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NaI:Tl-based radiation detector with improved light output and energy resolution

Inexpensive, commonly used NaI:TI scintillators have 50% of the market share, but due to mediocre light output of 44,000 photons/MeV and 6.5% energy resolution (at 662 keV) their application is limited. Proposed technology promises to improve NaI:TI-based scintillators' properties by providing unparalleled output while maintaining low costs. To do so a combinatorial approach was used for the discovery of scintillation materials yielding the highest luminescence and lowest energy resolution. In testing, the engineered crystals of NaI:Tl attained a light output of 52,000 photons/MeV and energy resolution of 4.9% (at 662 keV). Crossing below the 5.0% energy resolution mark provides a specific direction for the development of even better future samples.
Talk was presented by I.V.Khodyuk and SCINT15

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NaI:Tl-based radiation detector with improved light output and energy resolution

  1. 1. 1Ivan Khodyuk – SCINT15 Improvement of NaI:Tl light output and energy resolution by co-doping I.V. Khodyuk, S. Messina, T. Hayden, S.E. Derenzo, E.D. Bourret, G. A. Bizarri Lawrence  Berkeley  Na.onal  Laboratory,  Berkeley,  CA  -­‐  USA
  2. 2. 2Ivan Khodyuk – SCINT15 NaI  –  Performance  Engineering   Factor Level 1 Level 2 Level 3 Level 4 Dopant Tl - - - [Dopant], % 0.0 0.1 0.25 0.5 Co-dopant Mg Ca Sr Ba [co-dopant] 0.1 0.2 0.4 0.8 [Eu2+], % 1.0 0.5 0.1 0.0 Sequential trial of different compositions – 256 crystals Design of Experiment using L16 orthogonal array – 16 crystals Goal: Improvement of NaI Light Output and Energy Resolution by co-doping Benchmark: NaI:Tl – 44,000 ph/MeV and 6.3% at 662 keV Factorial (parametric) space to discover: Best value reported - Shiran et al.: NaI:Tl,Eu – 48,000 ph/MeV and 6.2% at 662 keV
  3. 3. 3Ivan Khodyuk – SCINT15 Design of Experiment -XRD -OE -XRL -PXR -XRF Response to Gammas -PHM Non-proportionality in house and at the ALS Advanced characterization: -TSL, -OSL, -Afterglow, -ICP/GDMS Powder chemistry & melt-mix crystal synthesis mm-size crystals processing Single crystal growth cm-size crystals processing Phase I Phase II Design  of  Experiment  +  HTCF   Multi-regressiondataanalysis Selected samples HighThroughputCharacterizationFacility
  4. 4. 4Ivan Khodyuk – SCINT15 Design  of  Experiment   # [Tl+] Co-d [co-d] [Eu2+] ER,% LO, ph/ KeV 0 0.1 - 0.0 0.0 7.0 43 1 0.0 Mg 0.1 1.0 8.5 24.6 2 0.0 Ca 0.2 0.5 6.4 37.3 3 0.0 Sr 0.4 0.1 9.9 14.5 4 0.0 Ba 0.8 0.0 21 5.1 5 0.1 Mg 0.2 0.0 13.4 18.3 6 0.1 Ca 0.1 0.1 6.9 41.6 7 0.1 Sr 0.8 0.5 8 35.5 8 0.1 Ba 0.4 1.0 13.1 4.1 9 0.25 Mg 0.4 0.5 20 12.4 10 0.25 Ca 0.8 1.0 7 33.9 11 0.25 Sr 0.1 0.0 6.1 29.9 12 0.25 Ba 0.2 0.1 5.9 47 13 0.5 Mg 0.8 0.1 17.5 33.4 14 0.5 Ca 0.4 0.0 10.9 22.6 15 0.5 Sr 0.2 1.0 12 23.8 16 0.5 Ba 0.1 0.0 17.5 16.7 Fractional factorial design using L16 orthogonal array 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 0 5 10 15 20 H omemade  reference C ommercial  reference     Energy  Resolution  @  662keV  (%) D es ign  number Mg C a S r B a B aMg C a S r B a Mg C a S r B aMg C a S r S tatistical  limit  for  44000  photons/MeV 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 0 5 10 15 20 25 30 35 40 45 50 H omemade  reference     Light  Output  (photons/keV) D es ign  number Mg C a S r B a Mg C a S r B a Mg C a B a S r Mg C a B a S r C ommercial  reference
  5. 5. 5Ivan Khodyuk – SCINT15 Experimental  design  output  -­‐  visualizaAon   Performance (ER) optimization in 4 dimensional parametric space
  6. 6. 6Ivan Khodyuk – SCINT15 OpAmum  composiAon  synthesis  (melt-­‐mix)   0 1000 2000 3000 4000 5000 0 100 200 300 400     Counts P MT 1  C hannel  S 4 L Y  =  46200  ph/MeV * E R  =  5.4% *LO corrected for PMT QE Multi-regression analysis Optimal composition Factor Level 1 Level 2 Level 3 Level 4 [Tl+] 0.0 0.1 0.25 0.5 Co-dopant Mg Ca Sr Ba [co-dopant] 0.1 0.2 0.4 0.8 [Eu2+] 1.0 0.5 0.1 0 NaI: 0.25%Tl, 0.1%Eu, 0.2%Ca Quick optimal composition synthesis and performance evaluation
  7. 7. 7Ivan Khodyuk – SCINT15 OpAmum  composiAon  synthesis  (Bridgman)   NaI: 0.25%Tl+, 0.1%Eu2+, 0.2%Ca2+ – nominal concentrations in the melt Part of boule [Tl+], ppm wt [Ca2+], ppm wt [Eu2+], ppm wt nominal in melt 3470 540 1000 top 14641 580 890 center 1500 490 940 bottom 880 580 940 Inductively Coupled Plasma Mass Spectrometry (ICP-MS) results: Conclusions: 1) Significant Tl segregation during the Bridgman growth; 2) Parts of the crystal with lower [Tl+] show better ER and LO 42 43 44 45 46 47 48 49 50 51 52 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0      top  center  bottom Energy  Resolution  @  662keV  (%)   L ight  O utput  (photons /keV ) 5.2%  (51.1ph/keV ) S tatis tical  limit  for  44000  photons /MeV R eference  NaI:T l  #0 C ommercial  NaI:T l
  8. 8. 8Ivan Khodyuk – SCINT15 NaI:TEC  –  OpAmum  composiAon  (Bridgman)   NaI with lower concentration of Tl+ – 0.1 mole % in the melt was grown using same Bridgman furnace 550 600 650 700 0.0 0.2 0.4 0.6 0.8 1.0 1.2     Normalized  counts G amma  energy  (keV )  NaI:T l  commercial  reference  -­‐  6.3±0.2%  NaI:T l,C a,E u  co-­‐doped  -­‐  4.9±0.2% 52000 ph/MeV 4.9% at 662keV NaI:TEC (Tl, Eu, Ca) – with 52,000 ph/MeV and 4.9% resolution at 662 keV
  9. 9. 9Ivan Khodyuk – SCINT15 NaI:Tl  vs  NaI:TEC  characterizaAon  (i)   250 300 350 400 450 500 550 600 650  NaI:T E C  NaI:T l  reference     XRL  emission  intensity,  arb.  un. W avelength,  nm 0 1000 2000 3000 4000 5000  NaI:T l  reference  NaI:T E C     Counts/bin T ime  (ns ) NaI:T l  -­‐  195  ns NaI:T l,  E u,  C a  -­‐  195  ns  (20% )                                                    1790  ns  (80% ) X-ray luminescence Scintillation decay time XRL emission max at 450nm 80% of the light emitted through “long” 1.8µs component
  10. 10. 10Ivan Khodyuk – SCINT15 NaI:TEC  characterizaAon  (ii)   NaI:Tl reference NaI:TEC
  11. 11. 11Ivan Khodyuk – SCINT15 NaI:TEC  characterizaAon  (ii)   6s à 6p 4f à 5d Tl+ Eu2+ [Eu2++Vac] Tl+
  12. 12. 12Ivan Khodyuk – SCINT15 NaI:Tl  vs  NaI:TEC  characterizaAon  (iii)   -  Non-proportionality was measured at the ALS (LBNL) using micro-tomography beamline -  Systematic change of Photon-nPR curve at 6-60keV enregy range Photon non-proportional response Early stages of scintillation process are affected bythe co-doping of NaI:Tl NaI:Tl LO 44ph/keV à ER 6.3% NaI:TEC LO 52ph/keV à ER 5.9% à ER 4.9%
  13. 13. 13Ivan Khodyuk – SCINT15 Conclusion   •  Design of experiment (fractional factorial design) has been used to speed up discovery of Eu2+ and IIA influence on scintillation performance of NaI:Tl and will be applied to other materials and factors •  Optimal composition – NaI:TEC (0.1%Tl+, 0.1%Eu2+, 0.2%Ca2+) determined with multi-regression analysis gives 52000 photons/MeV and 4.9% grown by Bridgman •  NaI:TEC under X-rays and optical excitation is emitting light predominantly through Eu2++Vac cluster with max at 450nm and main decay component of 1.8µs
  14. 14. 14Ivan Khodyuk – SCINT15 Acknowledgements The authors would like to thank S. Hanrahan, D. Wilson, and Dr. J. Powell for their technical and engineering support and Drs. G. Gundiah, M. Gascon, E. Samulon, D. Perrodin and T. Shalapska for their scientific input. Combinatorial and high throughput material synthesis part of this work was supported by the US Department of Homeland Security/DNDO and crystal growth effort by the US Department of Energy/NNSA/DNN R&D and carried out at Lawrence Berkeley National Laboratory under Contract no. AC02-05CH11231. This work does not constitute an express or implied endorsement on the part of the government.

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  • yatha222

    Mar. 13, 2017

Inexpensive, commonly used NaI:TI scintillators have 50% of the market share, but due to mediocre light output of 44,000 photons/MeV and 6.5% energy resolution (at 662 keV) their application is limited. Proposed technology promises to improve NaI:TI-based scintillators' properties by providing unparalleled output while maintaining low costs. To do so a combinatorial approach was used for the discovery of scintillation materials yielding the highest luminescence and lowest energy resolution. In testing, the engineered crystals of NaI:Tl attained a light output of 52,000 photons/MeV and energy resolution of 4.9% (at 662 keV). Crossing below the 5.0% energy resolution mark provides a specific direction for the development of even better future samples. Talk was presented by I.V.Khodyuk and SCINT15

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