US 3461335 A
Description (OCR text may contain errors)
W. E- LOTHALLER Aug. 12, 1969 5 GLOW'DiSCHARGE TUBES CONTAINING A RADIOACTIVE-'PRIMER INVENTOR. WOLFGAN G E.LOTHALLER Filed June 26, 1967 U i d States Patent: v
3,461,335 GLOW-DISCHARGE TUBES CONTAINING A RADIO-ACTIVE PRIMER Wolfgang Erich Lothaller, Leidschendam, Netherlands,
assignor, by mesne assignments, to US. Philips Corporation, New York, N.Y., a corporation of Delaware Filed June 26, 1967, Ser. No. 648,743 Claims priority, application Netherlands, July 9, 1966, 6609664 Int. Cl. H013 17/20 U.S. Cl. 313226 5 Claims ABSTRACT OF THE DISCLOSURE A glow-discharge tube employing a gas-filling consisting of a major amount of a first rare gas, a minor amount of a second heavier rare gas, and a radio-active primer.
The invention relates to a glow-discharge tube having a gas filling consisting of a rare gas, which tube also contains a quantity of radio-active material for neutralizing the static delay in ignition.
In glow-discharge tubes without a priming electrode, the neutralization of the static delay in ignition requires the use of a comparatively large quantity of radio-active material, i.e., up to 100 ,uC. This requires stringent precautions to be taken during manufacture. Even use is made of a B-emitter so that no radio-active radiation is emitted outside the tube. Safety measures made with regard to the fear for breaking of the glass bulbs sometimes do not permit the use of apparatus in which large numbers of tubes are arranged. These regulations sometimes are so stringent that even the use of considerably smaller quantities of radio-active material exclusively for neutralizing the delay in ignition of the discharge to that of a priming electrode in which a delay of 0.1 sec. is still permissible, is hardly possible.
In a glow-discharge tube having a gas filling consisting of a rare gas and moreover a quantity of radio-active material, according to the invention, the gas filling also contains a small quantity of a heavier rare gas which with the principal gas does not produce a Penning eflect and does not form molecular ions with the main gas either.
Because the admixture with the principal gas does not produce a Penning effect and that the quantity available is small, its influence not only on the ignition voltage but also on the burning voltage is very small so that the admixture only results in a slight variation of the discharge properties of the glow-discharge tube.
The radio-active material forms not only ions of the principal gas, but also ions of the admixture. The ions of the principal gas disappear rapidly by volume recombination of the molecular ions formed. The ions of the principal gas may also transmit their charge to atoms of the admixture. The ions formed of the admixture have such a low concentration that they cannot form molecular ions, and since they cannot form molecular ions either with the atoms of the principal gas, a volume recombination is not possible. As a result, the ions of the admixture disappear only slowly so that their concentration is comparatively high, even with a low intensity radio-active composition. The tube according to the invention consequently has the advantage that the strength of the radioactive composition required for neutralizing the static delay in ignition can be considerably smaller than in the known tubes.
A gas filling suitable for the use in accordance with the invention may consist of argon containing 0.1 to 1% of krypton.
The invention will be described more fully with reference to the drawing in which the sole figure is a partly developed perspective view of a discharge tube according to the invention.
In the figure, reference numeral 1 denotes a base of powdered glass and 2 a glass envelope which terminates on the upper side in a sealing point 3. Cathode 4 is secured by bulb-Welding to the end of a lead-in wire 5 and the anode 6 to the end of a lead-in wire 7. Priming electrode 10 is welded to the end of a lead-in wire 11 and ignition electrode 8 extends as far as notch 12. in the cathode without projecting into the space between the anode and the cathode. The priming electrode 10 extends as far as in the notch 13 in the anode, also without projecting into the space between the anode and the cathode. The cathode 4 is coated on the rear side with a nickel coating 14. Because of symmetry, the anode 6 also is provided on its rear side with a nickel coating 15. Otherwise, the electrodes consist of molybdenum plates.
vOn the base of the tube a dot of finely-divided titanium powder 17 is provided in which tritium is absorbed. The strength of this radio-active composition is 0.1 c. The tube has a gas fillingat a pressure of 1000 torr which consists of agron containing 0.5% of krypton.
After the pumping treatment, the surfaces of the electrodes are cleaned by sputtering so that a dark deposit 16 is formed on the wall of the tube. The tube of the construction described has an anode-cathode breakdown voltage of more than 280 v. and an auxiliary anode ignition voltage of approximately 130 v. The operating voltage is v. and the operating current is 3 ma. The current from the anode to the priming electrode 10, required for preventing delays in ignition in the main discharge path is 10 ,ua.
The influence of the krypton addition on the operating voltage and on the ignition voltage is extremely small. Because of the krypton, however, the strength of the tritium composition can be considerably reduced, while attaining a delay in ignition of only 0.1 sec. for the priming discharge. In the absence of the krypton, this quantity would have to be approximately 1 ,uc. in order to obtain the same delay in ignition.
While the invention has been described with reference to a particular embodiment thereof, other modifications will be apparent to those skilled in this art without departing from the spirit and scope of the invention as defined in the appended claims.
What is claimed is:
1. A glow-discharge tube comprising an envelope containing a pair of electrodes and an ionizable medium consisting essentially of a first rare gas, and a small quantity of heavier rare gas which with the main gas does not produce a Penning effect and does not form molecular ions with said main gas, and a quantity of radioactive material having a strength substantially less than that 3 required in the absence of said heavier rare gas dispose within said envelope for reducing static ignition delay.
2. A glow-discharge tube as claimed in claim 1 in which the first rare gas is argon and the heavier rare gas is krypton which is present in an amount of 0.1 to 1% by 5 volume.
3. A glow-discharge tube as claimed in claim 2 in which the radioactive material is tritium.
4. A glow-discharge tube as claimed in claim 3 in which the radioactive material has a strength of 0.1 o.
5. A glow discharge tube as claimed in claim 4 in which the tritium is absorbed in titanium.
References Cited UNITED STATES PATENTS H M 1,481,422 1/1924 Holst et a1. 313-226 2,629,842 2/1953 Townsend 313-224 X JAMES W. LAWRENCE, Primary Examiner RAYMOND F. HOSSFELD, Assistant Examiner U.S. Cl. X.R. 3l32l0, 224