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Showing 1 to 20 of 43 for “"Helium 4"”.
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Thermal vacancies in HCP helium-4
Activation energies of thermal vacancies have been determined in hcp $\sp4$He as a function of molar volume. A sensitive strain gauge was used to measure the temperature dependence of the pressure in twenty crystals between 18.17 and 20.9 cm$\sp3$/mole. Absolute lattice parameters at low …
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Thermal vacancies in hcp helium-4
Activation energies of thermal vacancies have been determined in hcp 4He as a function of molar volume. A sensitive strain gauge was used to measure the temperature dependence of the pressure in twenty crystals between 18.17 and 20.9 cm3/mole. Absolute lattice parameters at low temperatures were …
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Electroproduction of Neutral Pion Off Helium-4
… electron beam impinging on a 30 cm long, 6 atm Helium-4 gaseous target. In order to ensure that the process is coherent, a new Radial Time Projection Chamber was used to detect and identify low energy recoil <em>α</em>-particles. The Beam Spin Asymmetry in the coherent deep exclusive regime was …
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The Ground State of Liquid Helium-4
Made available in DSpace on 2015-05-12T21:41:29Z (GMT). No. of bitstreams: 2 license.txt: 4848 bytes, checksum: 96035ab3f5e1c23cc7138a224ce498bd (MD5) 6408414.PDF: 1387465 bytes, checksum: 28a061df455a53488735ec3db059706e (MD5) Previous issue date: 1964
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Vacancies in low-density hcp helium-4 solids
… and thermally-activated excitations in helium solids have been extensively examined by a variety of experimental and theoretical studies. Although these excitations are typically identified as vacancies, large discrepancies arise in exactly what their nature and role are in the …
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Measurements of Vortex Diffusivity in 2d Superfluid Helium-4
We measure for the first time the characteristics of vortex induced superfluid flow dissipation at temperatures well below the Kosterlitz-Thouless superfluid transition temperature. Our studies are with films of coverage .25 < (sigma)(,s) < 1.9 superfluid atomic layers and with .55 < T(,KT) < …
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An absolute measurement of the photodisintegration of Helium-4
A measurement of the differential cross section has been performed for the photodisintegration of ⁴He into a proton plus a triton. This reaction is highly sensitive to the electromagnetic currents in the nucleus which arise from the exchange of mesons between nucleons. The study of light nuclei …
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Phase separation in solid mixtures of helium-3 and helium-4
Phase separation temperatures have been determined in bee 3He-4He mixtures as a function of 3He concentration and melting pressure from measurements of changes in the x-ray lattice parameter and peak shape. A new rigid tail dilution refrigerator cryostat is used to study 3 He-4He crystals with 3He …
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Elastic photon scattering from helium-4 between 23 and 73 MeV
Elastic photon scattering cross sections were measured for $\sp4$He at 45 and 135 degrees. These measurements were performed at energies between 23 and 73 MeV using the University of Illinois tagged photon facility. The principal contributions to the scattering in this energy range are the nuclear …
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Three Particle Effects in the Pair Distribution Function for Helium-4 Gas
Made available in DSpace on 2015-05-12T21:41:44Z (GMT). No. of bitstreams: 2 license.txt: 4848 bytes, checksum: 96035ab3f5e1c23cc7138a224ce498bd (MD5) 6808126.PDF: 3301878 bytes, checksum: 5d5bbaf019ddb2ac87575167eb31e594 (MD5) Previous issue date: 1967
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Momentum density of hcp and liquid helium-4 by inelastic neutron scattering
Submitted by Carolyn Mead (cmead2@illinois.edu) on 2011-06-08T16:10:35Z No. of bitstreams: 1 1983_hilleke.pdf: 5067231 bytes, checksum: d2a10e07e8841e9e47edb13560536a33 (MD5)
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The Thermal Boundary Conductance Between a Thin Helium-4 Film and Its Substrate
Made available in DSpace on 2015-05-13T15:22:12Z (GMT). No. of bitstreams: 2 license.txt: 4848 bytes, checksum: 96035ab3f5e1c23cc7138a224ce498bd (MD5) 7811287.PDF: 1409589 bytes, checksum: 5610bad69d0141a2b330853e44e933b2 (MD5) Previous issue date: 1978
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Landau Model for Films and Interfaces of Superfluid Helium-4 at T = 0k
We use a Landau theory appropriate to an inhomogeneous superfluid at temperature T = 0 to describe structural and dynamical effects at a gas/superfluid interface and for a superfluid film on an inert attractive substrate. The parameters of the theory are determined phenomenologically by fitting …
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Phonon-Quasiparticle Interactions in Dilute Solutions of Helium-3 in Superfluid Helium-4
Made available in DSpace on 2015-05-12T21:41:51Z (GMT). No. of bitstreams: 2 license.txt: 4848 bytes, checksum: 96035ab3f5e1c23cc7138a224ce498bd (MD5) 6910837.PDF: 3738795 bytes, checksum: d05611352ccb1c73625c42d04566eed5 (MD5) Previous issue date: 1968
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Combined X-Ray and Thermal Conductivity Study of Hexagonal-Close-Packed Helium-4
Made available in DSpace on 2015-05-12T21:41:54Z (GMT). No. of bitstreams: 2 license.txt: 4848 bytes, checksum: 96035ab3f5e1c23cc7138a224ce498bd (MD5) 7013302.PDF: 2755643 bytes, checksum: 5c70d685e133a8e1a642b5e8cf648376 (MD5) Previous issue date: 1969
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Combined x-ray and thermal conductivity study of hexagonal-close packed helium-4
… measurements made on hexagonal-close-packed helium-4 are reported for specimens whose quality and orientation were determined directly by an x-ray method. The specimens, 2.2mmin diameter by 23 mm long, were held in a nylon container. They were obtained by unidirectional growth from the fluid …
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Magnetic Properties of Dilute Solutions of Liquid Helium-3 in Helium-4 Atlow Temperatures
Made available in DSpace on 2015-05-12T21:41:39Z (GMT). No. of bitstreams: 2 license.txt: 4848 bytes, checksum: 96035ab3f5e1c23cc7138a224ce498bd (MD5) 6706722.PDF: 3003856 bytes, checksum: 3c9248d82e28939f7e6830c7aa4fd472 (MD5) Previous issue date: 1966
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X-ray diffraction study of vacancies in bcc helium-3 and bcc helium-4
Submitted by Carolyn Mead (cmead2@illinois.edu) on 2011-06-13T17:02:41Z No. of bitstreams: 1 1982_granfors.pdf: 4976253 bytes, checksum: e552b132221ed1a25b853f6b916a974f (MD5)
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Thermal vacancies and phase separation in bcc mixtures of helium-3 and helium-4
… of the absolute lattice parameter of the helium crystals with an accuracy of 300 ppm, and measurements of changes in lattice parameter to better than 60 ppm. The phase separation of the concentrated 3He-4He mixtures has been studied in detail with the x-ray measurements. Vacancy …
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