In-situ azimuthal sample rotation within a horizontal-field cryomagnet for small-angle neutron scattering

Abstract

We present an in-situ azimuthal rotation stage for small-angle neutron scattering measurements. The stage provides an azimuthal rotation range of $315^\circ$ about the stage normal. At the reference sample-stick orientation, the stage normal is parallel to the incident neutron beam, so that the sample rotates in the plane perpendicular to the beam. Combined with a sample stick rotation about a second, orthogonal axis, the stage provides control of the magnetic-field direction relative to the crystal axes, while the field remains fixed in the laboratory frame. For a 5 mm diameter incident beam, sample-stick rotations of approximately $\pm315^\circ$ are accessible with negligible additional attenuation from the holder. The commercial rotator is specified for operation between 1 and 373 K and in magnetic fields up to 35 T, making the stage nominally compatible with the full temperature (1.8 to 320 K) and field (0 to 6.8 T) ranges of the used cryomagnet. As a working example, we characterize its performance on a spherical single crystal of MnSi between 20 and 35 K and in fields up to 183 mT, observing local sample heating during operation of $\sim$20 mK per $5^\circ$ step. We illustrate the design considerations behind the holder construction, with specific notes for mounting spherical samples, and discuss the resulting performance and limitations.