6533b86efe1ef96bd12cc6d5

RESEARCH PRODUCT

Positronium spectroscopy at a LINAC-based slow positron source

subject

description

The slow positron facility TEPOS at the Giessen electron LINAC (36 MeV, 120 µA) has been used to produce an intense beam of moderated positrons which is magnetically guided over a distance of 9 m. At a transportation energy of 100 eV about 106 slow e+/s could be extracted out of the magnetic field (0.01 T) and have been electrostatically focussed inside a microwave guide. A small fraction of the positrons form positronium in the excited staten=2. The spontaneous emission of Lyman-α photons (λ=243 nm) from the 2P-states is observed by a photomultiplier. Microwave induced fine-structure transitions 23S1©23P2,1,0 have been observed at 8617(2), 13010(3) and 18494(2) MHz by an increase of the Lyman-α counting rate. The present errors take into consideration only statistical contributions; systematic errors in the same order of magnitude may originate from frequency dependent variations of the microwave power. The observed linewidth exceeds the natural linewidth of 50 MHz by Doppler-effect and power broadening. Values around 100 MHz could be reached at the lowest applied power levels.