The anode material in an electron‐beam‐controlled gas laser strongly influences the uniformity of the sustainer discharge, because the backscattering of the beam electrons from the anode is different for different atomic numbers. As a result of switching from aluminum to, for instance, uranium, there is a 60% increase in the ionization near the anode, according to Monte Carlo computations for a typical planar laser configuration. This effect can cause a 30–60% drop in the local electric field, depending upon the field dependence of the electron‐ion recombination coefficient. As an example for studying this effect, we have considered a 150‐keV beam passing through an 0.8‐mil Ti window into a 26‐cm‐wide planar cavity containing a 3:2:1 mixture of He, CO2, and N2 at 1 atm and 293 K, with Eave=4.5 kV∕cm. Window power loading, electron attenuation, electron energy distributions, and sustainer field distributions were calculated for the two different anode materials.