World's Largest Fast-Growth Crystal Grown At Lawrence Livermore Lab

The pyramid-shaped KDP (potassium dihydrogen phosphate) crystal measures approximately 26 inches by 21 inches by 23 inches high. It was grown in a record 52 days using a special rapid-growth technique that delivers twice the yield originally projected.

The enormous crystal will be sliced into plates for use in the National Ignition Facility (NIF), a giant laser under construction at Lawrence Livermore. The crystal plates (1/2 inch thick and 16-1/2 inches square) will be used to convert the laser's infrared light beams to ultraviolet light just before the beams strike the laser target.

The National Ignition Facility, whose primary purpose will be to help maintain the safety and reliability of the nation's nuclear weapons stockpile, will require as many as 600 crystal plates.

Based upon a Russian technique pioneered by Natalia Zaitseva, now at Livermore, the Lab's improved rapid-growth process begins with a synthetic, thumbnail-sized seed crystal placed inside a six-foot-high tank filled with nearly a metric ton of supersaturated KDP solution at 150 degrees Fahrenheit. The temperature is gradually decreased to maintain supersaturation as the growing crystal extracts salt from the solution.

The record size of the latest crystal was achieved by giving the solution a transfusion of additional salt though a device called a continuous filtration system, which helps maintain crystal quality.

"This technique offers the possibility of producing even larger and higher quality crystals in the future," said Ruth Hawley-Fedder, group leader for the Livermore crystal growing team. "Our newest recordholder could have grown even larger, but we simply ran out of room in our growth tank."

The improved technique has been shared with commercial crystal suppliers who are producing crystals for NIF. About half the required crystals have been produced.

"Ruth and her team brought large-scale rapid-growth technology to the reliability needed to realize savings of millions of dollars for both construction and later operation of NIF," said Alan Burnham, deputy system manager for NIF final optics.

The previous crystal record-holder weighed 650 pounds. It was also produced at Livermore, using an earlier variant of the rapid-growth technique.

Founded in 1952, Lawrence Livermore National Laboratory is a national security laboratory, with a mission to ensure national security and apply science and technology to the important issues of our time. Lawrence Livermore National Laboratory is managed by the University of California for the U.S. Department of Energy.