US2598215A - Ionization chamber - Google Patents

Description

May 27, 1952 c. J. BORKOWSKI ET AL 2,598,215

IONIZATION CHAMBER Filed Jan. 9, 1946 FTE.E..

Patented May 27, 1952 IONIZATION CHAMBER Casimer J.

Borkowski and Ralph H. Firminhac,

Oak Ridge, Tenn., assignors to the United States of America as represented by theUnited States Atomic Energy Commission Application January 9, 1946, Serial No. 640,106 2 Claims. (01. 313-54) The present invention relates to radiation measuring apparatus, and more particularly to ionization chambers for measuring alpha particle emission.

It is frequently desirable to collect dust particles or the like on a relatively large surface such as a sheet of filter paper, and then to be able to determine the radioactivity as an indication of the activity of the dust particles.

An object of the invention is the provision of an ionization chamber which will accommodate a large surface sample such as a sheet of filter paper.

Another object of the invention is to provide an alpha counting chamber having substantially fifty percent geometry.

Other objects and advantages of the invention will become apparent from the following description, when read in connection with the accompanying drawing, wherein is illustrated a preferred embodiment of the invention.

In the drawing,

Fig. 1 is a side view in section of an ionization chamber constructed in accordance with the invention; and

Fig. 2 shows diagrammatically one suitable connection to a pre-amplifier.

The ionization chamber shown to illustrate the invention comprises a right cylindrical container In having its lower end screw threaded to receive a removable end disc II, and having its upper portion partitioned off by a wall l2 to form a compartment suitable for receiving a pre-amplifier tube or the like. The upper face of the disc II has secured thereto a shouldered block [3 of insulating material which supports, in coaxial relation in the container ill, a cylindrical tube M which becomes the high voltage electrode when connected as described below. A central rod-like collecting electrode I5 is supported by the partition I2 to extend along the axis of the high voltage electrode M.

The base of the high voltage electrode M has secured thereto a spring contact member I6, which is adapted to make wiping contact with a high voltage lead ll extending through the Wall of the container l0 and suitably supported by an insulator [8. With this arrangement, the

high voltage is not applied to the electrode I4 until it is safely in position and the high voltage is removed when the disc II is unscrewed for removal. In order to prevent sparking due to accidental contact between the high voltage electrode l4 and the lead I! during insertion and removal a sleeve [9 of insulating material, such 2 as rubber, is provided around the high voltage electrode 4.

By unscrewing the end disc II, the high voltage electrode HZ may be easily removed from the interior of the container H3, and a sheet 20 of paper or foil may be curled and inserted inside the hollow electrode is, thereby giving maximum geometry of approximately fifty percent for counting alpha emission from the paper or foil 20 when the electrode I4 is returned to the position shown in the drawing.

Anyone skilled in the art can readily devise a suitable circuit for counting the alpha emission from the sheet 28. One suitable circuit is indicated in Fig. 2. a

While for the purpose of illustrating the invention a preferred embodiment thereof has been described in detail, it is to be understood that the invention is not limited thereto but is of the scope of the appended claims.

We claim:

1. An ionization chamber including a container having therein a tubular high voltage electrode, a rod collecting electrode extending along the axis of the tubular electrode, the container having a removable end wall engaging one end thereof in screw-threaded relation to facilitate ready removal of said tubular electrode, the tubular electrode being mounted thereon and removable therewith, the tubular electrode in operative position normally extending upwardly from the removable end wall to form a specimen holder for a tubular specimen contaminated with radioactivity, holding said specimen therewithin to surround said rod electrode, thereby providing improved chamber geometry.

2. An ionization chamber for counting radioactive foils, filter papers, and the like which can be formed into tubular specimens, comprising a cylindrical container threaded at one end to receive a removable end cap; means at the opposite end of said container for mounting a rod collecting electrode extending coaxially thereof; a specimen holder comprising a tubular, electrically conductive member mounted perpendicular to and electrically insulated from said end cap, and adapted to receive said specimens at its open end and to hold said specimens in tubular configuration against its inner surface, said specimens thereby being disposed concentrically about said rod when said cap is in operative position; a high voltage lead insulated from and carried by said container and extending inwardly thereof; and a spring contact conductively connected to and carried by said specimen holder, said lead 3 and said contact being so disposed as to make FOREIGN PATENTS firm electrical contact when said cap is in op- Number Country Date erative assembly and to break contact when said 296 769 Great Britain 25' 1929 cap is turned for disassembly.

CASIMER. J. BORKOWSKI. 5 OTHER REFERENCES RALPH H. FIRMINHAC. Strong: Procedures in Experimental Physics. 1942 ed., pub1.,by Prentip rHall; New-York, pgs. REFERENCES CITED 1 262 The following references are of record in the. file of this patent: 0

UNITED STATES PATENTS.

Number Name Date 2,197,453 Hassler Apr. 16,- I940 2,440,167 Broxon et a1. A r. 20, 1948 15

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