CRITICAL VELOCITY OF VORTEX NUCLEATION IN ROTATING SUPERFLUID HE-3-A

We have measured the critical Velocity upsilon(c) at which He-3-A in a rotating cylinder becomes unstable against the formation of quantized vortex lines with continuous (similarity-free) core structure. We fin d that upsilon(c) is distributed between a maximum and a minimum limit , which we ascribe to a dependence on the texture or the orbital angul ar momentun axis (I) over cap(r) in the cylinder. Slow cooldown throug h T-c in rotation yields (I) over cap(r) textures for which the measur ed upsilon(c)'s are in good agreement with the calculated instability of the expected (I) over cap texture.