Comparative study of new scintillation materials in application to the border detection equipment IA

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Comparative study of new scintillation materials
in application to the border detection equipment
IAEA Research Contract No 12596

• Marek Moszynski, Marcin Balcerzyk and Agnieszka
  Syntfeld, et al
• Soltan Institute for Nuclear Studies
• PL 05-400 Swierk-Otwock, Poland

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Objectives

• Requirements to the new detectors
• Sensitivity,
• Selectivity,
• As of now, the small hand-held instrumentations
  utilize mainly NaI(Tl) scintillation detectors
  and semiconductor CZT detectors.
• - NaI(Tl) a good sensitivity and moderate
  selectivity
• - CZT a good sensitivity and poor sensitivity

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Scientific Program

• LaCl3 and LaBr3 high selectivity
• CdWO4 (CWO) and CaWO4 (CaWO) high sensitivity
• The program was extended by the tests of 6LiI(Eu)
  crystal as a highly efficient neutron detector
• Tests of new photomultipliers for efficient work
  with LaBr3 crystal,

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Published papers

• M. Moszynski, M. Balcerzyk, W. Czarnacki, M.
  Kapusta, W. Klamra, A. Syntfeld, M. Szawlowski,
  Intrinsic Energy Resolution and Light Yield
  Non-proportionality of BGO, IEEE Trans. Nucl.
  Sci., 51(2004)1074.
• M. Balcerzyk, M. Moszynski, M. Kapusta,
  Comparison of LaCl3Ce and NaI(Tl) scintillators
  in ?-ray spectrometry, Nucl. Instrum. Meth.,
  A537(2005)50.
• M. Moszynski, M. Balcerzyk, M. Kapusta, A.
  Syntfeld, D. Wolski, G. Pausch, J. Stein, P.
  Schotanus, CdWO4 Crystal in Gamma-ray
  Spectrometry, IEEE Trans. Nucl. Sci.
  52(2005)3124.
• A. Syntfeld, M. Moszynski, M. Balcerzyk, M.
  Kapusta, D. Wolski, M. Majorov and P. Schotanus,
  6LiI(Eu) in Neutron and ?ray Spectrometry A
  High Sensitive Thermal Neutron Detection, IEEE
  Trans. Nucl. Sci. 52(2005)3151.

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Published papers

• M. Swoboda, R. Arlt, V. Gostilo, A. Loupilov, M.
  Majorov, M. Moszynski, A. Syntfeld, Spectral
  Gamma Detectors for Hand-held Radioisotope
  Identification Devices (RIDs) for Nuclear
  Security Applications, IEEE Trans. Nucl. Sci.
  52(2005)3111.
• M. Moszynski, M. Balcerzyk, W. Czarnacki, A.
  Nassalski, T. Szczesniak, H. Krus, V.B. Mikhalik,
  I.M. Solskii, Characterization of CaWO4
  scintillator at room and liquid nitrogen
  temperature, Nucl. Intstr. Meth., A553(2005)578.
  
• A. Syntfeld, R. Arlt, P. Dvornyak, V. Gostilo, A.
  Loupilov, M. Moszynski, M. Swoboda, Comparison
  of a Large Volume CdZnTe Detector with a LaBr3
  Scintillation Detector, presented at 2005 IEEE
  NSS/MIC Conference, submitted to IEEE Trans.
  Nucl. Sci.

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High energy resolution scintillators - LaCl3Ce
crystal

• Measured with 1x1 LaCl3Ce and 25 x 30 mm
  NaI(Tl) coupled to XP3212 PMT.
• Superior energy resolution of 4.2 for LaCl3Ce
  in comparison to NaI(Tl) (6.7)

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High energy resolution scintillators - LaCl3Ce
crystal

• LaCl3Ce is clearly superior to NaI(Tl) in terms
  of non-proportionality.
• Downward bending of proportionality starts at 20
  keV.

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High energy resolution scintillators - LaCl3Ce
crystal

• A comparison of energy resolution measured with
  LaCl3 and NaI(Tl) crystals.
• Note a much higher resolution of LaCl3 for gamma
  rays above 100 keV.

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High energy resolution scintillators - LaBr3Ce
crystal

• The ?-ray spectra from a 137Cs source measured
  with 1 x 1 LaBr3(Ce) and a large (30?15?12.1
  mm3) CP CZT.
• Note a better energy resolution of LaBr3.
• Light output above 60000 ph/MeV

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High energy resolution scintillators - LaBr3Ce
crystal

• The overall energy resolution measured for
  LaBr3(Ce) and CP CZT (compared to ?25 x 31 mm
  NaI(Tl).
• Note a superior energy resolution of LaBr3 above
  100 keV, and comparable to those observed with
  NaI(Tl) below 100 keV.

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High energy resolution scintillators - LaBr3Ce
crystal

• A comparison of the non-proportionality curves
  measured for the LaBr3(Ce) and NaI(Tl) (?25 x 31
  mm) crystals, respectively.

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Thermal stability of LaBr3
662 keV peak position
Number of photoelectrons and light output
M.M., et al.,G.Pausch, J. Stein, NIM A, in
press
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Scintillators with a high sensitivity - CdWO4
(CWO)

• Energy spectra of 662 keV ?-rays from a 137Cs
  source, as recorded with the 10 x 10 x 3 mm3 CWO
  (bottom panel) and with the ?25 mm x 30 mm
  NaI(Tl) (upper panel).
• Note a comparable peak-to-total ratio, while the
  ratio of a crystal volume is about 50.

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Scintillators with a high sensitivity - CdWO4
(CWO)

• Energy spectra of ?-rays from a 207Bi source (top
  trace) and that of the laboratory background
  (bottom trace), as recorded with a ?20x20 mm3 CWO
  crystal.
• Measurements are done with 12 µs shaping time
  constant in a spectroscopy amplifier.

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Scintillators with a high sensitivity - CdWO4
(CWO)

• A comparison of the non-proportionality curves
  measured for the small CWO and BGO crystals.
• Note the same non-proportionality curves,
  characteristic for heavy oxide crystals.

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Scintillators with a high sensitivity - CdWO4
(CWO)

• A comparison of the energy resolution of CWO and
  BGO crystals versus gamma rays energy. Error bars
  are within the size of the points.
• A better energy resolution measured with CWO is
  due to higher light output.

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Scintillators with a high sensitivity - CaWO4
(CaWO)

• Energy spectra of 662 keV ?-rays from a 137Cs
  source recorded with a CaWO crystal at room and
  LN2 temperatures.
• Crystal size 10x10x4 mm3

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Scintillators with a high sensitivity - CaWO4
(CaWO)

• Non-proportionality characteristics of CaWO, as
  measured at room and LN2 temperatures.
• CaWO response seems to be independent of the
  temperature.

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Scintillators with a high sensitivity - CaWO4
(CaWO)

• Energy resolution of CaWO versus ?-ray energy.
• Common curves for room and LN2 temperatures are
  observed.

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CWO and CaWO crystals

• High detection efficiency
• Good energy resolution of about 6.5
• Slow light pulses 8 14 ?s
• A good thermal stability of light output and
  non-proportionality,
• Large crystals of a good quality have to be
  developed

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6LiI(Eu) crystal as a very efficient neutron
detector

• The pulse height spectrum of thermal neutrons
  detected in 6LiI(Eu) crystal.
• A well defined peak at about 3.5 MeVee is
  observed, well above a background of gamma
  radiation.

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6LiI(Eu) crystal as a very efficient neutron
detector

• The sensitivity characteristic of 6LiI(Eu)
  crystal measured in relation to the neutron
  monitor NM2B.
• The 6LiI(Eu) of ?50 mm x 5 mm was used.
• The crystal was given us by Dr. Majorov from St.
  Petersburg.

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6LiI(Eu) crystal as a very efficient neutron
detector

• Energy spectrum of 662 keV ?-rays from a 137Cs
  source measured with 6LiI(Eu) crystal.

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New photomultipliers for the LaBr3 crystal
Courtessy to Photonis, Brive, France Two XP3422,
with QE of 35 and 42, were tested in our
laboratory.
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New photomultipliers for the LaBr3 crystal

• Excellent energy resolution due to high QE of
  PMT.
• The tested LaBr3 crystal belongs to the first
  batch of production at SGC.

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New photomultipliers for the LaBr3 crystal

• A comparison of the energy resolution measured
  with 25 mm x 30 mm NaI(Tl) coupled to the PMTs
  with standard and enhanced quantum efficiency.
• Note an excellent energy resolution for gamma
  rays below 100 keV.

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New photomultipliers for the LaBr3 crystal

• PMTs for a good linearity of LaBr3
• - Linear-focused dynode structure,
• - reduced number of dynodes to 7 or 8,
• - tappered voltage divider.
• A high energy resolution
• - high quantum efficiency of about 35 or more,
• - a smaller diameter of the crystal than that of
  the photocathode

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Conclusions

• The superior performance of LaBr3 crystal in the
  whole range of gamma-rays energy reflected in its
  high selectivity and good detection efficiency,
  better than that of NaI(Tl) crystal. A high
  linearity of the new crystal response should be
  pointed out too, which makes simpler isotope
  identification.
• A good energy resolution and high detection
  efficiency for gamma rays of small CWO and CaWO
  crystals. However, a larger crystal of 20 mm x 20
  mm exhibited a degradation of the light output
  and energy resolution. Further efforts are
  necessary to get large volume detectors of
  comparable performances.

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Conclusions

• A high detection sensitivity for thermal neutron
  detection of 6LiI(Eu) crystal and its a high
  selectivity against gamma ray background.
• Particularly, the comparative study of LaBr3 and
  CZT detectors of comparable size showed a better
  energy resolution of LaBr3. A poor charge
  collection in a large CZT limits still obtainable
  energy resolution.
• More efforts are necessary for a further
  development of larger volume CZT detectors with
  an energy resolution similar to that measured
  with small detectors.

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Conclusions

• However, a further work is necessary to select
  and to optimize photomultipliers for LaBr3,
  assuring particularly a good linearity of the PMT
  response.
• To utilize full capabilities of LaBr3 detector,
  the photomultipliers with a reduced number of
  linear-focused dynodes to 7 or 8 stages and
  characterize by high quantum efficiency of about
  35 is required.

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Acknowledgement

• The help of several Companies, as
• Saint-Gobain Crismatec, France
• SCIONIX, Holland
• Amcrys H, Ukraine
• Photonis, France
• target, Solingen, Germany is acknowledged.