Extending the Dynamic Range of Radiochromic Film Oliver Ettlinger Ion Instrumentation Workshop, LULI

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

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

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 Neely Central Laser Facility, STFC David Parker, Stuart Green and Francesca Fiorini University of Birmingham