Perfect Crystal Neutron Interferometry Research Articles

Three Phase-Grating Moiré Neutron Interferometer for Large Interferometer Area Applications.

We demonstrate a three phase-grating moiré neutron interferometer in a highly intense neutron beam as a robust candidate for large area interferometry applications and for the characterization of materials. This novel far-field moiré technique allows for broad wavelength acceptance and relaxed requirements related to fabrication and alignment, thus circumventing the main obstacles associated with perfect crystal neutron interferometry. We observed interference fringes with an interferometer length of 4 m and examined the effects of an aluminum 6061 alloy sample on the coherence of the system. Experiments to measure the autocorrelation length of samples and the universal gravitational constant are proposed and discussed.

Decoupling of a neutron interferometer from temperature gradients.

Neutron interferometry enables precision measurements that are typically operated within elaborate, multi-layered facilities which provide substantial shielding from environmental noise. These facilities are necessary to maintain the coherence requirements in a perfect crystal neutron interferometer which is extremely sensitive to local environmental conditions such as temperature gradients across the interferometer, external vibrations, and acoustic waves. The ease of operation and breadth of applications of perfect crystal neutron interferometry would greatly benefit from a mode of operation which relaxes these stringent isolation requirements. Here, the INDEX Collaboration and National Institute of Standards and Technology demonstrates the functionality of a neutron interferometer in vacuum and characterize the use of a compact vacuum chamber enclosure as a means to isolate the interferometer from spatial temperature gradients and time-dependent temperature fluctuations. The vacuum chamber is found to have no depreciable effect on the performance of the interferometer (contrast) while improving system stability, thereby showing that it is feasible to replace large temperature isolation and control systems with a compact vacuum enclosure for perfect crystal neutron interferometry.

Perfect crystal neutron interferometry and tensorial neutron tomography

Perfect crystal neutron interferometry may be applied in the tomographic study of magnetic structures in ferromagnetic solids. As a result of such investigations one can expect a complete 3D representation of the magnetisation distribution inside the sample. While the concept is comparable to absorption and phase contrast tomography, the tensorial technique involves 3D polarisation control and specific reconstruction algorithms due to path-ordering effects contained in the measured projections. We present the current status of related methodical development and outline the experimental and technical requirements essential for the application of this method. A 2D reconstruction example is given for a standardised simulated test sample using a reconstruction algorithm based on elimination of path-ordering effects by measurements at different neutron velocities.

Neutron interferometric reconstruction of magnetic domain structures

We propose a new method of investigating domain structures in ferromagnetic solids which combines neutron depolarization concepts with perfect crystal neutron interferometry.

Interferometric phase contrast tomography

The recently proposed implementation of the tensorial magnetic tomography concept into perfect crystal neutron interferometry is considered. The mathematical relations between the observables of neutron interference and standard depolarization experiments are given.

Quantum optical neutron beam tailoring

Abstract Perfect crystal neutron interferometry has provided the basis for the realization of many basic experiments for testing quantum mechanics with massive particles. The following quantum effects have been verified: 4π-symmetry of spinors, spin-superposition, gravity-induced quantum interference effects, the Aharonov-Casher effect, the magnetic Josephson effects, the scalar Aharonov-Bohm effect etc. More recently, steps towards neutron quantum optics have been undertaken. Measurements have dealt with the coherence properties of the neutron beam, the photon exchange between the neutron and various electromagnetic fields, the particle number-phase uncertainty, squeezing phenomena, and the Wigner-functional behavior of a neutron system. These achievements opened the field of direct Fourier spectroscopy which brings a direct access to the space and time dependent correlation functions which describe condensed matter. Various perspectives for further experiments in the field of fundamental and condensed m...

Measurement and characterization of the three-dimensional coherence function in neutron interferometry.

The spatial coherence function in all three orthogonal directions has been measured by means of perfect crystal neutron interferometry. It has been demonstrated that the coherence function is given by the Fourier transform of the related momentum distribution, which in turn is determined by the collimation and monochromatization of the beam incident upon and traversing the interferometer. Thus, a measurement of the coherence function can replace a measurement of the momentum distribution in certain cases. Retrieval of the coherence can be accomplished by phase echo and/or postselection methods. A complete retrieval of the coherence is impossible in principle due to unavoidable loss factors.

Neutron interferometric tests of quantum mechanics

Abstract Since the invention of perfect crystal neutron interferometry this technique has become an important tool in the realization of many textbook experiments in quantum mechanics. Widely separated coherent beams of thermal neutrons are produced and superposed by dynamical Bragg diffraction from a properly shaped perfect crystal. The observed interference patterns show the characteristic coherence properties of matter waves which arc influenced by the individual particle and by the properties of the experimental device. The verification of the 4π-periodicity of spinor wavefunctions and the realization of thc spin-superposition experiment on B macroscopic scale has become feasible by this technique. A new kind of a quantum beat effect with an energy sensitivity of 2.7 × 20−-19 eV has been observed in a double coil resonance experiment. The influence of gravity and of the Earth's rotation on the wavefunction become visible at a level of an elementary particle with non-zero mass. All the results are in agreement with the formulation of quantum mechanics but, nevertheless, they stimulate discussion about its interpretation. The particle-wave dualism becomes obvious on a macroscopic scale and with a beam of massive particles.

Time-dependent neutron interferometry: Evidence against wave packet collapse?

If the energy-absorbing radio-frequency spin-flipping device used in perfect crystal neutron interferometry is an intermediate measuring device, then the experimental results contradict the associated wave packet collapse and support the real existence of the de Broglie pilot waves in both arms while the neutron travels in only one.

Features of advanced neutron optical devices

The features of neutron interferometry and neutron magnetic resonance systems are described. The existence of widely separated coherent beams in perfect crystal neutron interferometry permits a great variety of experiments with matter waves in the field of basic quantum mechanics. For example, the phase of the spatial and spinor wave functions can be measured. Recent results on the 4π-symmetry of a spinor and the first direct verification of the spin-superposition law are discussed. Multiple Laue reflections are used to achieve an angular resolution up to 0.001 sec of arc, which permits the observation of wide slit diffraction effects. Neutron magnetic resonance systems allow a uniform energy shift of the neutrons and may be an important component in the future for the realization of systems for dynamical neutron polarization, monochromatization and focusing of neutrons into certain energy, space, angle or time intervals. Additional advantages exist for pulsed sources, very slow neutrons and highly monochromatic beams.