Structure of Heavy Ice Formed by Rapid Cooling of Heavy Water to a Temperature of 77 or 15 K

High-resolution measurements of a cold-neutron total cross-section in heavy ice were carried out by the combined use of a time-of-flight technique with a solid-mesitylene moderator for cold-neutron production. A careful study of several sharp peaks on the cross-section data reveals the presence of a high-degree of structural order in a direction parallel to, say, the c-axis for a hexagonal ice crystal. An attempt is made to estimate coherent elastic structure factors for heavy ice at 77 and 15 K on the basis of the observed cross-section data. It turns out that the structure factors thus obtained consist of a family of sharp peaks having both a monotonous rise with an increasing momentum transfer, and an abrupt fall at a certain value of the momentum transfer. The results of the present study suggest that information about the degree of structural ordering in the heavy ice may be obtained directly from the slope of the cold-neutron total cross-section curve

Synchronized UCN storage for superthermal SD_2 converter

We propose to experimentally verify a principle of a substantially new type of compact source for Ultra Cold Neutrons (UCN) in support of designing a practical source dedicated to researches on fundamental particle physics in the 21^ century such as the electro-weak interaction, the new models beyond the standard model, the gravity, and so on with improved sensitivity. The novelty of this UCN source is to efficiently accumulate UCN emitted in a pulsed scheme from a surface of a superthermal converter, solid deuterium (SD_2) by using a large kick-out velocity (～5 m/s) of UCN from the SD_2 surface and a moving membrane synchronized with pulsed proton beam. This will enable us to make a much more compact UCN source with a performance higher than others ever constructed. We perform experimental verification of the proposed concept by making use of a prototype assembly consisting of the SD_2 converter, a moving membrane, a compact UCN storage vessel and a UCN detector with pulsed proton beam. As a promising pre-moderator, solid mesitylene (C_6H_3(CH_3)_3) operated at low temperatures (≦ 20 K) is examined on the suitability for a pre-moderator satisfying a time structure condition required for the present method of synchronized UCN storage. This test will be done by observing the time dependence of the intensity and the energy spectra of cold neutrons from solid mesitylene with the TOF method. For this purpose, we will observe the time dependences of energy spectra for produced cold neutrons emerging out of the mesitylene pre-moderator by a TOF method

The neutron and its role in cosmology and particle physics

Experiments with cold and ultracold neutrons have reached a level of precision such that problems far beyond the scale of the present Standard Model of particle physics become accessible to experimental investigation. Due to the close links between particle physics and cosmology, these studies also permit a deep look into the very first instances of our universe. First addressed in this article, both in theory and experiment, is the problem of baryogenesis ... The question how baryogenesis could have happened is open to experimental tests, and it turns out that this problem can be curbed by the very stringent limits on an electric dipole moment of the neutron, a quantity that also has deep implications for particle physics. Then we discuss the recent spectacular observation of neutron quantization in the earth's gravitational field and of resonance transitions between such gravitational energy states. These measurements, together with new evaluations of neutron scattering data, set new constraints on deviations from Newton's gravitational law at the picometer scale. Such deviations are predicted in modern theories with extra-dimensions that propose unification of the Planck scale with the scale of the Standard Model ... Another main topic is the weak-interaction parameters in various fields of physics and astrophysics that must all be derived from measured neutron decay data. Up to now, about 10 different neutron decay observables have been measured, much more than needed in the electroweak Standard Model. This allows various precise tests for new physics beyond the Standard Model, competing with or surpassing similar tests at high-energy. The review ends with a discussion of neutron and nuclear data required in the synthesis of the elements during the "first three minutes" and later on in stellar nucleosynthesis.Comment: 91 pages, 30 figures, accepted by Reviews of Modern Physic

Handbook of neutron optics

Written by authors with an international reputation, acknowledged expertise and teaching experience, this is the most up-to-date resource on the field. The text is clearly structured throughout so as to be readily accessible, and begins by looking at scattering of a scalar particle by one-dimensional systems. The second section deals with the scattering of neutrons with spin in one-dimensional potentials, while the third treats dynamical diffraction in three-dimensional periodic media. The final two sections conclude with incoherent and small angle scattering, and some problems of quantum mec