A diode pumped solid state laser driver for inertial fusion energy

Abstract

A comprehensive conceptual design for a diode pumped solid state laser (DPSSL) as a driver for an inertial fusion energy (IFE) power plant is presented. This design is based on recent technical advances that offer potential solutions to difficulties previously associated with the use of a laser for IFE applications. The design was selected by using a systems analysis code that optimizes a DPSSL configuration by minimizing the calculated cost of electricity (COE). The code contains the significant physics relevant to the DPSSL driver, but treats the target chamber and balance of plant costs generically using scaling relations published for the Sombrero KrF laser concept. The authors describe the physics incorporated in the code, predict DPSSL performance and its variations with changes in the major parameters, discuss IFE economics and technical risk, and identify the high leverage development efforts that can make DPSSL driven IFE plants more economically competitive. It is believed that this study is a significant advance over previous conceptual studies of DPSSLs for IFE because it incorporates a new cost effective gain medium, applies a potential solution to the 'final optics' problem, and considers the laser physics in substantially greater detail. The result is the introduction of an option for an IFE driver that has relatively low development costs and that builds upon the mature laser technology base already developed for Nova and being developed for the proposed National Ignition Facility. The baseline design of the paper has a product of laser efficiency and target gain of qG -6.6 and a COE of 8.6 centsikW .h for a 1 GW(e) plant with a target gain of 76 at 3.7 MJ.Higher qG ( 2 11) and lower COEs ( 5 6.6 centsikW. h) can be achieved with target gains twice as high.

Laser crystals and ceramics: recent advances

“…Table 8 also lists several laser crystals with mixed anion pairs like chlorine-oxygen, fluorineoxygen, and sulphur-oxygen. Among them are the Yb 3+ -doped apatite structure family of crystals [48], Sr 5 (PO 4 ) 3 F, with unusually favourable laser gain characteristics that have been applied already in the development of a highpeak-power "Mercury" laser system for utilization in inertial fusion energy production [49,50].…”

“…[37,38,49,50]). To illustrate this expectation more clearly, the corresponding spectroscopic and thermal parameters of Y 2 O 3 :Nd 3+ ceramics as possible candidates for LD-pumped high-energy SSL systems for laser fusion reactor drivers have been plotted for comparison (Fig.…”

“…[38,56]). Experts from the Institute of Laser Engineering of Osaka University [38,56] prefer the Nd HAP-4 glass for LD-pumped laser drivers, while Sr 5 (PO 4 ) 3 F:Yb 3+ single crystals have been the focus of attention at the Lawrence Livermore Na- Figure 23 Comparative plot of certain spectroscopic and physical properties of selected Nd 3+ -and Yb 3+ -doped SSL materials (Nd HAP-4 glass [56], Sr5(PO4)3F:Yb 3+ for two lasing polarizations [49,50], and Yb 3+ -and Nd 3+ -doped Y3Al5O12 single crystals) which are undergoing experiments with the aim of producing LD-pumped slab amplifiers for laser fusion reactor drivers. The positions in the plot of Nd 3+ -doped laser SiO2 glass, disordered fluoride crystals, and Y2O3 ceramics are subject to refinement after full characterization of their properties.…”

<title>Diode-pumped solid state lasers (DPSSLs) for inertial fusion energy (IFE)</title>

“…The helium cooling gas removed heat from each surface at a flux up to >3 watts/cmZ before slab fracture occurred. This result was quite satisfactory, since IFE driver design analyses [4,16] indicate that the amplifier slabs in an optimized MxS-FAP IFE driver will require only about 0.75 watts /cm2 of heat flux removal per slab surface. Interferometric imaging of the thermally loaded Yb:S-FAP slab indicated that less than an optical wave of distortion was thermally induced in the slab, even at the highest loading imposed.…”

“…The development of efficient (>5070) room-temperature semiconductor laser diode arrays as power-scalable (>>kW) pump sources for solid state lasers has significantly improved the prospects for developing a solid state laser system with characteristics suitable for driving an IFE central electric power plant [1][2][3][4]: efficiency >1O? 'O and average output power >10 MW.…”