Recent experiments at the Giessen slow positron source TEPOS

Recent results for the K- and L-shell ionization of silver and gold, respectively, by positron and electron impact and for the energy loss of 6-20 keV positrons in thin foils obtained at the Giessen slow positron source TEPOS will be discussed. The measured cross section for inner-shell ionization by positron impact decreases more rapidly towards threshold compared to electron impact. This behaviour is confirmed by theoretical calculations performed in the plane wave Born approximation which include an electron exchange term and take the deceleration or acceleration of the incident positron or electron, respectively, in the target nuclear field into account. (orig.)