The National High Field Magnetics Lab in Tallahassee FL, known as the “Mag Lab”, houses some of the most powerful research magnets in the world.
Inside the Mag Lab
In the 1980s, the leading center for high magnetic field research was the Francis Bitter Magnet Laboratory run by the Massachusetts Institute of Technology (MIT). High-field magnetics was becoming important for the study of many areas in physics, chemistry and biology, and had already led to advances such as the Magnetic Resonance Imaging (MRI) scanners still being used in many hospitals.
In 1989, a partnership made up of Florida State University, the University of Florida, the Los Alamos National Laboratory and the State of Florida submitted a proposal to the National Science Foundation for the construction of a new high-field research center. Funding of $60 million was approved, and the facility, known formally as the National High Magnetic Field Laboratory (and informally as the “Mag Lab”), was located on the USF campus in Tallahassee. It was finished in October 1994 and dedicated with a speech by then-Vice President Al Gore.
In its research, the Mag Lab uses three different types of high-intensity magnets. While in the physics sense they are not much different than the ordinary magnets on your refrigerator door, they are specially designed to produce enormously intense magnetic fields.
The first type of super-magnets are “resistive”. These are assembled on-site at the dedicated fabrication lab using hundreds of thin silver and copper sheets called “Bitter plates”. When completed, these form a huge metal magnet with a channel running down the middle (the “bore”) where the magnetic field is concentrated, and several smaller channels where water can flow through to cool the magnet during operation.
Another family of magnets used at the lab are “superconducting“. These are assembled from certain metals that, when supercooled to near absolute zero with liquid helium, become “superconducting”—they allow electric current to pass through them without any electrical resistance.
The third class of super-magnets are “hybrids”. These are a combination of the other two types, and consist of a resistive magnet core surrounded by a helium-cooled superconducting magnet.
All of these systems are electromagnets. Unlike the magnets on your refrigerator, which are made of iron that has become permanently magnetized, electromagnets are temporary and only produce a magnetic field when an electric current is passed through them. Because the high-field electromagnets used in the Mag Lab require enormous amounts of current, the facility has its own dedicated 56 megawatt power plant which generates enough electricity to run a small city, but which is used solely to power the immense research magnets. There are separate plumbing systems to pump water through the magnets for cooling, and also a cryogenics facility to produce liquid helium to be used in the superconducting magnets.
When the Mag Lab opened, it featured new high-field magnets that were, at the time, the most powerful in the world. In the years since then, newer and even stronger versions have appeared. The power of the Lab’s resistive magnets grew steadily, from 27 tesla to 36.2 tesla. The strongest continuous-field hybrid magnet measures 45 tesla.
In 2008, construction began on what would be one of the most powerful magnets in the world, known as a “pulsed magnet”. Located at the Los Alamos National Lab and weighing nine tons, this hybrid super-magnet produced brief pulses, just a few thousandths of a second, measuring over 100 teslas. Newer versions can reach 300 teslas.
Since the Mag Lab’s super-magnets are paid for by the National Science Foundation, they are free for researchers to use, provided that they openly publish their results. Scientists who wish to use the Mag Lab’s facilities must apply with a description of their experiment, and if they are accepted the Lab will assign them time on whichever one of the magnets is best-suited for their needs.
The magnets are used for a wide variety of research. One customer is the Pentagon, which is interested in electromagnets for use in its futuristic magnetic railgun—a type of cannon that instead of gunpowder uses pulses of electromagnetism to drive a projectile along a metal rail at super-high speeds. NASA is also interested in the railgun concept as a potential way to launch small satellites into low-earth orbit.
In biological and medical science, magnets are at the core of Magnetic Resonance Imaging (MRI) and Nuclear Magnetic Resonance (NMR) systems. These allow 3-dimensional views inside living tissues, right down to the cellular level. Higher magnetic fields give better resolution, which can lead to better diagnostic tools for hospitals.
In materials science, more powerful versions of similar magnetic imagers are used to scan crucial machine parts for potential flaws, of significant importance for the aerospace and nuclear industries. Since many materials change their physical properties in the presence of a magnetic field, the high field magnets can also be used to investigate potential new semiconductor materials for electronics and computers, as well as possible warm-temperature superconductors.
In physics, magnetic fields are used to contain and manipulate “plasma”, a high-temperature state of matter which is important in astronomy and in nuclear fusion research. And in chemistry, NMR spectroscopy is allowing scientists to look at the detailed configurations of molecules. This has been particularly useful for geologists who want to study minerals that are subjected to high pressures and temperatures inside the Earth’s crust.
Once each month, the Mag Lab opens its doors to the public for free guided tours. Visitors are led through the workshop where resistive magnets are assembled from Bitter plates, then led through the various buildings which house the superconducting and hybrid supermagnets as well as the cryogenics center and electrical power plant.
Hidden History 