CHINESE JOURNAL OF PHYSICS VOL. 50, NO. 2 April 2012 3 He Neutron Spin Filters at the JCNS: Towards Wide-Angle Polarization Analysis and the Separation of Coherent/Incoherent Scattering from Non-Deuterated Biological Objects A. Ioffe, E. Babcock, S. Mattauch, V. Pipich, A. Radulescu, and M. S. Appavou J¨ ulich Centre for Neutron Science, Forschungszentrum J¨ ulich GmbH, Outstation at FRM II, Lichtenbergstr. 1, 85747 Garching, Germany (Received September 8, 2011) Polarization analysis is an important technique for polarized neutron scattering as it is allowing to obtain the full information about the vector magnetization in the sample that is critically important for detailed understanding of physical properties of new magnetic materials. Here we compare some of the major considerations between two different methods for polarization analysis – supermirror based analyzers and polarized 3 He neutron spin filters ( 3 He NSF) to be used for wide-angle, high-divergence applications like high Q-range small- angle neutron scattering (SANS). We will present the state-of-the-art in-situ (or on-beam) 3 He NSF avoiding the well-known problem of the time decay of 3 He (and neutron beam) polarization. In the simplified 1-dimensional version polarization analysis allows for the separation of coherent and incoherent scattering, making it a potentially important technique for studies of non-deuterated biological objects that themselves produce unavoidable incoherent back- ground because of a high hydrogen content. The power of the method will be demonstrated by experiments at biological samples, where the signal to noise ratio was increased by about a factor of 100 for high Q values above 0.1 ˚ A −1 . PACS numbers: 03.75.Be, 61.05.fg, 75.25.-j I. INTRODUCTION The Juelich Centre for Neutron Science (JCNS) the currently operates 10 neutron scattering instruments at the most modern European steady power reactor FRM II in Garching, Germany. A few of these instruments are newly built, while others, have been transferred from the Juelich research reactor DIDO after its shutdown in 2005, and have undergone very significant upgrades. One important characteristic of the JCNS instrumentation is the orientation towards the wide use of polarized neutrons: actually about 80% of JCNS instruments are designed to be polarized or to use polarized neutrons as an option. Almost all JCNS instruments are equipped with large-area position sensitive detectors allowing for simultaneous data collection in a wide range of the momentum transfer Q, in order to achieve the maximal possible efficiency of the scattered neutrons. As it is well known that polarization analysis always results in a significant intensity penalty (practically a factor of about 10), we pay special attention to the polarization analysis of neutron beams scattered in a wide angle spanned by such large-area detectors to compensate for above- http://PSROC.phys.ntu.edu.tw/cjp 137 c  2012 THE PHYSICAL SOCIETY OF THE REPUBLIC OF CHINA