Vortex Mutual Friction in Rotating SuperfluidHe3-B

We have measured the resistive and reactive mutual friction coefficients $B$ and $B^{\prime }$ in rotating superfluid ${}_{}{}^3{}_{}{}^{}\mathrm{He}$-$B$ at pressures of 1.6, 10, 20, and 29.3 bars. Near $T_c$, $\frac{B{\rho }_n}{\rho }$ diverges as ${(T_c-T)}^a$, with $a\approx -0.7\mathrm{}$, and $\frac{B^{\prime }{\rho }_n}{\rho }-2\mathrm{}$ tends to zero. Coefficients $d_{\parallel }$ and $d_{\perp }$ that relate the force to ${\mathrm{v}}_n-{\mathrm{v}}_L$, the relative velocity of normal fluid and vortex lines show relaxation-dissipation behavior tending slightly towards resonant dissipation. Within our experimental error there is no clear indication of the expected vortex core transition in our data at 20 and 29.3 bars.