First and second viscosity measurements in superfluid ³He-B

By means of diaphragm-driven flow experiments in ³He-B in a thin slab geometry, we have measured the first and second viscosities, η and ₃ at pressures of 0, 5, 10 and 29.3 bar. Our measurement of ₃ has better established theoretical foundations than previous measurements and also extends to higher pressures. ₃ and η were deduced from the frequency dependence of the flow dissipation determined from bandwidth measurements for several normal modes of the diaphragm; a first order slip correction was used in the determination of η. Near T_c, ₃ α (1 - T/T_c)^-1/2 in accordance with theoretical predictions but below T/T_c ~ 0.6 we observe a rapid drop in ₃ signifying a departure from the hydrodynamic limit.