New magnetic behavior discovery may help nuclear fusion reactions easier to start

Researchers have uncovered a new kind of magnetic behavior that could help make nuclear fusion reactions easier to start.

Alexander Thomas, assistant professor of nuclear engineering and radiological sciences, said that they have to compress the fuel to a temperature and density similar to the core of a star.

Once those conditions are reached, the hydrogen fuel begins to fuse into helium.

Two methods dominate for confining the fuel, made of hydrogen atoms with extra neutrons, so that fusion can begin. Magnetic confinement fusion uses magnetic fields to trap the fuel in a magnetic 'bottle,' and inertial confinement fusion heats the surface of the fuel pellet until it blows off in a way that causes the remaining pellet to implode.

Archis Joglekar, a doctoral student in nuclear engineering and radiological sciences, said that one of the concerns with nuclear fusion is to squeeze this very spherical fuel pellet perfectly into a very small spherical pellet.

To avoid pushing the ball of fuel into an irregular shape that won't ignite, the fuel must be exposed to uniform heat that will cause its surface layer to evaporate all at once. As this layer pushes off at high speed, it applies equal pressure to all sides of the pellet and causes it to shrink to one thousandth of its original volume. When that happens, the fuel begins to fuse.

The heat comes from about 200 laser beams hitting the inside of a hollow metal cylinder with the fuel pellet sitting at its heart.

When the laser light hits the metal, it turns some of the surface metal into plasma, or a soup of electrons and free atomic nuclei. The laser and the heat drive the electrons to move in a way that sets up a magnetic field circling the laser spot.

The magnetic field acts as a boundary for the electrons-they can't cross it.

The team showed that the flow of hot electrons could drive the magnetic fields around neighboring laser spots together, causing them to join up. Instead of forming a barrier between the laser spots, the joined fields open a channel between them.