The 14.5 Tesla FT-ICR Magnet

Vital Statistics Strength 14.5 tesla Type Superconducting Bore size 104 mm (about 4 inches) Online since September 2004 Cost $2 million Weight 7,600 kg (8.4 tons) Homogeneity 10 parts per billion

Overview

This is the highest performing magnet of its kind, used with a Fourier Transform Ion Cyclotron Resonance (FT-ICR) mass spectrometer. The instrument is capable of picking out trace amounts in mixtures down to a billionth of a gram and has set world records for its accuracy.

The MagLab operates several ICR magnets; this is the flagship instrument. (A 21 tesla superconducting system is in the development phase.) This 14.5 tesla machine is used to analyze complex chemical mixtures such as crude oil, which can be made up of tens of thousands of different types of molecules. It is also used to determine the molecular structure of proteins, sugars and DNA. In addition, this magnet can be used for counterterrorism efforts, because it can identify the chemical fingerprint of explosives and accelerants.

Detail of FT-ICR mass spectrum
of crude oil.

As you can tell from the photo above, this magnet is oriented differently than the others you’re reading about on these pages. ICR magnets are positioned horizontally rather than vertically – like a soda can that is knocked over rather than an upright. This orientation makes it easier to use the instrument with the bulky vacuum manifold that keeps the experimental space in a vacuum, necessary for ICR experiments. And speaking of soda cans, that’s about the size of the cyclotron inside this large magnet, which is the heart ot the instrument. In ICR, the particles of a sample are charged, and those ions are sent spinning around the cyclotron by the magnetic field in such a way that they can be measured and counted by the spectrometer and let scientists know exactly what’s in there. (The spectrometer is located in the foreground of the photo, in front of the cylindrical magnet.) One particularly impressive feature of this instrument is that the magnetic field is very even across the relatively large space – 10 centimeters (4 inches) by 10 centimeters – in which those ions spin around. Scientists call that “high homogeneity,” which essentially means that the magnetic field barely deviates from 14.5 tesla.

Links

• What's a Superconducting Magnet?
  As defined by a MagLab expert (audio file).
• What's ICR?
  A collection of resources on the subject.
• What's in an Oil Drop? An Introduction to FT-ICR
  An oil drop is a phenomenally complex mix of immense (relatively speaking) molecules called hydrocarbons. Using FT-ICR, scientists can analyze oil and other macromolecules with amazing precision, uncovering important secrets in the process.
• ICR Program