IFE power plant design principles. Drivers. Gas laser drivers

When attention turns from physics to inertial confinement power plants, gas lasers become more interesting, due to high pulse rate and high efficiency. Two kinds of gas laser recently have been of particular interest as inertial fusion drivers: the electron beam pumped krypton fluoride (KrF) laser and the flashlamp or discharge pumped iodine laser. The krypton fluoride laser has become the first choice because of its broad amplification bandwidth while its shorter wavelength does not need conversion. It also has a high pulse rate, acceptable overall efficiency, low cost, and adequate optical smoothing capability. The kinetics of electron beam pumped KrF lasers has been extensively studied and is discussed here, in addition to the electron beam pumped KrF amplifiers and the system architecture for krypton fluoride lasers. The physical properties of photolytically pumped iodine lasers are discussed briefly. Six development issues for KrF lasers are listed in the concluding comments: (i) the ability to produce laser pulses with taylored temporal profiles; (ii) predictions of modelling and experimentation indicate that amplified spontaneous emission (ASE) does not pose a fundamental limit to the size of KrF amplifiers; but these results will have to be confirmed with larger amplifiers; (iii) the beam transport efficiency should be increased; (iv) in view of the inherent broadband capability of KrF lasers and the demonstrated effective amplification of pulses of 170 /cm bandwidth the time is appropriate to investigate the propagation of such broadband pulses on a multistage electron beam pumped system; (v) more extensive investigations of nonlinear propagation effects are required to assess whether they would cause losses during the propagation of high intensity laser pulses through the long air paths to the target; (vi) as in the krypton fluoride laser one molecule of fluorine is consumed for every photon emitted. However, the extraction efficiency of the laser light varies inversely with fluorine concentration. Therefore, experimental work is required to verify model predictions of optimal operating conditions. 24 refs, 5 figs