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14.20 o8 c gaedtke


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Research 6: C Gaedtke

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14.20 o8 c gaedtke

  1. 1. Development and characterisation of a new fibre optic dosimeter C. Gaedtke1, G. V. M. Williams1, S. G. Raymond2, J. Donaldson3, L. Greig3, and J. Steel3 • Materials: fluoroperovskites • Photoluminescence measurements • Optically stimulated luminescence • Radioluminescence studies • Fibre optic dosimeter • Characterization of dosimeter 1 SCPS, Victoria University, PO Box 600, Wellington 6140, New Zealand 2 IndustrialResearch Limited, PO Box 31310, Lower Hutt 5040, New Zealand 3 Blood and Cancer Centre, Wellington Hospital, Private Bag 7902, Wellington, New Zealand
  2. 2. Materials – Fluoroperovskites• Motivation: Searching for new materials that have good transparency, high sensitivity, and with a response to radiation that is comparable to that of tissue.• NaMgF3:Eu2+, NaMgF3:Mn2+, Rb:MgF3:Eu2+, RbCdF3:Mn2+ Zeff = 7.6 for tissue Zeff = 10.43 for 0.1 % Mn2+ in NaMgF3 Zeff = 12.33 for 0.05 % Eu2+ in NaMgF3 Zeff = 31.5 for 0.2 % Eu2+ in RbMgF3 Zeff characterizes a materials response to low energy x-rays (α Z4/E3 for photoelectric effect)
  3. 3. Materials – Fluoroperovskites• Transparent polycrystalline samples are made by mixing the starting materials in stoichiometric ratio in a glassy carbon crucible• samples were heated slightly above the melting temperature and then slow cooling down to below the melting point Orthorhombic fluoroperovskite structure
  4. 4. Optically stimulated luminescence (OSL) and radioluminescence (RL) measurements X-irradiation photostimulated luminescence Irradiation, trapping and RL OSL emission conduction band F (A0)* photo- (A0)* electron stimulationX-rays hole A + A0 A0 valence band
  5. 5. Photoluminescence measurementsNaMgF3:Eu2+ 4f65d(Eg) Wavenumber 6P 5/2 6P 7/2 8S 7/2 QPL excitation and emission from NaMgF3: 0.2% Eu2+ Eu2+ configurational coordinate diagrambulk material in phosphorescence mode in NaMgF3:Eu2+
  6. 6. Photoluminescence measurementsRbMgF3:Eu2+ PL excitation and emission from RbMgF3: 0.2% Eu2+ in Eu2+ configurational coordinate diagram phosphorescence mode in RbMgF3:Eu2+
  7. 7. Photoluminescence measurementsPL excitation and emission in phosphorescence modeNaMgF3: 1% MnRbMgF3: 5% Mn Energy levels of Mn2+ in a crystal field 10Dq
  8. 8. Optically stimulated luminescenceOSL measurements of Eu2+ doped samples in phosphorescence mode after 18 hours ofirradiation with the 241Am source RbMgF3: 0.2% Eu2+ NaMgF3: 0.2% Eu2+
  9. 9. Optically stimulated luminescenceOSL measurements of Eu2+ doped samples in phosphorescence mode after 18 hours ofirradiation with the 241Am source RbMgF3: 5% Mn NaMgF3: 1% Mn
  10. 10. RadioluminescenceRL measurements of Mn2+ doped bulk materials during irradiation with the 241Am sourceRbMgF3: 0.2% Mn2+ NaMgF3: 1% Mn2+irradiation overnight irradiation over the weekend
  11. 11. RadioluminescenceRL measurements of Eu2+ doped bulk materials during irradiation with the 241Am sourceRbMgF3: 0.2% Eu2+ NaMgF3: 0.2% Eu2+irradiation overnight irradiation over the weekend
  12. 12. RadioluminescenceRL measurements of Eu2+ doped nano particles (pressed into small pellets) during irradiation withthe 241Am source NaMgF3: 1% Eu2+ irradiation over the weekend
  13. 13. Radioluminescence (RL) and optically stimulated luminescence (OSL) measurments• Real-time radiation dose and dose rate for radiation protection, non-destructive testing, and in medicine for monitoring radiation dose during radiotherapy or for dose verification and validation• Advantages of OSL dosimeters: • Retains dose information for a long time • Higher sensitivity than organic scintillators • Different shape of materials, can be made as nano particles, bulk transparent polycrystalline materials or 2D sheets • Can be nearly tissue equivalent E.G. Yukihara and S.W.S. Mc Keever, „Optically stimulated luminescence (OSL) dosimetry in medicine“, Phys. Med. Biol., 53, R351, (2008)
  14. 14. Fibre optic dosimeterWe have a patent on Exposure to 10.5 µGy/sthe fluoroperovskite 241Am 60 keV γ-rays,materials and a patent then OSL stimulated atapplication on the 505 nmdevice.
  15. 15. Characterization of the fiber optic dosimeter• Different fluoroperovskite compounds have been attached to the end of an optical fibre. Tested using the 241Am source at IRL and the linear accelerator at Wellington hospital operating at 6MV• Second set of measurements involved collaboration with the Wellington Hospital medical physicists• Can be used in different modes: – Total dose readout: will reset the dosimeter – Latest dose readout: when there is a series of irradiation, readout of each irradiation is possible – Pulsed dose rate monitoring: IR stimulated pulsed OSL – Continual low dose rate monitoring: RL – Continual high dose monitoring: RL and blue stimulation
  16. 16. Characterization of the fiber optic dosimeterSetup at Wellington Hospital Recent RL measurements at Wellington Hospitalshowing the linear accelerator with the bulk materials
  17. 17. Summary• response to radiation that is comparable to that of tissue• Fluoroperovskites show good PL, OSL and RL response and therefore used in application• Characterisation in Wellington Hospital showed that bulk materials have a linear response to dose• Further studies on nano particles as RL signal is dose independent• Characterization of our fluoroperovskites at linear accelerator at Wellington Hospital