A series of measurements on the high pressure (up to 18 bar) coaxial e-beam pumped Ar/Xe laser has been made at high power loading (up to 25 MW/cm~2) for various Xe mole fraction in Ar. We found that the optimum laser gas composition in our system was 0.4% Xe in Ar which was independent of the total gas pressure. At the optimum gas composition the output energy increased with increasing total gas pressure up to 16 bar, but the intrinsic efficiency reached a maximum at the total gas pressure of 8 bar. It was also found that at the optimum power deposition for both the 2.63μm and 2.65μm transitions the ratio of the integrated optical energy to that of the 1.73μm transition had a minimum in most cases at the optimum gas mixture for various gas pressures. This ratio increased with increasing gas pressure. The experimental results suggested that besides the 2-body Xe quenching at high Xe fraction and electron collision mixing at high power depositions the heavy particle quenching from Ar at high gas press A series of measurements on the high pressure (up to 18 bar) coaxial e-beam pumped Ar / Xe laser has been made at high power loading (up to 25 MW / cm 2) for various Xe mole fractions in Ar. We found that the optimum laser gas composition in our system was 0.4% Xe in Ar which was independent of the total gas pressure. At the optimum gas composition the output energy increased with increasing total gas pressure up to 16 bar, but the intrinsic efficiency reached a maximum at the total gas pressure of 8 bar. It was also found that at the optimum power deposition for both the 2.63 μm and 2.65 μm transitions the ratio of the integrated optical energy to that of the 1.73 μm transition had a minimum in most cases at the The experimental results suggested that besides the 2-body Xe quenching at high Xe fraction and electron collision mixing at high power depositions the heavy particle quenching from Ar at high gas press