Neutron multilayers structures for fundamental experiments in UCN optics Alexander I.Franka*, Sergey V. Balashov", Victor I.Bodflarchuka, lija V.Bondekoa, Alberto CimmiflOc, Peter Geltenbortd, Peter Høghøj', Tony Kleinc, Dmitry A.Korneeva, Alexander V.KOZ1OVa, Sergey V.Masalovich" aFr Laboratory ofNeutron Physics, Joint Institute for Nuclear Research, 141980, Dubna, Russia b Russian Research Center "Kurchatov Institute", 123 1 82, Moscow, Russia C School of Physics, The University of Melbourne, Melbourne, Australia. d Institut Laue-Langevin, Grenoble, France ABSTRACT The experience in manufacturing and testing of neutron multilayer structures, interference filters, is described. Construction of a gravity UCN spectrometer based on the use of such devices is also reported. Some results of the test experiment of the UCN dispersion law performed with such a spectrometer are presented. Among them are the resonant mode mixing effect due to scattering by the roughness. Some possibilities of new experiments based on a similar method are investigated. Keywords: UCN, multilayers, interference filter, resonant transmission, neutron spectrometry, mode mixing, dispersion law, quasi-energy. 1. INTRODUCTION It is well known that the energy of ultra cold neutrons (UCN) is, by definition of UCN, of the same order as the effective potential of the neutron interaction with the medium, U=—--pb' (1) where m is the neutron mass, p is the density of nuclei and b is the coherent scattering length. The typical value of the potential, U, is of the order of I O7eV. Thus UCN can be stored in matter traps which are widely used in a number of fundamental experiments'3. At the same time, due to the relatively large wavelength and small energy, UCN are the unique object for a number quantum experiments not related to storing. One of such possibilities arises from impressive progress in manufacturing of different multilayer structures which are widely used now in applied neutron and X-rays optics. This technique permits the design and preparation of an arbitrary one-dimensional potential structure, U(z), by depositing a number of thin films with different scattering amplitude density, pb. The more impressive example of such quantum multilayer systems is so-called Neutron Interference Filter which is the neutron analog of the optical Fabry-Perot interferometer. In the present paper we intend to report the experience in manufacturing of interference filters as well as some possibilities of its application in different neutron optical experiments. Some of them are in progress now and others only proposed. A. Seregin first proposed in 1977 to prepare a three-layer structure with a potential which has a form of two humped barrier4 (see fig.!). If the thickness of the inner layer is not very small, the well width is enough for the formation of the *Correspondence: Email: franknf.jinr.ru Part of the SPIE Conference on EUV, X-Ray, and Neutron Optics and Sources Denver, Colorado • July 1999 360 SPIE Vol. 3767 • 0277-786X/99/$1 0.00 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 05/15/2014 Terms of Use: http://spiedl.org/terms