  Differentially pumped capillaries, i.e., capillaries operated in a pressure
gradient environment, are widely used for nonlinear pulse compression. In this
work, we show that strong pressure gradients and high gas throughputs can cause
spatiotemporal instabilities of the output beam profile. The instabilities
occur with a sudden onset as the flow evolves from laminar to turbulent. Based
on the experimental and numerical results, we derive guidelines to predict the
onset of those instabilities and discuss possible applications in the context
of nonlinear flow dynamics.
