The DDIA was designed just prior to the beginning
of the RGC phase I program (DURHAM et al., 2002b; WANG et al., 2003a).
The prototype system was built by Livermore Labs under the supervision
of Durham. The first experiments at a synchrotron were carried out
at Brookhaven National Labs during RGC phase I in 2002. Based on
the success of this system, three more DDIAs have been built, one
which remains at Brookhaven Labs, one at GSECARS in Chicago, and
one with Green at UC Riverside. Another has been built at the Bayerisches
Geoinstitut in Bayreuth, Germany. The original Livermore DDIA is
now at Minnesota with Mei and Kohlstedt. The DDIA is derived from
the Japanese designed DIA, a cubic anvil system that compresses
a cubic assembly with a single hydraulic ram. Such a device has
been running routinely at the NSLS beamline since about 1990 and
at GSECARS since their beginning. The DDIA modification adds two
rams, one to drive the top anvil and one for the bottom. With three
rams in place one can maintain a constant pressure with the main
ram as the differential rams push to shorten the entire sample assembly.
The solid medium sample assembly includes pistons, usually made
of corundum, that transmit the force of the deforming anvils to
the sample as a differential stress. Since stress and strain are
measured directly in the sample, the strength of the pressure medium
is not important, only the sample stress vs strain rate. The sign
of the deforming stress in this system can be reversed by retracting
the deforming rams. This feature adds to the flexibility of the
DDIA.
The rotational Drickamer (RDA) is a modified version of Drickamer
apparatus in which a rotational actuator is added to a conventional
Drickamer apparatus (Fig. 4). After pressurization (and heating),
one of the anvils can be rotated causing shear strain to a sample.
The motivation for the design of this apparatus was twofold: (i)
because of its design, the support for anvils in a rotational Drickamer
apparatus is nearly identical to that of a conventional Drickamer
apparatus for static experiments. Consequently, one can conduct
deformation experiments under the P-T conditions similar to those
for static experiments. Using a tungsten carbide anvils, deformation
experiments have been performed to ~18 GPa, ~1800 K (stability field
of ringwoodite), (ii) also because of the geometry of deformation,
there is no limitation in the maximum strain.
 
(left) Schematic of the DDIA by Bill Durham. The DDIA high pressure
device is driven by one main ram indicated by the big arrows. This
ram drives the top and bottom anvils together and the side anvils
(2 of the 4 are illustrated) are driven into the sample chamber
by a wedge type effect. The upper and lower anvils have each an
additional ram that can drive them independently of the main ram
and hence independently of the side anvils. During deformation,
the main ram may need to be backed off of the sample in order to
maintain a constant pressure (which can be monitored by the diffraction
observations).
(middle) A RDA installed at Yale mineral physics lab.
(right) Cell design for the double-stage (6/2) configuration tested
in the DDIA by GSECARS. In DDIA-30, the cubic cell will be about
35 mm edge length and the second-stage Drickamer anvils will be
10 mm in diameter.
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