Polarized Ultra-Cold Neutron Transport for Neutron Beta Decay Asymmetry Measurements

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Nuclear beta decay was important in motivating the Standard Model, andit continues to be of importance in searches for physics beyond the Standard Model.The simplest system for studying beta decay is the neutron. By measuring theneutron's lifetime (from the Ft value) and the neutron's beta asymmetry A, onehas enough information to independently determine the weak vector and axial-vectorcouplings, GV and GA. An approved experiment (located at Los Alamos) will again measure the A coefficient,utilizing Ultra-Cold Neutrons (UCN), dramatically reducing systematic errors otherwisepresent due to beam-induced backgrounds and incomplete polarization. The keyfeatures are 1) the ability to port the neutrons to a significant distance awayfrom their production site, 2) vetoing events when the beam pulse is on target,and 3) obtain 100% polarization using an axial magnetic field. This proposal covers efforts to develop an optimum coating fortransporting polarized neutrons, and implementing a suitable DAQ system for the experiment.It appears pulsed-laser-deposition (PLD) diamond films may be suitable.A successful campaign to make suitably coated guides would havean significant impact, not just for this experiment, but planned futureexperiments as well.5