Nuclear radiation detectors function by detecting nuclear particles or radiation using two main principles: ionization and excitation of atoms. There are two main types of radiation detectors: gas-filled detectors like ionization chambers which measure ionization produced in a gas, and scintillation counters which use a scintillator material to produce light pulses from incident radiation that are then converted to electrical signals. Common radiation detectors include Geiger-Muller tubes, which use a gas-filled tube and high voltage to produce a cascade of ion pairs to detect radiation, and scintillation counters, which use a scintillator and photomultiplier tube to convert radiation interactions into light and then an electrical signal.

1. NUCLEAR
INSTRUMENTATION
SHALET K S
Asst. Prof.

2. The instrument which used to detect the nuclear particles
or radiation are called Nuclear radiation detectors.
These are based on the principle of excitation or ionization
of atoms of medium in which the incident charged particles
pass through.
INTRODUCTIONINTRODUCTION

3. 1) Charged particles
 - particlesα
 Protons
 Fast moving electrons
1) Uncharged particles
 neutrons
1) Electromagnetic radiations
1) - particlesȖ
2) X-rays
TYPES OF RADIATIONTYPES OF RADIATION

4. RADIATION DETECTERRADIATION DETECTER
Radiation detection has two effects :
1- ionization

5. 2- excitation

6. We have two types of radiation detection :
1- gas filled – ionisation chamber( used for non-
imaging )
2- (scintillator) ( used for imaging )
Gas-filled detectors function by measuring the
ionization that radiation produces within the gas .

7. Gas filled detectorsGas filled detectors

8. Ionization chamberIonization chamber

9. The ionization chamber is the simplest of all gas-filled
radiation detectors, and is widely used for the detection and
measurement of certain types of ionizing radiation: X-rays,
gamma rays and beta particles.
Conventionally, the term "ionization chamber" is used exclusively
to describe those detectors which collect all the charges created
by direct ionization within the gas through the application of an
electric field.

10. Working PrincipleWorking Principle
main function of an ionization detecter is to measure the ion
pairs created when ionization mediation through the gas . the ion
pairs are attached either in the positive or negative electrodes
which are then connected the battery therefore reading
measurement of ionizing radiation.

12. • The Geiger counter is an instrument used for measuring
ionizing radiation used widely in such applications as
radiation dosimetry, radiological protection,
experimental physics and the nuclear industry.
• It detects ionizing radiation such as alpha particles, beta
particles and gamma rays using the ionization effect
produced in a Geiger–Müller tube; which gives its name to
the instrument.
• It is perhaps one of the world's best-known radiation
detection instruments.
Geiger Muller CounterGeiger Muller Counter

13. Basic components of GM tube.
• A Geiger counter consists of a Geiger-Müller tube, the sensing
element which detects the radiation, and the processing
electronics, which displays the result.
• The Geiger-Müller tube is filled with an inert gas such as
helium, neon, or argon at low pressure, to which a high
voltage typically 400-600 V is applied.

14. 1. When a single gamma or beta ray entering the tube, a small
amount of ionization is produced.
2. The center electrode which is at high positive potential
attracts the electrons and gives them energy to produce
further ionization until the whole volume contains ion pairs.
3. The electrons are rapidly collected.
4. The voltage on the center electrode drops and the slow
positive ions go to
the outer wall.
5. After 400µsec
(Dead time) the tube is
ready to repeat the
Process.
Principle of operation

16. scintillation counter is an instrument for detecting and
measuring ionizing radiation by using the excitation effect of
incident radiation on a scintillate material, and detecting the
resultant light pulses.
Scintillation CounterScintillation Counter

18.  It consists of a scintillator which generates photons in
response to incident radiation. a sensitive photomultiplier tube
(PMT) which converts the light to an electrical signal and
electronics to process this signal. Scintillator consists of a
transparent crystal, usually a phosphor, plastic or organic
liquid.
•When an ionizing particle passes into the scintillator
material, atoms are ionized along a track.
•The photon from the scintillation strikes a
photocathode and emits an electron which accelerated by
a pulse and produce a voltage across the external
resistance
•This voltage is amplified and recorded by an
electronic counter.

19.  When high energy atomic radiations are incident on a surface
coated with some fluorescent material, then flashes of lights
are produced.
 The scintillations are detected with the help of a
photomultiplier tube that gives rise to an equivalent electric
pulse.

20.  It consists of a scintillator which generates photons in response
to incident radiation. a sensitive photomultiplier tube (PMT)
which converts the light to an electrical signal and electronics
to process this signal. Sciontillator consists of a transparent
crystal, usually a phosphor, plastic or organic liquid.

21. End of Lesson