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Synthesis and Characterization of Plastic Scintillators for J-PET Scanner

This study focuses on the synthesis and characterization of plastic scintillators for the construction of the J-PET scanner. The optical properties, such as light yield, emission spectra, and decay time, were measured. The technical attenuation length of the scintillator strips was also determined. The aim is to develop plastic scintillators with high light transparency for the J-PET construction.

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Synthesis and Characterization of Plastic Scintillators for J-PET Scanner

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  1. Synthesis andcharacterizationof the plasticscintillatorsfor the total-bodyJ-PET scanner Łukasz Kapłon Faculty of Physics, Astronomy and Applied Computer Science Jagiellonian University 28.06.2019

  2. Outline • Chemistry of plastic scintillators • Optical propertiesmeasurement: - lightyield - emission spectra - decaytime • Technicalattenuation lengthof long plastic scintillatorstrips

  3. Motivation • Develop plastic scintillators with high light transparency for J-PET construction. • Measure properties of commercial scintillators and choose the best for prototypes building.

  4. ScintillationPrinciples: lightemissionmechanism

  5. ScintillationPrinciples: chemicalcomponents

  6. ScintillationPrinciples: cell casting polymerization • 1. fast heating from room temperature 20 °C to 60 °C in 1 hour, 40 °C/h, • 2. slow heating from 60 °C to 180 °C in 60 hours, 2 °C/h, • 3. polymerization in 180 °C during 20 hours, • 4. cooling from 180 °C to 90 °C in 30 hours, 3 °C/h, • 5. first annealing in 90 °C for 4 hours, • 6. cooling from 90 °C to 60 °C in 10 hours, 3 °C/h, • 7. second annealing in 60 °C for 4 hours, • 8. cooling from 60 °C to 20 °C room temperature in 10 hours, 4 °C/h.

  7. ScintillationPrinciples:lightyield of scintillators Light yield (LY)is a conversion efficiency of radioactive energy deposited in scintillator into light and is expressed in light photons generated per megaelectronvolt of deposited energy (photons/MeV) by radiation quanta or particle. Comparing light yieldof produced plastic scintillators to light yieldof anthracene or stilbene crystal scintillators is known as relative light yield. Amax Amaxscintillator – middle of Compton edge for sample Amaxstilbene – middle of Compton edgefor sdandard

  8. ScintillationPrinciples: emission and absorption spectra 1-4 wt. % p-Terphenyl+ POPOP ~0.05 wt. % Absorption (green) and emission (red) spectra of twofluorescentsubstancescommonlyused in plastic scintillators Emissionspectrum of plastic scintillator with p-Terphenyl and POPOP p-Terphenylemission spectrum overlaps with POPOP absorption spectrum

  9. ScintillationPrinciples: lightpulseproperties Decay time can be defined as time over which the light signal from scintillator decreases to 1/e of its maximum value. To measure decay time of plastic scintillators time-correlated single photon counting (TCSPC) was used. where following symbols denote: K - normalization constant Θ – time of the gamma quantum interaction with scintillator t - time td - decay time of the final light emission tr - average time of the energy transfer to the wavelength shifter σ - standard deviation reflects total uncertainty of light emission from scintillator and TCSPC components: excitation diode, photomultiplier tube and electronics.

  10. Results

  11. Commercial plastic scintillators

  12. Technicalattenuation length • The aim of this measurement was to determine technical light attenuation length of plastic scintillator stripsused forJ-PETmodules construction. • The technical attenuation length (TAL) of a plastic scintillator bar is defined as the length of scintillator reducing the light signal by a factor of eand depending upon: • bulk transmission of the scintillator, • scintillatorthickness, • shape of scintillator, • reflective propertyof the surfaces. + y0 A1 – amplitude x - distancefrom lightdetector t1 - technicalattenuation length y0 - background 500 to 1000 mm longscintillators

  13. Plastic scintillatorstripsused in J-PET

  14. Overlapping of 365 nmUV lamp emission spectra and scintillator absorption UV light

  15. Setup for TAL measurements • In measurement following equipment was used: • UV lampwith 365 nm wavelength of maximum emission; • silicon PIN photodiode BPW 34 Bwith 2.73x2.73mm2 active area; • digital multimeterRigol DM 3064; • powersupply ZUE 5352 M; • aluminiumrail with 8 mm diameterholesdrilledevery 50 mm.

  16. Summary results

  17. Summary results

  18. Summary • Plastic scintillatorswith the different chemical compositions weresynthesized. • Time-temperature cycles were established for polymerization in smallcylinders as well as for polymerization in the glass mold allowing to manufactureplastic scintillator strips. • Spectroscopic and optical properties of these polystyrene scintillators weremeasured. Relative light output, decay time, emission spectra were measured to develop best composition. • Technicalattenuation lengths were measured to choose the best scintillator for J-PET construction.

  19. Thankyou

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