Isolated neutron stars undergoing non-radial oscillations are expected to emit gravitational waves in the kilohertz frequency range. To date, radio astronomers have located about 1,300 pulsars, and can estimate that there are about 2×108 neutron stars in the galaxy. Many of these are surely old and cold enough that their interiors will contain matter in the superfluid or superconducting state. In fact, the so-called glitch phenomenon in pulsars (a sudden spin-up of the pulsar's crust) is best described by (...) assuming the presence of superfluid neutrons and superconducting protons in the inner crusts and cores of the pulsars. Recently there has been much progress on modelling the dynamics of superfluid neutron stars in both the Newtonian and general relativistic regimes. We will discuss some of the main results of this recent work, perhaps the most important being that superfluidity should affect the gravitational waves from neutron stars (emitted, for instance, during a glitch) by modifying both the rotational properties of the background star and the modes of oscillation of the perturbed configuration. Finally, we present an analysis of the so-called zero-frequency subspace (i.e., the space of time-independent perturbations) and determine that it is spanned by two sets of polar (or spheroidal) and two sets of axial (or toroidal) degenerate perturbations for the general relativistic system. As in the Newtonian case, the polar perturbations are the g-modes which are missing from the pulsation spectrum of a non-rotating configuration, and the axial perturbations should lead to two sets of r-modes when the degeneracy of the frequencies is broken by having the background rotate. (shrink)

Neutron matter-wave optics provides the basis for new quantum experiments and a step towards applications of quantum phenomena. Most experiments have been performed with a perfect crystal neutron interferometer where widely separated coherent beams can be manipulated individually. Various geometric phases have been measured and their robustness against fluctuation effects has been proven, which may become a useful property for advanced quantum communication. Quantum contextuality for single particle systems shows that quantum correlations are to some extent more demanding (...) than classical ones. In this case entanglement between external and internal degrees of freedom offers new insights into basic laws of quantum physics. Non-contextuality hidden variable theories can be rejected by arguments based on the Kochen-Specker theorem. (shrink)

An experimental apparatus based on neutron interferometry is is presented which can in principle decide the question whether the empty waves of de Broglie really exist or not.

We compare a “Mach-Zehnder interferometer in time” for cold neutrons with its well-known spatial counterpart and demonstrate the intimate connection between space and time for both setups. Further, we outline a combined space-time interferometer, which coherently splits a wavepacket in longitudinal and lateral direction. On the way towards time interferometry “neutron computer holography” seems to be an attractive application. It allows the three-dimensional reconstruction of an object from the scattered intensity, but in contrast to holography with light, there is (...) no need for a reference wave. On the other hand, the possible resolution is worse than in the light case. (shrink)

The first nuclear engineers emerged from the Manhattan Project in the USA, UK and Canada, but remained hidden behind security for a further decade. Cosseted and cloistered by their governments, they worked to explore applications of atomic energy at a handful of national labs. This unique bottom-up history traces how the identities of these unusually voiceless experts - forming a uniquely state-managed discipline - were shaped in the context of pre-war nuclear physics, wartime industrial management, post-war politics and utopian energy (...) programmes. Even after their eventual emergence at universities and companies, nuclear workers carried the enduring legacy of their origins. Their shared experiences shaped not only their identities, but our collective memories of the late twentieth century. And as illustrated by the Fukushima accident seven decades after the Manhattan project began, this book explains why they are still seen conflictingly as selfless heroes or as mistrusted guardians of a malevolent genie. (shrink)

A brief history of Neutron Interferometry is presented, from a personal perspective. Comments and a message from Professor Sam Werner are included.

The ArgumentEinstein's mass-energy relationship was not confirmed experimentally until 1933 when Bainbridge showed that the Cockcroft-Walton experiment afforded a test of it. Earlier, however, it had been used constantly in the analysis of nuclear reactions, as can be seen in those involved in the determination of the mass of the neutron. Chadwick in 1932 was convinced that the neutron mass was about 1.0067 amu (atomic mass units), indicating that the neutron was a proton-electron compound, since that figure (...) was less than the sum of the proton and electron masses. Chadwick's value was challenged in 1933 by Lawrence, who proposed a much lower value of 1.0006 amu, and by Curie and Joliot, who proposed a much higher value of 1.011 amu.Much controversy ensued; eventually, Chadwick and Goldhaber showed in 1934 that the neutron mass was about 1.0080 amu, greater than the sum of the proton and electron masses, proving that the neutron was a new elementary particle (which could decay spontaneously), and providing conclusive experimental support for excluding electrons from the nucleus. These results remained unchanged with further refinements in the last decimal place, the entire pursuit of which provided still further vindication of Einstein's massenergy relationship. (shrink)

ABSTRACT This essay focuses on the history of one of the “atomic patents.” The patent, which described a process to slow down neutrons in nuclear reactions, was the result of experimental research conducted in the 1930s by Enrico Fermi and his group at the Institute of Physics, University of Rome. The value of the patented process became clear during World War II, as it was involved in most of the military and industrial applications of atomic energy. This ignited a controversy (...) between Fermi and U.S. government representatives over royalties to be paid for use of the process during and after the war. The controversy sheds new light on the role that the management of patents played in the context of the Manhattan Project and in the postwar U.S. nuclear program, encompassing issues of power and economic influence in the relationship between scientists, the military, and public administrators. The invention covered by Patent No. 2,206,634 covers the basic process used in the research and development leading up the production of atomic energy and the production of the atomic bomb. Such invention is of continuing importance in the production of fissionable materials and atomic weapons. The Chairman: So Jones might make the greatest invention in the field and be deprived of any award for it? Captain Lavender: If he did not want to accept the award that was offered to him. (shrink)

The wave-particle dualism becomes very obvious in matter wave interference experiments. Neutron interferometers based on wave front and amplitude division have been developed in the past. Most experiments have been performed with the perfect crystal neutron interferometer, which provides widely separated coherent beams allowing new experiments in the field of fundamental, nuclear, and solid-state physics. A nondispersive sample arrangement and the difference of stochastic and deterministic absorption have been investigated. In case of a deterministic absorption process the attenuation (...) of the interference pattern is proportional to the beam attenuation, whereas in case of stochastic absorption it is proportional to the square root of the attenuation. This permits the formulation of Bell-like inequalities which will be discussed in detail. The verification of the4π symmetry of spinors and of the quantum mechanical spin-superposition experiment on a macroscopic scale are typical examples of interferometry in spin space. These experiments were continued with two resonance coils in the beams, where the results showed that coherence persists, even if an energy exchange between the neutron and the resonator system occurs with certainty. A quantum beat effect was observed when slightly different resonance frequencies were applied to both beams. In this case, the extremely high energy sensitivity of2.7×10 −19 eV was achieved. This effect can be interpreted as a magnetic Josephson-effect analog. Phase echo systems and experiments with pulsed beams show how interference phenomena can be made visible by a proper beam handling inside and behind the interferometer. All the results obtained until now are in agreement with the formalism of quantum mechanics but stimulate the discussion about the interpretation of this basic theory. (shrink)

"Elements of Neutron Interaction Theory" is a first-year textbook for graduate students in nuclear engineering, dealing with the interactions of neutrons, photons, and charged particles with nuclei, atoms, and electrons. The aim of the book is to present, as simply as possible, those aspects of neutron interaction theory which follow directly from conservation laws and elementary quantum mechanics. It is intended to be understood by anyone who has obtained the equivalent of a bachelor's degree in physics, chemistry, or (...) one of the engineering disciplines. No mathematical background beyond differential equations and elementary vector analysis and no physics background beyond elementary modern physics is assumed. (shrink)

This column is about the heaviest neutron star ever observed, an object that produces the largest gravitational fields ever directly measured. This discovery by X-ray astronomers was reported at the Spring Meeting of the American Physical Society, held April-1998 in Columbus, Ohio. As will be discussed below, the very large mass of the neutron star has important implications for our understanding of the strong nuclear force at very large densities.

Initially Einstein, Podolsky, and Rosen (EPR) and later Bell shed light on the non-local properties exhibited by subsystems in quantum mechanics. Separately, Kochen and Specker analyzed sets of measurements of compatible observables and found that a consistent coexistence of these results is impossible, i.e., quantum indefiniteness of measurement results. As a consequence, quantum contextuality, a more general concept compared to non-locality, leads to striking phenomena predicted by quantum theory. Here, we report neutron interferometric experiments which investigate entangled states in (...) a single-particle system: entanglement is, in this case, achieved not between particles, but between degrees of freedom i.e., between spin, path, and energy degrees of freedom. Appropriate combinations of the spin analysis and the position of the phase shifter in the interferometer allow an experimental verification of the violation of a Bell-like inequality. In addition, state tomography, tomographic analysis of the density matrix of a quantum system, and Kochen-Specker-like phenomena are presented to characterize neutrons’ entangled states and their peculiarity. Furthermore, a coherent energy manipulation scheme is accomplished with a radio-frequency (RF) spin-flipper. This scheme allows the (total) energy degree of freedom to be entangled: the remarkable behavior of a triply entangled GHZ-like state is demonstrated. (shrink)