Performance of the multidetector NSE spectrometer SPAN at BENSC

The neutron spin-echo spectroscopy (NSE) precession field, which is created by three pairs of coils with diameters 1, 3 and 4.8 m, respectively, is th e peculiarity in the design of SPAN. Each pair is mounted in a Helmholtz-li ke fashion, with the electric currents oriented oppositely to each other, o ne coil above and one coil below the horizontal scattering plane. The cente rs of all coils are placed on the same vertical axis, which crosses the sam ple position. The NSE field is horizontal with axial symmetry. Particular c are has been taken to shape the magnetic field around the sample, which is weak, vertical and very homogeneous. We present a first series of NSE measu rements, which show that only little held adjustment is required to satisfy the exact echo condition (phase) simultaneously for a range of scattering angles and confirm the high axial symmetry of the precession field. The res ults show that the new magnetic field configuration of SPAN allows for mult idetector NSE over a wide angular range. (C) 1999 Elsevier Science B.V. All rights reserved.