A promising way to solve this challenge is to generate energy by the fusion of the positively-charged nuclei of the hydrogen isotopes deuterium and tritium. Enough deuterium is available in the ocean to sustain a population of eight or more billion people for thousands of years, and the waste products of a fusion reactor are small amounts of helium gas (which is inert and so harmless), modest amounts of short-lived radioactive substances, and heat which is used to generate electricity. Fusion reactors can not undergo a melt-down like a fission reactor, and fusion reactors do not produce nuclear wastes that can be used to make nuclear weapons.
Building a fusion device is a great scientific and technological challenge that draws on all areas of physics, but especially on ideas discussed in Physics 162 related to electric and magnetic fields. The idea is to use ultracold superconducting magnets (at about ten degees above absolute zero) to generate strong magnetic fields that act as a "bottle" that will confine a superhot (300,000,000 K!) plasma of electrons and of positively charged deuterium and tritium nuclei in a toroidal region so that the nuclei, through their large speeds, can overcome their electrical repulsion and so approach each other closely enough (about one proton diameter) to undergo fusion that produces He nuclei and neutrons with an excess of energy. The kinetic energy of the fusion products is used to heat water to produce steam that turns turbines to generate the electricity used by people and by industry. The electricity is produced by taking advantange of one of the fundamental laws of electrodynamics, Faraday's law, which describes mathematically how a time-varying magnetic field produces an electric field that can drive currents in wires.
The challenge of heating an initially room-temperature gas of hydrogen to 300,000,000 K in a controlled way itself requires multiple applications of Physics 162 ideas: using Faraday's law to create an enormous axial electrical current to start the heating of the plasma, shining high-intensity microwaves that are tuned to resonant frequencies of the gyrating electrons and nuclei, and using electric fields to accelerate deuterium and tritium nuclei close to the speed of light, and then shooting the resulting high-intensity high-energy neutral beam into the plasma to heat the plasma and fuel it. In turn, measuring the electric and magnetic fields of the plasma by various devices gives important information about what the plasma is doing as it undergoes fusion.
Despite the enormous attraction of fusion and despite a world-wide
collaboration that has lasted over fifty years and that has cost tens
of billions of dollars, a working reactor has not yet been
successfully designed. The main difficulty again involves
162 physics: the rapid motion of the charged nuclei and electrons
(the latter move at about one hundredth the speed of light!)
constitutes an electrical current that creates a substantial magnetic
field. This field, when combined with the magnetic field generated by
the external superconducting magnets, can open up "holes" in the
magnetic bottle that causes the entire plasma to leak out within a few
microseconds, bringing fusion to a halt. It is a difficult physics and
math problem to determine how to adjust the hundreds of magnets in
real time to compensate for the magnetic field generated by the
complex plasma dynamics and so keep the plasma confined for sustained