Saturday, March 22, 2008

Lab Ninjas - ANIMAL edition

I like to think of myself as a lab person. I think on average, I have a decent knowledge of the technical aspects of noble gas analysis. I have built a He extraction line from scatch, I've been involved with upgrades, repairs, routine maintenance, and exploratory surgery on both He and Ar extraction lines. I feel confident in my ability to put together noble gas labs quickly without paying a technician or lab mercenary (that is a special note for all you search committee members out there). I can dumpster dive, resuscitate broken pumps, and leak test with the best of them. Well, that is what I used to think.

Thanks to Dr. Chèvre I recently realized just how much more there is to learn. The good Dr. recently told me about the ANIMAL facility at Auburn University. ANIMAL is an acronym (one that many thermochronologists must be jealous of) for Auburn Noble Isotope Mass Analysis Laboratory. It is the noble gas (mainly Ar/Ar) facility at Auburn, run by Willis Hames and Mehmet Billor (can't find his web page). What makes it amazing though is not just the acronym, it is the fact that the entire apparatus, magnetic sector mass spectrometer included, was built by hand at Auburn, specifically for their lab. Honestly I'd never considered building a mass spectrometer, I figured it was something I'd buy (if I was ever in that position). I've now spent a lot of time on their website, looking at the pictures they have from the development and construction of the machine, looking at their calibration data, it is just amazing. It appears to be a great collaborative effort, involving geologists, material scientists, chemists, physicists, and engineers. Combining experience, resources, and skills, they put this things together from scratch.....and it works! There are even all of these great pictures of students helping to build the thing, polishing the flight tube, wrapping the coil of the magnet, etc.

There are a few things I love about this. First, the design of the machine is actually pretty innovative. Both the extraction line and the mass spectrometer have been optimized in such a way as to significantly reduce the internal volume of the extraction line. The primary modification of the extraction line that impresses me is the lasing system. Most lasing systems have a laser port and sample holder that are attached to the extraction line via stainless steel flex tubes. The laser port is mounted on a motorized stage, so it can be moved under a fixed laser, and samples can be maneuvered into place. this works well, but flex hoses are kind of a pain to deal with. By length, they have much more internal volume than straight tubes, and they are also blessed with much more internal surface area. Both of these facts are negatives from the point of view of signal size and blanks. Some flex hoses are necessary, but it is nice to avoid them when possible. At ANIMAL, the laser port is fixed, using short straight tubing, while the laser beam is mobile.

They call this set up the "flying optic." Basically, the optics of the laser are set up so that both the laser itself and the samples remain stationary, but the mirrors that aim the laser are movable. You can see in the picture above that one of the samples in the sample chamber is glowing hot.

The second great innovation deals with the size of the flight tube. The flight tube of a mass spectrometer can be one of the larger contributions to the overall volume of the extraction line. Large volumes are harder to pump out, but more importantly, the size of your signal is a function of the partial pressure of the gas in your system. Large volumes mean lower pressures, and smaller signals. Many commercial mass spectrometers have flight tube volumes of ~2 liters. ANIMAL is 80% smaller, with an internal volume of ~0.4 liters (that data comes from their website).

So this is all fantastic. One other thing that I think is cool is that they built a viewport into the ion source of the mass spectrometer. That means you can actually see the filament and electrical doohickeys working. I am not sure if this helps in the operation of things, but it is really cool, and doesn't seem to compromise their blanks at all.

So the ANIMAL lab is a good example of Lab Ninjas at work. If you have some time and are interested at all in mass spectrometers it is worth spending some time on their site.


C W Magee said...

Do you know the volume of Grenville turner's super* Xenon machine?

* Well, super back when I was a student- must be old by now...

"Ain't From Around Here" said...

You said it Yankee! No one knew the "South will rise again" not in the name of State's Rights, but doohickeys!