A scintillation counter is an instrument for detecting and measuring ionizing radiation by using the excitation effect of the incident radiation on the scintillating material and detecting the resultant light impulses.
2. DEFINATION
A scintillation counter is an instrument for detecting and measuring ionizing
radiation by using the excitation effect of the incident radiation on the
scintillating material and detecting the resultant light impulses.
3. PRINCIPLE
The basic principle of operation involves the radiation reacting with a scintillator, which produces a series
of flashes of light of varying intensity when charged particles pass through them.
The intensity of the flashes is proportional to the energy of the radiation
These counters are suited to measure the energy of gamma radiation and therefore can be used to
identify gamma-emitting isotopes
4. SCINTILLATION COUNTER –PRINCIPLE OF OPERATION
Three classes of phosphors is used:
o Inorganic crystal
o Organic crystal
o Plastics phosphors
The light created in the scintillator strikes the photocathode of a
photomultiplier tube , releasing at most one photoelectron per
photon
Using a voltage potential, this group of primary electrons is
electrostatically accelerated and focused ,so that they strike the first
dynode with enough energy to release additional electrons
5. DETECTION MATERIALS
The scintillators consists of a transparent crystal, usually a phosphor, plastic or organic liquid that
fluoresces when struck by ionizing radiation
Cesium iodide in crystalline form is used as the scintillators for detection of protons and alpha particles
Sodium iodide containing a small amount of thallium is used as a scintillator for the detection of gamma
waves and zinc sulfide is widely used as a detector of alpha particles
Zinc sulfide is the material Rutherford used to perform scattering experiment
Lithium iodide is used in neutron detectors
10. APPLICATIONS
Scintillation counters are used to measure radiation in a variety of applications including hand held
radiation survey meters, personnel and environmental monitoring for radioactive contamination,
medical imaging, radiometric assay, nuclear security and nuclear plant safety
These are designed for freight terminals, border security, ports, weight bridge applications, scrap metal
yards and contamination monitoring of nuclear waste
Several products have been introduced into the market utilizing scintillation counters for detection of
potentially dangerous gamma-emitting materials during transport
They are mounted on pick up trucks and helicopters for rapid response in case of security situation due
to bombs or radioactive waste