Roger Pynn

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Papers by Roger Pynn

Inter-particle correlations in a hard-sphere colloidal suspension with polymer additives investigated by Spin Echo Small Angle Neutron Scattering (SESANS)

Soft Matter, 2014

24pWG-11 Development and application of multiple sextupole magnet for focusing of polychromatic neutron beam

Meeting Abstracts of the Physical Society of Japan (Nihon Butsuri Gakkai koen gaiyoshu), 2008

Mesoporous Silica Formation Mechanisms Probed Using Combined Spin–Echo Modulated Small-Angle Neutron Scattering (SEMSANS) and Small-Angle Neutron Scattering (SANS)

ACS Applied Materials & Interfaces, 2020

The initial formation stages of surfactant-templated silica thin films which grow at the air−wate... more The initial formation stages of surfactant-templated silica thin films which grow at the air−water interface were studied using combined spin−echo modulated small-angle neutron scattering (SEMSANS) and small-angle neutron scattering (SANS). The films are formed from either a cationic surfactant or nonionic surfactant (C 16 EO 8) in a dilute acidic solution by the addition of tetramethoxysilane. Previous work has suggested a two stage formation mechanism with mesostructured particle formation in the bulk solution driving film formation at the solution surface. From the SEMSANS data, it is possible to pinpoint accurately the time associated with the formation of large particles in solution that go on to form the film and to show their emergence is concomitant with the appearance of Bragg peaks in the SANS pattern, associated with the two-dimensional hexagonal order. The combination of SANS and SEMSANS allows a complete depiction of the steps of the synthesis that occur in the subphase.

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Entangled Neutron Beams: A possible new avenue to exploring Quantum Materials

Bulletin of the American Physical Society, 2020

Improving polarized neutron imaging for visualization of the Meissner effect in superconductors

Review of Scientific Instruments, 2019

The Polarized Neutron Imaging technique provides a non-invasive method of characterizing localize... more The Polarized Neutron Imaging technique provides a non-invasive method of characterizing localized magnetic fields inside superconductors. However, complete understanding of the magnetic field distribution has yet to be realized experimentally due to the complexity of the interaction between neutron polarization and magnetic field. In this article, we show that a well-defined and controlled magnetic field through the neutron path contributes to simplify the data analysis and makes future quantitative polarized neutron imaging possible. This is demonstrated in a set of experiments that visualize the magnetic field distribution inside and around the superconductors. The experimental results demonstrate that proper guide field setup allows the visualization of the magnetic field expulsion at the surface of the superconductor in the zero-field cooling condition, as well as the magnetic field trapped inside the superconductor under field cooling condition.

format_quoteThe spin-up and spin-down neutron state intensities were measured, enabling calculation of polarization changes with precision.format_quote

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A polarised neutron study of linear and non-linear spin fluctuations in CsNiF3

Journal of Physics C: Solid State Physics, 1984

ABSTRACT

Comparison of dynamical theory and phase-object approximation for neutron scattering from periodic structures

Journal of Applied Crystallography, 2011

Dynamical theory (DT) calculations have been successfully developed to explain neutron spin-echo ... more Dynamical theory (DT) calculations have been successfully developed to explain neutron spin-echo resolved grazing-incidence scattering from diffraction gratings. The theory, without any adjustable parameters, has been shown in previous publications to accurately reproduce the sensitivity of the spin-echo polarization signal to sample specifications and scattering geometry. The phase-object approximation (POA), which is computationally less demanding than the DT, has also been used to analyze neutron spin-echo polarization data obtained from diffraction gratings. In this paper, POA and DT calculations are compared for neutron scattering from various diffraction gratings in different geometrical settings. POA gives a good description of the data for transmission cases, where the neutron beam is incident at large angles to the average grating surface. However, for the grazing-incidence reflection cases that were studied, the POA does not fit the data using the independently determined ...

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Compact spherical neutron polarimeter using high-Tc YBCO films

Review of Scientific Instruments, 2016

We describe a simple, compact device for spherical neutron polarimetry measurements at small neut... more We describe a simple, compact device for spherical neutron polarimetry measurements at small neutron scattering angles. The device consists of a sample chamber with very low (<0.01 G) magnetic field flanked by regions within which the neutron polarization can be manipulated in a controlled manner. This allows any selected initial and final polarization direction of the neutrons to be obtained. We have constructed a prototype device using high-T c superconducting films and mu-metal to isolate regions with different magnetic fields and tested device performance in transmission geometry. Finite-element methods were used to simulate the device's field profile and these have been verified by experiment using a small solenoid as a test sample. Measurements are reported using both monochromatic and polychromatic neutron sources. The results show that the device is capable of extracting sample information and distinguishing small angular variations of the sample magnetic field. As a more realistic test, we present results on the characterization of a 10 µm thick Permalloy film in zero magnetic field, as well as its response to an external magnetic field.

format_quoteMeasured tensor elements T_y_y and T_x_x demonstrated consistent behavior, confirming effective polarization control in the solenoid measurements.format_quote

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Study of Longitudinal Fluctuations in CsNiF3 by Means of Inelastic Polarized Neutron Scattering

Springer Proceedings in Physics, 1987

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Probing magnetic correlations with spin-echo modulated small angle neutron scattering (SEMSANS)

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2021

Abstract The first measurements of magnetic correlation functions are presented using time-of-fli... more Abstract The first measurements of magnetic correlation functions are presented using time-of-flight Spin-echo modulated small angle neutron scattering (SEMSANS) on the Larmor instrument at the ISIS pulsed neutron source. The accessible length scale is beyond that of the conventional SANS. A simplified model is presented to calculate the expected correlation functions for various magnetisation fields applied to the sample. As an example, we present the experimental data of a soft iron sample at various configurations of magnetisation field.

LENS: 2013 Facility Overview

Physics Procedia, 2014

Formation of an oscillatory magnetization near the reentrant superconducting transition in HoMo6S8

Physica B+C, 1981

ABSTRACT

Optimization of resolution functions for neutron scattering

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 1990

... 538 Nuclear Instruments and Methods in Physics Research A287 (1990) 538550 NorthHolland OPTIM... more

But of course

Nature, 1988

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Off-specular scattering in neutron reflectometry

Journal of Neutron Research, 1999

an aff!rmative action/equal opportunity employer, is operated by the University of California for... more an aff!rmative action/equal opportunity employer, is operated by the University of California for the U.S. Department of Energy under contract W-7405-ENG-36. By acceptance of this article, the publisher recognizes that the U.S. Government retains a nonexclusive, royalty-free license to publish or reproduce the published form of this contribution, or to allow others to do so, for U.S. Government purposes. The Los Alamos National Laboratory requests that the publisher identify this article as work performed under the auspices of the U.S. Department of Energy. Form No. 836 R5 d)5-faJbU'fiO&$ f '~+ s LWGU;&Ef\lf 1s bp:LtMi7 L A ' ST 2629 1 OB1 DISCLAIMER This report was .prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, make any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commerciai product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. DISCLAIMER Portions of this document may be illegible in electronic image products. Images are produced from the best available original document. PLEASE NOTE: Some figures are on the end sheets, not in the text itself.

format_quoteDWBA accuracy diminishes significantly when height correlation length exceeds approximately 500 times the neutron wavelength.format_quote

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New Double Magnon Modes in Planar Antiferromagnetic Chains in a Field

Le Journal de Physique Colloques, 1988

Planar antiferromagnetic chains in a field provide a good support for the study of non linear exc... more

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Time-Dependent Effects in Disordered Materials

Ti me-Dependent Effects in Disordered Materials NA TO ASI Series Advanced Science Institutes Seri... more Ti me-Dependent Effects in Disordered Materials NA TO ASI Series Advanced Science Institutes Series A series presenting the results of activities sponsored by the NA TO Science Committee, which aims at the dissemination of advanced scientific and technological knowledge, with a view to strengthening links between scientific communities.

$Examples of uniformly sized microspheres used for model studies of disordered materials. (A) Slow diffusion-limited aggregation of 1.1-ym spheres in a plane producing a “snowflake”-like crystal with den- drites after several months. (B)1.1-m spheres dispersed in water (gray) packing into a planar polycrystal- line lattice. The different shadings in blue indicate different orientations of the grains. This systems may be used for model studies of annealing and interfacial melting. (C) Ramified fracture pattern resulting from a uniform contraction of 3.5-»m polystyrene spheres in a plane. This process takes place as a regular lattice of water-dispersed spheres dries out. (D) Colloidal flow of 1.9-um water-dispersed spheres induced by gravitation in a vertical Hele-Shaw cell (glass plates separated by 25 um). This exemplifies a chaotic process for fluid flow in the case of zero interfacial tension between two fluids. (A.T. Skjeltorp)$

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Elastic neutron scattering evidence for a charge transfer change in TTF-TCNQ (tetrathiofulvalene tetracyanoquinodimethane) at high pressure

Solid State Communications, 1979

ABSTRACT

Quantum Entangled-Probe Scattering Theory

We develop an entangled-probe scattering theory, including quantum detection, that extends the sc... more We develop an entangled-probe scattering theory, including quantum detection, that extends the scope of standard scattering approaches. We argue that these probes may be revolutionary in studying entangled matter such as unconventional phases of strongly correlated systems. Our presentation focuses on a neutron beam probe that is mode-entangled in spin and path as is experimentally realized in [1], although similar ideas also apply to photon probes. We generalize the traditional van Hove theory [2] whereby the differential cross-section is written as a properly-crafted combination of two-point correlation functions. Tuning the probe's entanglement length allows us to interrogate spatial scales of interest through enhancements in this correlation function.

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Wide Angle Spherical Neutron Polarimetry at Oak Ridge National Laboratory

Developing Wide Angle Spherical Neutron Polarimetry at Oak Ridge National Laboratory Spherical Ne... more Developing Wide Angle Spherical Neutron Polarimetry at Oak Ridge National Laboratory Spherical Neutron Polarimetry (SNP) analyzes complex magnetic structures through distinguishing contributions from nuclear-magnetic interference and chiral structure in addition to nuclear magnetic scattering separation. This analysis is achieved through determining all components in the polarization transfer process. Currently, wide-angle SNP is being realized at Oak Ridge National Laboratory (ORNL) for multiple beamlines including: the polarized triple-axis spectrometer (HB-1) and general-purpose small angle neutron scattering instrument (CG-2) at the High Flux Isotope Reactor (HFIR), as well as the hybrid spectrometer (HYSPEC) at the Spallation Neutron Source (SNS). The SNP device consists of three units: incoming/outgoing neutron polarization, sample environment and a zero-field chamber. The incoming/outgoing neutron polarization regions use high-T_c superconducting YBCO films and mu-metal to ac...

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