Casimir-Polder interaction of neutrons with metal or dielectric surfaces

We predict a repulsive Casimir-Polder-type dispersion interaction between a single neutron and a metal or dielectric surface. Our model scenario assumes a single neutron subject to an external magnetic field. Due to its intrinsic magnetic moment, the neutron then forms a magnetisable two-level system which can exchange virtual photons with a nearby surface. The resulting dispersion interaction between a purely magnetic object (neutron) and a purely electric one (surface) is found to be repulsive. Its magnitude is considerably smaller than than the standard atom-surface Casimir-Polder force due to the magnetic nature of the interaction and the smallness of the electron-to-neutron mass ratio. Nevertheless, we show that it can be comparable to the gravitational potential of the same surface.Comment: 5 pages, 3 figure

Interferenz Experiment mit sehr kalten Neutronen: Eine Machbarkeitsstudie von Lloyd’s Spiegel am Institut Laue-Langevin

Abweichender Titel nach Übersetzung der Verfasserin/des VerfassersLloyds Spiegel wie er von Humphrey Lloyd 1831 beschrieben wurde ist ein vielseitiges optisches Instrument. Heutzutage findet es vor allem in den Gebieten der Unterwasserakustik und der optischen Oberflächenanalyse Verwendung. In dieser Arbeit wird die Machbarkeit einer Umsetzung von Lloyds Spiegel mit sehr kalten Neutronen untersucht. Aufgrund offener Fragen wie z.B. der scheinbaren Inkompatibilität von Allgemeiner Relativitätstheorie und Quantenmechanik, dem Phänomen der Dunklen Materie und der Dunklen Energie, und der Antimaterie-Materie Asymmetrie, werden neuartige Experimente benötigt, die Einblick geben in bisher nicht untersuchte Parameterbereiche. Eine Umsetzung von Lloyds Spiegel mit sehr kalten Neutronen könnte einen solchen Einblick eröffnen, wie in Pokotilovski (2011) und in Pokotilovski (2013b) vorgeschlagen. In dieser Arbeit wird das quantenmechanische Verhalten von Neutronen untersucht, die eine Region mit einem vertikal ausgerichteten Spiegel durchqueren, um Bedingungen einer experimentellen Umsetzung abzuleiten. Darauf aufbauend wird eine Simulation des erwarteten Interferogram vorgestellt, um die benötigte Messzeit abzuschätzen. In Übereinstimmung mit den theoretischen Überlegungen wird ein NeutronenoptikAufbau,wieeramInstitut Laue-Langevin umgesetzt wurde und welcher den Neutronenstrahl für das Interferometer aufbereitet, vorgestellt. Abschließend werden Entwicklungen einer ortsaufgelösten Detektion von Neutronen mithilfe von Bor-beschichteten CR39 Plättchen präsentiert, wie sie für dieses Experiment benötigt werden.The Lloyds mirror as described by Humphrey Lloyd in 1831 is a simple but powerful instrument in optical studies. Todays foremost applications are the optical inspection of flat surfaces and as a tool in underwater acoustics. This thesis discusses and investigates the feasibility of an implementation of Lloyds mirror with very-cold neutrons. Due to current open questions in physics as for example the apparent incompatibility of general relativity and quantum mechanics, the phenomenon of dark energy and dark matter, and matter antimatter asymmetry, novel experimental insights into yet unexplored parameter spaces are needed. Lloyds mirror realized with matter wave especially very-cold neutrons could offer such new insights as proposed in Pokotilovski (2011) and in Pokotilovski (2013b). In this thesis the quantum mechanical behavior of neutrons that transverse a region in front of a mirror is studied theoretically to infer the requirements of an experimental realization. It is concluded with a simulation of the expected interferogram to estimate the required measurement time. In accordance with the theoretical studies, the results of an experimental realization of the required beam preparation section at the very-cold neutron beam at the PF2 at the Institut Laue-Langevin are presented. Finally, a spatial detection mechanism using boron-based CR39 imaging plates adapted to the needs of this experiment is demonstrated.25

Ultracold neutron storage in a bottle coated with the fluoropolymer CYTOP

The fluoropolymer CYTOP was investigated in order to evaluate its suitability as a coating material for ultracold neutron (UCN) storage vessels. Using neutron reflectometry on CYTOP-coated silicon wafers, its neutron optical potential was measured to be 115.2(2) neV. UCN storage measurements were carried out in a 3.8 l CYTOP-coated aluminum bottle, in which the storage time constant was found to increase from 311(9) s at room temperature to 564(7) s slightly above 10 K. By combining experimental storage data with simulations of the UCN source, the neutron loss factor of CYTOP is estimated to decrease from 1.1(1)$$\times 10^{-4}$$ to 2.7(2)$$\times 10^{-5}$$ at these temperatures, respectively. These results are of particular importance to the next-generation superthermal UCN source SuperSUN, currently under construction at the Institut Laue-Langevin, for which CYTOP is a possible top-surface coating in the UCN production volume

Testing gravity at short distances: Gravity Resonance Spectroscopy with qBounce

Neutrons are the ideal probes to test gravity at short distances – electrically neutral and only hardly polarizable. Furthermore, very slow, so-called ultracold neutrons form bound quantum states in the gravity potential of the Earth. This allows combining gravity experiments at short distances with powerful resonance spectroscopy techniques, as well as tests of the interplay between gravity and quantum mechanics. In the last decade, the qBounce collaboration has been performing several measurement campaigns at the ultracold and very cold neutron facility PF2 at the Institut Laue-Langevin. A new spectroscopy technique, Gravity Resonance Spectroscopy, was developed. The results were applied to test various Dark Energy and Dark Matter scenarios in the lab, like Axions, Chameleons and Symmetrons. This article reviews Gravity Resonance Spectroscopy, explains its key technology and summarizes the results obtained during the past decade

Testing gravity at short distances: Gravity Resonance Spectroscopy with qBounce

International audienceNeutrons are the ideal probes to test gravity at short distances – electrically neutral and only hardly polarizable. Furthermore, very slow, so-called ultracold neutrons form bound quantum states in the gravity potential of the Earth. This allows combining gravity experiments at short distances with powerful resonance spectroscopy techniques, as well as tests of the interplay between gravity and quantum mechanics. In the last decade, the qBounce collaboration has been performing several measurement campaigns at the ultracold and very cold neutron facility PF2 at the Institut Laue-Langevin. A new spectroscopy technique, Gravity Resonance Spectroscopy, was developed. The results were applied to test various Dark Energy and Dark Matter scenarios in the lab, like Axions, Chameleons and Symmetrons. This article reviews Gravity Resonance Spectroscopy, explains its key technology and summarizes the results obtained during the past decade

The PanEDM neutron electric dipole moment experiment at the ILL

The neutron's permanent electric dipole moment dn is constrained to below 3 × 10−26e cm (90% C.L.) [1, 2], by experiments using ultracold neutrons (UCN). We plan to improve this limit by an order of magnitude or more with PanEDM, the first experiment exploiting the ILL's new UCN source SuperSUN. SuperSUN is expected to provide a high density of UCN with energies below 80 neV, implying extended statistical reach with respect to existing sources, for experiments that rely on long storage or spin-precession times. Systematic errors in PanEDM are strongly suppressed by passive magnetic shielding, with magnetic field and gradient drifts at the single fT level. A holding-field homogeneity on the order of 10−4 is achieved in low residual fields, via a high static damping factor and built-in coil system. No comagnetometer is needed for the first order-of-magnitude improvement in dn, thanks to high magnetic stability and an assortment of sensors outside the UCN storage volumes. PanEDM will be commissioned and upgraded in parallel with SuperSUN, to take full advantage of the source's output in each phase. Commissioning is ongoing in 2019, and a new limit in the mid 10−27e cm range should be possible with two full reactor cycles of data in the commissioned apparatus

The PanEDM Neutron Electric Dipole Moment Experiment at the ILL

International audienceThe neutron's permanent electric dipole moment dn is constrained to below 3 × 10−26e cm (90% C.L.) [1, 2], by experiments using ultracold neutrons (UCN). We plan to improve this limit by an order of magnitude or more with PanEDM, the first experiment exploiting the ILL's new UCN source SuperSUN. SuperSUN is expected to provide a high density of UCN with energies below 80 neV, implying extended statistical reach with respect to existing sources, for experiments that rely on long storage or spin-precession times. Systematic errors in PanEDM are strongly suppressed by passive magnetic shielding, with magnetic field and gradient drifts at the single fT level. A holding-field homogeneity on the order of 10−4 is achieved in low residual fields, via a high static damping factor and built-in coil system. No comagnetometer is needed for the first order-of-magnitude improvement in dn, thanks to high magnetic stability and an assortment of sensors outside the UCN storage volumes. PanEDM will be commissioned and upgraded in parallel with SuperSUN, to take full advantage of the source's output in each phase. Commissioning is ongoing in 2019, and a new limit in the mid 10−27e cm range should be possible with two full reactor cycles of data in the commissioned apparatus

Acoustic Rabi oscillations between gravitational quantum states and impact on symmetron dark energy

International audienceThe standard model of cosmology provides a robust description of the evolution of the Universe. Nevertheless, the small magnitude of the vacuum energy is troubling from a theoretical point of view 9 . An appealing resolution to this problem is to introduce additional scalar fields. However, these have so far escaped experimental detection, suggesting some kind of screening mechanism may be at play. Although extensive exclusion regions in parameter space have been established for one screening candidate—chameleon fields 10$^{,}$17 —another natural screening mechanism based on spontaneous symmetry breaking has also been proposed, in the form of symmetrons 11 . Such fields would change the energy of quantum states of ultracold neutrons in the gravitational potential of the Earth. Here, we demonstrate a spectroscopic approach based on the Rabi resonance method that probes these quantum states with a resolution of ΔE =2 × 10$^{−15}$ eV. This allows us to exclude the symmetron as the origin of dark energy for a large volume of the three-dimensional parameter space