The success of e-beam sterilization relies on accurate product dose mapping demonstrating that adequate dose can be delivered to the product. In most cases, the dosimeters should be able to measure as closely as possible the dose to the surface of the product, and the dosimeters should have adequate spatial resolution to be able to measure dose in fields with strong dose gradients (ISO/ASTM 52303).

In this study, we investigate the ability of two dosimeters frequently employed in dose mapping to measure product surface dose. Alanine pellet dosimeters (ISO/ASTM 51607), which are typically 5 mm diameter and 3 mm thickness, are widely used due to their high accuracy and robustness though their geometric properties might limit their applicability in certain applications. Alternatively, thin radiochromic films (ISO/ASTM 51275), such as Risø B3 (18 μm), offer a flexible and adaptable dosimetry approach with sub-mm resolution while allowing for precise placement and conforming to complex shapes and contours. We used Monte Carlo models to assess the ability of alanine pellets and Risø B3 film to measure surface dose when placed at a PMMA or steel cylinder and irradiated from one side with 10 MeV electrons. Irradiation geometry is shown in Figure 1.

The results are expressed as the dose ratio between dose to the dosimeters and the dose to water in a thin layer at the surface. As shown in Figure 2, the Risø B3 film more closely mimics the dose of the water surface layer.  For angles up to 75^◦ the alanine pellet performs well but notable deviations are observed at higher angles with as much as 84% at 105^◦. Consequently, we advocate for the selection of dosimeter to be dependent on the product complexity.