The beam homogeneity and stored energy of discharge pumped KrF excimer amplifiers are critically dependent on the preionization level of the active medium and on the rise time of the electric excitation pulse. Here a scheme is presented to increase the effectiveness of the preionization and to improve the rise time of the pump pulse by the use of the auto-spark-gap UV preionization of increased gap separation. The modified charging circuit has been proven to enhance the discharge quality and the amplification properties of the excimer module. The increased temporal jitter of the preionization sparks of large gap separation is eliminated by an additional pre-preionization scheme. The circuit is especially well suited for short-pulse KrF amplifiers.