Optimization of scintillator-reflector optical interfaces for the LUT Davis model

Area of Science:

• Nuclear medicine and high-energy physics
• Scintillation detector design and optimization
• Monte Carlo simulation in radiation detection

Background:

• Accurate modeling of light transport and collection is critical for scintillator-based gamma detectors.
• Previous models showed good agreement but overestimated light output for rough surfaces with reflectors at specific depths.
• Suboptimal optical coupling conditions were suspected as the cause of discrepancies.

Purpose of the Study:

• Investigate suboptimal optical experimental configurations affecting light collection in scintillation detectors.
• Quantify light loss due to factors like gaps, grease infiltration, and air interfaces.
• Improve the accuracy of Monte Carlo simulations for detector performance estimation.

Main Methods:

• Developed a model to compute crystal reflectance from 3D surface measurements, stored in look-up tables (LUTs) for GATE Monte Carlo software.
• Optimized the LUT algorithm to enhance reflectance computation accuracy for rough surfaces.
• Investigated light loss from air/grease mixtures in crystal-reflector and crystal-photodetector couplings, considering gaps and infiltration.

Main Results:

• A small gap (0.2 mm) between reflector and crystal caused 10%-12% light loss.
• Grease infiltration reduced light output, dependent on extent and amount.
• 5% air in the crystal-photodetector coupling caused a 2%-4% light output decrease.
• These factors explain discrepancies between simulations and experiments for ESR and Teflon reflectors.

Conclusions:

• Simulations assuming ideal coupling overestimate light output for scintillation detectors with different surface finishes.
• Accurate detector performance estimation requires careful consideration of practical limitations like imperfect couplings.
• A user interface was developed to compute custom LUTs for high-fidelity modeling.