College Park, Maryland      June 6 - 10 , 2004

TP44: Consequences of the interaction between dynamical diffraction and the Sagnac effect in LLL perfect single crystal interferometers

K.C. Littrell (Intense Pulsed Neutron Source, Argonne National Lab)

The LLL perfect single crystal interferometer is an exciting tool for exploring a variety of topics of fundamental importance in understanding quantum mechanics and for precision measurement of neutron scattering lengths. One of the limiting facors in many neutron interferometry experiments is the overall size of the interferometer. Hence, ever-larger interferometers would seem to be preferable. However, according to the theory of dynamical diffraction, neutrons that nearly but not exactly satisfy the Bragg condition take different trajectories through the crystal, splitting into two current branches at blade of the interferometer; thusthere are sixteen mutually interfering wavefunctions that contribute to the measurement of an interferogram. This complexity gives rise to shifts in the measured phase difference and a loss of contrast of the interferogram in the presence of potentials which are dependent on the spatial differences between the trajectories of the neutron through the interferometer. This effect has already been experimentally verified for the gravitational potential; here we discuss the similar effects of dynamical diffraction on the phase shift due to the Sagnac effect and their consequences on the observable contrast in large-scale interferometers.

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