research article detection efficiency of nai(tl) detector ......the nai(tl) detector decreased with...

Research ArticleDetection Efficiency of NaI(Tl) Detector in511ndash1332 keV Energy Range

I Akkurt1 K Gunoglu2 and S S Arda1

1 Fen-Edebiyat Fakultesi Fizik Bol Suleyman Demirel University 32260 Isparta Turkey2 Teknsk Bil MYO Suleyman Demirel University 32260 Isparta Turkey

Correspondence should be addressed to I Akkurt iskenderakkurtsduedutr

Received 13 August 2013 Revised 9 December 2013 Accepted 15 December 2013 Published 12 March 2014

Academic Editor Jakrapong Kaewkhao

Copyright copy 2014 I Akkurt et alThis is an open access article distributed under the Creative CommonsAttribution License whichpermits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

As it is important to obtain accurate analytical result in an experimental research this required quality control of the experimentalsystem Gamma spectrometry system can be used in a variety of different fields such as radiation andmedical physics In this paperthe absolute efficiency peak to valley ratio and energy resolution of a 310158401015840 times 310158401015840 NaI(Tl) detector were determined experimentallyfor 511 662 835 1173 1275 and 1332 keV photon energies obtained from 22Na 54Mn 60Co and 137Cs radioactive sources

1 Introduction

With the start of using radioactive sources in a varietyof different fields such as health physics industry energyand environmental application nuclear radiation detectorsbecome the most fundamental instruments as radiationis hazardous for health In a radiation measurement anaccurate knowledge of the detector spectral performance isrequired As the radiation can travel large distances betweenthe interactions in the detector material before detectionis possible the detectors do not have 100 efficiency Inthe radiation measurement one of the most importantcharacteristics of a detector is the efficiency of the detectorGamma spectrometry is one of themost widely used detectorsystems in this field and its performance directly dependson the knowledge of the detection efficiency The detectionefficiency is a measure of the percentage of radiation that agiven detector detects from the overall yield emitted fromthe source It can vary with the volume and shape of thedetector material absorption cross-section in the materialattenuation layers in front of the detector and distance andposition from the source to the detector [1]

Detection efficiency of a detector system depends ondifferent parameters and thus various kinds of the efficiencydefinitions are used to cover those parameters

(i) Absolute efficiency it is the ratio of the number ofcounts recorded by the detector to the number ofgamma rays emitted by the source (in all directions)

(ii) Intrinsic efficiency it is the ratio of the number ofpulses recorded by the detector to the number ofgamma rays hitting the detector

(iii) Full-energy peak (or photopeak) efficiency it is theefficiency for producing full-energy peak pulses onlyrather than a pulse of any size for the gamma ray

Especially in the radioactivity measurement the absoluteefficiency of the detector must be known It is defined as theratio of the number of counts recorded by the detector (119873

119888)

to the number of radiation (119873119904) emitted by the source (in all

directions) as represented in the following formula

120576abs =119873119888

119873119904

(1)

Absolute efficiency of the detector depends not only ondetector properties but also on the details of the countinggeometry

Various experimental and calculation works have beenreported for the detection efficiency work [2ndash6]

Hindawi Publishing CorporationScience and Technology of Nuclear InstallationsVolume 2014 Article ID 186798 5 pageshttpdxdoiorg1011552014186798

2 Science and Technology of Nuclear Installations

Pb shield

NaI(Tl)detector

HV MCA

Amplifier

Source

Figure 1 Schematic view of the experimental system

Figure 2 Gamma ray spectrum obtained from 137Cs source

Table 1 The present activity and half-life of the radioactive sourcesused to obtain energies

Nuclide Activity (micro Ci) Half-life (day)22Na 0706 950854Mn 0348 3123137Cs 0970 11020060Co 0843 19255

For the gamma ray spectrometry the absolute efficiencyand energy resolution are important parameters to be deter-mined Those parameters are usually done using a functionto fit the efficiency at a wide energies range as the numberof energy peaks obtained from radioactive sources is limitedFor these purposes the absolute efficiency and the energyresolution of the NaI(Tl) detector have been determinedexperimentally at 511 662 835 1173 1275 and 1332 keV ener-gies obtained from 22Na 54Mn 60Co and 137Cs radioactiveisotopes

2 Experimental Methods

The gamma ray spectrometry consists of a 3 times 310158401015840 NaI(Tl)detector and this is connected to 16384-channelMultichannelAnalyser (MCA) The spectrum obtained from MCA isanalyzed using the Genie 2 software obtained from Canberra[7ndash9] In order to reduce the background level of the systemthe detector is shielded using 6 cm lead on all sides Aschematic view of the system has been displayed in Figure 1The 4 different radiation sources (22Na 54Mn 60Co and137Cs) that give 511 662 835 1173 1275 and 1332 keV gammaray energy were placed at 5 different distances (05 1 3 5 and10 cm) from the face of detector and the measurement hasbeen performed for each source Eachmeasurement has beendone for a period of 60min to obtain good statistics in theevaluation of each gammapeak Typical gamma ray spectrumfor 137Cs and 60Co sources taken with the NaI(Tl) detectoris given in Figures 2 and 3 In Table 1 the present activity

Figure 3 Gamma ray spectrum obtained from 60Co source

Effici

ency

()

Energy (keV)

y = minus1E minus 05x2 + 00119x + 12442

R2 = 0937

1E + 02 1E + 03 1E + 041E + 00

1E + 01

1E + 02

Figure 4 Detection efficiency of NaI(Tl) detector as a function ofgamma ray energies (source placed at 05 cm distance to the detectorface)

Table 2The energies and emission probabilities of the radioisotopesource [11]

Nuclide Energy (keV) Emission probability ()22Na 51100 17800

127460 999454Mn 83483 8559137Cs 66166 853060Co 117323 9985

133248 9998

and half-life of the radioisotope sources are given and inTable 2 the energies and emission probabilities of theradioisotope source are given

3 Results and Discussions

The properties such as detector efficiency energy calibrationand energy resolution of a NaI(Tl) detector have beenmeasured for 6 different gamma ray energies

31 Efficiency Calibrations The detection efficiency of theNaI(Tl) detector was obtained using (1) for each gamma rayenergy emitted by the 22Na 54Mn 60Co and 137Cs radioactive

Science and Technology of Nuclear Installations 3

0

4

8

12

16

20

0 2 4 6 8 10 12

Effici

ency

()

Distance (cm)

511keV

0

4

8

12

16

20

0 5 10 15

Effici

ency

()

Distance (cm)

662keV

0

4

8

12

16

20

0 5 10 15

Effici

ency

()

Distance (cm)

835keV

0

1

2

3

4

5

6

0 5 10 15

Effici

ency

()

Distance (cm)

1173keV

0

1

2

3

4

5

6

0 5 10 15

Effici

ency

()

Distance (cm)

1275keV

0

1

2

3

4

5

6

0 2 4 6 8 10 12

Effici

ency

()

Distance (cm)

1332keV

y = 97583xminus0739

R2 = 09617

y = 92546xminus0859

R2 = 0983

y = 78032xminus0886

R2 = 09766y = 3219xminus0755

R2 = 09751

y = 29476xminus058

R2 = 09038

y = 25043xminus066

R2 = 08931

Figure 5 Variation of detection efficiency of NaI(Tl) detector as a function of distance

isotopes The obtained results have been displayed as a func-tion of gamma ray energy in Figure 4 As can be seen fromthis figure there is a great variety of analytical functions thatis used to describe the efficiency dependence on the energyThe solid line represents a second degree polynomial fitthat gives a good description with the correlation coefficientbetween the efficiency values and the gamma ray energieswhich is about 1198772 = 094

As the detection efficiency of the NaI(Tl) detector canvary with the distance to the detector face the efficiencieshave been obtained for 5 different distances from the detectorThe results are displayed in Figure 5 for 5 different distancesand 6 different energies It can be seen from this figure thatthe detection efficiency has decreased exponentially with theincreasing distance from detector face

The obtained results have been compared with thecalculation obtained using the same detector size [10]

The comparisons have been displayed in Figures 6 and 7where 05 and 10 cm distances have been used A goodagreement between experimental and calculated results wasobtained as can be seen from these figures

32 Energy Calibrations and Resolution The detector systemshould be calibrated before using in radiation detection inorder to covert channel number to energy scale This iscarried out under laboratory conditions that mimic as closelyas possible the experimental conditions Several radioactivesources (at least 3 different energy peaks) are used to getcertain peak to see channel numberThis is usually done using137Cs and 60Co radioactive sources as they produce 120574-rayenergy of 662 1170 and 1332 keV respectively In Figure 8 the120574-ray spectrum obtained from those sources and related fithas been displayed


06

05

04

03

02

01

0

Effici

ency

0 250 500 750 1000 1250 1500

Energy (keV)

Present dataYalcin et al

R2 = 09075

R2 = 09993

y = minus00001x + 02354

y = minus00002x + 04465

Figure 6 Comparison of measured and calculated detection effi-ciency of NaI(Tl) detector (source placed at 05 cm distance to thedetector face)

006

005

004

003

002

001

0

Effici

ency

0 250 500 750 1000 1250 1500

Energy (keV)


y = minus1E minus 05x + 00184


R2 = 09105

R2 = 08284


The energy resolution of a detector system is obtainedfrom the peak full width at one-half of the maximum height(FWHM) of a single peak using the following equation

119877 =FWHM119864119900

times 100 (2)

Here119877 is energy resolution and119864119900is the related energy It will

provide the separation for two adjacent energy peaks whichwill lead to identification of different nuclide in spectrumThe measured energy resolution of the NaI(Tl) detector isdisplayed in Figure 9 as a function of gamma ray energy Itcan be seen from this figure that the energy resolution ofthe NaI(Tl) detector decreased with the FWHM with theincreasing gamma ray energy

1250

1000

750

500

250

0

Cou

nts

3000

2000

1000

0En

ergy

(keV

)0 4000 8000 12000

Channel

Co-60Cs-137

662keV

1170keV

1332keV

Figure 8 Energy spectrum and calibration fit for 137Cs and 60Cosources

9

8

7

6

5

4

3

2

1

0

FWH

ME

()

400 600 800 1000 1200 1400

Energy (keV)

R2 = 09673

y = minus00038x + 95101

05 cm

Figure 9 Energy resolution of the NaI(Tl) detector obtained for05 cm distance

4 Conclusions

Thedetection efficiency and energy resolution for theNaI(Tl)scintillation detectors were measuredThe variation of detec-tion efficiency with the gamma ray energy and detectiondistance was also investigated It was found from this workthat the detection efficiency depends on gamma ray energyand also source distance to the detector


Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

This work has been supported partly by the SuleymanDemirel University Foundation Unit (3312-YL2-12) andpartly by the State Planning Unit (DPT2006K-120470) inTurkey

References

[1] K Debertin and R G Helmer Gamma- and X-Ray Spectrome-try with Semiconductor Detectors North-Holland 1988

[2] L Zikovsky and B Chah ldquoA computer program for calculatingGe(Li) detector counting efficiencies with large volume sam-plesrdquo Nuclear Instruments and Methods in Physics Research Avol 263 no 2-3 pp 483ndash486 1988

[3] Y S SelimM I Abbas andMA Fawzy ldquoAnalytical calculationof the efficiencies of gamma scintillatorsmdashpart I total efficiencyfor coaxial disk sourcesrdquo Radiation Physics and Chemistry vol53 no 6 pp 589ndash592 1998

[4] A Jehouani R Ichaoui andM Boulkheir ldquoStudy of theNaI(Tl)efficiency by Monte Carlo methodrdquo Applied Radiation andIsotopes vol 53 no 4-5 pp 887ndash891 2000

[5] M I Abbas ldquoAnalytical formulae for well-type NaI (Tl) andHPGe detectors efficiency computationrdquoApplied Radiation andIsotopes vol 55 no 2 pp 245ndash252 2001

[6] A Gultekin G Kaynak and O Gurler ldquoDetermination of fullenergy peak efficiency of HpGe detector from 595 to 13325keVrdquo Indian Journal of Pure and Applied Physics vol 44 no 4pp 281ndash286 2006

[7] I Akkurt and H Akyıldırım ldquoRadiation transmission of con-crete including pumice for 662 1173 and 1332 keV gamma raysrdquoNuclear Engineering and Design vol 252 pp 163ndash166 2012

[8] I Akkurt and A Alkhayatt ldquoThe effect of barite proportion onneutron and gamma-ray shieldingrdquo Annals of Nuclear Energyvol 51 pp 5ndash9 2013

[9] B Mavi and I Akkurt ldquoNatural radioactivity and radiationhazards in some building materials used in Isparta TurkeyrdquoRadiation Physics and Chemistry vol 79 no 9 pp 933ndash9372010

[10] S Yalcin O Gurler G Kaynak and O Gundogdu ldquoCalculationof total counting efficiency of a NaI(Tl) detector by hybridMonte-Carlo method for point and disk sourcesrdquo AppliedRadiation and Isotopes vol 65 no 10 pp 1179ndash1186 2007

[11] R B Firestone and L P Ekstrom ldquoTable of RadioactiveIsotopes Database Version 21rdquo 2004 httpielblgovtoi

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Power ElectronicsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

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Renewable Energy

Submit your manuscripts athttpwwwhindawicom


StructuresJournal of


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EnergyJournal of


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High Energy PhysicsAdvances in

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014


Pb shield

NaI(Tl)detector

HV MCA

Amplifier

Source

Figure 1 Schematic view of the experimental system

Figure 2 Gamma ray spectrum obtained from 137Cs source

Table 1 The present activity and half-life of the radioactive sourcesused to obtain energies

Nuclide Activity (micro Ci) Half-life (day)22Na 0706 950854Mn 0348 3123137Cs 0970 11020060Co 0843 19255

For the gamma ray spectrometry the absolute efficiencyand energy resolution are important parameters to be deter-mined Those parameters are usually done using a functionto fit the efficiency at a wide energies range as the numberof energy peaks obtained from radioactive sources is limitedFor these purposes the absolute efficiency and the energyresolution of the NaI(Tl) detector have been determinedexperimentally at 511 662 835 1173 1275 and 1332 keV ener-gies obtained from 22Na 54Mn 60Co and 137Cs radioactiveisotopes

2 Experimental Methods

The gamma ray spectrometry consists of a 3 times 310158401015840 NaI(Tl)detector and this is connected to 16384-channelMultichannelAnalyser (MCA) The spectrum obtained from MCA isanalyzed using the Genie 2 software obtained from Canberra[7ndash9] In order to reduce the background level of the systemthe detector is shielded using 6 cm lead on all sides Aschematic view of the system has been displayed in Figure 1The 4 different radiation sources (22Na 54Mn 60Co and137Cs) that give 511 662 835 1173 1275 and 1332 keV gammaray energy were placed at 5 different distances (05 1 3 5 and10 cm) from the face of detector and the measurement hasbeen performed for each source Eachmeasurement has beendone for a period of 60min to obtain good statistics in theevaluation of each gammapeak Typical gamma ray spectrumfor 137Cs and 60Co sources taken with the NaI(Tl) detectoris given in Figures 2 and 3 In Table 1 the present activity

Figure 3 Gamma ray spectrum obtained from 60Co source

Effici

ency

()

Energy (keV)

y = minus1E minus 05x2 + 00119x + 12442

R2 = 0937

1E + 02 1E + 03 1E + 041E + 00

1E + 01

1E + 02

Figure 4 Detection efficiency of NaI(Tl) detector as a function ofgamma ray energies (source placed at 05 cm distance to the detectorface)

Table 2The energies and emission probabilities of the radioisotopesource [11]

Nuclide Energy (keV) Emission probability ()22Na 51100 17800

127460 999454Mn 83483 8559137Cs 66166 853060Co 117323 9985

133248 9998

and half-life of the radioisotope sources are given and inTable 2 the energies and emission probabilities of theradioisotope source are given

3 Results and Discussions

The properties such as detector efficiency energy calibrationand energy resolution of a NaI(Tl) detector have beenmeasured for 6 different gamma ray energies

31 Efficiency Calibrations The detection efficiency of theNaI(Tl) detector was obtained using (1) for each gamma rayenergy emitted by the 22Na 54Mn 60Co and 137Cs radioactive


0

4

8

12

16

20

0 2 4 6 8 10 12

Effici

ency

()

Distance (cm)

511keV

0

4

8

12

16

20

0 5 10 15

Effici

ency

()

Distance (cm)

662keV

0

4

8

12

16

20

0 5 10 15

Effici

ency

()

Distance (cm)

835keV

0

1

2

3

4

5

6

0 5 10 15

Effici

ency

()

Distance (cm)

1173keV

0

1

2

3

4

5

6

0 5 10 15

Effici

ency

()

Distance (cm)

1275keV

0

1

2

3

4

5

6

0 2 4 6 8 10 12

Effici

ency

()

Distance (cm)

1332keV

y = 97583xminus0739

R2 = 09617

y = 92546xminus0859

R2 = 0983

y = 78032xminus0886

R2 = 09766y = 3219xminus0755

R2 = 09751

y = 29476xminus058

R2 = 09038

y = 25043xminus066

R2 = 08931








06

05

04

03

02

01

0

Effici

ency

0 250 500 750 1000 1250 1500

Energy (keV)


R2 = 09075

R2 = 09993

y = minus00001x + 02354

y = minus00002x + 04465


006

005

004

003

002

001

0

Effici

ency

0 250 500 750 1000 1250 1500

Energy (keV)




R2 = 09105

R2 = 08284



119877 =FWHM119864119900

times 100 (2)



1250

1000

750

500

250

0

Cou

nts

3000

2000

1000

0En

ergy

(keV

)0 4000 8000 12000

Channel

Co-60Cs-137

662keV

1170keV

1332keV


9

8

7

6

5

4

3

2

1

0

FWH

ME

()

400 600 800 1000 1200 1400

Energy (keV)

R2 = 09673

y = minus00038x + 95101

05 cm


4 Conclusions





Acknowledgments


References
















FuelsJournal of







Advances in



Journal of


Renewable Energy





RotatingMachinery


EnergyJournal of


















0

4

8

12

16

20

0 2 4 6 8 10 12

Effici

ency

()

Distance (cm)

511keV

0

4

8

12

16

20

0 5 10 15

Effici

ency

()

Distance (cm)

662keV

0

4

8

12

16

20

0 5 10 15

Effici

ency

()

Distance (cm)

835keV

0

1

2

3

4

5

6

0 5 10 15

Effici

ency

()

Distance (cm)

1173keV

0

1

2

3

4

5

6

0 5 10 15

Effici

ency

()

Distance (cm)

1275keV

0

1

2

3

4

5

6

0 2 4 6 8 10 12

Effici

ency

()

Distance (cm)

1332keV

y = 97583xminus0739

R2 = 09617

y = 92546xminus0859

R2 = 0983

y = 78032xminus0886

R2 = 09766y = 3219xminus0755

R2 = 09751

y = 29476xminus058

R2 = 09038

y = 25043xminus066

R2 = 08931








06

05

04

03

02

01

0

Effici

ency

0 250 500 750 1000 1250 1500

Energy (keV)


R2 = 09075

R2 = 09993

y = minus00001x + 02354

y = minus00002x + 04465


006

005

004

003

002

001

0

Effici

ency

0 250 500 750 1000 1250 1500

Energy (keV)




R2 = 09105

R2 = 08284



119877 =FWHM119864119900

times 100 (2)



1250

1000

750

500

250

0

Cou

nts

3000

2000

1000

0En

ergy

(keV

)0 4000 8000 12000

Channel

Co-60Cs-137

662keV

1170keV

1332keV


9

8

7

6

5

4

3

2

1

0

FWH

ME

()

400 600 800 1000 1200 1400

Energy (keV)

R2 = 09673

y = minus00038x + 95101

05 cm


4 Conclusions





Acknowledgments


References
















FuelsJournal of







Advances in



Journal of


Renewable Energy





RotatingMachinery


EnergyJournal of


















06

05

04

03

02

01

0

Effici

ency

0 250 500 750 1000 1250 1500

Energy (keV)


R2 = 09075

R2 = 09993

y = minus00001x + 02354

y = minus00002x + 04465


006

005

004

003

002

001

0

Effici

ency

0 250 500 750 1000 1250 1500

Energy (keV)




R2 = 09105

R2 = 08284



119877 =FWHM119864119900

times 100 (2)



1250

1000

750

500

250

0

Cou

nts

3000

2000

1000

0En

ergy

(keV

)0 4000 8000 12000

Channel

Co-60Cs-137

662keV

1170keV

1332keV


9

8

7

6

5

4

3

2

1

0

FWH

ME

()

400 600 800 1000 1200 1400

Energy (keV)

R2 = 09673

y = minus00038x + 95101

05 cm


4 Conclusions





Acknowledgments


References
















FuelsJournal of







Advances in



Journal of


Renewable Energy





RotatingMachinery


EnergyJournal of




















Acknowledgments


References
















FuelsJournal of







Advances in



Journal of


Renewable Energy





RotatingMachinery


EnergyJournal of





















FuelsJournal of







Advances in



Journal of


Renewable Energy





RotatingMachinery


EnergyJournal of

















research article detection efficiency of nai(tl) detector ......the nai(tl) detector decreased with...

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