Extending the Dynamic Range of Radiochromic Film

Extending the Dynamic Range of Radiochromic Film

Oliver EttlingerIon Instrumentation Workshop, LULI

07-06-2012

1

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