NMR study of the effect of flow on3He-B

We have used a plastic diaphragm to generate flow in superfluid³HeB, through a cylindrical geometry, whilst monitoring the transverse NMR frequency. It was found that the critical flow velocity needed to induce NMR frequency shifts was dependent on the magnetic field. The results are explained by a numerical calculation of the texture in the³HeB, under the influences of magnetic field, fluid flow and surface energy terms. Also presented are measurements of the B phase NMR longitudinal frequency, derived from the magnitude of the flow-induced change in the transverse frequency. A flow-induced texture transition, which caused a dramatic narrowing of the NMR lineshape, is described.