The Positronsource at ELBE
The Elbe Positron Source (short EPOS) is a unique positron source for material science. It consists of three subsystems:
- Mono Energetic Positron Spectroscopy
- (short MEPS) From the primary ELBE electron beam a monoenergetic positron beam is created by pair production at a thungsten target. The unique time structure of the ELBE beam is thereby transfered on the positron beam which results in a pulsed positron source with high repetition rate, high intensity and choosable energy. With this beam measurements at surfaces and thin layers can be done easily.
- Gamma-induces Positron Spectroscopy
- (short GiPS) At the bremsstrahlung facility a gamma beam is created. When hitting the sample this produces positrons (again by pair production) which are the detected. This beam is suitable for thick samples (>= 1cm³) of solids and liquids.
- Conventional Positron Spectroscopy
- (short CoPS) More facilities with conventional β+-sources (like ²²Na) are available for complementary lifetime and doppler broadening spectroscopy.
MEPS and GiPS
Because of the unique time structure of the positron beam both MEPS and GiPS are not limited to doppler broadening spectroscopy (DBS and CDBS), but also for lifetime spectroscopy and the age momentum correlation called AMOC. The high intensity of the beam accounts for short measurement time which make it possible to study temperatur depends behaviour and maybe even dynamic transitions.For MEPS the energy of the positron beam can be choosen between 0.2 and 30keV which allows research on different sample thickness. Surface measurements and depth profiles are also possible, even for positron lifetime spectroscopy (probably for the first time).
The EPOS system is built up by the Interdisciplinary Center of Materials Science (CMAT) of the Martin-Lither-University in cooperation with the Research Center Dresden-Rossendorf. It is meant for material research and is explicitely open for external users.For more information please visit the EPOS-Homepage [http://positron.physik.uni-halle.de/EPOS].