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, and a “Griggs” modified piston-cylinder apparatus. Each type of apparatus is described in more detail below.
We currently use the D-DIA apparatus located at the 6BMB beam line at the Advanced Photon Source (this beam line facility was formerly 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.
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. We can deform samples at strain rates between 10-3/sec and 10-6/sec. We can also conduct hydrostatic experiments. The apparatus allows us to simulate the conditions in the upper ~50 km of the Earth’s crust.