US2521315A - Geiger tube - Google Patents

Description

Sept- 1950 J. A. VlCT OREEN 2,521,315

GEIGER TUBE Filed 001.4, 1947 'INVENTOR.

JOHN A. VICTOREEN Patented Sept. 5, 1950 GEIGER TUBE JohnA. Victoreen, Cleveland, Ohio, ass'ignor to The Victoreen Instrument Company, Cleveland,

Application October 4, 1947, Serial N0. 778,007 I This invention relates to improvements in tubes for indicating the presence of energized particles of radiation, and more particularly to so-called Geiger tubes.

Although heretofore Geiger tubes have been constructed which have fulfilled the limited purpose iorwhich they were intended, with the advent of advances in nuclear physics and the adaptation of such knowledge to industrial as Well as medical uses, it becomes more desirable to provide tubes which are useful other than for mere laboratory application.

Among the disadvantages of the prior tubes was the fact that the life thereof was limited. Inasmuch as the change in the tube is of a gradual nature, and which may not be recognized by, the commercial user, it is desirable to provide tubes having a longer life, and wherein the characteristics remain fixed over a long period.

Among the things that enter into the use of a tube for commercial apparatus is the geometry of the tube. It is desirable to have certain geometrical limits maintained in order that the tube will react in a predetermined manner, and in order that tubes may be manufactured having predetermined characteristics.

By the present invention I have provided an improved geometry of the tube which permits more stable operation. 1

As is well known to those versed in the art, the tube usually comprises an outer electrode and a coaxial inner electrodeacross which a potential is placed. The tube is filled with a noble gas, and the electrodes maintainedat a potential difference just below the corona discharge point. When an energized particle of radiation passes through the wall of the tube, ionization of the gas is efiected causing a current to flow. In order that the current flow thus started is not self maintained, a quantity of quenching gas is included in the tube, which, in the absence of the energized particle of radiation, causes the ionization to cease and the current flow to stop.

It is by this principle that particles may be counted and thus enable the user to determine not only the presence of these particles, but the frequency and quantity. Ordinarily, such particles may include alpha, beta, and gamma rays. Obviously, the type of rays which will energize the tube may vary to an extent depending on the type of wall used in the tube. As a matter of fact, the tube may also be designed to indicate the presence of any kind of rays that may be emitted from radio-active materials and 5 which will penetrate the wall.

8 'Claims. (Cl. 25027.5)

The quenching of the tube is well known and has commonly been effected by the use of a slight amount of organic vapor such as a' small quantity of ethyl alcohol vapor placed in the tube along with the rare gas. The use of the larger gas molecules, such as ethyl alcohol, in a tube of this character is accompanied by a gradual destruction of the quenching vapor which is broken down or disassociated into its components. Eventually, the quenching gas breaks down to such an extent that it becomes inefiective and/or changes the characteristics of the tube. This all pointsto a predetermined limit of tube life and a limitation on the number of counts that can be obtained before it must be replaced. Inasmuch as the gas and vapor pressure must be held within critical limits, this militates against using a larger quantity of liquid or gas in a reservoir because the mere presence of this material in a reservoir would cause an increase in the vapor pressure and change it so that it might have undesirable characteristics.

By my present invention,.I provide a tube wherein the destroyed vapor is replenished. This results in an increased life and enables a tube to maintain and hold constant characteristics over a longer period of time.

Still other advantages of the invention, and the invention itself, Will become more apparent from the following description of an embodiment thereof, which description is illustrated by the accompanying drawings and forms a part of this invention.

In the drawings:

Fig. l is a diagrammatic view illustrating the geometric relations in a tube of my invention.

Fig. 2 is a sectional view of a tube constructed according to my invention; and r Fig. 3 is a similar view illustrating a modification of my invention.

In the drawings, like parts are designated by like reference characters.

As shown in Fig. l, the tube of my invention includes a cylinder [0 which may be of glass or other suitable material. An electrode H which may be a small diameter wire extends axially into the cylinder, being brought in through a press E2. The electrode H terminates spaced from the end of the cylinder as indicated at Hi, the end usually being insulated by a small glass bead. The interior of the cylinder is coated with a conducted material 54, indicated by the shaded area,which coating starts at the point !5 and is continued to the end, being connected at its end by a lead l6 which extends through the press I? and is in electrical contact with the interior coating at the end of the cylinder. If desired, the coating l4 could be replaced by a metal cylinder disposed inside the tube.

As previously stated, the envelope is, in the main, cylindrical, and the center electrode equally spaced from the wall. The ends of the cylinder conform to a portion of a sphere, the radius of which is indicated by the arrow l8, the axis of which is in the plane of the end of the coating at the upper end. The other end of the tube is likewise spherical as indicated by the arrow IS, the :axis of the sphere being located at the end l3 of the electrode. It will thus be seen that the center electrode is exactly equally spaced at all points from the outer electrode. A tube is thus provided which is perfectly symmetrical and with an electrode so placed that its end is on a perfect radius from the outer wall on each end. The tube may be filled with gasand vapor through the tubular extensions 20 disposed at either or both ends indicated by the dotted lines, which tubes are heated and pinched: off after filling with gas. This type of construction lends itself to efficient manufacture with standard tubu-lati'ons and eliminates the need for extra inlet tubes for filling with gas. Having the tubes 20 coaxial with the rest of the tube also permits a balanced construction which facilitates manufacture since it is a balanced construction as the tubes may be supported at the center on the manifold. It also eliminates the side tube which has a tendency to be broken off easily during use. The construction also permits the tube to be placed in a cylindrical probe since no side tubes are in the way.

In Fig. 2, I have shown another modification of my invention. There is shown the tube wall 13 having the interior coated as indicated by the shaded lines with silver or other material. ends of the tube have sealed therein in metal tubes 38 and 3| which may be of a material having a coeihcient of expansion similar to that of glass, of which the. so-called Kovar metal is an example. The center electrode l I in this instance is supported at. the upper end by a glass bead 32, one end of which extends into the tube 3!. A wire 33 is secured to the other end of the bead 32 and extends through the tube 3|. The bottom end of the electrode H is provided with a helical spring part 34 which extends into the tube 30. From the spring portion the wire extends through the tube 30. The construction lends itself to fabricating the center electrode structure and allowing it. to be placed in position with the desired tension thereon. The fabricated electrode is inserted through the two tubes, the upper end is located to provide the desired geometry for the end of the electrode after which a drop of solder is applied to the wire and tube to secure the supporting wire 33 in position and seal the tube. The tube is then conditioned with the desired pressure of gas and quenching vapor which are admitted through the lead tube 35, after which the lead tube 35 may be pinched to seal it, as indicated at 35, or sealed by solder at its end.

It will be noted that the tube 3| is provided with a quantity of loose material indicated at 31. This is a reservoir of quenching material as will be more clearly apparent and is held in by a small quantity of glass wool 38 adjacent the bead 32.

Fig. 3 discloses another modification of my in- The Vided with a coating of conducting material as indicated by the shade lines. The ends of the tube are provided with glass tubular extensions 40 and 4|. The upper electrode support in this instance comprises a glass rod 42 which is provided with a pair of spaced annular flanges 43 and 44'. The lower end of the stem has secured thereto the center electrode I I which is provided with a helical spring portion disposed in the lower tube H. The end of the electrode extends out the end of the stem which may be sealed thereto by heating and forming a press 45.

It will be noted that this arrangement likewise lends itself to prefabrication of the center electrode and enables it to be quickly and easily positioned in the tube. The tube construction lends itself to fabrication from standard tubulations.

The contact for the outer electrode may be made at 53, the lead extending through a tip 5| in which it is sealed and connected interiorly to the coating.

A tube 52 may be provided through which the gases may be admitted after which it is sealed off.

The flanges ere-43 cooperate with the: tubular extension as to provide an annular chamber around the stem 42. The lower end of this chamber is packed with a small quantity of glass wool 53. Above the glass wool and disposed in the chamber isv a quantity of solid material 5'54 which has the desired vaporization point. This material may be in a loose granulated state. or it may be pressed in the form of a slug having a central opening through which the stem 52 extends. After the material is in position the end of the tube may be heat sealed to the flange 43.

The quenching vapor, as previously stated, may be any one of a number of organic materials. In order to carry out the replenishing feature of my invention, I contemplate the use of a solid or granular material having a vapor pressure which meets equilibrium when enclosed. Such a material can be an organic material having a suitable vapor pressure which provides the desired quenching. Among those which are suitable are napthalene crystals, para-di=chlorbenzine and camphor. In the case of Fig. 3, the material can be compressed into the form of a slug and the chamber acts as a porous container which allows the vapor to escape. If desired, the solids could be actually enclosed in a porous container inside the tube, and as the pressure in the tube is reduced because of the disassociation of the gas, the materials will vaporize and maintain a constant partial pressure.

I also contemplate the use of a material which disassociates and reassociates automatically. One such material is ammonia (NHa). This will break down into N and H and will again combine in the presence of ultraviolet rays to again form NHs. There will, therefore, be an equilibrium established in the tube and a substantially continuous disassociation and reassociation causing a material increase in the life of the tube. In their free state the nitrogen and hydrogen have no effect on the operation of the tube.

I also contemplate the use of a liquid having a vapor pressure, which liquid is disposed in a reservoir having a chamber wall permeable to the vapor but impermeable to the liquid. Such a material could be water and the vapor permeable wall cellulose butyrate acetate. Another material would be absolute ethyl alcohol and a. chamber wall of gelatin. Regenerated cellulose and so-called nylon could also be used for the wall.

This wall could replace the "glass wool 53 shown in Fig. 3 if desired and be sealed in the stem 42 and the wall 40.

It will therefore be seen that I have provided a Geiger tube construction which lends itself readily to standard manufacturing processes. The tubes, being of a balanced construction, are readily secured to the standard exhaust manifold for removing the air and filling with gas. Furthermore, the construction lends itself to providing tubes which may be held within relatively close limits to a standard. The lack of the side tip of the tubes of Figs. 1 and 2 enables them to be readily placed in a cylindrical probe into which they may fit snugly without the danger of the tips becoming broken or cracked.

In the case of Fig. 2, the Kovar tubing lends itself ideally to servicing the tubes by re-exhausting and refilling should it be desired.

The construction of Fig. 3 assures that the center electrode can be suspended in the same geometric position relative to the outer electrode, and spring 34 assures that an undue amount of vibration will not break the electrode or cause it to assume different positions in the enevelope, permitting the tube to be used at any angle without materially efiecting its operation.

Having thus described my invention, 1 am aware that numerous and extensive departures may be made therefrom without departing from the spirit or scope of my invention.

I claim:

1. A Geiger tube including a container, electrodes in said container, an ionizable gas for said container, a reservoir containing an ionization quenching material, communicating with said container.

2. A Geiger tube including a container, electrodes for said container, an ionizable gas in said container, said container being formed with a reservoir and a solid material disposed in said reservoir and comprising a vaporizable organic material having the characteristic of vaporizing to provide a suitable vapor pressure, said vapor being a quenching material for said ionizable gas.

3. An apparatus of the class described comprising a substantially cylindrical container having ends curved on a radius substantially equal to the radius of the tube, an electrode extending axially through one end of the tube and terminating at the intersection of the radii for the other end.

4. An apparatus for the class described comprising a substantially cylindrical container having ends curved on a radius substantially equal to the radius of the tube, an electrode extend ing axially through one end of the tube and terminating at the intersection of the radii for the other end, a conductive coating for said tube.

5. An apparatus of the class described comprising a substantially cylindrical container having ends curved on a radius substantially equal to the radius of the tube, an electrode extending axially through one end of the tube and terminating at the intersection of the radii for the other end, a conductive coating for said tube, said conductive coating extending from the one end of the tube toward the other and terminating at the end of the tube through which the center electrode extends spaced from the end of the tube at the points on the wall of the tube opposite the point where the radii defining the end of the tube intersect.

6. An apparatus of the class described, a cylindrical glass container, a metallic coating on the inner wall of the container, lead-in tubes on the ends of the container coaxial therewith, a center electrode, means to support said electrode comprising a member disposed in one of said lead-in tubes and extending into the container, said member being formed with spaced flanges extending close to the Wall of the lead-in tube and a vaporizable organic material disposed in said lead-in tube in the space between said flanges.

7. An apparatus of the class described comprising a cylindrical container, a conductive coating for said container, lead-in tubes extending into the container from opposite ends axially of the container, a center electrode for said container comprising a supporting wire disposed and sealed in one of said lead-in tubes and having an insulating bead secured on one end, said electrode being secured in said bead and extending through said container into the lead-in tube at the other end, a helical spring formed in said electrode at the end disposed in said last mentioned lead-in tube and an extension of said electrode extending from said spring through said tube and held by said tube.

8. An apparatus of: the class described comprising a cylindrical container, a conductive coating for said container, metallic lead-in tubes extending into the. container from opposite ends axially of the container, a center electrode for said container comprising a supporting wire disposed and sealed in one of said lead-in tubes and having an insulating bead secured on one end thereof, said electrode being secured in said bead and extending through said container into the lead-in tube at the other end, a helical spring formed in said electrode at the end disposed in said last mentioned lead-in tube and an extensionoi said electrode extending from said spring through said tube and held by said tube.

JOHN A. VICTOREEN.

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

UNITED STATES PATENTS Number Name Date 2,122,222 Vingerhoets June 28, 1938 FOREIGN PATENTS Number v Country Date 87,583 Austria Mar. 10, 1922 296,769 Great Britain Apr. 25, 1929 472,110 Germany Feb. 22, 1929 OTHER REFERENCES .Korif: Electron and Nuclear Counters; D. Van Nostrand Co., New York, Apr. 1946, pp. 97-100 and 129.

Strong: Procedures in Experimental Physics: Prentice-Hall Inc., New York, page 261.

Korfi: Electron and Nuclear Counters; D. Van Nostrand Co., Inc., New York, pp. 124-128.

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