Spin Flipper, Neutron Polarimetry, and Simulation, for the n3He Experiment

The n3He experiment constructed on FnPB [Fundamental neutron Physics Beamline-13] probes the PV [parity violating] nuclear force by measuring the statistical distribution of decay protons which result from the interaction of helium-3 nuclei with a beam of cold neutrons. Pulses of neutrons at 60 Hz are generated by the SNS [Spallation Neutron Source] from a 1 GeV proton beam colliding with a liquid Mercury target. Spalled neutrons are then focused into an intense cold neutron beam thru the use of a liquid hydrogen moderator and a neutron guide making the beam an effective tool as a low energy probe of the nuclear force. An essential instrument for the experiment is the high efficiency spin flipper. This is a state- of-the-art device based on the theory of double cosine-theta coils, and specifically constructed to prevent interference with other instrumentation in the experiment. Details of spin flipper design and integration are reported along with polarimetry and polarimetry measurements of spin flipper efficiency and beam polarization. A target yield analysis is also performed which precludes the construction of a yield profile simulation.