SKM 2023 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 35: Poster Session II

CPP 35.4: Poster

Mittwoch, 29. März 2023, 11:00–13:00, P1

Determination of the roast-dependent pore size in coffee beans using positron lifetime spectroscopy — •Adrian Langrehr, Vassily Burwitz, Lucian Mathes, and Christoph Hugenschmidt — Forschungs-Neutronenquelle Heinz Maier-Leibnitz (MLZ), Technische Universität München, Lichtenbergstr. 1, 85748 Garching, Germany

Positron Annihilation Lifetime Spectroscopy (PALS) is an established method to determine the type and concentration of open volume defects in crystals as well as to investigate the free volume in polymers. Using ²²Na as β⁺emitting radioisotope in the so-called "sandwich" geometry we present the capabilities of our four-detector setup with digital readout and signal processing. The efficient readout of this PAL spectrometer produces 12 lifetime spectra simultaneously. Our study encompasses the comparison of three different methods to combine information contained in these 12 spectra. To demonstrate a use case of a biomaterial we measured the positron lifetimes in coffee beans as a function of the degree of roasting. The application of the so-called Tao-Eldrup model allows us to study the influence of the roasting parameters on the mean pore size on the nanometer scale.