Generation of ultra-short and energetic positron beam with a femtosecond compton light source

A scheme for generation of ultra-short and high-energy positron beam by impinging fs Compton gamma-ray beam on high-Z target is proposed. Our simulation shows that for 10 fs, ≤ 23 MeV Compton gamma-ray beam interacting with centimeter-class lead target, about 4 × 10⁷ positrons/s in the form of sub-100 fs pulses at several MeV can be produced. Such ultra-short and energetic positron beam has some potential for precise detection and diagnostics of microscopic structure, electron momentum distribution and defect state of condensed material, as well as investigating ultrafast dynamics in material and biological structures. (authors)