MCSTAS Simulation of the NSR apparatus

The NSR collaboration has designed a neutron spin polarimeter that can measure deviations in the average spin rotation of a beam of neutrons down to the 10E-7 rad/m level. The collaboration is considering using this polarimeter at the Missouri University Research Reactor to carry out experiments to test a predicted class of short range spin dependent forces that affect neutron polarization as they pass close to other dense masses of fermions. If these forces are demonstrated to exist this would extend the standard model of particle physics. Over the summer we developed a Monte Carlo simulation of the instrument in MCSTAS to estimate transmission rate for this instrument on a thermal rather than cold neutron beam and to begin the study of systematic errors. The simulation found that Helium polarization cells were more effective than supermirror polarizers tuned to cold neutrons. We find that about 0.2% of the neutrons that come out of the beam port at the MURR make it to the end of the beam and thus we could expect to measure a rotation angle at the level of 10^-7 radians in a couple months of beam time.