Figure 5-11: Representation of how the correction factor 'C' was computed using the photo-bleaching correlation curves and relevant equations 5.4.3. Comparison of fluorescence results In order to compare the effect of fluorescence loss against radiation dose for the
different scintillator types, the ratio of the spectra for the irradiated and un-
irradiated regions were computed. The ratio was computed using:
𝐹𝑙𝑢𝑜𝑟𝑒𝑠𝑐𝑒𝑛𝑐𝑒 𝑅𝑎𝑡𝑖𝑜 =
𝐹𝑙𝑢𝑜𝑟𝑒𝑠𝑐𝑒𝑛𝑐𝑒
𝑖𝑟𝑟
× 𝐶
𝑖𝑟𝑟
𝐹𝑙𝑢𝑜𝑟𝑒𝑠𝑐𝑒𝑛𝑐𝑒
𝑢𝑖
× 𝐶
𝑢𝑖
Here
‘irr’ and
‘ui’ represent the irradiated and un-irradiated regions of the same
sample respectively. The ratio was computed for fluorescence at 430 nm a nd
integrated over 300-500 nm. The plots of fluorescence ratio verses irradiation
dose for the various samples are shown in Figure 5-12 and Figure 5-13
respectively.
For fluorescence loss at 430 nm, EJ260 exhibits the least loss followed by EJ208.
The UPS923A scintillators perform comparably well with EJ208, particularly at
the higher dose exposures. The TileCal scintillators perform well against loss at
the low doses, but lose light much faster at higher doses. After 25 MGy, EJ200
performs on par with EJ208 and UPS923A.
51
Figure 5-12: Fluorescence loss at 430 nm. Figure 5-13: Fluorescence loss integrated over 300-500 nm Fluorescence loss at 430 nm fit = y 0 + ae (-bx) Dose (Gy) 1e+6
1e+7
1e+8
F luo res ce n ce I n ten sity
