Open AccessUsing the MCLIB Library: Small-Angle Instrument with Focusing-Mirror Collimation
Author(s) -
P.A. Seeger
Publication year - 1997
Language(s) - English
Resource type - Reports
DOI - 10.2172/659638
Subject(s) - optics , toroid , physics , collimated light , resolution (logic) , neutron , monte carlo method , scattering , conical surface , collimator , tangent , geometry , nuclear physics , plasma , laser , mathematics , computer science , statistics , artificial intelligence
Focusing mirrors in 1 or 2 dimensions can be used to increase the intensity in a small-angle instrument while maintaining high resolution. Using the recently added toroidal mirror region type in MCLlB (Monte Carlo library for neutron instrument design), we compare five mirror shares: the ideal ellipsoid the tangent toroid, 8 tangent toroidal segments, 8 tangential cylindrical segments, and 20 tangential cylindrical segments. A small-angle scattering instrument on a spallation source was simulated to study resolution. Comparisons show that the ellipsoid provides superior resolution, but that the 8 tangential toroids are a good compromise. A resolution of 0.00056 {Angstrom}{sup -1}(rms), or (-)(+)11% at Q = 0.005 {Angstrom}{sup -1}, was achieved in the simulation using neutrons in the wavelength range 4-15 A. The count rate is high because the full area of the moderator is viewed