Positron annihilation spectroscopy

Positrons penetrating into a material have a lifetime that depends on the annihilation site and can be experimentally determined.  Localization of positrons due to the presence of material defects leads to an increase of the positron lifetime. Such defects can be vacancies in metals or lattice sites of cathode materials in Li-Ionen batteries from which Li has been removed. This technique is called Positron Annihilation Lifetime Spectroscopy (PALS). PALS measurements are very sensitive and reproducible, while the interpretation of the data is challenging.

The momentum distribution of the annihilation radiation enables the determination of the chemical environment of the annihilation sites. This technique is called Doppler Broadening of Annihilation Radiation (DBAR). The interpretation of data is simpler compared to PALS, but more time is required for the experiments.

Three PALS and one DBAR spectrometers are available at the institute. Investigations at low temperatures can be carried out using a dedicated sample environment.