Fusion Science and Technology / Volume 64 / Number 2 / August 2013 / Pages 179-186
IFE / Proceedings of the Twentieth Topical Meeting on the Technology of Fusion Energy (TOFE-2012) (Part 1), Nashville, Tennessee, August 27-31, 2012
The United States Naval Research Laboratory (NRL) is developing the krypton fluoride (KrF) laser technology for a direct drive laser inertial fusion energy (IFE) power plant. The overall projected wall plug efficiency for KrF laser system is ~7%, including thermal management and optical losses. There are two KrF lasers at NRL. The first, Nike, provides up to 3 kJ of laser light per shot for experimental research in KrF laser-target interactions. The Electra Laser at NRL is a repetitively pulsed electron beam pumped 700 Joule KrF laser facility. The objective with Electra is to develop technologies to meet the IFE requirements for repetition rate, efficiency, and durability. Electra produces over 750 Joules in oscillator mode. Based on experiments, there is expected to be virtually no degradation in the laser focal profile, even at 5 Hz, high efficiency operation. Progress in durability has lead to achievement of KrF laser runs for 10 continuous hours at 2.5 Hz (90,000 shots) and 100 minutes at 5 Hz (over 30,000 shots). The main impediment to achieving long duration runs is the present pulsed power system that is based on spark gap switches. NRL has developed a new all solid state system that has operated for 11 million pulses continuously at 10 Hz and is based on components attaining 300 million pulses. These studies show an electron beam pumped KrF laser should be a viable approach for a laser fusion energy driver.