  The design and performance of the new Cold Neutron Chopper Spectrometer
(CNCS) at the Spallation Neutron Source in Oak Ridge are described. CNCS is a
direct geometry inelastic time-of-flight spectrometer, designed to cover
essentially the same energy and momentum transfer ranges as IN5 at ILL, LET at
ISIS, DCS at NIST, TOFTOF at FRM2, AMATERAS at J-PARC, PHAROS at LANSCE and
NEAT at HZB, at similar energy resolution. Measured values of key figures such
as neutron flux at sample position and energy resolution are compared between
measurements and ray tracing Monte Carlo simulations, and good agreement
(better than 20% of absolute numbers) has been achieved. The instrument
performs very well in the cold and thermal neutron energy ranges, and promises
to become a workhorse for the neutron scattering community for quasielastic and
inelastic scattering experiments.
