New capabilities in spectroscopy on pulsed sources: adjustable pulse repetition rate, resolution and line shape

Spectroscopy with cold neutrons is one of the most important areas of current superiority of reactor based instruments over those at spallation sources. This is particularly due to the capability of continuous source time-of-flight spectrometers to use instrumental parameters optimally adapted for best data collection rate in each experiment. These parameters include the pulse repetition rate and the length of the pulses to achieve optimal balance between resolution and intensity. In addition, the disc chopper systems used provide perfect symmetrical line shapes with no tails and low background. We present a set of novel techniques making up the IN500 project at Los Alamos, which is based on the combined use of extended pulse length, coupled moderator, disc chopper system and advanced neutron optical beam delivery. This development will enable Lujan center to surpass the best reactor sources in cold neutron spectroscopy by realizing for the first time all of the above key capabilities of steady state instruments on a pulsed spallation source. (author)