Upgrading scientific capabilities of the neutron interferometer in NPI Rez

Complete text of publication follows. Recently, the neutron interferometer set-up installed at NPI Rez has been reconstructed in order to improve the quality of the experimental results and to enlarge its flexibility for solving a wider range of physical problems. The LLL interferometer operates at λ = 0.1 nm and provides the output beam intensity (I0 + Ih) = 100 n/s with the interference pattern visibility of about 70%. A new sample holder permits positioning, rotation in a horizontal plane and tilt the sample in the both beams inside the interferometer. The upgraded interferometric facility was tested on the high accuracy measurement of the coherent scattering length of Si performed by a nondispersive phase difference method [1]. The result of this experiment is in a very good agreement with the results obtained from the measurements carried out in HMI Berlin and NIST Gaithersburg [2]. It proves that the coherent scattering lengths can be measured at our instrument with a relative uncertainty of 0.0002%. (author) [1] A. Ioffe and M. Vrana, Phys. Lett. A 231 (1997) 319.; [2] A. Ioffe et al., Phys. Rev. A 58 (1998) 1475