  Highly collimated, plasma-filled magnetic flux tubes are frequently observed
on galactic, stellar and laboratory scales. We propose that a single, universal
magnetohydrodynamic pumping process explains why such collimated, plasma-filled
magnetic flux tubes are ubiquitous. Experimental evidence from carefully
diagnosed laboratory simulations of astrophysical jets confirms this assertion
and is reported here. The magnetohydrodynamic process pumps plasma into a
magnetic flux tube and the stagnation of the resulting flow causes this flux
tube to become collimated.
