Cavitation Density of Superfluid Helium-4 around 1 K

Using an optical interferomertric method, the homogeneous cavitation density of superfluid helium at $T=0.96$K is measured and found to be ${\rho }_{cav}=0.1338\pm 0.0002\mathrm{g}\mathrm{.}\mathrm{c}{\mathrm{m}}^{-3}$. A well established equation of state for liquid helium at negative pressures converts this to the cavitation pressure $P_{cav}=-5.1\pm 0.1$bar. This cavitation pressure is consistent with a model taking into account the presence of quantized vortices, but disagrees with previously published experimental values of $P_{cav}$.