US3430087A

US3430087A - Sensitive,quick response ionization chamber

Info

Publication number: US3430087A
Application number: US592690A
Authority: US
Inventors: Randolph G Taylor
Original assignee: US Department of Navy
Current assignee: US Department of Navy
Priority date: 1966-11-04
Filing date: 1966-11-04
Publication date: 1969-02-25
Anticipated expiration: 1986-02-25

Description

Feb. 25, 1969 R. TAYLOR 3,430,087

SENSITIVE, QUICK RESPONSE IONIZATION CHAMBER Filed NOV. 4, I966 INV ENT OR RANDOL PH 6. TAYLOR BY flfi Z fiwwb AGENT m ATTORNEY United States Patent f 1 Claim ABSTRACT OF THE DISCLOSURE This invention is directed to an ionization chamber having a cylindrical anode with an axially disposed wire electrode operable for detection of ionizing radiation in a range of from about 0.5 to about 8.0 angstrom units with a fast recovery. Fast response is brought about by modification of the cathode to include vane-like screen structures secured thereto by brazing, welding, or any other suitable manner. The vane-like structures extend radially out from the cathode with their outer edges spaced from the anode. The tube is provided with a gas filling of krypton or argon with a beryllium window through which the ionizing radiation enters the chamber.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

The present invention relates to ionization chambers and more particularly to an improved ionization chamber which has a fast response time.

In general, conventional ionization chambers comprise two electrodes in a surrounding of a desired gas at a desired pressure. Radiation entering the ionization chamber ionizes the gas molecules therein to produce ions. The negatively charged ions produced will travel to the anode whereas the positively charged ions travel in the opposite direction to the cathode. The resulting output of the tube is a measure of the intensity of the ionizing radiation which enters into the ionization chamber.

Heretofore, ionization chambers have been used in a stationary environment and also mounted upon rotating rockets or satellites and fired into the atmosphere. Ionization chambers fired into the atmosphere on a rotating rocket or satellite responds to incident radiation each revolution of the rocket and should respond sufiiciently fast that the peak signal of one event is telemetered to a ground station prior to a response from any succeeding event due to radiation excitation. Ionization chambers used heretofore are slow in their response time and therefore when mounted on a rotating rocket, the signal of one event is superimposed on the output of the succeeding event thereby giving a false signal. Normally, satellites in order to obtain desired stability, rotate at a revolution of from 2 to 3 revolutions per second. The prior art ionization tubes operate satisfactorily at about one revolution per second. Thus, for good operation of the prior art tube the rocket spinning rate must be reduced to at least one revolution per second or lower; however, at one revolution per second the rocket misbehaves and does not follow the intended flight pattern.

The ionization tube of the present invention overcomes the drawbacks of the prior art ionization tubes by modification of the cathode which enables one to measure radiation in a range from about 0.5 to about 3.0 angstrom units depending on the type and thickness of the window, and the gas filling within the tube. This ionization tube operates satisfactorily even at a rotational rate of about 5.0 revolutions per second of the rocket.

3,430,087 Patented Feb. 25, 1969 ice It is therefore an object of the present invention to provide an ionization tube which has a quick response time.

Another object is to provide an ionization tube which will operate satisfactorily for rockets spinning at a spiiining rate up to at least 5 revolutions per second.

Still another object is to provide an ionization chamber which is satisfactory to study solar radiation by use of spinning rockets or satellites.

Yet another object is to provide an ionization chamber useful on a rocket for upper air research in determining radiation in a range of from 0.50 to 3.0 angstrom units and from 2.0 to 8.0 angstrom units.

Other objects and advantages will be apparent to those skilled in the art upon the consideration of the following description and the attached drawing, wherein:

FIG. 1 is a cross-sectional view of a preferred embodiment of the invention; and

FIG. 2 is a cross-sectional view taken along the lines 22 through FIG. 1 which illustrates the relationship of the radial metallic extensions secured to the cathode.

The improvement in ionization chambers illustrated by the present invention is brought about by securing equiangularly spaced thin metallic radial vane-like collector surfaces to the cathode. The collector surfaces may be formed of screen material and welded or brazed to the cathode along the entire length thereof. Thus, the addition of the screen collector surfaces allows the electric field produced by a potential of 50 to volts to be extended throughout the volume of the tube resulting in a faster response.

Now referring to the drawing, wherein like reference characters represent like parts throughout the figures, there is shown by illustration an ionization chamber made in accordance with the present invention. As shown, FIG. 1 illustrates a cylindrical housing of stainless steel or any other suitable metal which is closed at one end and open at the opposite end. The cylindrical housing forms the anode 11 which surrounds an axially disposed cathode 12 such as a Wire or rod which is insualted from the anode structure by any suitable means 13. Secured to the cathode by welding, brazing, or any other suitable method are four equi-angularly spaced wire mesh collector surfaces 14 which extend along the entire length of the cathode wire. The wire mesh collector surfaces 14 extend toward the inner surface of the anode in spaced relationship therewith with their edges parallel with the anode surface. The bottom edge of the wire mesh collector surfaces extends downwardly to the insualtor 13 and rests thereon such that the lower edge of the collector surface is spaced from the enclosed end of the anode. The open end of the anode structure is closed by a radiation permeable window 15 which may be secured over a wire mesh support structure 16 which prevents the window from being pulled in when the tube is evacuated. The window may be made of beryllium having a thickness of about 5 mil to about 50 mil. The window is sealed within a shoulder 17 in the anode in a vacuum tight relationship by any suitable sealant and the tube is evacuated to a desirable pressure and filled with a gas depending on the wave length range to be detected.

In making a tube having an anode of about one inch in diameter with a cathode of about one inch in length for the detection of radiation having a range of about 0.50 to about 3.0 angstrom units, the gas filling in the tube should be krypton. The tube is evacuated through tube 21 to a pressure of 10 millimeters of mercury and a gas filling of krypton is injected into the tube to a pressure of 1520 millimeters of mercury at 0 centigrade. The window is formed of a 50 mil beryllium. In order to produce an ionization tube for detection of radiation in a range between about 2.0 and about 8.0 angstrom (LP)(273+RT) AP=adjusted pressure LP=list pressure given for tube filling at centigrade RT=room temperature in degrees centigrade.

In operation of the tube for detecting radiation in the range given above, the tube is formed as described above with the listed gas pressures with a window of the dimensions given. Ionizing radiation passes through the window into the area confined by the anode thereby ionizing the gas therein. The positive ions are drawn toward the vanelike structures attached to the cathode and the negative ions are drawn to the anode structure. Since the vane-like structure attached to the cathode extends outwardly from the cathode to a close tolerance with the anode it can be seen that the ions directed toward the cathode will strike the cathode surface much faster than in a tube which is not provided with the vane-like structure. Thus, all of the ions confined within the anode structure will be directed to the cathode structure in a much faster time which will result in producing an output in accordance with the incident radiation. Thus, when the tube is positioned on a rocket which is fired into the upper atmosphere and rotates as the rocket moves through the upper atmosphere, the tube, as described above, will operate with sufficiently fast response that the rotational rate of the rocket may be at least revolutions per second. The tube, as described above, will have a suificiently fast response time that the peak output will be reached before the rocket has completed its revolution wherein the tube will have passed through its peak output and back down to its normal state wherein it is ready to receive additional ionizing radiation and give an accurate measure of the intensity of the radiation. Thus, a tube made as described above will not permit a signal from one ionizing event to be superimposed on the signal of another or any succeeding event.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claim the invention may be practiced otherwise than as specifically described.

What is claimed and desired to be secured by Letters Patent of the United States is:

1. A sensitive, quick response, ionization chamber which comprises:

a cylindrical metallic anode closed at one end and open at the opposite end to form a housing,

a cathode,

said cathode extending through said closed end of said anode on and along the axis thereof and insulated therefrom,

a plurality of equi-angularly spaced radially extending vane-like structures secured electrically to said cathode, extending along the length thereof within said housing and spaced from said anode,

a window through which radiation enters into said ionization chamber,

said window enclosing said open end of said anode,

said window being formed of beryllium with a thickness of from about 5 mil to about mil in thickness,

an ionizable gas filling in said ionization chamber selected from the group consisting of argon and krypton,

said gas filling having a pressure of from about 760 to about 1520 mm. of mercury,

whereby said ionization chamber operates for detection of radiation in a range from about 0.50 to about 8.0 angstrom units.

References Cited UNITED STATES PATENTS 2,566,089 8/1951 Linder 313-93 2,599,352 6/1952 Schneider 31393 2,604,600 7/1952 Neufeld 31393 2,648,781 8/1953 Herzog et al. 31393 2,837,656 6/1958 Hendee et al. 31393 2,874,304 2/ 1959 Lichtenstein 313-93 2,951,942 9/ 1960 Kramish 250- 83.1 3,219,869 11/1965 Schmidt 313-93 3,322,991 5/1967 Sterk et a1 313-93 JAMES W. LAWRENCE, Primary Examiner.

R. F. HOSS-FELD, Assistant Examiner.

US. Cl. X.R. 313-184, 217