A coherent positron beam for reflection high-energy positron diffraction.

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 ∼107 e+/s/cm2/rad2/V which is comparable to that obtained using brightness enhancement technique. The beam parallel and normal coherence lengths are over 100 and 40 Å, respectively, which are long enough to observe diffraction patterns associated with large surface super-structures. RHEPD patterns from a Si(111)-(7×7) reconstructed surface have been successfully observed with a much better quality than previously reported. [ABSTRACT FROM AUTHOR]