10 September 2015

Homogeneity: At the MagLab, it’s in more than milk

Homogeneous magnets make data clearer for scientists. The MagLab has some of the most homogeneous magnets in the world.

The 36 tesla series connected, shown here under construction in July 2015, will be the most homogeneous resistive magnet in the world.

36 tesla series connected hybrid magnet under construction

By JOSH PALM

The word, "homogeneous" can describe the consistency of fat particles in milk. It also describes the consistency of magnetic field strength inside the hollow center (or bore) of a magnet, where scientists at the MagLab put their experiments.

People like homogeneous milk. But why do scientists at the MagLab like highly homogeneous magnetic fields?

Well, high homogeneity means higher resolution; higher resolution makes things easier to see.

And for certain types of research conducted at the MagLab — mostly nuclear magnetic resonance (NMR) experiments — this increased visibility is incredibly important.

For example, say you wanted to make a better anti-flu drug. You'd need to locate the virus's weak spot, so that you could configure your drug molecule to attack it.

When a scientist wants to look more closely at the atomic make-up of a substance that's already inside a magnetic field, they fire radio frequencies at it. The substance then sends its own signal back, which the scientist can use to determine the location of certain atoms inside it. But if the field strength of the magnet isn't consistent, the information the scientists collect will be vague, and the location of the atoms uncertain. It's like trying to look through a telescope that is out of focus.

We use three types of magnets here at the MagLab: resistive, superconducting and hybrid (a combination of resistive and superconducting).

Resistive magnets can be very strong, but usually aren't highly homogeneous because their fields are not that stable. There are exceptions, however: The MagLab's “Keck” magnet produces a 25 tesla field that is very homogeneous for a resistive magnet. Also, in the fall of 2015, the MagLab upgraded its power supply, resulting in a tenfold improvement in the field stability of the lab's resistive magnets — great news for scientists doing research here!

Another improvement: The lab's new 36 tesla series connected hybrid magnet, scheduled to go online in 2016, will have a field of 36 teslas and be considerably more homogeneous than the Keck. In fact, it will be the most homogeneous powered magnet ever built.

Superconducting magnets, however, can do even better, thanks to their more stable fields. One of our most notable superconducting magnets is the 900 MHz NMR magnet. The largest MRI scanner in the world, it produces a field of 21.1 teslas that is just about as homogeneous as it gets for magnets.

Now that's what we call milking a magnet for all it's worth!


Photo: Stephen Bilenky.