RU6648U1 - IONIZATION GAMMA CAMERA - Google Patents

Abstract

1. Ionization gamma chamber with gas filling, comprising a cylindrical body with a well and a plane-parallel electrode system, characterized in that the electrode system is made of a material with a large atomic number, for example, steel, zirconium, niobium, molybdenum or their alloys, in the form of ring plates in the area of the well and disk plates in the gap between the blank bottom of the well and the chamber flange. 2. The gamma camera according to claim 1, characterized in that xenon is used as a filler gas under high pressure.

Description

IONIZATION GAMMA CAMERA

The inventive utility model of an ionization gamma camera (hereinafter referred to as the IHC) relates to means for measuring the activity of gamma radiation sources.

Known sealed, neutron ionization chambers of control systems and protection (CPS) of nuclear reactors, compensated for the influence of external gamma radiation by differential inclusion of one part of the chamber, sensitive to neutron and gamma radiation and the second part, sensitive only to gash radiation / I / .

A distinctive feature of these chambers is a plane-parallel electrode system with a small (1.6 mm) distance between the high-voltage and collecting electrodes, which made it possible to achieve a saturation current mode with a relatively small chamber voltage (up to 500 V) in the operating range of the radiation power.

In FIG. I shows the design of the CPS camera - an analogue of the claimed IHC.

The sealed housing 2 of the camera acts as a guard electrode. A plane-parallel electrode system 3.4 with an interelectrode gap of 1.6 mm, mounted on racks 5, supported by ceramic insulators I, is similar to the essential features of the claimed IHC.

The CPS camera cannot be effectively used to solve the problem under consideration because of the lack of a pocket in it to accommodate the measured ... source of gamma radiation.

.;. ., D

Known IHC installation. UPGI- / 2 /, taken by the author for

electrodes. A well 10 with a blank bottom for accommodating a measured gamma radiation source in it is similar to an essential feature of a useful camera model.

A feature of these chambers is the independence of the ionization current from the displacement of the measured source inside the well over a fairly wide range.

The disadvantages of the IHC installation UPGI-1 include:

-low sensitivity (see table), which required the use of an electrometric device for measuring ionization currents up to 10 A, with its characteristic zero drift and gain instability;

-dependence of the ionization current of the chambers on the barometric pressure (the chambers are not tight), temperature and humidity.

The objective of the claimed IHC is to provide ionization

currents from 10 to 10 A when measuring the activity of sources

7 14 gamma radiation from 10 to 10 Bq, the values of which can be

It would be measured with high-precision serial digital devices (for example, Щ-300) without the use of an electrometric preamplifier / 3 /.

This problem is solved by the inventive gas-filled IGC (Fig. 3), containing a cylindrical housing I with a well 3 and a plane-parallel electrode system 4,5, characterized in that the electrode system is made of a material with a large atomic number (for example, steel, zirconium, niobium, molybdenum or their alloys) in the form of annular plates in the area of the well and disk plates in the gap between the blank bottom of the well and the flange of the chamber body.

High sensitivity of the claimed IHC in comparison with the prototype (see table) is achieved:

- a more complete conversion of the gamma radiation power of the measured source into electric current due to an increase in the output of photos and Compton electrons from the larger surface of plane-parallel electrodes made of a material with a large atomic number;

-increasing the solid angle of measurement of the gamma radiation of the source to almost 4P by performing an additional sensitive chamber volume between the bottom of the well and the chamber flange;

-use as xenon filler gas under

P pressure 10 kg / cm.

In FIG. 3 shows the design of the claimed IHC and its connection diagram, where:

1- camera body - security electrode;

2- metal-ceramic pressure glands;

3- well;

4- plates of a high-voltage electrode (ring and disk);

5- plates of the collecting electrode (ring and disk);

6- racks of the electrode system with spacer sleeves;

7- ceramic support insulators;

8- measured source of gamma radiation;

9- case;

10- high voltage source;

The IHC is mounted in a radiation protection unit installed in a hot chamber. With cables 12, the camera is connected to a high voltage source 10 and to a measuring device 11,

An operator using a television tool lowers into a case 9 a certified (for example, exemplary) source, whose activity is close to the activity of the manufactured source. Installs a case with a source in the chamber well and registers its ionization current I Q

It similarly measures the ionization current of the chamber from the manufactured source 1 ..,. „, Whose activity is determined

from the expression:

A A.obr. I Bq G arr. zg.

The table shows the geometric dimensions and sensitivities of cameras No. I and No. 2 (prototype) of the UPGI-1 installation and an experimental sample of the claimed IHC, tested under production conditions / 5 /.

The table shows that the specific sensitivity of the experimental sample of the utility model of the IHC is two orders of magnitude higher than the specific sensitivities of the IHC No. I and No. 2.

The achieved level of sensitivity of the utility model IHC

allowed to measure ionization currents from sources with activity

7 10 Bq and above with the serial Shch-300/5 / device.

SOURCES OF INFORMATION

1.A.B., Dushtriev, E.K. Maliev. Neutron ionization chambers for reactor technology. M. Atomizdat 1975

2.F.M. Karavaev. Measurement of nuclide activity. M. Standards Publishing House 1972

3. PO Lighthouse. Terms of Reference for design and development work of the radiometric installation. No. 939-1837, 1996

4.B. Wexler, L. Groshev, B. Isaev. Ionization methods for radiation studies. M.-L. State publishing house of technical and theoretical literature. 1949

5. PO Lighthouse. Test report of an experimental sample of an ionization gamma camera with a well and a plane-parallel electrode system. No. 938-2735 of June 28, 1996.

Claims (2)

1. A gas-filled ionization gamma chamber containing a cylindrical body with a well and a plane-parallel electrode system, characterized in that the electrode system is made of a material with a large atomic number, for example, steel, zirconium, niobium, molybdenum or their alloys, in the form of ring plates in the area of the well and disk plates in the gap between the blank bottom of the well and the chamber flange. 2. The gamma camera according to claim 1, characterized in that xenon is used as a filler gas under high pressure.