US2552723A - Ray detection tube - Google Patents

Description

y 1951 F. KCDURY RAY DETECTION TUBE 2 Sheets-Sheet 1 Filed June 30, 1948 Frederic Koury INVENTOR.

ATTORNEY May 15, 1951 F. KOURY RAY DETECTION TUBE 2 Sheets-Sheet 2 Filed June 30, 1948 o x I o w m w w w w w o o o o O 0 O o 8 7 6 5 4 3 2 l.

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Freder 6m. ATTORNEY Patented May 15, 1951 RAY DETECTION TUBE Frederic Koury, Somerville, Mass, assignor to Sylvania Electric Products Inc., Salem, Mass, a, corporation of Massachusetts Application June 30, 1948, Serial No. 36,090

11 Claims.

This invention relates to ray detection tubes, such as tubes of the Geiger-Mueller type, and particular y to tubes used for beta and gamma rays, although the invention is not confined to such uses.

Such tubes generally comprise a cylindrical metal cathode surrounding a wire anode in a gas.

An Object of the invention is to provide a rugged and inexpensive tube for ray detection. This is achieved by making the cathode as an integral part of the tube of glass or the like containing the device. The cathode is a metal layer or layers directly bonded to the inner surface of the glass tube. The metal layer is preferably silver, bonded to the glass by a layer of silver oxide or the like, and covered by an additional layer of other and more ray-responsive metal, if desired. In some cases, and particularly if a filling containing halogen vapors is used, this may be covered by a protective layer, for example, of; chromium, platinum, palladium, rhodiurn, iridium or chrome-iron.

Other objects, advantages and features of the invention will be apparent from the following specification and its accompanying drawings, in which:

Figure l is a perspective view, shown broken away and partly in section, of a beta-ray tube according to the invention;

Figure 2 is a perspective view, shown broken away and partly in section of a device according to the invention;

Figure 3 is a perspective view, shown broken away and partly in section of a gamma ray tube according to the invention; and

Figure 4 is a graph showing the response in counts per minute versus voltage of a standard copper cathode tube and of a tube coated with silver according to my invention. The latter curve is marked A.

In the figures, the glass tube i has on its interior surface a metallic silver layer 3, held to the glass by the thin bonding layer 2 of silver oxide. This layer may be produced by the method described in my copending application Serial No. 36,689, filed June 30, 1948, now abandoned, for a High Voltage Condenser. The silver layer will be of metallic color, while the oxide layer will show through the glass as a sort of straw-brown color. Where the tube is for beta rays, the silver layer itself may be the final one, if desired, or may have a layer of some other metal over it lor example plated over it, if desired. Where the tube is for gamma rays, a coating 4 of bis- 2 muth may be plated over the silver layer, as for example in Figure 2, for high efficiency.

The metallic coatings may end a short distance from the end 5 of the tube through which the lead-in wires extend. The metallic coating will ordinarily end some distance from the other end B in a gamma ray tube such as in Figure 3, for example, in order to allow room for anchoring the support wire 7 to the end 8. In Figure 2, the lead-in wire 8 which may for example be of Kovar or other metal capable of being sealed to the glass used, has the anode wire 9 welded or otherwise afixed thereto. The insulating tube it, for example or" glass, shields the lead-in 8 and anode 9 until it enters the cathode cylinder 3. An insulating glass bead l9 also surrounds the wire 9 at the other end of the cathode 3 to shield it from high fields at that point. The helical spring it keeps the anode wire 9 taut.

In Figures 1. and 2, the silver coating 3 and the oxide 2 thereunder may also end a short distance from the end I?! if desired, but it preferably extends to the end l2, which may be flanged over to fit a metal window 3, which may be of a light metal such as aluminum or beryllium, of as small a thickness as possible, for example t to 1 mil. The Window 13 may be soldered directly to the silver coating on the glass. The coating of other metal 3 may also extend to the end it if it is of a metal capable of being soldered. The solder used should be one which will withstand the baking generally given the tube during the usual exhaust procedure.

In the tubes of Figures 1 and 2, the lead-in wire it may be of tungsten and may extend directly into the bulb coaxial with the coating 2, for example, and be of sufficient diameter to be self supporting, with the insulating bead I5 on its end to reduce the field at that point. The tube iii should extend over the lead-in l4 near the end 5 for the same reason as in Figure 3. A second lead-in wire may be sealed into the bulb and connected to cathode metal coatings 2, 3 in some suitable manner, for example by soldering, puddling, or by means of a split ring it which expands into connection with the cathode metal 2, 3 and is attached to the lead-in wire it, at its beaded end.

If the wire Ill is too Weak for self support a supporting spider may ex end from it to the coat ings 3, E, E3, the spider ccmprising radial wires broken by beads or the like for insulation.

If the coating 3 in Figure 2 is of silver, the coating 3 of bismuth and a coating It over that (shown broken away for convenience) of platinum, palladium, rhodium, iridium, chromium or chrome-iron, the tube will be a combined beta and gamma ray tube responding to either type of ray, and will also resist the corrosive efiect of a halogen gas filling. The additional coating l8 may be omitted if halogen is not used.

The gas filling may be any of the usual mixtures, such as air with 98% neon, or may be a mixture of a rare gas and a halogen vapor such as bromine or chlorine, for example 26 cm. of mercury pressure of neon, with 0.8% argon and 0.2% chlorine. This is especially useful in the tube of Figure 2, and gives a low voltage self quenching tube. The protective layers mentioned are useful with such a filling. With the thin windows of Figures 1 and 2, the gas pressure must be fairly high approaching half an atmosphere or more, to prevent blowing the thin window in or out too much.

Mica may sometimes be used instead of metal for the window l3, and may be affixed hermetically by means known in the art.

When a halogen gas filling is used, the anode wire 9 is preferably of stainless steel rather than tungsten, because the stainless steel resists the corrosive effect of the halogen. The anode wire, if not of a metal suitable for sealing through the glass used in tube 5, may be spot-welded to a lead-in wire of suitable material, or may be beaded or otherwise arranged with several layers or tubes of glass to form a graded seal in the manner well known in the art.

The Word glass is used in a broad sense in this application, and includes materials such as quartz and the like.

, What I claim is:

. l. A ray detection device comprising a glass tube, a gas filling therein, an anode therein, a firmly adherent coating of silver on the inside surface of said tube as a cathode, and a coating of bismuth over the silver coating.

2. The device of claim 1, including a coating over the bismuth of a metal in the following group: chromium, platinum, palladium, rhodium, iridium.

3. The combination of claim 1, in which there is a thin bonding coating of silver oxide between the silver coating and the glass.

4. The combination of claim 2, in which there is a thin bonding coating of silver oxide between the silver coating and the glass.

5. A ray detection device comprising: a glass tube closed at one end and flared at the other; a firrn1y-adherent coating of silve on the inside surface of said glass tube having a silver oxide bond to the glass and including a coated area over the flared end of the glass tube, and a thin metal window transparent to beta rays and joined to the adherent silver coating on to the flared portion of said tube; a gaseous filling in said tube; and an anode in said tube.

6. A ray detection device comprising a glass tube closed at one end and flared at the other, a firmly adherent coating of silver on the inside surfaceor" said glass tubeto act as a cathode, a coating of bismuth over the silver coating, a thin window transparent to beta rays sealed to the flared portion of said tube, a gaseous filling in said tube, and an anode in said tube.

7. The combination of claim 6, a coating over the bismuth of one of the following metals: chromium, platinum paladium, rhodium, iridium; and in which the gas filling includes a halogen.

8. The combination of claim 6, and a layer of silver oxid diffused into the glass between the latter and the silver coating to act as a firmlyadherent bond therebetween.

9, The combination of claim 7, and a layer of silver oxide diffused into the glass between the, latter and the silver coating to act as a firmlyi adherent bond therebetween.

10. A ray detection device including a glass tube, a gas filling therein, an, anode therein, a coating of silver bonded to the inside surface of said tube by silver oxide, and a bismuth coating over the silver coating.

11. A ray detection device comprising a glass tube closed at one end and flared at the other, a coating of silver on the inside surface of the glass tube to act as a cathode, a layer of silver oxide diffused into the glass between the latter and the silver coating to act as, a firmly adherent bond and between a thin window transparent to beta rays and sealed to the flared portion of said tube, a gaseous filling in said tube, and an anode in said tube.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,884,665 Greiner Oct. 25, 1932 2,409,498 Keston Oct. 15, 1946 2,4423% Reid May 25, 19.48 2,475,603 Friedman July 12, 1949 OTHER REFERENCES Liebson andFriedman: Review of Scientific Instruments, vol. 19, No. 5 of May 1948, pp.

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