laser gas tube, Figs. 2 and 3, comprises a stack of apertured metal discs 14-20 insulated from each other by oxide coatings, and secured together by adhesive or insulated screws 24, 25 with intermediate sealing rings 29, 32, a gas discharge path being provided by central apertures 21 in the discs, while aligned holes 26 grouped about the central apertures provide paths for a liquid coolant, the seals being protected from ultra-violet radiation and ionic bombardment of the gaseous active medium by shoulders 33, 34, 35 formed on the metal discs. The discs are made of aluminium with the oxide coating applied by an anode oxidization process, and the sealing rings may be formed of gold, indium or a plastics material. The active medium may be a single gas or a mixture from the Group Ar, Ne, Kr, Xe and Hg. The discs are assembled in groups, each group 36, 39 having respective inlet and outlet ducts 37, 38 for a coolant such as water. The disc groups 36, 39 are separated by an auxiliary ignition anode disc 57, this disc being made of uncoated aluminium and sealed into the disc stack by sealing rings 59 protected by shoulders 60. Each end of the disc stack is terminated by an outer annular structure 41, 42 providing a conical tapering entry 45 into the gas discharge path formed by apertures 21. A flange ring 52 is movable with respect to this structure, and the two components are coupled together by a metal sealing bellows 53, the arrangement permitting thermal expansion. Each flange ring of the gas tube is secured by screws 51 to a flange 50 of a respective anode and cathode chamber 1, 2, Fig. 1. Each chamber includes a respective annular anode and cathodes 5, 9 and is coupled to a resonator mirror 8, 12. A gas pressure equalizing path is provided by a separate tube 4, but in a modification this component is omitted and certain of the holes 26 in the discs used for this purpose. A low resistance voltage divider (not shown) is connected across the anode-cathode voltage and is regularly connected to the auxiliary anode discs 57 in the stack. A high resistance voltage divider (not shown) is regularly connected to the single discs 14-20, but in a modification connection is made to the coolant paths, the insulating oxide layer on the discs being removed from adjacent the coolant channels 26, 27. In a modification, the gas tube has windows at the Brewster angle.