Patent GB-963700-A (GB)
Title: Improvements in high pressure discharge lamps
IPC: H01J61/56
Filed: 1960-08-12
Abstract: 963,700. Discharge lamps. PATENT-TREUHAND-GES. FUR ELEKTRISCHE GLUHLAMPEN. Aug. 12, 1960 [Aug. 14, 1959; July 15, 1960(2)], No. 27999/60. Heading H1D. High pressure discharge lamp has an input loading of more than 10<SP>4</SP> watts per c.cm., a discharge vessel containing at least two electrodes and filled with gases, particularly rare gases, or with metal vapours or gases and metal vapours, and means for magnetic contraction and stabilization of the discharge are comprising at least two magnetic poles, inside or outside the discharge vessel, so arranged in the neighbourhood of the discharge are that along the discharge path or at least that part of the discharge path along which the arc is to be contracted and stabilized a non-homogeneous magnetic field is produced which is formed of sharply curved lines of force which lie substantially in planes normal to the discharge. The rare gas discharge lamp shown in Fig. 3 comprises a quartz glass vessel 9, two main electrodes 10, an auxiliary electrode 11, and two magnets 13 of cobalt or of an alloy of cobalt and iron producing a non-homogeneous magnetic field forcing the arc against a metallic wall consisting of separate tungsten rods 14 insulated from each other and from the electrodes 10. The magnets 13 are secured by non-magnetic steel means to the middle of the tungsten rods 14. In the arrangement shown in Fig. 4, the discharge vessel 9 contains the pole shoes 17a of an electromagnet, the core 17 of which is located outside the discharge vessel. The lamp shown in Fig. 5 has a discharge vessel 20 of non- magnetic metal such as brass, a window 21 of quartz glass made gas-tight by a lead ring 22, tungsten electrodes 23, and pole shoes 18 producing a non-homogeneous magnetic field forcing the discharge arc against a wall 19 formed of tungsten rods. The electrodes 23 and rods 19 are embedded in hard glass such as Duran glass. The filling is of xenon with an operating pressure of about 25 atmospheres. In the arrangement shown in Fig. 6 a non- magnetic metal discharge vessel 26 has a vacuum-tight window 29 and a metallic wall 27 in the form of a concave mirror against which the arc is forced and which reflects light on to the concave portion 25 of the metal vessel and through the window 29. Where metal discharge vessels are used a getter of zirconium or titanium is provided. Figs. 7 and 7a show a lamp comprising a quartz glass discharge vessel 30 filled with xenon at 3-10 atmospheres cold pressure, a cathode 31, an anode 32, an ignition electrode 33, and a metallic wall formed by the front face 34 of a tungsten rod 35 in lateral recesses of which are mounted two magnetic poles 36. The front face 34 of the rod 35 is provided with a coating 5Á thick of aluminium oxide 37 formed as a reflector and the side of the rod 35 remote from the discharge arc and, if desired, parts of the poles 36 are provided with a tantalum carbide layer 38. The lamp shown in Figs. 8 and 8a has two horn-like electrodes 39 and a tungsten or molybdenum wall 40 carrying a U-shaped magnet 41 and a magnet 42 on the side of the wall 40 remote from the discharge arc. The side of the wall 40 facing the discharge is coated with a layer of aluminium oxide 43 of 10Á thickness. The discharge arc is forced into the U-form 44 by the fields of the magnets 41 and 42. Figs. 9 and 9a show a rare gas lamp comprising a quartz glass discharge vessel 45 containing an anode 46, cathode 47, and five tungsten rods 48 insulated from each other. The non-homogeneous magnetic field at the discharge arc 49 is produced by a pair of magnets 50 outside the discharge vessel and the non-homogeneity is increased by a further pair of magnets 51. The side of the metallic wall remote from the discharge arc can be provided with a coating of tantalum carbide or carbon enhancing its heat radiation characteristics, and can be provided on the side facing the discharge arc with a coating of rhodium or platinum for increasing its work function and reflecting characteristic. The side of the metallic wall facing the discharge arc can have a coating of insulating high melting point oxides such as aluminium oxide, beryllium oxide or silicon dioxide of 1Á-10Á thickness. North and south poles can so alternate along the main axis of the discharge path and in a plane perpendicular thereto that the arc is forced into a serpentine form. The discharge vessel can be spherical or elongated. The filling can be mercury to which further metal vapours and small or large quantities of permanent gases such as xenon, krypton or argon, or nitrogen can be added. It is stated that the lamps can be used for impulse operation in kinematographic apparatus.