Apparatus and Capabilities of the High Pressure Lab
The High Pressure Laboratory houses two solid-media experimental devices: A Walker-style multianvil press and a Boyd-England style piston-cylinder. The multianvil is capable of achieving pressures from ~4 to nearly 24 GPa, and the piston-cylinder spans a pressure range of ~0.5 to nearly 4 GPa. Thus, in combination, these two presses can achieve conditions relevant to regimes ranging from the mid-crust to the mantle transition zone on Earth; from deeper crust to nearly the core-mantle boundary on Mars; and from deepest crust to beyond the center of the core on the Moon.
Panoramic view of one half of the lab.
Panoramic view of the other half of the lab.
In the sections below, brief overviews of each apparatus and how they are used are given. Click on the thumbnail images or the linked text in each caption to bring up larger versions of each photo.
The multianvil consists of a Walker-style "hatbox" in a Clifton 2000-ton hydraulic press.
The sample is placed into a tube of rolled rhenium, which functions as a resistance heater, and which is then loaded into a ceramic octahedron, as shown here.
The finished octahedron has two tungsten-rhenium thermocouple leads mounted radially, with the junction close to the sample capsule in the midpoint of the rhenium heater tube.
The octahedron is placed in a set of eight tungsten carbide cubes that have had corners truncated to match the triangular faces of the octahedron.
The cubes are then placed into the "hatbox" in the space formed by the six anvils that transform the directed force of the hydraulic press to hydrostatic pressure on the sample. This view shows the hatbox before the upper three anvils are put into place.
The hatbox is then slid into position in the press, which is then pumped up to the desired pressure. Here, Jana Berlin, our LPI intern in summer of 2002 (and who took several of the photos on this page), poses with the press.
Temperature is controlled with a programmable Eurotherm controller, mounted with its other electronics in this cabinet.
After the experiment, the cube setup is carefully disassembled, as our JSC postdoc Dimitri Xirouchakis is doing in this view.
After the experiment, the octahedron is mounted in an epoxy disk and ground to expose the sample, and is then finely polished for microanalysis using either the electron microprobe or the SIMS (ion microprobe).
Piston Cylinder Press
The principles behind operation of the piston-cylinder are essentially the same as those for the multianvil. The sample is packed into a cylindrical assembly that goes into the core of a pressure plate. Pressure plates have either half-inch or 3/4-inch diameters, with higher pressures being possible in the former compared to the latter. Piston-cylinders allow work on quite large samples, up to four times larger than in the multianvil. We currently have a non-endloaded Quickpress, manufactured by Depths of the Earth, capable of achieving pressures of 0.5 to 2.5 GPa. We are in the process of commissioning a second, endloaded press that will be able to reach pressures near 4.0 GPa, which will provide excellent overlap with our multianvil devices. We use both talc-pyrex and salt-pyrex cells for piston-cylinder experimentation. The talc-pyrex cells are generally used for volatile-bearing runs, and the salt-pyrex are used for nominally anhydrous work. Both are set up to allow us to use the same capsules as we do in our 8mm (up to 10 GPa) multianvil cells, eliminating one possible source of discrepancy between the two techniques.
The Quickpress is shown here. It occupies a quite small footprint and we affectionately refer to it as our "desktop p/c". The press frame is on the right, with a 10-ton extraction jack beside it; to the left is the electronics control box for setting run temperatures. The hand pump on the right exerts pressure on the sample.
A closer view of the pressure vessel, showing the sample ram below, the pressure vessel with coolant hoses attached in the center, pressure readout to the left. After an experiment, the vessel swings to the left on a supporting bracket so that it can be positioned over the extraction jack for removal of the cell after an experiment.
Lab Work areas
Here are some shots showing the fully-installed lab's working areas, so you can get an idea of the layout for performing the routine tasks involved in doing experiments.
Here's where the octahedral assembles are fabricated and drilled, and where inner parts are cut to size.
A stainless steel table holds several furnaces and drying ovens where assemblies are fired and sample materials stored; there is also welding apparatus.
Here's the alcove where we have a variety of sample prep and polishing equipment.
The lab is well laid out with a variety of workspace areas.
We have a range of microscopes for examining run products and assembling some of the tinier bits.
We have a late-model computer that will eventually run the controllers for the two presses, and which has all the usual software for your data-crunching needs.
Finally, as every experimentalist knows, there is a large portion of voodoo in what we do-- some procedures survive for no better reason than "it's always been done that way." Accordingly, it pays to give proper due to good luck totems to maximize the chance for success in an experiment. These are ours.