DE6607224U - LARGE AREA COUNTING TUBE FOR MEASURING GAS-SHAPED RADIONUCLIDES - Google Patents

Description

large area counter tube for gas measurement

Radionuclides

For the Hesse gaseous Hadionaklide it is known "ice box-shaped Large area counter tube to use, through which aas to measuring hadionuclide which is superimposed on a counting gas »passed through will. Sin such a large-area counter tube has a Heß counting system and two on it in a common gas space opposite side? subsequent external counting systems, the rom measuring counting system separated by retracted cathode grids are.

The plateau of the measuring counting system has in this known embodiment a box-shaped large-area counter tube has a relatively high steepness. For example, this moves around $ 28 per 100 Y Spatmufeg change. This steep slope is undesirable. In addition, a slightly higher sensitivity to evidence would often be desirable.

Both facts could be brought to more favorable values through the use of special close-meshed cathode grids. However, this would make production considerably more complicated such counter tube grids and in particular an increased risk of contamination. Therefore, this way has been used in practice so far do not label.

A much lower steepness of the counter tube plateau can also be achieved by using a cylindrical large area counter tube achieve with coaxial construction. However, counting tubes of this type have

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various disadvantages. Due to the cylindrical structure, the consolidation is much more complicated than that of one box-shaped large area counter tube with its simpler Geometry. In particular, it is difficult to produce very large effective areas compared to box-shaped large area counter tubes s with, for example, 25 χ 75 cm effective window area. In order to achieve the same sensitivity, one would have to use the DurchmoDDor of a cylindrical counter tube very strongly. However, this resulted in a correspondingly higher operating voltage necessary, which should be avoided as much as possible.

In contrast to this, the present discussion sets itself the task of through a specially designed structure of the cathode grid to achieve better plateau properties and higher detection sensitivity with a box-shaped large-area counter tube, without having to accept the disadvantages outlined here, which are associated with the use of particularly close-meshed cathode grids or choosing a cylindrical type of coaxial structure.

The new box-shaped large-area counter tube of the type described above is, according to the innovation, characterized in that the cathode grids are designed as double grids of two parallel individual grids each with a small distance from the counter tube readings. This results in a very significant flattening can be the plateau of the measuring counting system and an increase in ffachweisempfindlichV-ince of more than 50 i "compared to counting tubes achieve with single bars.

When measuring low-energy beta emitters, especially from Tritium, it is desirable that to achieve a particularly high Anti-pulse rate, which is used as the anti-coincidence rate of the counting rates from the HeB counting system " and outside counting systems can be obtained only a lot

few of the beta particles from the measurement-counting system by the Cathode grid through into the neighboring outdoor counting systems succeeded.

In one embodiment of the innovation, this is shown in a large-area counter tube intended for tritium measurement to a particularly large extent causes the mutual Abdas Bsppeigities bildeadea EAngoigittay is greater

as the mean range of the beta particles in the counting gas produced during tritium decay. This leaves oioh as graphically below / stated, easily proving that temporarily the! counting rates of the measuring-counting system and the external counting systems in coincidence sets and the Hess result with the count rate of the Hess counting system alone in comparison.

The innovation is illustrated below with the aid of the drawing Execution examples explained.

Bs show:

Figure 1 the new large-area counter tube, somewhat schematically, in cross section,

Figure 2 Krypton measurement curves recorded with the new counter tube,

FIG. 3 measurement curves of tritium recorded with the new counter tube. '

V '' '' "According to Figure 1 are in the three counting systems of the large area \ '. Counter tube 1 the anode wires 2, 3 and 4 · Instead of the usual simple cathode grids are visible here pairs of sitters 5 ^ nd 6, which form the above-mentioned double grids.

In Eigur 2, curve 7 shows a krypton measurement with one of these Large area counter tube with double grille. The curve, on the other hand, shows a measurement with under otherwise identical conditions

a counter tube that has only simple cathode mesh. It is it can be clearly seen that the anode voltage of interest from 3.1 to 3.2 kV dio curve 7 a much more pronounced one Has plateau and is there much flatter than curve 8. It can also be seen that the detection sensitivity with the double grid counter tube is considerably greater is than the one with the single grid counter tube.

In FIG. 3, the same measurements as in FIG. 2 are recorded with tritium, curve S representing the measurement; with double grid counter tube and curve 10 illustrates the measurement with a single grid counter tube. Here, too, the differences are clearly visible.

Claims (2)

Protection of sayings: 1. Box-shaped large area counter tube for Hessen gaseous Radionuclides, which have a Heß counting system in a common room and has two outside counting systems adjoining it on opposite sides, those of the measuring counting system are separated by retracted cathode grids, d a by geksnsseiobast-5 that the Eaihodesgitter as a double grid (5, 6) each consisting of two parallel single grids with small compared to the counter tube dimensions Distance are executed. 2. Large area counter tube according to claim 1 for measuring tritium, characterized in that the mutual Abotand of the double grille (5 or 6) forming the single grille is greater than the average range of the Tritium breakdown resulting beta particles in the counting gas.