Positrons

The small mass and the ability to precisely adjust their kinetic energy make positrons an excellent probe for solid-state research. As the antiparticle of the electron, the positron annihilates with an electron with a characteristic lifetime. The resulting annihilation radiation allows conclusions to be drawn about the local environment of the annihilation site. For example, the positron lifetime in an atomic vacancy is slightly longer than in the unperturbed crystal lattice. In this way, low vacancy concentrations of up to 10^-7/atom can be detected.

At NEPOMUC, the high-intensity positron beam is generated via pair production by absorbing high-energy gamma radiation. The NEPOMUC positron source is inside the tip of the beam tube SR-11. High-energy gamma radiation is generated by thermal neutron capture in cadmium. The pair production of positrons and electrons takes place in platinum foils. The positrons are formed into a beam using electric and magnetic fields and guided to various instruments at the NEPOMUC positron beamline facility.

In addition to the various instruments, the ‘open beam’ (OP) allows users to carry out positron beam experiments at NEPOMUC with their own experimental set-ups connected there.