RESEDA: double and multi-detector arms for neutron resonance spin echo spectrometers

Abstract

RESEDA is the new cold neutron resonance spin echo (NRSE) spectrometer at the FRM II in Munich. In order to measure simultaneously at two different scattering vectors, RESEDA is equipped with two complete secondary spectrometer arms. Both the primary and the secondary spectrometer arms contain identical spin precession regions. Depending on the operation mode, they are alternatively defined by NRSE coils at both sides of 2.6 m long zero field regions or by additional NSE coils used at small spin echo times down to 1 ps. Larger spin echo times up to 10 ns are reachable by means of the bootstrap NRSE setup. Double- or multi-arm spin echo setups as built at RESEDA can only be realized with the NRSE technique, thanks to the compactness of the NRSE coils and the magnetic shielding. At RESEDA, the whole spectrometer is surrounded by double Mumetal shielding. Magnetic stray fields are suppressed very effectively and, consequently, the two secondary spectrometer arms are not interfering. We describe the design of the double-arm spectrometer RESEDA and we report on measurements using both secondary spectrometer arms. Furthermore, we present the design of a new multi-detector NRSE coil and, finally, we will give a brief outlook on the development of a multi-detector MIEZE setup planned at RESEDA.