Measurements of low-level prepulse on Nike KrF laser

The krypton fluoride (KrF) laser is a leading candidate driver for inertial fusion energy. Some of the current fusion target designs call for targets with thin metallic coatings. These targets could be particularly susceptible to preheat by a low-level laser prepulse. Knowledge of the prepulse can be important in understanding and modeling the behavior of such targets. This paper presents measurements of low-level prepulse on target with the Nike KrF laser. Sources of prepulse are discussed and measurements are performed under several specific laser conditions in order to evaluate the relative contribution of these sources to the overall prepulse. Prepulse is found to be similar to 2x10(-7) from peak intensity for approximately 120 ns prior to the main laser pulse. Prepulse energy density on target is similar to 2 J/cm(2). The first laser amplifier in the time- and angle-multiplexed section of the laser is found to be the dominant source of prepulse. (c) 2005 American Institute of Physics.