Measurement of radial variation of 3.51-µm gain in xenon discharge tubes

Gain in a dc-excited 3.51-μm xenon-laser amplifier tube has been measured as a function of distance from the center of the discharge tube. At low excitation currents, this gain has a maximum on the axis, while at higher currents it has a local minimum on the axis. At the highest excitation currents reported, the gain coefficient goes negative at the center of the tube, but remains positive nearer the walls.