Speaker
Description
Positron Annihilation Lifetime Spectroscopy (PALS) is a unique and non-destructive method for characterizing atomistic defects in a wide range of materials. The use of positron beams for PALS offers significant advantages, such as the ability to probe thin layers, multilayers, and to obtain lifetime spectra with the highest quality.
The generation of positron beams for PALS experiments requires a delicate interplay of optimizing the phase space of the initial DC beam, followed by guiding, pulsing, and acceleration before it penetrates the target. The key element that distinguishes PALS beams from other positron beam methods is the pulsing stage, which ultimately determines the time resolution - a crucial parameter for lifetime measurements. At present, the most advanced pulsed positron beams for materials sciences worldwide are located at large-scale facilities: PLEPS at FRM-II [1], MePS at HZDR [2], and the pulsed beam systems at AIST (Japan) [3, 4].
The positron group at the University of the Bundeswehr Munich is currently developing a new laboratory-based pulsed positron system, driven by a 1.8 GBq sodium-22 source. In this contribution, we present the design of the current beamline components, which include the source-moderator stage, the energy filter, the pre-buncher, and the chopper.
[1]: P. Sperr et al.; Appl. Surf. Sci. 255 (2008) 35-38
[2]: A. Wagner et al.; AIP Conf. Proc. 1970 (2018) 040003
[3]: O’Rourke et al.; Def. Diff. Forum. 331 (2012) 75-91
[4]: K. Ito; JJAP Conf. Proc. 7 (2018) 011302
