Presenter: Hodari Sadiki James Mentor: Jacqueline A. Johnson PhD. Engineering

Transcription

1 Presenter: Hodari Sadiki James Mentor: Jacqueline A. Johnson PhD. Engineering

2 film-screen-system storage phosphor x-irradiation x-irradiation direct conversion x-rays optical photons film exposure stable radiation defects photostimulated luminescence (PSL) chemical development cassette scintillating screen film scintillating screen cassette digital image cassette storage phosphor support cassette 2

3 film system storage phosphor normal normal underexposed overexposed underexposed overexposed 3

4 4

5 5

6 In theory these work in the same way as storage phosphors that are used currently. Nano crystals produced by heating the glass matrix facilitates electron entrapment. Glass doped with rear earth Eu to facilitate better luminescence and image quality. Cheaper to produce than other storage phosphor plates in use today. Very good image resolution!!! 6

7 Eu-doped glass ceramic state-of-the-art CdWO 4 single crystal mouse phantom J. Johnson, S. Schweizer, B. Henke, G. Chen, J. Woodford, P. Newman, D. MacFarlane, Journal of Applied Physics 100, (2006) 7

8 Prepared from a modified recipe for fluorochlorozirconate (Z BLAN) glass and doped with the rear earth Europium. Glass ceramic plate 8

9 After preparation Z BLAN glass has very few nano particles present and rarely phosphorlaces. Heat treatments done at specific temperatures to facilitate crystal growth. before heat treatment after heat treatment Temperatures based on results from Differential Scanning Calorimeter (DSC). 9

10 Could replacing some or all of the BaCl 2 with SrCl 2 lead to better light output/a more efficient storage phosphor? o change would affect nano particle production. Effects on light output replacing some or all of the dopant Eu with the cheaper HoF3. o change affects the relative luminescence / light output of the glass ceramic. 10

11 Sample ZrF₄ BaCl₂ SrCl₂ NaF AlF₃ LaF₃ InF₃ EuCl₂ HoF₃ sum SrCl 2 Series JJ_ JJ_ JJ_ JJ_ JJ_ JJ_ JJ_ JJ_ JJ_ JJ_ JJ_ HoF 3 Series 11

12 Differential Scanning Calorimetry (DSC) o Identify the glass transition points. o Indentify changes of these points within one of the two series. X ray Diffraction (XRD)) o Identify the crystal structure of the nano particles present in the glass ceramic. o Observe changes in this crystal structure within a series. Photoluminescence (PL) o Changes in light output of the glass ceramics within a series. 12

13 13

14 Stacked Data SrCl2 Series at at C Counts Counts JJ136_2.0% JJ135_1.6% JJ134_1.2% JJ133_0.8% JJ132_0.4% JJ138_0% Theta 2 Theta (Degrees) (Degrees) 14

15 JJ % HoF3 JJ % HoF3 15

16 Stacked Data HoF3 Series at 250 C Counts JJ143_1.6% JJ144_1.2% JJ145_0.8% JJ146_0.4% JJ138_0% Theta (Degrees)

17 Wavelength (nm) C 300 C JJ % JJ % JJ % JJ % JJ % Sample and Amount of HoF3 Control 17

18 Wavelength (nm) C 300 C JJ % JJ % JJ % JJ % JJ % Sample and amount of HoF3 Control 18

19 SrCl 2 Series Addition of SrCl 2 to the Z BLAN glass recipe attenuated the growth of important nano crystals. Small amounts of SrCl 2 led to a slight broadening of the second glass transition phase. HoF 3 Series HoF 3 addition had no significant effect on the production of nano particles. PL results show that HoF 3 addition had only a limited effect on the change of the emission wavelength. Some amount of HoF 3 can be used to substitute the more expensive. 19

20 More tests involving the integration of the dopant HoF3 in the glass ceramics. Computed radiography (CR) tests on storage phosphor plates containing the HoF3 dopant. Continued research on the precipitation of BaCl2 nano crytals in the Z BLAN glass matrix. 20

21 1.Schweizer, S. and J.A. Johnson, Fluorozirconate based glass ceramic X ray detectors for digital radiography. Radiation Measurements, (4 5): p Chen, G., et al., Insights into phase formation in fluorochlorozirconate glassceramic storage phosphors. Applied Physics Letters, (19). 3. Schweizer, S., et al., New developments in X ray storage phosphors. Radiation Measurements, (4 6): p Schweizer, S [cited 2011 Jan 20]; Available from: de/ag/ag schweizer/research/x ray_storage_phosphors.html. 5. Schweizer, S. 2011; Available from: research.html. 21

22 Jacqueline A. Johnson, PhD Amer Lahamer, PhD Lee Leonard Tracy Hodge, PhD The C.L.A. Seven Jason Hah Raven Cross Lydia Brothers Andrea Eastes Shauna Albritton Julie King 22

23 QUESTIONS? 23