scholarly journals Density measurements in ice boreholes using neutron scattering

2003 ◽  
Vol 49 (167) ◽  
pp. 599-604 ◽  
Author(s):  
Elizabeth M. Morris ◽  
J. David Cooper
Keyword(s):  
Neutron Scattering ◽  
Count Rate ◽  
Fast Neutrons ◽  
Potential Contribution ◽  
Snow Density ◽  
Hydrogen Atoms ◽  
Density Profiles ◽  
Annual Variations ◽  
Neutron Probe ◽  
Calibration Equations

AbstractThis paper describes the use of a neutron probe to measure detailed stratigraphy in ice and snow. The Wallingford neutron probe, developed for measurement of soil moisture, consists of an annular radioactive source of fast neutrons around the centre of a cylindrical detector for slow (thermal) neutrons. In snow and ice, the fast neutrons lose energy by scattering from hydrogen atoms, and the number of slow neutrons arriving at the detector (the count rate) is related to the density of the medium. Calibration equations for count rate as a function of snow density and borehole diameter have been derived. Snow-density profiles from boreholes obtained using the probe show that, despite the smoothing produced by the neutron-scattering process, annual variations in density can be resolved. The potential contribution of the neutron probe to improvements in mass-balance monitoring is discussed.

First glaciological investigations at Ridge B, central East Antarctica

2021 ◽  
pp. 1-10
Author(s):  
Alexey A. Ekaykin ◽  
Alexey V. Bolshunov ◽  
Vladimir Ya. Lipenkov ◽  
Mirko Scheinert ◽  
Lutz Eberlein ◽  
...  
Keyword(s):  
East Antarctica ◽  
Snow Density ◽  
Deep Drilling ◽  
Surface Mass ◽  
Annual Variations ◽  
First Results ◽  
Vostok Station ◽  
Water Stable Isotope ◽  
Isotope Content ◽  
Firn Core

Abstract The region of Ridge B in central East Antarctica is one of the last unexplored parts of the continent and, at the same time, ranks among the most promising places to search for Earth's oldest ice. In January 2020, we carried out the first scientific traverse from Russia's Vostok Station to the topographical dome of Ridge B (Dome B, 3807 m above sea level, 79.02°S, 93.69°E). The glaciological programme included continuous snow-radar profiling and geodetic positioning along the traverse's route, installation of snow stakes, measurements of snow density, collection of samples for stable water isotope and chemical analyses and drilling of a 20 m firn core. The first results of the traverse show that the surface mass balance at Dome B (2.28 g cm−2 year−1) is among the lowest in Antarctica. The firn temperature below the layer of annual variations is −58.1 ± 0.2°C. A very low value of heavy water stable isotope content (-58.2‰ for oxygen-18) was discovered at a distance of 170 km from Vostok Station. This work is the first step towards a comprehensive reconnaissance study of the Ridge B area aimed at locating the best site for future deep drilling for the oldest Antarctic ice.

Determination of hydrogen ordering within the β-RH2+xphase (R= Ho, Y) using electron diffraction techniques

2000 ◽  
Vol 33 (5) ◽  
pp. 1246-1252 ◽  
Author(s):  
Elizabeth J. Grier ◽  
Amanda K. Petford-Long ◽  
Roger C. C. Ward
Keyword(s):  
Electron Diffraction ◽  
Neutron Scattering ◽  
Diffraction Pattern ◽  
Computer Simulations ◽  
Fluorite Structure ◽  
Long Range Order ◽  
Hydrogen Atoms ◽  
Ordered Structures ◽  
Diffraction Patterns

Computer simulations of the electron diffraction patterns along the [\bar{1}10] zone axes of four ordered structures within the β-RH2+xphase, withR= Ho or Y, and 0 ≤x≤ 0.25, have been performed to establish whether or not the hydrogen ordering could be detected using electron diffraction techniques. Ordered structures within otherRH2+x(R= Ce, Tb) systems have been characterized with neutron scattering experiments; however, for HoH(D)2+x, neutron scattering failed to characterize the superstructure, possibly because of the lowxconcentration or lack of long-range order within the crystal. This paper aims to show that electron diffraction could overcome both of these problems. The structures considered were the stoichiometric face-centred cubic (f.c.c.) fluorite structure (x= 0), theD1 structure (x= 0.125), theD1astructure (x= 0.2) and theD022structure (x= 0.25). In the stoichiometric structure, with all hydrogen atoms located on the tetrahedral (t) sites, only the diffraction pattern from the f.c.c. metal lattice was seen; however, for the superstoichiometric structures, with the excess hydrogen atoms ordered on the octahedral (o) sites, extra reflections were visible. All the superstoichiometric structures showed extra reflections at the (001)f.c.c.and (110)f.c.c.type positions, with structureD1 also showing extra peaks at (½ ½ ½)f.c.c.. These reflections are not seen in the simulations at similar hydrogen concentrations with the hydrogen atoms randomly occupying theovacancies.

scholarly journals Determination of Internal Density Profiles of Smart Acrylamide-Based Microgels by Small-Angle Neutron Scattering: A Multishell Reverse Monte Carlo Approach

Langmuir ◽  
2018 ◽  
Vol 34 (50) ◽  
pp. 15403-15415 ◽  
Author(s):  
Marian Cors ◽  
Lars Wiehemeier ◽  
Yvonne Hertle ◽  
Artem Feoktystov ◽  
Fabrice Cousin ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Neutron Scattering ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Reverse Monte Carlo ◽  
Density Profiles ◽  
Monte Carlo Approach

scholarly journals Instruments and Methods Snow Density Profiling by Nuclear Means

1966 ◽  
Vol 6 (43) ◽  
pp. 171-176
Author(s):  
Robert D. Leighty
Keyword(s):  
Soil Moisture ◽  
Field Investigation ◽  
Present Form ◽  
Snow Density ◽  
Nuclear Technique ◽  
Density Profiles ◽  
Snow Stratigraphy ◽  
Modes Of Processing ◽  
Nuclear Detectors ◽  
Nuclear Method

Abstract During the period 8–19 May 1963 a preliminary field investigation was conducted in Greenland to determine the feasibility of using a nuclear technique to determine snow and ice density profiles. A standard nuclear soil-moisture depth probe was used with two modes of processing and recording the nuclear pulses. Example data are compared with snow densities obtained by the standard weighing technique. The nuclear method was found to be feasible; however, deficiencies related to poor resolution render the probe unusable for detailed profiling of snow stratigraphy in its present form, but expected progress in nucleonics should enable improved resolution and accuracy to be achieved by improvement of nuclear detectors.

A High Count Rate Neutron Beam Monitor for Neutron Scattering Facilities

2013 ◽  
Vol 60 (2) ◽  
pp. 668-670
Author(s):  
Amanda K. Barnett ◽  
Michael N. Cox ◽  
Lowell Crow ◽  
Yacouba Diawara ◽  
Loren L. Funk ◽  
...  
Keyword(s):  
Neutron Scattering ◽  
Neutron Beam ◽  
Count Rate ◽  
High Count ◽  
High Count Rate ◽  
Beam Monitor

Quasi-elastic Scattering of Neutrons for the Study of Random Motions in Solids

1971 ◽  
Vol 26 (3) ◽  
pp. 575-584
Author(s):  
H. Stiller ◽  
T. Springer
Keyword(s):  
High Resolution ◽  
Elastic Scattering ◽  
Hydrogen Bonds ◽  
Neutron Scattering ◽  
Rotational Diffusion ◽  
Molecular Solids ◽  
Hydrogen Atoms ◽  
Incoherent Neutron Scattering ◽  
Random Motions ◽  
Incoherent Neutron

Abstract Investigations on motions of hydrogen atoms in metals, on rotational diffusion in molecular solids and on fluctuations of protons at hydrogen bonds are reviewed as examples for experiments with incoherent neutron scattering requiring high resolution.

A study of α -resorcinol by neutron diffraction

1956 ◽  
Vol 235 (1203) ◽  
pp. 552-559 ◽  
Keyword(s):  
Hydrogen Bonds ◽  
Neutron Diffraction ◽  
Oxygen Atom ◽  
Neutron Scattering ◽  
Benzene Ring ◽  
Unit Cell ◽  
The Other ◽  
Aromatic Molecule ◽  
Hydrogen Atoms ◽  
A Value

The first study of an aromatic molecule by neutron diffraction, leading to a Fourier projection of the neutron scattering density in the unit cell, gives a value of 1·08 ± 0·04 Å for the length of the C—H bonds which link hydrogen atoms to the benzene ring. The spirals of hydrogen bonds which bind together neighbouring molecules are found to consist of typical ‘long bonds’, with the proton much closer to one oxygen atom than to the other. The O—H distance is 1·02 Å, and it appears that the O, H, O atoms are not collinear.

scholarly journals Verification of He-3 proportional counters’ fast neutron sensitivity through a comparison with He-4 detectors

2020 ◽  
Vol 135 (7) ◽  
Author(s):  
Francesco Piscitelli ◽  
Giacomo Mauri ◽  
Alessio Laloni ◽  
Richard Hall-Wilton
Keyword(s):  
Neutron Scattering ◽  
Fast Neutron ◽  
Gamma Rays ◽  
Cold Neutron ◽  
Neutron Detection ◽  
Kinetic Studies ◽  
Ground Level ◽  
Fast Neutrons ◽  
Helium 4 ◽  
Helium 3

AbstractIn the field of neutron scattering science, a large variety of instruments require detectors for thermal and cold neutrons. Helium-3 has been one of the main actors in thermal and cold neutron detection for many years. Nowadays, neutron facilities around the world are pushing their technologies to increase the available flux delivered at the instruments; this enables a completely new science landscape. Complementary with the increasing available flux, a better signal-to-background (S/B) ratio enables to perform new types of measurements. For instance, in neutron reflectometry, the time resolution for kinetic studies is limited by the available S/B. An improved S/B opens the possibility of sub-second kinetic studies. To this aim, this manuscript re-examines the background sensitivity of today’s “gold standard” neutron detection. Fast neutrons and gamma rays are the main background species in neutron scattering experiments. The efficiency (sensitivity) of detecting fast neutrons, cosmic rays and gamma rays, for a Helium-3-based detector is studied here through the comparison with Helium-4 counters. The comparison with Helium-4 allows to separate the thermal (and cold) neutron from the fast neutron contributions in Helium-3-based counters which are otherwise entangled, verifying previous results from an indirect method. A relatively high sensitivity is found. Moreover, an estimate for the cosmic neutron fluence, also a source of background, at ground level at ESS is presented in this manuscript.

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