*Article* **Characterization of a Radiofluorogenic Polymer for Low-Energy Electron Beam Penetration Depth Visualization**

**Magdalena Maria Skowyra 1,\* , Christina Ankjærgaard <sup>1</sup> , Liyun Yu <sup>2</sup> , Lars René Lindvold <sup>1</sup> , Anne Ladegaard Skov <sup>2</sup> and Arne Miller <sup>1</sup>**


**Abstract:** Low-energy (80–300 keV) electron beam accelerators are gaining in importance in the radiation processing industry due to their ease of use and wide range of applications (e.g. product surface sterilizations or polymer curing and cross-linking). Due to their very low penetration depth (tens to hundreds of microns), currently used film dosimeters exhibit dose gradients over their thickness and do not resolve the dose response in the first microns of the irradiated material. Hence, the surface dose, defined as the dose in the first micron Dμ, cannot be measured directly. This study presents a polymer material as a dosimeter candidate for high-dose low-energy electron beam irradiations. The readout of the dose-dependent fluorescence intensity, originating from a pararosaniline dye reaction when irradiated, is measured using fluorescence microscopy. So far, no in-depth characterization of the material has been performed, leaving the stability and fluorescence properties of the material not fully optimized. We describe the improvements in polymer composition and the fabrication method, and characterize the material properties in terms of the thermal stability, glass transition temperature, refractive index, hardness, rheological behavior, and water affinity. All of these create a complex set of requirements a polymer needs to fulfill to become an effective dosimeter when measuring using confocal microscopy. The fluorescence readout procedure will be addressed in further studies.

**Keywords:** low-energy electron beam; fluorescence; polymer dosimeter; radiofluorogenic; 3D dosimetry
