Overview
The instrumentation suite at LENS reflects the facility's commitment to the study of large scales structures and innovation in neutron instrumentation. Typical neutron fluxes at the sample position greater than 104 n/km1.s so the facility concentrates on measurements of structure rather than dynamics in condensed matter systems. Novel aspects of the source that are exploited by these instruments include the cold neutron spectrum and the variable source frequency. The initial suite of instruments will include:
SANS
The SANS instrument will be a conventional pin-hole instrument that exploits the cold spectrum available from the LENS moderator to reach a minimum Q on the order of 0.05nm-1 with relatively corse geometric collimation in order to maximize the available flux. The sample position will be 8.0m from the moderator face, and the secondary flight path may be varied between 1.5 and 4.5m. The instrument's wavelength band runs from 0.45nm (set by a Be filter in the incident beam) to 1.3 or 2.0 nm (depending on the secondary flight path length and source frequency). Initially the instrument will employ an Ordella delay line 2-D area detector with 1cm resolution and will also include a detector in the beam stop to measure energy-dependent total cross sections simultaneously with small angle scattering.
SESAME
One of the beam lines at LENS is devoted to the development of a novel instrument that employs neutron spin-echo techniques to encode scattering angles. This technique greatly increases the efficiency with which neutrons are used, since it can provide very precise angular resolution even in the absence of a highly collimated beam. The technique requires a polarized beam of neutrons and various technologies are being explored to produce the spin-flips and precessions needed.
Optics Test Bench
The unique ability of the LENS source to provide a variety of pulse widths and repetition rates provides important opportunities for investigating optical components that could be used on a wide variety of instruments (including ones suitable for long-pulse or very cold neutron sources). One of the four neutron beam lines will be reserved, at least initially, for testing such components. Initially the beam will feed neutrons for the commissioning of the aCORN weak interaction experiment.
A conventional neutron radiography camera has also been constructed for performing non-destructive imaging of high-contrast subjects with cold neutrons. In addition, we are developing novel detector systems for performing high-energy neutron radiography from the small neutron source obtained when a small (1cm or less diameter) proton beam illuminates the Be target.
Moderator Testing
The LENS facility will make use of several of the above beam lines to conduct research into moderator performance. Emission spectra may be measured with 3He detectors on any of the beam lines. In addition to this, emission time distributions may be measured on the neutron optics beam line using a time-of-flight apparatus with a crystal analyzer that is cooled to 11K. The standard LENS moderator is capable of accurately condensing various gas mixtures, and the facility is capable of characterizing any moderator prototype that can fit within the 50cm diameter/50 cm tall cylindrical water reflector volume (assuming compatibility with the standard Be target geometry is maintained). Prospective users should contact LENS technical staff for details early in the process of designing any prototype systems to be studied to assure compatibility with the LENS target.
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