Jan. 4, 2000

World's Largest Fast-Growth Crystal Grown At LawrenceLivermore Lab

LIVERMORE, Calif. - The world's largest fast-growth crystal,weighing in at 701 pounds, has been grown by researchers at the U.S.Department of Energy's Lawrence Livermore National Laboratory.

The pyramid-shaped KDP (potassium dihydrogen phosphate) crystalmeasures approximately 26 inches by 21 inches by 23 inches high. Itwas grown in a record 52 days using a special rapid-growth techniquethat delivers twice the yield originally projected.

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

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

Based upon a Russian technique pioneered by Natalia Zaitseva, nowat Livermore, the Lab's improved rapid-growth process begins with asynthetic, thumbnail-sized seed crystal placed inside a six-foot-hightank filled with nearly a metric ton of supersaturated KDP solutionat 150 degrees Fahrenheit. The temperature is gradually decreased tomaintain supersaturation as the growing crystal extracts salt fromthe solution.

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

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

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

"Ruth and her team brought large-scale rapid-growth technology tothe reliability needed to realize savings of millions of dollars forboth 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 alsoproduced at Livermore, using an earlier variant of the rapid-growthtechnique.

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

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