XXV, No. 1, Pp. 1-68
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Dj. Stanković, Miloš Lj. Vujisić, Ljubinko D. Delić
GM counters are often used in radiation detection since they
generate a strong signal which can be easily detected. The working
principal of a GM counter is based on the interaction of ionizing
radiation with the atoms and molecules of the gas present in the
counter’s tube. Free electrons created as a result of this interaction
became initial electrons, i. e. start an avalanche process which
is detected as a pulse of current. This current pulse is independent
of the energy imparted on the gas, that being the main difference
between a GM counter and the majority of other radiation detectors.
In literature, the dependence on the incidence of radiation energy,
tube’s orientation and characteristics of the reading system are
quoted as the main sources of measurement uncertainty of GM counters.
The aim of this paper is to determine the dependence of measurement
uncertainty of a GM counter on the volume of its counter’s tube.
The dependence of the pulse current on the size of the counter’s
tube has, therefore, been considered here, both in radial and parallel
geometry. The initiation and expansion of the current pulse have
been examined by means of elementary processes of electrical discharge
such as the Markov processes, while the changes in the counter’s
tube volume were put to test by the space – time enlargement law.
The random variable known as the “current pulse in the counter’s
tube” (i. e. electrical breakdown of the electrode configuration)
has also been taken into account and an appropriate theoretical
distribution statistically determined. Thus obtained theoretical
results were then compared to corresponding experimental results
established in controlled laboratory conditions.
GM counter, enlargement law, measurement uncertainty
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