Upgraded OMEGA emits 45 kilojoules of ultraviolet light
Last month, the newly upgraded OMEGA laser at the University of Rochester (NY) generated 45-kJ ultraviolet pulses, well beyond the target of 30 kJ, reports Robert L. McCrory, director of the Laboratory for Laser Energetics. The giant Nd:glass laser generates more than 60 kJ at the fundamental wavelength; those pulses are converted with about 75% efficiency to the 351-nm third harmonic for fusion experiments, says John Sources. The $61 million upgrade multiplies Omega`s pulse energy by a factor of 25 and raises its peak power to 60 TW in pulses lasting 650 ps, exceeding the peak power from the Nova laser at Lawrence Livermore National Laboratory in California.
Both systems are designed for inertial-confinement-fusion experiments, but with an important difference. Omega is designed for direct-drive fusion, in which the laser energy deposited on the shell of the target causes it to implode, heating the contents to the temperatures and pressures required for fusion. Beam uniformity requirements are stringent, because the target must be illuminated evenly to implode smoothly. Even illumination is not critical for Nova, because it is used mostly for indirect-drive fusion, in which x-rays from a laser-heated surface plasma implode the target.