UV power balance on the OMEGA laser

The OMEGA laser at the University of Rochester's Laboratory for Laser Energetics is used for direct-drive inertial confinement fusion (ICF) experiments. To achieve highly symmetric implosions, it is necessary that all of the beams be power balanced. The definition of power balance must be tied to the physics of the ICF targets: in a given time interval what level of nonuniformity can be tolerated before the laser drive disrupts the implosion. We monitor the pulse shape on several of the OMEGA beamlines using multiplexed streak cameras. From a database of over 15,000 individual streaks we have determined that if all the OMEGA beams are energy balanced to the 1 percent level, the present system would have an overall power balance of better than 10-15 percent. This was determined by grouping individual traces by pulse shape and energy. A further improvement in power balance can be obtained by matching the electrical energy stored in Nd:glass amplifiers. This information is important because the first step in achieving power balance will be to energy balance the OMEGA laser. This research tells us what strategies for achieving energy balance will enhance power balance.