A scintillation counter is an instrument for detecting and measuring ionizing radiation by using the excitation effect of incident radiation on a scintillating material, and detecting the resultant light pulses or it can be defined as it is used to detect gamma rays and the presence of a particle. It can also measure the radiation in the scintillating medium, the energy loss, or the energy gain. The medium can be solid and liquid.  The phenomenon in which the nucleus of the atom of an element undergoes spontaneous and uncontrollable disintegration or decay and emit alpha, beta, or gamma rays  It is the property of some unstable atoms to spontaneously emit nuclear radiation to gain stability.  The heavy elements are called radioactive elements and rays emitted these elements are called radioactive rays.  The phenomenon of radioactivity is discovered by HENRI BACQUEREL IN 1896. Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration, or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is considered radioactive. Three of the most common types of decay are alpha decay (α-decay), beta decay (β-decay), and gamma decay (γ-decay), all of which involve emitting one or more particles.

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GOVERNMENPT NAGARJUNA P.G. COLLEGE
OF SCIENCE RAIPUR (C.G.)
M.Sc. MICROBIOLOGY
SEMESTER - 2
2022-23
WRITE UP ON
SOLID SCINTILLATION COUNTER
SUBMITTED BY :- SUBMITTED TO:-
SNEHA AGRAWAL DEPT.OF MICROBIOLOGY

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INDEX
 RADIOACTIVITY
 EXPERIMENT FOR RADIOACTIVITY
 MEASUREMENT OF RADIOACTIVITY
 SCINTILLATION COUNTER
 HISTORY
 TYPES
 DIFFERENCE BETWEEN SOLID AND LIQUID SCINTILLATION
COUNTER
 SOLID SCINTILLATION COUNTER
 PRINCIPLE
 INSTRUMENTATION
 WORKING
 APPLICATION
 ADVANTAGES
 DISADVANTAGES
 REFERENCE

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RADIOACTIVITY
 The phenomenon in which the nucleus of the atom of an
element undergoes spontaneous and uncontrollable
disintegration or decay and emit alpha, beta, or gamma rays
 It is the property of some unstable atoms to spontaneously emit
nuclear radiation to gain stability.
 The heavy elements are called radioactive elements and rays
emitted these elements are called radioactive rays.
 The phenomenon of radioactivity is discovered by HENRI
BACQUEREL IN 1896.
Radioactive decay (also known as nuclear
decay, radioactivity, radioactive disintegration, or nuclear
disintegration) is the process by which an unstable atomic
nucleus loses energy by radiation. A material containing unstable
nuclei is considered radioactive. Three of the most common types of
decay are alpha decay (α-decay), beta decay (β-decay), and gamma
decay (γ-decay), all of which involve emitting one or more particles.
EXPERIMENT FOR RADIOACTIVITY
 In this experiment a radioactive substance is kept between the
two plates one is positively (+ve) charged and other is
negatively (-ve) charged.
 It was observed that some radiations are attracted towards
negative (-ve) plate because they will have positive (+ve)
charge and are knows as alpha (α) rays.
Some are attracted towards positive (+ve) plate because
they will have negative (-ve) charged and are knows as beta (β) rays.

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Some radiation are neither attracted towards
positive (+ve) or negative (-ve) plate i.e. they are neutral charge and
are known as gamma (γ) rays
MESUREMENTS OF RADIOACTIVITY
 The radioactivity of a substance can be measured by Becquerel
is the SI unit for measurement of radioactivity. It is defined as
the number of disintegration per second.
 The radioactivity of radioactive substance is measured or
detected by instruments like :-
1. SCINTILLATION COUNTER
2. GAS FILLED CHAMBER
SCINTILLATION COUNTER
A scintillation counter is an instrument for detecting and measuring
ionizing radiation by using the excitation effect of incident radiation
on a scintillating material, and detecting the resultant light pulses
or it can be defined as it is used to detect gamma rays and the
presence of a particle. It can also measure the radiation in the
scintillating medium, the energy loss, or the energy gain. The
medium can be solid and liquid.
TYPES OF SCINTILLATION COUNTER
There are two types of scintillation counter based on the fluorescent
material used. They are:
1. solid scintillation counter
2. Liquid scintillation counter

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DIFFERENCE BETWEEN SOLID AND LIQUID
SCINTILLATION COUNTER
S.NO
.
SOLID SCINTILLATION
COUNTER
LIQUID SCINTILLATION
COUNTER
1. IT IS A RADIATION
DETECTOR WHICH
INCLUDES A
SCINTILLATION CRYSTAL TO
DETECT RADIATION AND
PRODUCES LIGHT PULSES.
IT IS A INSTRUMENT FOR
DETRMINING ACTIVITY OF A
LIQUID SAMPLE
2. USEFUL FOR GAMMA (γ)
EMITTING ISOTOPES.
USEFUL FOR QUANTIFYING ALPHA
(α) AND WEAK BETA (β) EMITTERS.
3. MOSTLY SCINTILLATOR
USED ARE INORGANIC
SCINTILLATORS AND
ORGANIC SCINTILLATORS.
HERE, IT CAN BE EITHER LIQUID
(ORGANIC SOLVENTS) OR SOLID
FORM (PLASTICS)
SOLID SCINTILLATION COUNTER
SOLID SCINTILLATION COUNTER (SSC) is an attractive
alternative and conventional instrument . With this method, a
sample is deposited directly onto a solid scintillating material, dried,
and counted in a scintillation counter. Solid scintillators have
several advantages. They are non volatile, toxic, or flammable, and
hence are safer to use. Waste disposal costs are reduced since the
sample is dried onto the solid scintillating material and may be
disposed of as solid waste.
The light emitted in scintillation can be detected by coupling it to
photomultiplier which convert the photon energy into an electrical

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pulse whose magnitude remains proportional to the energy of the
original radioactive event.
The crystal normally used are:
1. Sodium iodide : For gamma emitters
2. Zinc sulphide crystal : For alpha emitters
3. Anthracene : For beta emitters
HISTORY
The modern electronic scintillation counter was invented in 1944 by
sir samuel curran(UK). Previously scintillation events had to be
laboriously detected by eye using a spinthariscope which was a
simple microscope to observe light flashes in the scintillator.
PRINCIPLE
When high energy atomic radiations are incident on a surface
coated with some fluorescent material, then flashes of light (called
scintillation) are produced. The scintillation are detected with the
help of a photomultiplier tube , that gives rise to an equivalent
electric pulse.
These output electrical pulse can then be analyses
and counted electronically and gives rise to information regarding
the incident radiation. A solid scintillation counter is a radiation
detector which includes a scintillation crystal to detect radiation and
produce light pulses.
In the solid scintillation counters, the sample is placed in a vial, just
adjacent to a crystal or fluorescent material. Crystals are in turn

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placed near to the photomultiplier connected to a high voltage
supply and a scaler.
The solid scintillation counter is especially useful for gamma
emitting isotopes as these rays are electromagnetic radiation and
can collide well with the densely packed atoms of solid crystals.
The high atomic number and density of certain inorganic crystals
make them suitable for gamma spectroscopy with high detection
efficiencies.
SCINTILLATORS MAY BE CHARACTERISED INTO 2 MAIN
TYPES
1. ORGANIC SCINTILLATORS:-
A) Pure organic scintillators :- Anthracene, etc.
B) Liquid organic solutions :- pure organic scintillators
are dissolved in a suitable solvent &then we obtain liquid
organic scintillators.
C) Plastic scintillators :- pure organic scintillators after
dissolving in the solvent are subsequently polymerized.
2. INORGANIC SCINTILLATORS :-
NaI(Tl) :- Thallium activated Sodium Iodide
CsI(Tl) :- Thallium activated Cesium Iodide
CsI(Na) :- Sodium activated Cesium Iodide
INSTRUMENTATION
 RADIATION- The high energy ionizing radiation strike the
crystal.

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 SCINTILLATORS- It consist of a scintillator which generates
photons in response to incident radiation.
 LIGHT FLASHES- Flash or rays of light produced in a
transparent material by passing a particle
 PHOTOMULTIPLIER TUBE (PMT) –A sensitive
photomultiplier tube (PMT) which converts the light to an
electrical signal and electronics to process this signal.
 PHOTOCATHODE- A photocathode is a surface that convert
light (photons) into electrons by photoelectric effect.
 ELECTRICAL PULSE- A pulse may last from a fraction of a
nanosecond upto several seconds or even minutes.
 AMPLIFIER- It is an electronic device that measures the
peak of potential pulse.
 COUNTER- It measures the voltage of potential drop created
by the electrons.
WORKING
When ionizing incident radiation enters the scintillator, it interacts
with the material of the scintillator due to which the electrons enter
an excited state. Charged particles follow the path of the particle
itself. The energy of gamma radiation (uncharged) is converted to a
high energy electron either through the photoelectric effect.
The excited atoms of the scintillator material gradually
undergo de-excitation and emit photons in the visible range of light.
This emission is directly proportional to the energy of the incident
ionizing particle. The material shines or flows brightly due to
fluorescence.
The pulse of light emitted by the scintillator hits the
photocathode of the photomultiplier and releases at most one
photoelectron for each photon. These electrons are accelerated

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through electrostatic means by applying a voltage potential and are
targeted to hit the first dynode called the primary electrons. And
having enough energy to produce further electrons, these released
electrons are called secondary electrons. They strike the second
dynode, thereby releasing further electrons. This process occurs in a
photomultiplier tube. Each subsequent impact on the dynode
releases further electrons, and hence a current amplifying effect
occurs on the dynodes. Each subsequent dynode is at a higher
potential than the previous one, and so helps in enhancing the
acceleration. Likewise, the primary signal is multiplied throughout
10 to 12 stages. At the final dynode, highly sufficient numbers of
electrons are present to produce a pulse of high magnitude to
develop amplification. This pulse carries information about the
energy of the incident ionizing particle. The number of pulses per
unit time gives the significance of the intensity of radiation. And
finally counted in counter where it measures the voltage of
potential drop created by the electrons and saved the data for future
use.
APPLICATION
 It is widely used in screening technologies, RIA alternative
technologies, cancer research, scientists, physicians, engineers
& technicians.
 It also has its applications in protein interaction and detection,
academic research and pharmaceutical.
 Border security ,nuclear plant safety, national and homeland
security
 Used for the detection of alpha, beta and gamma emitters.

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ADVANTAGES
 Its counting rate is very fast.
 This instrument is also used to detect X-rays.
 It can detect lower levels of radiation.
DISADVANTAGES
 Hygroscopicity- A disadvantage of some inorganic crystals,
e.g. sodium iodide, is their hygroscopicity, a property which
requires them to be housed in an airtight container to protect
them from moisture.
 The cost per sample of scintillation counter is significantly
higher.
 The high voltage applied to the photomultiplier gives rise to
electronic events in the system which are not dependent on
radioactivity but which contribute to a high background count.
This effect is known as photomultiplier noise and can be
reduced by cooling the photmultiplier.
REFERANCE
 BIOPHYSICAL CHEMISTRY PRINCIPLES AND
TECHNIQUES BY UPADHYAYA AND UPADHYAY AND
NATH.
 A TEXTBOOK OF MICROBIOLOGY BBY R.C. DUBEY &
DR. D. K. MAHESHWARI.
 https://www.researchgate.net/publication/263209531_Liquid_a
nd_solid_scintillation_principles_and_applications

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