Search results for " Neutrons"
showing 10 items of 74 documents
Absorber materials for low-energy neutrons—Theoretical and experimental studies
2012
Abstract Absorber materials for low-energy neutrons are studied in the theoretical framework of quantum mechanics with a complex potential. Analytical expressions and numerical calculations of the neutron reflectivity for perpendicular and isotropic motion towards a surface for four different material classes are presented. Comparative experimental studies of four absorber materials have been carried out: Polyethylene, titanium, boron-10 and lithium stearate. In a quasi-storage experiment with ultracold neutrons the latter material features the highest absorption property.
Towards a new measurement of the neutron electric dipole moment
2009
International audience; The effort towards a new measurement of the neutron electric dipole moment (nEDM) at the Paul Scherrer Institut's (PSI) new high intensity source of ultracold neutrons (UCN) is described. The experimental technique relies on Ramsey's method of separated oscillatory fields, using UCN in vacuum with the apparatus at ambient temperature. In the first phase, R&D towards the upgrade of the RAL/Sussex/ILL apparatus is being performed at the Institut Laue-Langevin (ILL). In the second phase the apparatus, moved from ILL to PSI, will allow an improvement in experimental sensitivity by a factor of 5. In the third phase, a new spectrometer should gain another order of magnitud…
Transmission of very slow neutrons through material foils and its influence on the design of ultracold neutron sources
2009
At the Paul Scherrer Institute (PSI), a very intense source of ultracold neutrons (UCN) is being built. The UCN converter of solid deuterium must be contained in a vessel. Produced UCN leave that vessel through its top lid. To decide on the design of the vessel and the top lid, we have measured the transmission of neutrons with velocities between 3 and 20 m/s through different material foils. Contrary to expectations, we found that transmission through aluminium and aluminium alloys is equal or even higher compared to zirconium and reactor-grade zirconium alloys, respectively.
Improved instrument for the determination of the neutron electric charge
2015
Abstract We present an improved instrument for the determination of the neutron electric charge with ultracold neutrons. Several technical upgrades with respect to a former experiment will be discussed in detail. As a first test, we applied the apparatus to investigate the influence of gravitational attraction by means of a massive block of lead. The calculated sensitivity for a charge measurement is δ q n ≈ 2.14 × 10 − 20 e / day . Planned modifications increasing the sensitivity up to δ q n ≈ 1.34 × 10 − 21 e / day are demonstrated.
Direct Experimental Verification of Neutron Acceleration by the Material Optical Potential of SolidH22
2008
We have measured the acceleration of neutrons by the material optical potential of solid $^{2}\mathrm{H}_{2}$. Using a gravitational spectrometer, we find a minimal kinetic energy ${E}_{c}=(99\ifmmode\pm\else\textpm\fi{}7)\text{ }\text{ }\mathrm{neV}$ of neutrons from a superthermal ultracold neutron (UCN) source with solid $^{2}\mathrm{H}_{2}$ as an UCN converter. The result is in excellent agreement with theoretical predictions, ${E}_{c}=106\text{ }\text{ }\mathrm{neV}$.
nEDM experiment at PSI : data-taking strategy and sensitivity of the dataset
2018
We report on the strategy used to optimize the sensitivity of our search for a neutron electric dipole moment at the Paul Scherrer Institute. Measurements were made upon ultracold neutrons stored within a single chamber at the heart of our apparatus. A mercury cohabiting magnetometer together with an array of cesium magnetometers were used to monitor the magnetic field, which was controlled and shaped by a series of precision field coils. In addition to details of the setup itself, we describe the chosen path to realize an appropriate balance between achieving the highest statistical sensitivity alongside the necessary control on systematic effects. The resulting irreducible sensitivity is …
Ceramics, Marbles and Stones in the Light of Neutrons: Characterization by Various Neutron Methods
2016
In this chapter we give a brief overview of neutron based analytical investigations applied to study archaeological ceramics, and different types of stones. Since the vast majority of archaeological objects are made of ceramics and various stones—all are of geological origin—, one of the key objectives of these studies to determine the origin of raw material. This research is called provenance research, and a wide range of neutron based methods are applicable in it. Following a very basic, user-oriented description of the methods, we introduce examples from our everyday practice. The examples are about provenance of prehistoric stone tools, about the sources of 4th–3rd c. B.C. millennium li…
Determination of the irradiation field at the research reactor TRIGA Mainz for BNCT.
2009
For the application of the BNCT for the excorporal treatment of organs at the TRIGA Mainz, the basic characteristics of the radiation field in the thermal column as beam geometry, neutron and gamma ray energies, angular distributions, neutron flux, as well as absorbed gamma and neutron doses must be determined in a reproducible way. To determine the mixed irradiation field thermoluminescence detectors (TLD) made of CaF(2):Tm with a newly developed energy-compensation filter system and LiF:Mg,Ti materials with different (6)Li concentrations and different thicknesses as well as thin gold foils were used.
The magnet of the scattering and neutrino detector for the SHiP experiment at CERN
2019
The Search for Hidden Particles (SHiP) experiment proposal at CERN demands a dedicated dipole magnet for its scattering and neutrino detector. This requires a very large volume to be uniformly magnetized at B > 1.2 T, with constraints regarding the inner instrumented volume as well as the external region, where no massive structures are allowed and only an extremely low stray field is admitted. In this paper we report the main technical challenges and the relevant design options providing a comprehensive design for the magnet of the SHiP Scattering and Neutrino Detector.
Direct observation of coherent magnons with suboptical wavelengths in a single crystalline ferrimagnetic insulator
2019
In the field of magnetism, spin waves are a subject of great interest for fundamental and application-oriented research. Time-resolved scanning transmission x-ray microscopy, a technique that allows for direct spin-wave imaging below the optical resolution limit, is usually limited to thin layers deposited on x-ray transparent membranes. Here, the authors report on a preparation routine that makes single-crystalline materials accessible to this powerful technique. The latter is subsequently implemented on the ferrimagnetic insulator yttrium iron garnet, where spin waves down to 100-nm wavelength are observed.