Extending the Dynamic Range of Radiochromic Film
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Transcript of Extending the Dynamic Range of Radiochromic Film
Extending the Dynamic Range of Radiochromic Film
Oliver EttlingerIon Instrumentation Workshop, LULI
07-06-2012
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Overview• Radiochromic film calibration
– Film overview– Data extraction– HD-810, HD-V2 and EBT-2 comparisons
• Extending the dynamic range of RCF– Ultraviolet wavelengths and their benefits for HD-
810– Application to HD-V2 and EBT-2
Film Overview• HD-810:
– 10 – 400Gy– Optical
density proportional to dose and flux
• HD-V2:
– 10 – 1000Gy– Yellow marker
dye
• EBT-2:
– 1cGy – 40Gy– Greater low
energy sensitivity
Traditional Data Extraction• Calibration with known dose
exposures – cyclotron• Flatbed scanner – RGB scans and
independent channel analysis for improved range of dose data obtainable
• 2D spatial intensity profiles and beam divergence obtained
Traditional Data Extraction
100Gy
1000Gy
10000Gy
HD-810 and HD-V2
• Red Channel – <200Gy• Blue Channel – doses above 1kGy• At least 150kGy dose limit in blue –
much larger than previously obtained results*
• Red Channel – <1000Gy• Green channel – 1000Gy –
10kGy• Blue channel - >10kGy• Better Dose Range – reduced
sensitivity
*G. Scott et al. CLF Annual Report 2010-2011
HD-V2 and EBT-2
• Red channel – <1000Gy• Green channel – 1000Gy – 10kGy• Blue channel - >10kGy
• Thicker active layer – increased sensitivity
• Red/Green channel up to 100Gy• Blue Channel up to 1000Gy
Novel stack designs
Extending the Dynamic Range• Blue turns over
at ~30kGy• UV and IR do
not exhibit multi-valued nature in range observed
• Ultraviolet most suitable above 10kGy – gradient and range of transmission values
Transmission of multiple wavelengths through HD-810 film *
*G. Scott et al. CLF Annual Report 2010-2011
Andor 16-bit CMOS camera
UV (365 nm) bandpass filter RCF holder
UV (365 nm) LED array
Glass scatter screen
Results
Digitised using Nikon Flatbed Scanner
RGB Channels
UV Light Source
Reaching up to ~ 200kGy in ‘rings’ using calibration on next slide
Dose Extraction in UV• Analogous to
method for flatbed scanner
• Calibration obtained using known doses
Can this be extended to HD-V2 or EBT-2
Extending the Range of HD-V2• Should be
possible to use any of the three wavelength regimes up to 100kGy
• Blue preferable due to gradient – transmission range could be an issue?
Extending the Range of EBT-2• Desirable due
to high sensitivity
• No UV data due to negligible transmission at all doses• Both turn over at low doses
– no obvious extension of the range
Conclusions• HD-V2 has similar characteristics to
HD-810 but greater dynamic range• HD-V2 and EBT-2 should be used in
conjunction for better data collection• UV wavelengths extend the dynamic
range by at least an order of magnitude• Method already proven with real data
analysis
Acknowledgements• James Green, Ceri Brenner, Graeme
Scott and David NeelyCentral Laser Facility, STFC
• David Parker, Stuart Green and Francesca Fiorini
University of Birmingham