Nearly all interference experiments which can be done with atoms could be carried out with ions too. Beam splitters, magnifying optics, deflectors and some other useful elements for beam adjusting as well as image recording devices are available for ions. In addition, these composite charged particles interact with electromagnetic potentials. Therefore, aspects of the interaction of scalar- and vector-potentials (Aharonov-Bohm effects) in relation to the inner structure of the particles can be tested with an ion interferometer. An ion biprism interferometer consists of a coherent ion source, a wave front splitter (biprism), electrostatic lenses for magnifying the interference pattern and an image recording device for registration.
The extremely high stability and insensitivity to disturbances of all kinds of a new type of electron interferometer [1] makes it likely that an interferometer for ions with their even shorter wavelengths can be realized. Ion interferometry is a technique at least as promising as atom interferometry since it combines the powerful optics available for charged particles and interferometry with compound particles. As a highly coherent source of protons, positively charged hydrogen molecules He ions we use a specially treated `supertip' [2], cooled down during operation to 77 K or 10 K. The `supertip' is prepared in situ in the interferometer. During preparation its emission pattern is observed on the screen of a channnelplate image intensifier which can be inserted between the ion gun and the interferometer. For details of the preparation method see [3]the work of H. Kraus
The primary interference pattern behind the ion optical biprism is magnified by electrostatic quadrupole lenses, intensified by a channelplate image intensifier and coupled fiberoptically to a cooled slow scan CCD-camera. On-chip integration of single ion and electron events and image processing in a personal computer are provided in order to improve the signal to noise ratio.
F. Hasselbach and M. Nicklaus: `A Sagnac-experiment with electrons: Observation of the rotational phase shift of electron waves in vaccum', Phys. Rev. A 48 (1993), p.143-151.
P.R. Schwoebel and G.R. Hanson: `Beam current stability from localized emission sites in a field ion source', J. Vac. Sci. Technol. B3(1), p.215-219
R. Börret, K. Böhringer and S. Kalbitzer: `Current-voltage characteristics of a gas field ion source with a supertip', J. Phys. D23, p.1271-1277,
F. Hasselbach, H. Kraus, U. Maier: `Development of a bright, highly coherent field ion source', Optik Suppl. 6 (Vol. 100), p.6, (1995)
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