The GAMS4 flat crystal facility

A high-resolution flat-crystal gamma-ray facility, GAMS4, has been construc ted at the high-flux reactor at the Institut Laue-Langevin (ILL), Grenoble, France. The facility is located at the exit of a through-tube equipped to place sources in a neutron flux of approximate to 5.5 x 10(14) n cm(-2) s(- 1). Considerable care has been exercised to provide a precision gamma-ray m etrology station including vibration isolation, temperature control, enviro nmental monitoring, background suppression, and remote and automatic spectr ometer control. The diffraction angles are controlled and measured interfer ometrically and absolute angle calibration is established with a relative u ncertainty of approximate to 3 x 10(-7). The crystals are nearly perfect sp ecimens of Si and Ge whose lattice spacings are measured in meters and have a relative uncertainty of approximate to 5 x 10(-8). The resolution obtain ed with this Facility closely approaches dynamical diffraction predictions. Examples of measurements performed using this facility include (1) absolut e wavelengths standards and neutron binding energies, (2) lifetimes of nucl ear exited states, (3) determination of interatomic potentials, and (4) cry stal structure factors. GAMS4 is a scheduled ILL instrument with beamtime b eing awarded through the ILL proposal process. (C) 2001 Elsevier Science B. V. All rights reserved.