Effect of accelerated matter in neutron optics
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CLEI Experiment
Effect of Accelerated Matter in Neutron Optics A. I. Frank* , P. Geltenbort1) , M. Jentschel1) , D. V. Kustov2) , G. V. Kulin, V. G. Nosov3) , and A. N. Strepetov3) Frank Laboratory of Neutron Optics, Joint Institute for Nuclear Research, Dubna, Moscow oblast, 141980 Russia Received February 12, 2008
Abstract—Results of experiments aimed at observing the change in the energy of a neutron traversing an accelerated refractive sample are reported. The experiments were performed with ultracold neutrons, the energy transfer in these experiments being ±(2−6) × 10−10 eV. The results suggest the existence of the effect and agree with theoretical predictions to a precision higher than 10%. A similar effect was previously predicted for the change in the frequency of an electromagnetic wave traversing an accelerated dielectric slab. In all probability, the effect has a very general nature, but it is presently observed only in neutron optics. PACS numbers: 03.75.Be DOI: 10.1134/S1063778808100025
1. INTRODUCTION Throughout the history of the development of neutron optics, phenomena studied in it were as a rule known in ordinary optics. The line of research into neutron interaction with moving matter was not an exception in this respect. It was initiated in the late 1970s by the study of Horn and Zeilinger [1], where it was indicated that a translational movement of a sample is expected to cause a change in the phase of a transmitted wave. On the basis of the general law of neutron-wave dispersion in matter [2], ki2 = k2 − 4πρb2 ,
b = const,
(1)
where ρ is the spatial density of nuclear scatterers in matter; b is the volume-averaged coherent scattering length associated with them; and ki and k0 are the neutron wave numbers in a medium and a vacuum, respectively, it was concluded in [1] that this change in the phase may only be due to the movement of the boundaries of matter. By analogy with optics, neutron experiments that involved moving matter were called neutron Fizeau experiments. Despite an apparent analogy, phenomena accompanying the propagation of electromagnetic and neutron waves through moving 1)
Institute Laue–Langevin, Grenoble, France. Joint Institute for Nuclear Research, Dubna, Moscow oblast, 141980 Russia; Institute for Nuclear Research, National Academy of Sciences of Ukraine, pr. Nauki 47, 03680 Kyiv, Ukraine. 3) Russian Research Center Kurchatov Institute, pl. Kurchatova 1, 123182 Russia. * E-mail: [email protected] 2)
matter are substantially different. The distinctions in question were discussed in [3]. The shift of the electromagnetic-wave phase in experiments of Fizeau type is due to so-called Fresnel drag of the wave being considered by moving matter because of the relativistic character of the transformation of velocities in going over to the reference frame where the matter is at rest. Thus, the phase-shift effect in optical Fizeau experiments is of a volume character, but, in neutron experiments, the effect is only due to the movement of the boundaries of a sample and not to the movement o
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