Chapter 5
Ionization Counters
5.1 Introduction
Radiochemists handling radioactive materials must have a sound knowledge of various techniques used to detect and measure them. Furthermore, if a radioactive isotope
is to be used as a tool in any chemical process, one should be able to identify the
isotope, detect its presence and then analyze it quantitatively. In order to accomplish
these requirements, radiochemist is required to select a suitable radioactive material, decide the form (liquid, solid or gas) in which the sample is to be measured
for its activity, select a suitable counting system for the purpose and finally must be
able to take a decision about the period for which the counting should be done to
minimize the error of counting, etc. Therefore, in this chapter, discussions are made
in a sequence, which would help the reader to understand the various aspects of
ionization counting system and its limitations in counting some specific radioactive
isotope. When radiations interact with surrounding media (as discussed in Chap. 4),
they can produce ion-pairs, because they have enough energy to knock out electron
from the outermost shell of the interacting atoms. Argon gas, for example, after the
interaction with radiation produces a positively charged Ar
+ ion and an electron:
Radiation + Ar −→ Ar
+
+ e
−
Number of Ar
+ and e
− (known as ion-pairs) thus produced is directly proportional
to the number of interacting radiation. Therefore, if there is an instrument to measure
number of ion-pairs formed, then the amount of radiation and hence the amount of
radioactive material can be measured. Since the instrument counts the number of
ion-pairs formed, the radiation must interact, with a specific volume of the enclosed
gas. These conditions are met in an ionization counter.
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2021
M. Sharon and M. Sharon, Nuclear Chemistry,
https://doi.org/10.1007/978-3-030-62018-9_5
53
Ionization Counters
5.1 Introduction
Radiochemists handling radioactive materials must have a sound knowledge of various techniques used to detect and measure them. Furthermore, if a radioactive isotope
is to be used as a tool in any chemical process, one should be able to identify the
isotope, detect its presence and then analyze it quantitatively. In order to accomplish
these requirements, radiochemist is required to select a suitable radioactive material, decide the form (liquid, solid or gas) in which the sample is to be measured
for its activity, select a suitable counting system for the purpose and finally must be
able to take a decision about the period for which the counting should be done to
minimize the error of counting, etc. Therefore, in this chapter, discussions are made
in a sequence, which would help the reader to understand the various aspects of
ionization counting system and its limitations in counting some specific radioactive
isotope. When radiations interact with surrounding media (as discussed in Chap. 4),
they can produce ion-pairs, because they have enough energy to knock out electron
from the outermost shell of the interacting atoms. Argon gas, for example, after the
interaction with radiation produces a positively charged Ar
+ ion and an electron:
Radiation + Ar −→ Ar
+
+ e
−
Number of Ar
+ and e
− (known as ion-pairs) thus produced is directly proportional
to the number of interacting radiation. Therefore, if there is an instrument to measure
number of ion-pairs formed, then the amount of radiation and hence the amount of
radioactive material can be measured. Since the instrument counts the number of
ion-pairs formed, the radiation must interact, with a specific volume of the enclosed
gas. These conditions are met in an ionization counter.
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2021
M. Sharon and M. Sharon, Nuclear Chemistry,
https://doi.org/10.1007/978-3-030-62018-9_5
53