Experiment 5
Energy Resolution in Scintillation Detectors
Objective:
Calculate the energy resolution ( R ) of Gamma sources.
Theory:
An important aspect of a Gamma ray spectrometer is the ability to
distinguish between Gamma rays with slightly different energy. This
quality is characterized by the so called energy resolution which is
defined as the full width at half maximum (FWHM) of the photo peak at
a certain energy.
The energy resolution is the ratio of the full width at half maximum of a
given energy peak to the peak hight.
(1)
or
(2)
where, R is the resolution in percent.
ΔCH is the number of channel in the full width at half maximum of the
photo peak. This is the measured spread of the peak at one half the
maximum peak high.
CH0 is the channel number of the maximum of the photo peak.
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Count rate
Maximum
count
FWHM
Half maximum
count
ch1
ch0
ch2
ch.
Fig.1
Apparatus:
Scintillation detector.
Computer.
Two radioactive sources.
Procedure:
1- Connect the detector to computer.
2- Put Gamma source inside the detector.
3- From start in computer go to programs menu and then go to
spectech (spectrum technique).
4- Change the setting of the 700 kev to on.
5- Go to mode choice start to start detecting radiations.
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6- After 15 min go to mode and press stop.
7- Record the value of channel number (ch0) at the maximum counts.
8- Record the values of channel numbers (ch1 and ch2) at the half
maximum counts and calculate the width of the peak (Δch).
9- By right click on mouse and choose set ROI and then shade the
area under the peak.
10- Record the value of FWHM.
11- Calculate the energy resolution.
12- Repeat the same steps for the second source.
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Results:
Source description
Element
source
where,
4
ch0
ch1
Activity (A0)
( µCi )
ch2
Δch
Half life (t1/2)
( year )
FWHM
R1 (%)
R2 (%)
and
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