Creating extended, highly homogeneous plasma columns like that required by
plasma wakefield accelerators can be a challenge. We study the propagation of
ultra-short, TW power ionizing laser pulses in a 10-meter-long rubidium vapor
and the plasma columns they create. We perform experiments and numerical
simulations for pulses with 780 nm central wavelength, which is resonant with
the D2​ transition from the ground state of rubidium atoms, as well as for
pulses with 810 nm central wavelength, some distance from resonances. We
measure transmitted energy and transverse width of the pulse and use schlieren
imaging to probe the plasma column in the vapor close to the end of the vapor
source. We find, that resonant pulses are more confined in a transverse
direction by the interaction than off-resonant pulses are and that the plasma
channels they create are more sharply bounded. Off-resonant pulses leave a
wider layer of partially ionized atoms and thus lose more energy per unit
propagation distance. Using experimental data, we estimate the energy required
to generate a 20-meter-long plasma column and conclude that resonant pulses are
much more suitable for creating a long, homogeneous plasma.Comment: 12 pages, 14 figure