Neutron Response of LaBr3:Ce

Crystal Scintillators and Simulations

for PARIS

Oliver Roberts et al.

IOP Nuclear Physics Conference Birmingham 2009

Outline

Introduction to PARIS

Geant4 Simulations

LaBr3:Ce Crystals

Self Activation of 138La

Alpha Contamination

Neutron Response of LaBr3:Ce Scintillators

Summary & Conclusions

Motivation: PARIS

Energy range between

100keV and 50MeV

Inner shell of LaBr3:Ce, outer

shell of CsI:Na crystals

Different decay times allow

for discrimination of signals

Moveable source distance,

more physics cases Images courtesy of J.Strachan (STFC)‏

Geant4 Simulations

Basic prototype later

evolved into a shifted 4

geometry

Latest version uses

CAD designs with

beampipe, more

realistic

Absorption and Fold

tests were conducted

Geant4 Simulations

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

0

10

20

30

40

50

60

70

80

90

Absorption Efficiencies for Different Arrays

6x6 Array

8x8 Array

10x10 Array

Energy (MeV)

Absor

ption in

Detec

tor wa

ll (%)

Geant4 Simulations

1”x1”x4 LaBr3:Ce crystals with shifted detector

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5

10

15

20

25

30

35

40

45

50

Absorption Efficiencies for High Energy Gammas

6x6 Array

8x8 Array

10x10 Array

Energy (MeV)

Absorption

(%)

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0

10

20

30

40

50

60Comparison between AGATA and 2"x2"x4" LaBr3:Ce

LaBr3:Ce 2x2x4

AGATA 180 (En File)

Energy (MeV)

Absorpt

ion (%)

Geant4 Simulations

Fold Distribution Cubic Array

Fold Distribution of AGATA

Chamber sizes are the same, less counts for AGATA, different distribution due to geometry

Still an area of ongoing work

LaBr3:Ce Crystals

High resolution scintillators, ~3% at 662keV

When doped with cerium, high light output (~60,000 photons/MeV)

Good Timing resolution of FWHM~260ps

Fast decay time (~25ns)

Peak emission wavelength in blue-UV part of the EM spectrum (380nm), very compatible with PMTs.

Self Activation of 138La

Alpha Contamination

227Ac (t1/2=21.2yrs), appears in the same group (IIIB) as Lanthanum

Experimental Set-up

241Am/9Be source was

used.

Dynamic range

inconsistent due to

saturation in PMT.

Working voltage reduced

by 300V as spectra were

non-linear

Neutron Response of LaBr3:Ce

Detectors

Summary & Conclusions

Simulations with LaBr3:Ce crystals were used to compare two potential geometries for PARIS array.

Tests done on inorganic Lanthanum halide crystals (LaBr3:Ce) with the neutron source has revealed the background spectrum before neutron capture.

Calibrated spectra was presented revealing gamma lines from 140La, 80Br and 82Br after activation.

Future Simulations/Tests at York

Continuing work with

simulations using an

AGATA style geometry

with LaBr3:Ce crystals

A Phoswich

arrangement involving

CsI(Tl) crystal and a

novel silicon detector

PMT will be

investigated at York.

Acknowledgement of CollaboratorsD. Jenkins1, M. Ciemała2, P. Joshi1, J. Strachan7, A.

Smith8, B.Wadsworth1, A.Maj2, F. Camera6, D.R.

Chakrabarty4, M. Chełstowska2, S. Courtin3, O.

Dorvaux3, M. Kmiecik2,Ch. Schmitt10, Suresh

Kumar4, M. Labiche7, K. Mazurek2, J. Pouthas5, M.

Rousseau3, O. Stezowski9, and the rest of the

PARIS collaborators

1University of York, United Kingdom2Institute of Nuclear Physics PAN, Krakow, Poland

3IPHC Strasbourg, France4BARC Mumbai, India

5IPN Orsay, France6INFN Milano, Italy

7STFC Daresbury, United Kingdom8University of Manchester, United Kingdom

9IPN Lyon, France10GANIL, Caen, France

References

W.J.Kerman. Self-Activity in Lanthanum Halides. IEEE Trans. Nucl. Sci., 53:395-400,2006.

C.Hoel et al. Pulse Shape Discrimination of La Halides. Elsvier, NIM, A540:205-208, April 2005.

C.M.Rozsa, P.R.Menge, and M.R.Mayhugh. BrilLance Scintillators Performance Summary. Saint-Gobain Crystals, Scintillation Products, April 2008. www.detectors.saint-gobain.com.