A wide-aperture x-ray preionized XeCl laser with a capcitor-transfer-type excitation circuit is described. The characteristics of an x-ray generator is investigated through the measurements of x-ray dose, x-ray pulse shape, electron-beam current and acceleration voltage. It is found that the x-ray dose, the peak electron-beam current and the peak acceleration voltage are proportional to the 3.1 power, the 2.1 power and the 0.6 power of charging voltage, respectively. The maximum output energy of 2.7 J is extracted with an electrical efficiency of 1.4% from an active volume of 3cm× 5 cm×80 cm. The highest electrical efficiency of 2.3 % is achieved with an output energy of 2.2 J by the optimization of the primary and secodary capacitances.