A novel, active, mode‐locking scheme for producing single, line‐tunable, high‐power ultrashort CO2‐laser pulses is described. Using an auxiliary grating‐tuned cw CO2 laser for injection locking on the 9R(16) line, the Q‐switched, mode‐locked, and cavity‐dumped 10‐atm CO2 laser produces single, detection‐limited (≪500 ps) pulses of 5‐mJ energy at λ=9.29 μm. Details are given on the traveling‐wave GaAs Pockels cells, both of which are controlled by a single, ultraviolet (UV) triggered spark gap. The time‐locked output pulse is delayed by precisely 300.7 ns with ≪±50 ps jitter against the UV triggered spark gap, so the laser pulse is synchronizable to an external event to ≪±250 ps. To drive the transverse‐electric (TE) 10‐atm amplifier section, instead of the conventional Marx bank or inductance‐capacitance (LC) generator, a new type of circuit is used. The automatically preionized, double‐sided LC inversion circuit uses only one spark gap, and a detailed description with operating characteristics is provided.