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Roger Pynn - One of the best experts on this subject based on the ideXlab platform.
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a novel neutron spin echo technique for measuring phonon linewidths using magnetic Wollaston prisms
Journal of Applied Crystallography, 2014Co-Authors: Roger PynnAbstract:A new method of implementing neutron spin echo measurement of phonon linewidths on a triple-axis neutron spectrometer is introduced, based on recently developed superconducting magnetic Wollaston prisms. Each arm of the spectrometer is composed of two Wollaston prisms with a rectangular field region between them. By introducing triangular and rectangular field regions, loci of constant spin echo phase can be manipulated easily to achieve the so-called phonon focusing condition. Unlike the neutron resonance spin echo method, which is tuned by physically tilting the field boundaries, the new device can be tuned electromagnetically to achieve the phonon focusing condition. By adjusting the field configurations, the linewidths of phonon excitations with high energy and large group velocity can be measured. By employing superconducting films to define the various field regions, high neutron transmission and good neutron polarization efficiency can be obtained.
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superconducting magnetic Wollaston prism for neutron spin encoding
Review of Scientific Instruments, 2014Co-Authors: S R Parnell, W A Hamilton, Brian B Maranville, T Wang, R Semerad, David V Baxter, J T Cremer, Roger PynnAbstract:A magnetic Wollaston prism can spatially split a polarized neutron beam into two beams with different neutron spin states, in a manner analogous to an optical Wollaston prism. Such a Wollaston prism can be used to encode the trajectory of neutrons into the Larmor phase associated with their spin degree of freedom. This encoding can be used for neutron phase-contrast radiography and in spin echo scattering angle measurement (SESAME). In this paper, we show that magnetic Wollaston prisms with highly uniform magnetic fields and low Larmor phase aberration can be constructed to preserve neutron polarization using high temperature superconducting (HTS) materials. The Meissner effect of HTS films is used to confine magnetic fields produced electromagnetically by current-carrying HTS tape wound on suitably shaped soft iron pole pieces. The device is cooled to ∼30 K by a closed cycle refrigerator, eliminating the need to replenish liquid cryogens and greatly simplifying operation and maintenance. A HTS film ensures that the magnetic field transition within the prism is sharp, well-defined, and planar due to the Meissner effect. The spin transport efficiency across the device was measured to be ∼98.5% independent of neutron wavelength and energizing current. The position-dependent Larmor phase of neutron spins was measured at the NIST Center for Neutron Research facility and found to agree well with detailed simulations. The phase varies linearly with horizontal position, as required, and the neutron beam shows little depolarization. Consequently, the device has advantages over existing devices with similar functionality and provides the capability for a large neutron beam (20 mm × 30 mm) and an increase in length scales accessible to SESAME to beyond 10 μm. With further improvements of the external coupling guide field in the prototype device, a larger neutron beam could be employed.
Kevin M Ansdell - One of the best experts on this subject based on the ideXlab platform.
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medium to low pressure pelitic gneisses of fraser lakes zone b Wollaston domain northern saskatchewan canada mineral compositions metamorphic p t t path and implications for the genesis of radioactive abyssal granitic pegmatites
Canadian Mineralogist, 2012Co-Authors: Christine L Mckechnie, Irvine R Annesley, Kevin M AnsdellAbstract:The Fraser Lakes Zone B is a U–Th–REE deposit hosted by granitic pegmatite and leucogranite located in the Wollaston Domain of northern Saskatchewan, Canada, in close proximity to the uranium-rich Athabasca Basin. Here, these magmatic rocks are hosted within Paleoproterozoic metasedimentary gneisses of the Wollaston Group and the underlying Archean orthogneisses. The intrusive bodies at Fraser Lakes Zone B are interpreted to have formed from crustal melts generated by upper-amphibolite- to granulite-facies metamorphism during the ca . 1.8 Ga Trans-Hudson orogeny. Three pelitic gneiss host-rock samples with the least petrographic evidence of later alteration and suitable assemblages for P–T–t constraints were analyzed with an electron microprobe. Mineral assemblages in the pelitic gneisses, combined with chemical zoning in garnet, garnet–biotite and Ti-in-biotite geothermometry, and GBPQ geobarometry, suggest a peak T of about 750 to 780°C and a P of about 6 to 8 kbar, followed by isothermal decompression to a pressure of about 3 kbar. The low-P (retrograde) part of the P–T path is partially constrained by the presence of spinel in some pelitic gneiss samples. These constraints on temperature and pressure are consistent with partial melting, which would have generated significant amounts of melt via biotite-dehydration reactions. Evidence for this is in the form of abundant leucosome in the pelitic gneisses; however, these are generally not connected to the mineralized pegmatites. Instead, melt generated from similar rocks at slightly deeper crustal levels is believed to have crystallized within a structural trap at Fraser Lakes Zone B to form the U–Th–REE-mineralized granitic pegmatites and leucogranites.
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radioactive abyssal granitic pegmatites and leucogranites in the Wollaston domain northern saskatchewan canada mineral compositions and conditions of emplacement in the fraser lakes area
Canadian Mineralogist, 2012Co-Authors: Christine L Mckechnie, Irvine R Annesley, Kevin M AnsdellAbstract:The Fraser Lakes area in the Wollaston Domain, in northern Saskatchewan, Canada, is located 25 km from the southeastern edge of the uranium-rich Athabasca Basin; it hosts a number of U- and Th–REE-bearing granitic pegmatites and leucogranites. At Fraser Lakes Zone B, the pegmatites and leucogranites intrude the deformed contact between Paleoproterozoic metasedimentary gneisses of the Wollaston Group and Archean orthogneisses, and have characteristics typical of the Abyssal pegmatite subclass. For two examples of Group-A U- and Th-enriched pegmatite and leucogranite, and two examples of Group-B Th- and LREE-enriched pegmatite and leucogranite samples that have minimal petrographic evidence of later alteration, we analyzed selected minerals by electron microprobe to provide constraints on the age and temperature of intrusion. The Group-A pegmatites contain uraninite with variable CaO and SiO 2 , indicative of later recrystallization, uranoan thorite spatially associated with complexly zoned zircon (with some intermediate solid-solution between the two minerals), rare coffinite, and titaniferous magnetite and ilmenite where they intrude the Archean orthogneisses. CHIME dating of the most pristine uraninite yielded ages between 1.85 and 1.80 Ga, consistent with crystallization from the pegmatite-forming melt. The Group-B pegmatites contain monazite-(Ce) with significant Th substitution, uranoan thorite, zircon (also showing extensive solid-solution toward thorite), and rare xenotime and pyrochlore. CHIME dating of monazite from the Group-B pegmatites gave older ages of ca. 2.1 to 2.2 Ga, suggesting that they are xenocrysts from the source region of the melt. Biotite dehydration reactions have led to significant development of leucosome in the host pelitic gneisses, and likely resulted in the formation of granitic melt at depth.
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provenance and tectonic setting of paleoproterozoic metasedimentary rocks along the eastern margin of hearne craton constraints from shrimp geochronology Wollaston group saskatchewan canada
Precambrian Research, 2008Co-Authors: Hai Thanh Tran, Kevin M Ansdell, Kathryn M Bethune, K E Ashton, Michael A HamiltonAbstract:Abstract Single detrital zircon grains from various parts of the Wollaston Group, a Paleoproterozoic metasedimentary succession deposited along the southeastern margin of the Hearne Province, northern Saskatchewan, Canada, were analyzed by SHRIMP U–Pb geochronological techniques. Zircon analyses are mostly concordant and yield ages ranging from ca. 2800 to 1780 Ma, although distinct age populations were detected in all samples. The stratigraphically oldest sample (Geoch 4) is dominated by a bimodal distribution of zircon ages (ca. 1.90 and 2.4–2.6 Ga), which is similar to that preserved in the sample (Geoch 2) from the middle portion of the Wollaston Group. The stratigraphically youngest sample (Geoch 9) contains ca. 2.1 Ga zircons, as well as zircons with the same ages as observed in Geoch 4 and Geoch 2. Zircon ages older than 2450 Ma appear to be consistent with the age of the Hearne Province basement, suggesting that part of the sedimentary detritus was locally derived. Zircons with ages in the 2430–2350 Ma range, found in all samples, may have been derived from a more distant source, such as Rae Province rocks that were affected by the recently identified Arrowsmith orogeny. Significant amounts of 1920–1880 Ma zircon grains are found in all samples; these are interpreted to represent sedimentary detritus derived from juvenile volcanic terranes. Zircons younger than 1860 Ma are interpreted to be the product of post-Wollaston Group thermal overprinting. Our data, together with field relationships and geochemical data, suggest that most of the preserved Wollaston Group was deposited in a back-arc to foreland basin environment. It received detritus from both Archean continental crust to the west and a juvenile continental magmatic arc, likely located to the east, as the youngest zircon ages are not consistent with the age of Taltson Orogen rocks to the west.
Greg Collins - One of the best experts on this subject based on the ideXlab platform.
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timing of sediment hosted cu ag mineralization in the trans hudson orogen at janice lake Wollaston domain saskatchewan canada
Mineralium Deposita, 2019Co-Authors: Jose Perello, Victor A Valencia, Paula Cornejo, John A Clifford, Alan J Wilson, Greg CollinsAbstract:The Janice Lake Cu-Ag mineralization in the Wollaston Domain of northern Saskatchewan is hosted by a metasedimentary sequence in the upper part of the Wollaston Supergroup of the Trans-Hudson orogen. The Wollaston Supergroup was deposited between ~ 2070 and 1865 Ma in a foreland basin setting constructed over Archean basement of the Hearne craton. The Trans-Hudson orogen underwent final collision and peak metamorphism at ~ 1810 Ma, during consolidation of Laurentia and its amalgamation with the Columbia supercontinent. Titanite is a common constituent of the post-peak metamorphic assemblages of Trans-Hudson lithotectonic units and accompanied disseminated sediment-hosted Cu sulfide mineralization at Janice Lake. Titanite crystals, intergrown with chalcocite over a strike-length of ~ 2 km of Cu-bearing stratigraphy, were dated by the ID-TIMS and LA-ICP-MS U-Pb methods, returning an age range from 1780 to 1760 Ma and a weighted average age of 1775 ± 10 Ma. The titanite ages effectively date the associated chalcocite-dominated sediment-hosted Cu-Ag mineralization and its formation during initial post-orogenic uplift and cooling, ~ 30 myr after peak metamorphism. The age-range and tectonic setting of the Janice Lake mineralization confirms that sediment-hosted Cu mineralization was an integral part of the metallogenic endowment of Columbia and that its emplacement coincided with the continental-scale Trans-Hudson orogeny rather than with diagenesis and extensional basin development ~ 100 myr earlier.
David V Baxter - One of the best experts on this subject based on the ideXlab platform.
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high resolution neutron larmor diffraction using superconducting magnetic Wollaston prisms
Scientific Reports, 2017Co-Authors: Hao Feng, S R Parnell, W A Hamilton, A Thaler, Lowell Crow, Wencao Yang, Amy Jones, Hongyu Bai, M Matsuda, David V BaxterAbstract:The neutron Larmor diffraction technique has been implemented using superconducting magnetic Wollaston prisms in both single-arm and double-arm configurations. Successful measurements of the coefficient of thermal expansion of a single-crystal copper sample demonstrates that the method works as expected. The experiment involves a new method of tuning by varying the magnetic field configurations in the device and the tuning results agree well with previous measurements. The difference between single-arm and double-arm configurations has been investigated experimentally. We conclude that this measurement benchmarks the applications of magnetic Wollaston prisms in Larmor diffraction and shows in principle that the setup can be used for inelastic phonon line-width measurements. The achievable resolution for Larmor diffraction is comparable to that using Neutron Resonance Spin Echo (NRSE) coils. The use of superconducting materials in the prisms allows high neutron polarization and transmission efficiency to be achieved.
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superconducting magnetic Wollaston prism for neutron spin encoding
Review of Scientific Instruments, 2014Co-Authors: S R Parnell, W A Hamilton, Brian B Maranville, T Wang, R Semerad, David V Baxter, J T Cremer, Roger PynnAbstract:A magnetic Wollaston prism can spatially split a polarized neutron beam into two beams with different neutron spin states, in a manner analogous to an optical Wollaston prism. Such a Wollaston prism can be used to encode the trajectory of neutrons into the Larmor phase associated with their spin degree of freedom. This encoding can be used for neutron phase-contrast radiography and in spin echo scattering angle measurement (SESAME). In this paper, we show that magnetic Wollaston prisms with highly uniform magnetic fields and low Larmor phase aberration can be constructed to preserve neutron polarization using high temperature superconducting (HTS) materials. The Meissner effect of HTS films is used to confine magnetic fields produced electromagnetically by current-carrying HTS tape wound on suitably shaped soft iron pole pieces. The device is cooled to ∼30 K by a closed cycle refrigerator, eliminating the need to replenish liquid cryogens and greatly simplifying operation and maintenance. A HTS film ensures that the magnetic field transition within the prism is sharp, well-defined, and planar due to the Meissner effect. The spin transport efficiency across the device was measured to be ∼98.5% independent of neutron wavelength and energizing current. The position-dependent Larmor phase of neutron spins was measured at the NIST Center for Neutron Research facility and found to agree well with detailed simulations. The phase varies linearly with horizontal position, as required, and the neutron beam shows little depolarization. Consequently, the device has advantages over existing devices with similar functionality and provides the capability for a large neutron beam (20 mm × 30 mm) and an increase in length scales accessible to SESAME to beyond 10 μm. With further improvements of the external coupling guide field in the prototype device, a larger neutron beam could be employed.
Rudolf Kilias - One of the best experts on this subject based on the ideXlab platform.
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scaphopoda typen und typoide mollusca im zoologischen museum in berlin
Mitteilungen aus dem Museum für Naturkunde in Berlin. Zoologisches Museum und Institut für Spezielle Zoologie (Berlin), 1995Co-Authors: Rudolf KiliasAbstract:Catalogue of the Types of Scaphopoda (Mollusca) in the Collections of the Zoological Museum in Berlin This paper provides a list of the type specimens of Scaphopoda (Mollusca) in the collections of the Zoological Museum in Berlin. It includes thirty-two types of species, described by Wilhelm Dunker, Frederick Wollaston Hutton, Siegfried H. F. Jaeckel, Eduard von Martens, Ludwig Plate, George Brettingham Sowerby and Henry Suter. Collection and bibliographical data are provided for the specimens.
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polyplacophora typen und typoide mollusca im zoologischen museum in berlin
Mitteilungen aus dem Museum für Naturkunde in Berlin. Zoologisches Museum und Institut für Spezielle Zoologie (Berlin), 1995Co-Authors: Rudolf KiliasAbstract:Catalogue of the Types of Polyplacophora (Mollusca) in the Collections of the Zoological Museum in Berlin This paper registers the type specimens of Polyplacophora (Mollusca) in the collections of the Zoological Museum in Berlin. It includes hundred-one types of species, described by Edwin Ashby, W. T. Bednall, William Healey Dall, Frederic Wollaston Huttton, Tom Iredale, Hugo Frederic Nierstrasz, Georg Pfeffer, Henry Augustus Pilsbry, Ludwig Plate, Jean Rene Constantin Quoy & J. P. Gaimard, Alphonse Tremeau de Rochebrune, George Ossian Sars, Leopold von Schrenck, Henry Suter, Johannes Thiele, Kurt von Wissel. Collection and bibliographical data are provided for the specimens.
