Köln 2025 – wissenschaftliches Programm

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HK: Fachverband Physik der Hadronen und Kerne

HK 23: Poster

HK 23.39: Poster

Dienstag, 11. März 2025, 17:30–19:00, Foyer Physik

Energy loss and stopping power of alpha particles in graphenic carbon and areal density measurements — •Konstantina Botsiou for the Super-FRS Experiment collaboration — GSI Helmholtzzentrum für Schwerionenforschung GmbH, Darmstadt, Germany

A method for measuring areal densities based on alpha particle energy loss was undertaken. It was applied to graphenic carbon (GC) foils from two manufacturers, KETEK and Applied NanoTech. The method is highly precise for thin foils, but the accuracy depends on the stopping power model.

Experimental stopping power data, deduced from the energy loss measurements of alpha particles (in the energy range 5–5.8 MeV) in foils of known areal density (measured from mass and area), was used for selecting the stopping power model. The Bethe formulation, with the respective corrections for this energy regime, was used to describe the stopping power data. The free parameter of the fit was the adjusted mean excitation energy, I_adj, defined as ln[I_adj] = ln[I_m] + (C/Z)_β=1, where C/Z the shell correction. With this method, accuracies of 0.5 ± 2% for KETEK foils and 0.01 ± 0.4% for Applied NanoTech foils with areal densities of 0.2 mg/cm² were demonstrated.

This study was motivated by the need for a non-destructive method to measure the areal densities of GC foils produced by KETEK GmbH. This is particularly relevant for components like vacuum windows and stripper foils in accelerator systems, as well as for production targets and degraders in radioactive ion beam facilities.

Keywords: Energy loss; Stopping power; Mean Ionization Potential; Areal density