The EPOS system at the radiation source ELBE at For-schungszentrum Dresden-Rossendorf

The heart of the radiation source ELBE at the Forschungszentrum Dresden-Rossendorf (FZD) is a 40-MeV LINAC with an average current of 1 mA. Due to its superconducting technology, the time structure is different from conventional LINACs. Electron bunches as short as 2 ps with a 26 MHz repetition rate can be used in continuous operation (cw) mode. This is an ideal host for an intense positron source. After organizing SLOPOS-9 in Rossendorf, it was decided to add EPOS (ELBE Positron Source) to the existing experiments at ELBE. EPOS consists of two LINAC-based setups, Gamma-induced Positron Spectroscopy (GiPS) and Monoenergetic Positron Spectroscopy (MePS). The GiPS setup, where positrons are produced inside the whole sample volume by pair production using a pulsed gamma beam, is unique so far. Here, bulky samples such as coarse powders, dispersions, but also liquids or whole devices of non-destructive testing can be investigated by all positron techniques important for materials science (lifetime spectroscopy, age-momentum correlation, and coincidence Doppler broadening spectroscopy). The same techniques will be applied at the MePS setup, where slow, mono-energetic positrons will be generated by moderation to study near-surface layers. This system is still under construction. The EPOS system will be completed by two conventional setups, a continuous slow positron beam and a positron lifetime/ Doppler spectrometer, both operated by 22Na sources.