Journal of Low TemperaturePhysics, rcbl.35, Nos. 5~ 6, I979 Anisotropy and Flow in 3He-A* R. L. Kleinbergt Department of Physics, University of California--San Diego, La Jolla, California (Received October 30, 1978) Thermally driven counterflow in 3He-A is investigated, using techniques that exploit the anisotropy of the fluid. The results are discussed in terms of both uniform-texture and helical-texture hypotheses. Anisotropy of heat flow is observed]or the first time and a limitation of the superfluid velocity is strongly suggested. INTRODUCTION Superfluid 3He-A is not a simple liquid. On the theoretical side it is characterized as lJeing a BCS-superfluid-like state possessing two lightly coupled anisotropy axes. The variations of these axes in time and space give rise to a "textured" anisotropy which will influence and be influenced by currents and fields. On the experimental side, an unprecedented profusion of magnetic effects have been observed, and, although not as much has been done in the area, flow effects promise to be as complicated. This paper presents the most direct measurements of thermally driven flow made to date. It is organized into a number of sections: (1) the two-fluid model; (2) effects influencing the orientation of the anisotropy axes in bulk; (3) a textural phase diagram; (4) experimental; (5) temperature measure- ment and heat leak; (6) comment on interpretation; (7) field ramping measurements: uniform texture hypothesis; (8) field turnoff measurements: uniform texture hypothesis; (9) anisotropy of heat transport: uniform texture hypothesis; (10) results: helical texture theory. 1. THE TWO-FLUID MODEL Keeping in mind Henry Hall's 1 dictum that it is best to be wary of an "excessive desire for analogies with 4He," we should learn what we can from that very extensively studied liquid. 2'3 *This work was supported by the U.S. Department of Energy under contract EY-76-S-03- 0034, P.A. 143. tPresent address: Exxon Research and Engineering Company, Linden, New Jersey. 489 0022-2291/79/0600-0489503.00/0 ,~ 1979Plenum Publishing Corporation