A Coherent positron beam for reflection high-energy positron diffraction

Kawasuso, Atsuo; Ishimoto, Takayuki*; Maekawa, Masaki; Fukaya, Yuki   ; Hayashi, Kazuhiko; Ichimiya, Ayahiko

A 10 keV positron beam has been developed using coaxially symmetric electromagnetic lenses for reflection high-energy positron diffraction (RHEPD) experiments. The beam brightness is 10 e/sec/cm/rad/V which is comparable to that obtained using brightness enhancement technique. The beam parallel and normal coherence lengths are over 100 and 40 , respectively, which are long enough to observe diffraction patterns associated with large surface super-structures. RHEPD patterns from a Si(111)-(77) reconstructed surface have been successfully observed with a much better quality than previously reported.