Growth of Large Crystals for the National Ignition Facility
In order to meet the needs of the National Ignition Facility at the Lawrence Livermore National Laboratory (LLNL) for hundreds of half-meter-scale, high-quality single-crystal plates of potassium dihydrogen phosphate, KH2PO4 (KDP) (see Figure 1.1.1) and deuterated potassium dihydrogen phosphate, KD2PO4 (DKDP), the Laser Program at LLNL undertook a major effort to develop a method for growing these crystals at high production rates. This effort resulted in a production technology capable of producing half-meter boules at 5 to 10 times the rates previously possible. In addition, this effort led to a mechanistic understanding of the physics of KDP growth as well as the connection between growth defects and optical performance.
FIGURE 1.1.1 This potassium dihydrogen phosphate (KDP) crystal, weighing 701 pounds and measuring approximately 26 inches by 21 inches by 23 inches high, was produced in a record 52 days through a rapid-growth process perfected at the Lawrence Livermore National Laboratory (LLNL). A crystal of this size would have taken 2 years to grow using conventional methods. The enormous crystal was sliced into plates for use in the National Ignition Facility (NIF), a giant laser under construction at LLNL. The crystal plates (½ inch thick and 16½ inches square) are used to convert the laser’s infrared light beams to ultraviolet light just before the beams strike the laser target. About 500 of these plates are needed for NIF. SOURCE: Courtesy of Lawrence Livermore National Security, LLC, Lawrence Livermore National Laboratory, and the Department of Energy under whose auspices the work was performed.