Spatially very homogeneous gas discharges with long-pulse duration have been realized in HCl-based rare-gas halide gas mixtures at over-atmospheric pressures. A low inductive three-electrode prepulse–mainpulse configuration with two discharge volumes has been used as excitation circuit. The energy transfer efficiency of the pump circuit is very high and reaches 87%. Furthermore, the rise time of the discharge current is very short, in order to improve the discharge stability for high pump powers. Experiments in Xe/HCl/Ne mixtures reveal spatially very homogeneous discharges for up to 370 ns (FWHM) with a power deposition of 260 kW cm⁻³. For discharges in Kr/HCl/Ne mixtures, we also observe very homogeneous discharges for pump power densities of more than 500 kW cm⁻³. Discharges in mixtures with a krypton concentration of 100 mbar and 0.5 mbar HCl are homogeneous for 300 ns against 200 ns when 1 mbar of HCl is used.