Monday, January 14, 2013

Project 365: Day 325

Question of the day: Uhhh what is it that you sell again?

Answer: NMR Spectrometers of course!

So what exactly is an NMR? Well I'm not going to go into all of the details but it's basically a big magnet with a box of electronics. You take your test tube and put it in the magnet, then use the electronics to "zap" your sample and then the result is that the sample then emits a signal that you record. The signal tell you lots and lots of information about whatever you have in your test tube.

The most special part of the whole machine is the magnet. Our magnets are super conducting magnets that are made from taking miles and miles of very special (and expensive wire) and winding it into a coil. Then we cool the coil down to ~ 4K (that's Kelvin, as 4 degrees above absolute zero or about -450F!!) using liquid helium. Once the coil is cold we run electricity through it - slowly ramping up the current - until we fill the wire with as much current as it can take. Then we remove the power supply, close a switch (so the coil becomes a closed circuit loop) and essentially the current just goes around and around forever creating a persistant super conducting magnet. 

Ok so now that I've lost all of you with my completely non-technical and non-eloquent description, it's time to show you the magnet! This is what we call a 300MHz magnet which has a magnetic field strength of ~ 7 Tesla. This is the smallest magnet that we manufacture and sell. This magnet has been cut open so that you can see what it looks like inside.  
So at the very inside (the white thing) is the magnet coil (there is also one on the floor to the left of the magnet). The coil is sitting inside a thermally insulated container called a cryostat which consists of several dewars. OK, so the coil is sitting inside a dewar (painted yellow) that is filled with liquid helium. Then there is an empty section (blue) that is a vacuum to prevent thermal conduction (this is how a thermos works!). The next dewar (red) is the liquid nitrogen bath (at about 77K or -321F). The liquid nitrogen helps to slow down the rate of evaporation of the helium (because helium is expensive and non-renewable and nitrogen is cheap and easy to produce).  Then there is another vacuume section that also has tons of thin foil-like sheets again to help to prevent thermal conduction. And then there is the final outter casing.

A typical modern superconducting magnet needs to be filled with nitrogen once per week and filled with helium a couple times per year.  A standard 300MHz NMR Spectrometer (with a magnet like the one above) will cost about $150-200,000 (of course that includes all of the electronics as well).

And so now you know a little bit more about what I do... not that you asked!

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