High Pressure Experimentation

The pressures found in Earth’s interior can be achieved in the laboratory using a wide variety of experimental devices ranging from cold seal bombs, which work something like a pressure cooker, to shock guns that fire puck shaped projectiles at the sample producing short lived pulses of extremely high pressure. We use the full range of high pressure techniques in the High Pressure Science and Engineering Center at UNLV. In Pamela’s lab, we use the “large volume” press called the Deformation-DIA, a “Griggs” modified piston-cylinder apparatus, and the Diamond Anvil Cell (DAC). Each type of apparatus is described in more detail below.

Deformation-DIA Apparatus

We use the D-DIA apparatus located at the X17B2 beam line at the National Synchrotron Light Source (NSLS) to conduct deformation experiments (currently we are working on olivine and quartz. The apparatus can pressurize samples to approximately 15 GPa and also deform samples at a controlled rate. The D-DIA apparatus is a module that fits inside a large hydraulic press. It consists of 6 WC or diamond tipped anvils, the top and bottom of which move independently. The sample, which is placed between the anvils, is encased inside an epoxy or mullite cube. During the course of the experiment, synchrotron x-rays pass through gaps in the anvils and diffracted x-rays are collected by ten detectors. The diffracted x-rays are used to record the elastic deformation of the samples' crystal lattice that occurs during deformation.

Sample Assembly Components

We use a sample assembly which consists of more than a dozen parts that fit in a 3mm hole in a 6mm cube. Below is a cross section of the cube showing the assembly.

The major parts of the sample assembly are fabricated by the machine shop at Stony Brook which is funded by COMPRES. The following is a list of the sample assembly components:

• Boron epoxy cube or mullite sphere with pyrophyllite seats (from ASU)
• Alumina sleeves
• Graphite furnace and contacts
• 90% NaCl, 10% BN or 100% BN confining media sleeve
• Ni jacket
• Outer pistons which are composed of crushable Al2O3
• Side or top entry W25%Re W3%Re thermocouple

Diamond Anvil Cell

The Diamond Anvil Cell (DAC) utilizes two gem quality diamonds to produce pressure in the sample, which is placed between the tips of the diamonds. The sample is held in place by a rhenium gasket. In collaboration with Dr. Oliver Tschauner, we are using the DAC to deform single crystals. DACs can generate a wide range of pressures up to and even exceeding those found in the center of the earth.

Piston Cylinder

We have a Griggs modified piston cylinder in Pamela's lab. Our Griggs apparatus can achieve around 1.5 GPa. The sample assembly contains a furnace that allows us to heat samples to about 1300˚C. For more details on how the Griggs machine works, click here.