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The Diamond Anvil Cell (DAC)

The development of diamond anvil cell technology has resulted in tremendous gains in knowledge of the physical world through scientific investigation of the behavior of matter under a wide range of pressures.  In Earth and planetary sciences, laboratory experiments utilizing high pressure and temperature offer the only means to examine directly the conditions of deep planetary interiors.  Fundamental questions about phase transformations, crystal structure and the nature of atomic bonding can be answered using high-pressure techniques.  Finally, the use of high pressure to synthesize new materials, to study the behavior of existing materials and to tune material physical properties provides tremendous potential for advances in applied materials research.

 

Diamond, in addition to being recognized as the hardest and least compressible material, has the important property of being transparent to most of the spectrum of electromagnetic radiation, including g-ray, X-ray, portions of ultraviolet, visible, and most of the infrared region.  The DAC is based upon the opposed-diamond configuration, in which a sample is placed between the polished culets of two diamonds and is contained on the sides by a metal gasket.  In this configuration, very little force is required to create extremely large pressures in the sample chamber, and, because of the transparency of diamond, the sample may be examined in situ (while at elevated pressure) by optical microscope, spectroscope (Raman, infrared, Brillouin), and diffraction techniques.

Opposed diamond anvils

Configuration with a
metal foil gasket
Diamond Anvil Cell Diagram

The diamond anvils are skillfully cut from natural, gem quality stones to have 16 pavilion facets, a 70% table, and a working surface (culet). The anvils are cut to correct crystallographic orientation [table and culet parallel to the (100) diamond plane] and care is taken to insure parallelism of the table and culet.

The culet of the diamond anvil is typically 0.6 mm in diameter. This size insures that pressures of up to 20 GPa (GPa = 10 kbar = 10,000 bar = 9,870 atm) can be achieved (depending upon the choice of DAC). To perform studies to higher pressures, diamonds cut with smaller, beveled culets are recommended.

A) Diamond supports
B) Diamond anvils
C) Inconel gasket

The selection of diamond type and culet size should be based upon the experimental techniques which are to be employed and the maximum pressure to be achieved.

Diamond Type Experimental Techniques
Type I Diffraction
Optical
Type I
(Low-fluorescence)
Raman
Diffraction
Optical
Type IIa Infrared
Diffraction
Optical

 

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Copyright 2008 by High Pressure Diamond Optics, Inc.
Last updated: August 12, 2008