Physics and Engineering of Radiation Detection

3.4. Ionization Chambers 181

i 1 iout=i 1 −i 2 i 2

+− +−

HV HV

−

−+

α+−+−+ +

− −

+

+

−

−

+ +

−

Boron

+

−

Neutron

γ

Li

Figure 3.4.11: Working princi-

ple of the compensated ioniza-

tion chamber. Here i 1 repre-

sents the current due to neu-

trons andγ-rays whilei 2 is due

toγ-rays only.

3.4.E ApplicationsofIonChambers..................

Ionization chambers are extensively used in a variety of applications due to their
simplicity in design and manufacturing, durability, radiation hardness, and low cost.
Some of their common applications include diagnostic x-ray measurements, portable
dose monitoring, radiation intensity monitoring, anduse in smoke detectors.

3.4.F AdvantagesandDisadvantagesofIonChambers

It should be noted that there is no such thing as auniversal detectorthat could be
used in any application. Some detectors, such as ionization chambers, can be used
in a variety of applications, however most are designed and built according to the
particular applications and requirements. Therefore talking about advantages and
disadvantages of detectors is somewhat relative. Still, due to the versatility of ion-
ization chambers we will have a general look at their advantages and disadvantages.
Let us first discuss some of their advantages.

Insensitivity to applied voltage:Since the ionization current is essentially

independent of the applied voltage in the ion chamber region, therefore small

inevitable fluctuations and drifts in high voltage power supplies do not deterio-

rate the system resolution. This also implies that less expensive power supplies

can be safely used to bias the detector.

Proportionality:The saturation current is directly proportional to the energy

deposited by the incident radiation.

Less Vulnerability to Gas Deterioration: There is no gas multiplication

in ionization chambers and therefore small changes in the gas quality, such as

increase in the concentration of electronegative contaminants, does not severely