A.G. Klein

Schrödinger inviolate: Neutron optical searches for violations of quantum mechanics

Abstract A number of neutron optical experiments carried out over the past decade have searched for possible violations of the Schrodinger equation. Among the hypothetical effects considered were: non-linearities, the effects of quantum gravity and quanternionic forms. The relevant experiments are reviewed along with some new proposals.

Neutron interference by division of wavefront

A novel type of neutron interferometer was constructed and tested employing a split cylindrical zone plate with neutrons of 20 A wavelength. Its performance and relative merits are discussed.

Neutron reflection interferometry : physical principles of surface analysis with phase information

It is shown that the analysis of surface layers by neutron reflection interferometry is considerably enhanced by performing the reflectometry with phase information. We discuss two methods of providing such information. One method involves physically adding an extra reference layer, whose amplitude and phase are known theoretically. The other uses the Lloyds mirror configuration, in which a directly propagating ray that interferes with the reflected ray supplies the phase information. The methods have much in common with holography.

Refractive-index-profile determinations by using Lloyd’s mirage

A method is presented for the experimental determination of refractive-index profiles for planar media of monotonically decreasing refractive index, such as those used for optical waveguides. The technique is based on a generalization of the classical experiment of Lloyds mirror, involving the interference pattern formed by a point source and its mirage, i.e., its reflection in such a graded planar medium.

Novel optics for conditioning neutron beams II: Focusing neutrons with a “Lobster-Eye” optic

Abstract Square-channel capillary, or “Lobster-Eye” arrays, have been shown to be the optimum geometry for array optics. This configuration leads to a novel class of conditioning devices for X-ray and neutron beams. We present the first results of the focusing of neutrons with a lead glass square-channel array. This array designed for soft X-rays performs comparably with neutrons.

Observation of Aharonov–Bohm effects by neutron interferometry

The special and unique techniques of neutron interferometry have been used to observe a number of topological effects. These include the quantum mechanical phase shift of a neutron due to the Earths rotation (the quantum analog of the Michelson–Gale–Pearson experiment with light), the phase shift of a particle carrying a magnetic moment (a neutron) encircling a line charge (the Aharonov–Casher effect) and the scalar Aharonov–Bohm effect, observed with a pulsed magnetic field solenoid and time-of-flight neutron detection. On the occasion of the 50th anniversary of the Aharonov–Bohm paper, we provide an overview of the neutron interferometry technique and a description of these three historic experiments.

Focussing of slow neutrons with cylindrical zone plates

Abstract We report on the successful focussing of a slow neutron beam by means of a cyclindrical Fresnel zone plate.

Fizeau effect for neutrons passing through matter at a nuclear resonance

Abstract We have measured the phase shift of a neutron de Broglie wave induced by the motion of Sm-149 through which the neutron is propagating. This experiment differs from a number of ‘neutron Fizeau’ experiments carried out in recent years. The observed phase shift is caused by the motion of the matter itself, and not by the motion of its boundaries, as was the case with the earlier experiments. In this regard our experiment is a true neutron analog of the famous Fizeau experiment of 1859, where phase shift of the light wave interference pattern was induced by the motion of matter.

Direct measurement of rotation by a laser speckle method

The laser speckle pattern produced by the coherent illumination of a small circular portion of a doubly exposed photograph contains enough information to reveal not only the displacement but also the rotation of a rigidly moving two-dimensional field. The displacement of the field is contained in the resulting parallel speckle fringe spacing in the usual way. The magnitude of the rotation of the field, however, may be determined by measuring the radius of the circular region within which these displacement speckle fringes appear. Photographs and analyses of the resulting speckle patterns are presented. Non-rigid two-dimensional motion and its relation to incompressible fluid flow is also discussed.

Resolving Power of Zone Plates

Abstract The performances of different types of zone plate are analysed and compared. It is shown that, with a modified geometry, the resolution closely matches that of a diffraction-limited lens.