  We present the scheme for a rubidium vapor source that is used as a plasma
source in the AWAKE plasma wakefield acceleration experiment. The plasma
wakefield acceleration process requires a number of stringent parameters for
the plasma: electron density adjustable in the (1-10)$\times$10$^{14}$cm$^{-3}$
range, 0.25% relative density uniformity, sharp ($<$10cm) density ramps at each
end, density gradient adjustable from -3 to +10% over 10m, and %-level density
step near the beginning the plasma column. We show with analytical and direct
Simulation Monte Carlo results that the rubidium density in the proposed source
should meet these requirements. Laser ionization then transfers the above
neutral vapor parameters to the plasma.
