Dresden 2014 – wissenschaftliches Programm

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MI: Fachverband Mikrosonden

MI 2: Untersuchung von kondensierter Materie mittels Positronen-Annihilation

MI 2.3: Vortrag

Montag, 31. März 2014, 11:00–11:15, MER 02

Implementing the Munich Scanning Positron Microscope at NEPOMUC — •Marcel Dickmann¹, Christian Piochacz^2,3, Werner Egger¹, Gottfried Kögel¹, Peter Sperr¹, Christoph Hugenschmidt^2,3, and Günther Dollinger¹ — ¹Universität der Bundeswehr München, LRT2, D-85577 Neubiberg, Germany — ²Technische Universität München, Physik Department E21, D-85748 Garching, Germany — ³FRM2, Technische Universität München, D-85748 Garching, Germany

Positron annihilation lifetime spectroscopy is a very sensitive method to analyze non-destructively small open volume defects, e.g. vacancies, vacancy clusters, and dislocations. Defect-types and their concentrations can be determined. The Munich Scanning Positron Microscope (SPM) generates a focused, pulsed low-energy positron beam for positron lifetime measurements with a high lateral resolution ≥ 1 µm. By varying the beam energy, depth resolutions in the sub-µm range can be obtained, which makes 3D defect microscopy possible. With the SPM defect distributions close to crack surfaces have been successfully studied in pure copper and in the alloy Al 6013. The main limitation in these studies was the low count-rate obtainable with conventional laboratory positron sources, which leads to exceedingly long measurement times. Therefore, to increase the beam intensity, the SPM is transferred to the high intense positron source NEPOMUC at the FRM II research reactor in Munich. To match the stringent requirements on positron beam brilliance of the SPM, an interface, that increases the phase space density of the NEPOMUC beam, was built, and successfully tested.