Advanced Laser Driver for Inertial Fusion Energy

Inertial confinement fusion (ICF) offers to tap almost unlimited sources of inexpensive energy. While ICF has been demonstrated at the Department of Energy (DOE) Lawrence Livermore National Laboratory (LLNL), its commercialization to inertial fusion energy (IFE) is impeded by the lack of an efficient and economical laser driver. Drivers for todays ICF facilities generate only a few pulses per day because of the waste heat deposited into the gain elements. To attain pulse frequencies of 10 to 20 Hz for commercial IFE, the drive laser must undergo revolutionary changes: 1) reduced waste heat, 2) new laser materials with high-thermal conductivity for efficient removal of residual heat, which are also producible in large sizes (~30 cm), 3) wall-plug efficiency ~20%, and 4) reduced driver size and cost. Aqwest is developing a new class of laser amplifiers known as the edge-pumped disk laser (EPDL). Results of our Phase I effort reported herein show that EPDL offers an efficient, modular, and economical approach to building high- pulse energy amplifiers scalable in a straightforward way to a full-size laser driver for IFE. We showed that Yb:YAG- based EPDL amplifier for IFE offers offers superior wall-plug efficiency with comparably smaller and less costly pump diodes than recently considered alternatives. Scalability of the EPDL-based laser driver over a broad range of sizes was theoretically validated. Based on these results, we prepared a concept design of the driver amplifier showing very compact and robust packaging. The Phase II project will build on these results to develop and test a laser amplifier module on a 1/25th of energy scale (1/5-th linear scale) in a configuration directly scalable to a full-size IFE amplifier. This will experimentally validate the gas-cooled EPDL and its scalability. This module may serve as a prototype building block for a future development of a subscale 400-J drive laser at 20 Hz. Other applications of the EPDL-based laser driver include laser acceleration of nuclear particles and research in high-density matter. Funding of Phase II project will greatly advance the ICF maturity and its transition to commercial IFE for generation of electricity. EPDL also has major commercial applications ranging from laser material processing (cutting, welding, additive manufacturing), lidar, and lasercom for satellite communication.