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A National Network Of Accelerators Dedicated To Material Irradiation (EMIR)
Hosting Legal Entity
Lujan Neutron Scattering Center at Los Alamos Neutron Science Center (LANSCE) of Los Alamos National Laboratory
Coordinating Country
United States
RI Keywords
condensed-matter, local structure, magnetism, nanomaterials
Lujan Center, Group Office TA-53, Bldg. 622, Rm. 220, LANSCE, Los Alamos National Lab, Los Alamos, NM 87545 USA
Pharos is designed for studies of fundamental excitations in condensed-matter systems.
Application Area
Pharos is designed for studies of fundamental excitations in condensed-matter systems.

Pharos can accommodate the full range of inelastic scattering experiments on liquid, polycrystalline, and single-crystal samples. This includes phonon and spin-wave dispersions, phonon density-of-states, magnetic excitations, momentum distributions, spin-orbit and crystal-field levels, chemical spectroscopy, and measurements of S(Q, ω) in disordered systems. In addition, the low-angle detectors are available for use at distances between 4 and 10 meters with scattering angles down to 0.65°, thus making it suitable for high-resolution inelastic studies (< 1% resolution) at low Q.
Pharos provides 2% to 4% incident energy resolution and uses a high-speed Fermi chopper to obtain monochromatic incident energies in the range from 10 meV to 2 eV. The sample is positioned 20 meters from a chilled-water moderator. The spectrometer consists of an evacuated, shielded flight path with 10 m2 of meter-long position-sensitive detectors located at a distance of 4 meters from the sample and covering scattering angles between -10° and 145°. Phonon dispersion of Pb at room temperature as measured by Pharos. The intensity of phonon branches are shown as a function of energy transfer and scattering angle. The data can be used to obtain the forces between Pb atoms and verify first-principles electronic-band structure calculations used in equation-of-state efforts. Specifications: - Incident energy resolution: ??Ei/Ei = 2% - 4% - Moderator-chopper distance: 18 m - Chopper-sample distance: 2 m - Moderator: Chilled water at 283 K - Fermi chopper frequency: 60 - 600 Hz - Fermi chopper diameter: 10 cm - Fermi chopper slit spacing: 1 mm or more - Sample size: up to 5 cm x 7.5 cm - Detectors: 10 m2 of meter-long position-sensitive detectors at 4"m from the sample and scattering angles between -10° and 145°; 1 m2 of detectors in forward scattering position can be moved up to 10 m from the sample.