Spherical thermal counterflow of superfluid 4He

We generate quantum turbulence in spherically symmetric thermal counterflow of superfluid 4He driven by a central heater and probe it by second sound attenuation. We show that normal fluid turbulence forms above a certain critical threshold and, in the absence of shear flow, draws energy from a preexisting random tangle of quantized vortices corresponding to Vinen-type turbulence. This experiment can serve as a model flow for cosmological phenomena relating cosmic strings to quantized vortices, for processes occurring in neutron stars, or cosmological structure formation within superfluid models of dark matter.