The process of nuclear fusion, which is widely studied, involves the formation of heavier nuclei by atomic nuclei with low atomic numbers. This results in a lot of energy being released. Inertial confinement is a method that produces nuclear fusion reactions. This involves the use of powerful lasers to explode a fuel capsule and create plasma.
Massachusetts Institute of Technology (MIT), University of Delaware and University of Rochester recently demonstrated what happens to this implosion if one applies a strong magnet field to the fuel capsule that is used for inertial confinement fusion. Their paper was published in Physical Review Letters. It shows that strong magnetic fields can flatten the inertial fusion implosions.
Arijit Bose, one the researchers behind the study, said that a millimeter-sized spherical capsule was imploded using high power lasers for nuclear fusion in inertial confinement fusion. The magnetic field applied to the implosions can be used to bind charged plasma particles to the Bfield, increasing their chances of fusion. Magnetic field can only restrict plasma particle motion in the direction of the field lines. It cannot limit plasma particle motion in the direction of the applied field lines. This can cause differences in the directions that can affect the implosion shape.
Many physicists have studied the potential effects of magnetizing-fusion implosions over the past decade. However, most of their studies were numerical and did not test hypotheses under experimental conditions.
Bose and his coworkers decided to run a series test to empirically examine the effect of strong magnetization on the shape of inertial-fusion implosions. The experiments were designed to investigate the properties of strongly magnetized plasmas by creating unique plasma conditions. These conditions are magnetized for both plasma ions as well as electrons.
Bose said, "It is important to note that magnetization of plasma particles is difficult to achieve and has not been studied using high power lasers." To conduct our tests, we used a 50T magnetic field that was much stronger than those used in the previous experiments. We also used shocks to drive implosion experiments at OMEGA's laser facility. This field flattened our implosion's shape, making it more oblate.
The OMEGA laser facility at the Laboratory for Laser Energetics, Rochester, New York, was where the researchers conducted their experiments. They used high B-fields, that is, magnets with strengths 1000 times greater than typical bar magnets, to heat a millimeter-sized spherical capsule. The laser-driven shock heated the capsule to more than 100 million K.
Bose stated that shock heating and the applied B-field created unique plasma conditions with strongly magnetic electrons and ions, which were crucial for the experiments. We then discovered that the oblate-shaped plasma was caused by heat flow suppression (perpendicularly to the direction the magnetic field).
This team of researchers has provided valuable insights into inertial fusion implosions, as well as the magnetic field effects on them. The method they described could be used in the future by other teams to create strongly magnetized electrons or ions in experimental settings using high-powered lasers.
Bose said, "Most importantly, we were first to observe how the applied magnetic field flattened implosion shapes." "In our next studies we plan to use our paper's'recipe" to perform more experiments to produce strongly magnetized electrons.