On the Bottom Half

PhD - The Series

No, I have no plans to bore you with the ongoings of academia, I'll hopefully entertain you with my "above average" turn of phrase discussing the mechanically engaging bits of my PhD research. Hopefully, this will turn into a multipart series where I can address questions you have after each video segment.

The first segment is covering the experimental apparatus, called a piston cylinder. A piston cylinder is used to simulate very high pressures and temperatures. The essence of such a device is basically this: a sample charge is prepared in a precious metal capsule, then that charge is encased in a small graphite furnace and compressed inside a tungsten steel cylinder up to very high pressure. Current is fed through the entire apparatus, and graphite being an excellent resistor, much like your oven element, heats up and glows white hot, providing the necessary temperature for the experiment.

The basic components of a piston cylinder are an hydraulic ram, a pressure jacket, a piston, and an experiment charge including a small cylindrical graphite furnace. You place the experiment between the top and bottom of the hydraulic ram inside the pressure jacket and squish the piston into the pressure jacket, via the ram, where it compresses the experiment. Passing current through the entire apparatus, the graphite heats up. The elevated pressure and temperature are used to simulate, in very small volumes, the conditions found deeper in the Earth's crust. Exotic setups can simulate conditions in the very deep Earth - say 700 km, but they require double rams where a much larger ram squishes a smaller ram, which squishes the experiment. These can take up an entire room and require diamonds to actually transmit the pressure to the experiment.

Cooling water is needed to flow through the pressure jacket so that it does not melt, and large gauge cabling is used to transmit the power required through the experiment.

The setup here is small and can simulate up to 25 kbar, which is approximately the pressure you would experience at 80 km depth.

On to the video...



Questions?

P.S. I hope to have rehearsed a little more for the next one... maybe I'll even get creative and see what I can achieve with iMovie. More to follow. I know, I know... promises, promises...

posted by Kyle @ 22:48