Layout and performance of the polarizing guide system for the J-NSE spectrometer at the FRM II

The neutron spin-echo instrument, J-NSE, that has been moved from the ELLA guide hall at the FRJ-2 in Julich to the guide hall of the new FRM II reactor, needs an intense beam of polarized neutrons. Polarization of the short wavelengths is achieved in a bent section of about 8 m and radius 160 m, with a m = 3 FeSi multilayer coating. Due to the total reflection of Fesi, longer wavelengths (lambda similar or equal to 10-20 (A) over circle) pass unpolarized and need an additional short polarizer at the entrance of the instrument. After the bent section within a 10 m straight guide section a turn of vertical polarization to longitudinal guide field is performed and a selector is inserted. Then about 10m of tapered Ni-58 covered guide follows, which end with a cross-section of 60 x 60 mm(2). We present the design criteria and first measurements on the performance of this guide concept. (c) 2007 Elsevier B.V. All rights reserved.