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1. PROPORTIONAL
COUTER

3. OBJECTIVES
Introduction
construction
Principle
Operation
Working
Uses
Advantage
Disadvantage
PROPORTIONAL COUNTER

4. Classification of detectors

5. oIt is a ion collection based detector which
is used to Detect the nuclear particles or
radiations.
oIt is classified in gaseous state detectors
Introduction

6. CONSTRUCTION
Thin metalic wire
strip

7. o It contains cylinder metallic tube filled with argon and
methane gas.
o The ratio of argon and methane gas is 9:1 at one
atmospheric pressure .
o Metallic wire (tungsten) act as a anode.
o Metallic tube act as a cathode.
o The wire is connected to pulse amplifire.

8.  When a particle of low specific ionization passes
through an ionisation chamber the pulse produced is
too small to be detected.
 When applied voltage is increased in chamber is
increased it start works in proportinal region.
PRINCIPLE

10. Operation
 E =
𝑉
𝑟 ln(
𝑏
𝑎
)
Where:-
V = applied potential difference
b = radii of the cylinder
a = radii of an axial wire
r = distance from the central wire

11. When a charged particle or radiation such as ᾳ, ᵦ-
particle or ϒ-ray photon enters an ionisation
chamber, ionisation of gas take place resulting in an
ion pair formation.
Positive ion chamber.
Electron central wire.

12. In this multiplication or gas amplification, the number of
ions increases exponentially.this process is cumulative and is
called avalanche.

13. Dependency of avalanche
Radius of anode wire.
Radius of tube.
Applied voltage.
Nature of gas.

14. The value of gas multiplication factor ‘M’ is give by 103 in
this region.
 M=
𝑛
(1−𝑛𝑝)
Here
n=number of secondary electrons produced by the primary eletrons.
p=the probability of production of photoelectrons.

15. The shape of the voltage pulse does not depend on the
track of the primary ions.

16. Uses
The proportional counter permits both the counting
and energy determination of particles even of very
low energy.
It can be used as a spectrometer.
They are also used for detection of neutrons, fission
fragments etc.
Counting ᾳ-particle in the presence of ᵦ-particle and
ϒ-rays.

17. Disadvantage
This counter is that the amplification
factor depends on the applied voltage.
The applied voltage must be
maintained constant within the narrow
limit because a slight change in voltage
changes the gas amplification.

18.  Harish Kumawat 15CS15
 Harsh Bansal 15CS16
 Harshit gupta 15CS17
 Hemant Khorwal 15CS18
 Hemraj Saini 15Cs19
 Himani Sharma 15CS20
 Hitesh Runthala 15CS21
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