Accurate alpha-particle stopping Power measurements in Graphenic Carbon foils and its application to high-precision, non-destructive areal density determination

This study presents a high-precision, non-destructive method for determining the areal density of thin graphenic carbon (GC) foils using alpha-particle energy loss. This approach avoids the need for destructive mass and area measurements—such as laser cutting—thereby preserving the foil for further applications. Two types of GC foils with areal densities around 0.2 mg/cm², sourced from KETEK GmbH and Applied NanoTech Inc., were investigated using a three-isotope mixed alpha source emitting particles in the (5.0–5.8) MeV energy range. The developed method demonstrated that the areal-density estimates agreed within 2% for KETEK foils and within 0.5% for Applied NanoTech foils. Experimental stopping powers were extracted by combining energy-loss data with independently measured foil masses and areas. These values were benchmarked against theoretical models, highlighting the influence of the chosen stopping-power model on measurement accuracy. A modified Bethe formalism incorporating Barkas and Bloch corrections, along with an empirically adjusted mean excitation energy Iadj, provided the most consistent results—yielding agreement within 2% across the studied energy range. The results reveal a clear difference in stopping power between the two GC foils, attributed to differences in their electronic structure, as reflected in distinct Iadj values: (85 ± 1) eV for Applied NanoTech and (73 ± 2) eV for KETEK. The study emphasizes the role of the stopping-power model in determining measurement accuracy and how the structure of GC affects the (effective) stopping power. While the method is robust for thin foils, angular straggling and the non-linear energy dependence of the stopping power may limit accuracy when applied beyond the thin-target approximation. This work provides stopping-power data relevant for benchmarking Monte Carlo codes and modeling energy deposition in carbon materials—of particular interest for accelerator related technology and radio-pharmaceutical applications. In medical physics, stopping power relates directly to the concept of linear energy transfer (LET), which governs the biological effectiveness of alpha-emitting isotopes in targeted therapies. The precision achieved in this study allows for reliable, non-destructive areal density determination, offering valuable insights into the structure-dependent stopping power in emerging carbon materials.