  Superfluid helium nanodroplets are an ideal environment for the formation of
metastable, self-organized dopant nanostructures. However, the presence of
vortices often hinders their formation. Here, we demonstrate the generation of
vortex-free helium nanodroplets and explore the size range in which they can be
produced. From x-ray diffraction images of xenon-doped droplets, we identify
that single compact structures, assigned to vortex-free aggregation, prevail up
to $10^8$ atoms per droplet. This finding builds the basis for exploring the
assembly of far-from-equilibrium nanostructures at low temperatures.
