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The rock and ice mechanics lab at Lamont-Doherty is led by PIs Heather Savage, Christine McCarthy and Ben Holtzman. We are in the process of growing our lab and building our experimental program. Along with a team of postdocs, undergrads, grads, and longtime staff engineer Ted, we are rehabilitating and revamping some of the old equipment and building new rigs for exciting new experiments on both rock and ice. You can follow along with our progress here.

Friday, 15 June 2012

Fault Paleothermometers, aka the smelly oil-making experiment

Exciting stuff happening this week in the rock mechanics lab. My aluminum plates for the ice rig arrived today so I started marking up the center lines and worked on my design to figure out precisely where we will drill holes for the tie rods.

MEANWHILE Heather, Rachel, and Pratigya have been making great strides in their paleothermometer project! 

The idea for the study is that certain organic matter can be used as an indicator of temperature. With time and temperature, particular organics go through known reactions. The reactions can only go one way, so the altered material captures the peak temperature, even after things cools down. During an earthquake, fault rocks are believed to get pretty hot from frictional heating, but the extent of this has not been well constrained. Heather and Pratigya came up with the idea that if they can analyze the thin layer of sedimentary rock in the middle of the fault zone to look for specific altered organic material, this will tell them the temperature range that the fault experienced. For a better description of the project, check out this cool TED-style talk they gave at a Lamont community seminar. Before they can really start analyzing the fault rocks, however, they need to establish good reference values. So they are now taking crushed up sedimentary rock and are systematically heating it to known temperatures and durations. Here the team troubleshoots the new rig and starts developing the experimental protocol.
They heat the crushed up rock rapidly (simulating frictional heating in faults) in the tube below (that they call a "bomb") with that heating coil wrapped around the outside. Although the times, temps, and pressures are considerably less than what, say, large reserves of organic material in the earth experience, the initial stages of the reaction are similar to those that create petroleum. Even though they are working with only a teaspoon or so of material, the smell is simply horrendous. It's like being in the middle of an oil refinery. 
They measure the temperature inside the bomb with thermocouples and monitor it with the panel of meters below. The Omega black box underneath is called a data acquisition system (DAQ) and is used to send data to the computer.
Here the undergraduate intern Rachel starts an experiment by turning on the gas while Ted looks on.

Wednesday, 13 June 2012

building a meter panel from scratch

Parts are beginning to come in for the new ice rig. I'm getting excited about putting things together. One thing that I knew I could begin working on while we wait is the electronics to run the rig. We'll have a tower sitting next to the friction apparatus, which will have panels for temperature control, load and position monitoring, signal conditioners for the strain gauges etc. The easiest of these to wire up, in my opinion, is the temperature control. So I started there first. The triax was once used for high temperature work and so it had a panel of thermocouple meters that I could salvage. However, that panel wouldn't fit into my tower, so I had to start from scratch. Here is a pretty piece of painted aluminum specifically made for this purpose (circa 1970 I suspect). First I measured and penciled on my desired cuts,...
...loaded it into the milling machine,...
...and got to work.
I made five squares that will hold the meters, five half-inch holes to hold the fuses, and 10 tiny holes to hold five switches and five blanks (in case something comes up in the future). 

The next step was to fit all those pieces in their places and wire it up. I first wired it up just like it was done before, so Ted could draw me a circuit diagram for the existing set up. Then I could decide what I wanted my rig to do instead and make the appropriate changes. In this case I will have one meter that will control the temperature of the cryostat and the other four will just be monitoring the temperature in various parts of the rig.  I attached all the thermocouples (blue type Ts for low temp work) and Voila!