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Q: Fachverband Quantenoptik und Photonik

Q 32: Materiewellenoptik

Q 32.3: Talk

Wednesday, March 4, 2009, 14:30–14:45, Audi-B

Focussing a Helium atom beam by reflection from a concave surface — •Christian Schewe, Bum Suk Zhao, Gerard Meijer, and Wieland Schöllkopf — Fritz-Haber-Institut, Berlin

Results of 1-dimensional focussing of a Helium-atom beam reflected from a concave, cylindrical surface are presented. The atomic beam is created by a supersonic expansion and collimated by a skimmer and two slits, variable in size (5-20 µm). For grazing incident angles of a few milliradian the beam is coherently reflected by quantum reflection [1]. Beam profiles at the focus are measured by cutting off the intensity by scanning a knife edge with a piezo (analogy to waist measurement by a razor blade in laser optics). The width of the focus is limited by the source size, by spherical aberration and by diffraction effects. We tune the deBroglie-wavelength by changing the temperature of the atom beam source to see how diffraction influences the focus’ width and shape. The smallest focus achieved so far is 1.0±0.1 µm.

[1] Zhao et al., Phys. Rev. A, 78 010902(R), (2008).