arXiv subjects

Tobias Jenke

Publications and source records attributed to Tobias Jenke.

At least 19 recordsLinked to original sources

arXiv2026

Neutron Interferometers from Stacked Holographic Photopolymer Gratings

Long-wavelength neutron interferometry using discrete optical elements is notoriously challenging due to stringent alignment and stability requirements. Here, we introduce a monolithic double-Laue neutron interferometer fabricated from a stack of commercial Bayfol HX photopolymer films. By recording holographic gratings simultaneously in multiple layers, we create a robust device that is inherently aligned, bypassing traditional stability problems. We demonstrate the device's function by observing the characteristic interference fringes in the diffracted intensity of both light and very cold neutrons. The interferometer is then used to perform in-situ characterization of the neutron beam's spectral profile, demonstrating its utility as a compact spectrometer. Our work establishes stacked holographic gratings as a simple, versatile, and powerful platform for matter-wave interferometry and metrology.

physics.optics↗

arXiv2026

Experimental test of symmetron-field based dark energy model using neutron interferometry

We report phase shift measurements of neutron matter waves propagating in vacuum and low-pressure Argon gas, using a technique developed for neutron interferometric scattering length measurements. The experiment probes additional phase shifts induced by couplings to scalar fields. From the absence of such effects, we set stringent constraints on a scalar symmetron-field, a leading candidate for quintessence dark energy.

hep-ph↗

arXiv2026

Commissioning measurements for a very cold neutron interferometer based on nanodiamond-polymer composite gratings

Over the past decade, holographic nanodiamond-polymer composite gratings have been developed and optimized as high-efficiency diffractive elements for very cold neutrons (VCN), for use as mirrors and beam splitters in a triple-Laue (LLL) interferometer. We report their optical characterization and, crucially, their neutron-optical performance, including diffraction efficiency and angular selectivity under VCN conditions. We further demonstrate their integration into a VCN interferometer. The layout of the interferometer and its first implementation at the beamline are described, highlighting practical considerations for long-term operation. We discuss avenues for performance improvement, in particular grating fabrication refinements. These results establish nanodiamond-polymer composite gratings as viable components for VCN interferometry and pave a way toward precision neutron phase measurements in the very cold regime.

physics.optics↗

arXiv2026

Further search for magnetic-field-induced neutron disappearance in an ultracold neutron beam

We report the results of the second iteration of an experiment searching for neutron-hidden-neutron oscillations in a beam of ultracold neutrons, conducted at the PF2 facility of the Institut Laue Langevin (ILL). Oscillations were tested via neutron disappearance as a function of an applied magnetic field, in the context of a phenomenological two-parameter model assuming zero hidden potentials. The magnetic field was varied in a step-wise manner in order to resonantly enhance the oscillation probability at different mass splittings ($δm$) across a 60--1550 peV range. No evidence for neutron disappearance is observed and conservative limits on the neutron-hidden-neutron oscillation period ($τ_{nn'}$) have been set at 95 % confidence level: $τ_{nn'} > 200$ms for $|δm| \in [60, 400]$ peV and $τ_{nn'} > 100$ ms for $|δm| \in [400, 1550]$ peV

hep-ex↗

arXiv2025

Generalized Boundary Conditions for the qBounce Experiment

Discrepancies between theory and recent qBounce data have prompted renewed scrutiny of how boundary conditions are implemented for ultracold neutrons bouncing above a mirror in Earth's gravity. We apply the theory of self-adjoint extensions to the linear gravitational potential on the half-line and derive the most general boundary condition that renders the Hamiltonian self-adjoint. This introduces a single real self-adjoint parameter $λ$ that continuously interpolates between the Dirichlet case and more general (Robin-type) reflecting surfaces. Building on this framework, we provide analytical expressions for the energy spectrum, eigenfunctions, relevant matrix elements, and a set of sum rules valid for arbitrary $λ$. We show how nontrivial boundary conditions can bias measurements of $g$ and can mimic or mask putative short-range ''fifth-force''. Our results emphasize that enforcing self-adjointness-and modeling the correct boundary physics-is essential for quantitative predictions in gravitational quantum states. Beyond neutron quantum bounces, the approach is broadly applicable to systems where boundaries and self-adjointness govern the observable spectra and dynamics.

quant-ph↗

arXiv2025

Holographic hyperbranched polymer nanocomposite grating with exceptionally large neutron scattering length density modulation amplitudes

Nanoparticle-polymer composite gratings incorporating ultrahigh-refractive-index hyperbranched polymers as organic nanoparticles have demonstrated exceptional light optical properties, yet their potential for neutron diffraction applications remains unexplored. We report on the neutron optical properties of a holographically structured hyperbranched-polymer-dispersed nanocomposite grating at a quasi-monochromatic neutron wavelength of 2 nm. We show that neutron diffraction measurements performed at the SANS-I instrument of the Paul Scherrer Institute (Switzerland) reveal exceptionally high neutron scattering length density modulation amplitudes. These scattering length density modulation amplitudes are the highest reported to date. Very high neutron diffraction efficiency is expected with the use of thicker uniform gratings and longer neutron wavelengths, with low angular and wavelength selectivity constraints.

physics.optics↗

arXiv2025

High-Density Ultracold Neutron Source for Low-Energy Particle Physics Experiments

SuperSUN, a new superthermal source of ultracold neutrons (UCN) at the Institut Laue-Langevin, exploits inelastic scattering of neutrons in isotopically pure superfluid $^4$He at temperatures below $0.6\,$K. For the first time, continuous operation with an intense broad-spectrum cold neutron beam is demonstrated over 60 days. We observe continuous UCN extraction rates of $21000\,$s$^{-1}$, and storage in the source with saturated density $273\,$cm$^{-3}$. The low-energy $\textit{in-situ}$ UCN spectrum is alterable via accumulation and holding delays, opening new possibilities in fundamental and applied physics.

physics.ins-det↗

arXiv2025

Photosensitive materials for neutron optics

Photosensitive materials with ever-improving properties are of great importance for optical and photonics applications. Additionally, they are extremely useful for designing components for neutron optical devices. We provide an overview on materials that have been tested and successfully used to control beams of cold and very cold neutrons based on diffractive elements. Artificial gratings are generated and optimized for the specific application in mind. We discuss the needs of the neutron optics community and highlight the progress obtained during the last decade. Materials that have been employed so far along with their properties are summarized, outlining the most promising candidates for the construction of an interferometer for very cold neutrons.

physics.optics↗

arXiv2025

Application of nanodiamond-polymer composite holographic gratings in a very cold neutron interferometer

In recent decades, photosensitive materials have been used for the development of optical devices not only for light, but also for cold and very cold neutrons. We show that holographically recorded gratings in nanodiamond-polymer composites (nDPC) form ideal diffraction elements for very cold neutrons. Their advantage of high diffraction efficiency, combined with low angular selectivity as a two-port beam splitter, meets the necessary conditions for application in a very cold neutron interferometer. We provide an overview of the latest achievements in the construction of such a triple Laue interferometer. A first operational test of the interferometer is planned immediately after this conference in May 2025.

physics.optics↗

arXiv2023

Multilayer volume holographic gratings from Bayfol HX: light and neutron optical characteristics

During the last decade a number of volume holographic media have been investigated that could serve not only as diffractive optical elements (DOEs) for light but also for slow neutrons. In this contribution we discuss the light optical properties of a stack of two gratings separated by an optically inert slice recorded in a Bayfol HX photopolymer. While the refractive-index modulation of the gratings for light is remarkable, the corresponding neutron optical analogue is, so far, in the medium range of other materials investigated. We therefore aim at possible improvements which are discussed in this manuscript.

physics.optics↗

arXiv2023

qBounce: First Measurement of the Neutron Electric Charge with a Ramsey-type GRS Experiment

The qBounce collaboration built over the last years a new Ramsey-type Gravitational Resonance Spectroscopy (GRS) experiment. After commissioning between 2016 and 2018, the setup was able to measure the Ramsey transitions with GRS for the first time. Here we present a search of the hypothetical charge of the neutron as an application of GRS to study nonstandard model interactions. This article will describe the measuring principle and the setup in detail.

hep-ex↗

arXiv2022

A Novel Nuclear Emulsion Detector for Measurement of Quantum States of Ultracold Neutrons in the Earth's Gravitational Field

Hypothetical short-range interactions could be detected by measuring the wavefunctions of ultracold neutrons (UCNs) on a mirror bounded by the Earth's gravitational field. The Searches require detectors with higher spatial resolution. We are developing a UCN detector for the with a high spatial resolution, which consists of a Si substrate, a thin converter layer including $^{10}$B$_{4}$C, and a layer of fine-grained nuclear emulsion. Its resolution was estimated to be less than 100 nm by fitting tracks of either $^{7}$Li nuclei or $α$-particles, which were created when neutrons interacted with the $^{10}$B$_{4}$C layer. For actual measurements of the spatial distributions, the following two improvements were made: The first was to establish a method to align microscopic images with high accuracy within a wide region of 65 mm $\times$ 0.2 mm. We created reference marks of 1 $μ$m and 5 $μ$m diameter with an interval of 50 $μ$m and 500 $μ$m, respectively, on the Si substrate by electron beam lithography and realized a position accuracy of less than 30 nm. The second was to build a holder that could maintain the atmospheric pressure around the nuclear emulsion to utilize it under vacuum during exposure to UCNs. The intrinsic resolution of the improved detector was estimated by evaluating the blur of a transmission image of a gadolinium grating taken by cold neutrons as better than 0.56 $\pm$ 0.08 $μ$m, which included the grating accuracy. A test exposure to UCNs was conducted to obtain the spatial distribution of UCNs in the Earth's gravitational field. Although the test was successful, a blurring of 6.9 $μ$m was found in the measurements, compared with a theoretical curve. We identified the blurring caused by the refraction of UCNs due to the roughness of the upstream surface of the substrate. Polishing of the surface makes the resolution less than 100 nm.

physics.ins-det↗

arXiv2021

Spectra of Neutron Wave Functions in Earth's Gravitational Field

The time evolution of a quantum wave packet in the linear gravity potential is known as Quantum Bouncing Ball. The qBounce collaboration recently observed such a system by dropping wave packets of ultracold neutrons by a height of roughly 30 microns. In this article, space and momentum spectra as well as Wigner functions of the neutron wave functions in the gravitational field of the Earth are analyzed. We investigate the quantum states in the "preparation region", into which they transition after exiting a narrow double-mirror system and where we would expect to observe free fall and bounces in classical physics. For this, we start from the stationary solutions and eigenvalues of the Schrödinger equation in terms of Airy functions and their zeros. Subsequently, we examine space and momentum distributions as well as Wigner functions in phase space for pure and mixed quantum states. The eventual influence of Yukawa-like forces for small distances of several micrometers from the mirror is included through first order perturbation calculations. Those allow us to study the resulting modifications of space and momentum distributions, and phase space functions.

quant-ph↗

arXiv2020

Gravity Resonance Spectroscopy and Dark Energy Symmetron Fields

Spectroscopic methods allow to measure energy differences with unrivaled precision. In the case of gravity resonance spectroscopy, energy differences of different gravitational states are measured without recourse to the electromagnetic interaction. This provides a very pure and background free look at gravitation and topics related to the central problem of dark energy and dark matter at short distances. In this article we analyse the effect of additional dark energy scalar symmetron fields, a leading candidate for a screened dark energy field, and place limits in a large volume of parameter space.

hep-ph↗

arXiv2019

Happy Birthday, Ultra-Cold Neutron!

What is driving the accelerated expansion of the universe and do we have an alternative for Einstein's cosmological constant? What is dark matter made of? Do extra dimensions of space and time exist? Is there a preferred frame in the universe? To which extent is left-handedness a preferred symmetry in nature? What's the origin of the baryon asymmetry in the universe? These fundamental and open questions are addressed by precision experiments using ultra-cold neutrons. This year, we celebrate the 50th anniversary of their first production, followed by first pioneering experiments. Actually, ultra-cold neutrons were discovered twice in the same year, once in the eastern and once in the western world. For five decades now research projects with ultra-cold neutrons have contributed to the determination of the force constants of nature's fundamental interactions, and several technological breakthroughs in precision allow to address the open questions by putting them to experimental test. To mark the event and tribute to this fabulous object, we present a birthday song for ultra-cold neutrons with acoustic resonant transitions, which are based solely on properties of ultra-cold neutrons, the inertial and gravitational mass of the neutron, Planck's constant, and the local gravity. We make use of a musical intonation system that bears no relation to basic notation and basic musical theory as applied and used elsewhere but addresses two fundamental problems of music theory, the problem of reference for the concert pitch and the problem of intonation.

nucl-ex↗

arXiv2019

Proof of Principle for Ramsey-type Gravity Resonance Spectroscopy with qBounce

Ultracold neutrons (UCNs) are formidable probes in precision tests of gravity. With their negligible electric charge, dielectric moment, and polarizability they naturally evade some of the problems plaguing gravity experiments with atomic or macroscopic test bodies. Taking advantage of this fact, the qBounce collaboration has developed a technique - gravity resonance spectroscopy (GRS) - to study bound quantum states of UCN in the gravity field of the Earth. This technique is used as a high-precision tool to search for hypothetical Non-Newtonian gravity on the micrometer scale. In the present article, we describe the recently commissioned Ramsey-type GRS setup, give an unambiguous proof of principle, and discuss possible measurements that will be performed.

physics.ins-det↗

arXiv2019

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

The 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. 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 - 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 ultra-cold 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 E=2 x 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.

hep-ph↗

arXiv2018

Multifold paths of neutrons in the three-beam interferometer detected by tiny energy-kick

A neutron optical experiment is presented to investigate the paths taken by neutrons in a three-beam interferometer. In various beam-paths of the interferometer, the energy of the neutrons is partially shifted so that the faint traces are left along the beam-path. By ascertaining an operational meaning to "the particle's path", which-path information is extracted from these faint traces with minimal-perturbations. Theory is derived by simply following the time evolution of the wave function of the neutrons, which clarifies the observation in the framework of standard quantum mechanics. Which-way information is derived from the intensity, sinusoidally oscillating in time at different frequencies, which is considered to result from the interfering cross terms between stationary main component and the energy-shifted which-way signals. Final results give experimental evidence that the (partial) wave functions of the neutrons in each beam path are superimposed and present in multiple locations in the interferometer.

quant-ph↗