It is one o'clock on the morning of Dec. 5, 2022, at the Lawrence-Livermore nuclear weapons laboratory's National Ignition Facility (NIF). A powerful laser housed in a building the size of three U.S. football fields fires a single infrared pulse of light that persists for a few billionths of a second. The pulse splits into 192 beams that transform into ultraviolet light and focus from all sides on a single gold box the size of a pencil eraser. The box holds a BB-size fuel pellet made of frozen deuterium and tritium -- two types or "isotopes" of hydrogen.
The laser light heats the pellet to millions of degrees, the temperature of the sun's center. The heat causes the gold to emit x-rays that "implode" a diamond shell enclosing the fuel pellet. This compresses and heats the hydrogen isotopes inside. At such high temperatures, these hydrogen atoms move at hundreds of kilometers per second, and because they are squeezed together they frequently collide. Their high speeds cause them to hit with such force that their tiny nuclear centers stick together, forming helium nuclei. This is nuclear fusion.
Fusion achieves the alchemists' dream of converting one chemical element into another, but the experiment's purpose was not to create gold. In the conversion of hydrogen to helium, a small fraction of the mass of hydrogen is converted (via Einstein's famous formula E = mc2) into other forms of energy such as heat. Hydrogen bombs use this heat to create an explosion that can destroy a city. But the point of the NIF experiment was to use this energy to create steam to power a generator to provide electricity.
The experiment was a breakthrough because, for the first time, there was an "energy gain" from a fusion reaction: The energy of the heat released exceeded the energy of the laser pulse that created it.
But it's a long way from this experiment to useful electricity. A power plant based on NIF would need to implode about 10 pellets every second. Nearly a million fuel pellets would have to be made, blasted and cleared away every day.
Another fly in the ointment: The NIF lasers are highly inefficient, requiring hundreds of times more energy than they create as laser light. Factoring this in turns the energy gain into a huge energy loss.
Fusion energy has been an engineering dream for decades. We have obtained electricity from nuclear fission (splitting) since 1951, but electricity from nuclear fusion (combining) is expected to be more sustainable.
All previous approaches to fusion energy have been quite different from NIF's approach. The idea has been to use magnetic fields to shape a gaseous form of deuterium and tritium into a toroidal (doughnut) configuration and heat this gas by magnetically squeezing it or by running an electric current through it. Most of these recent experimental fusion reactors have followed the "tokamak" design developed in the Soviet Union during the 1960s.
The leading tokomak device today is the "ITER" experimental reactor under construction in France. It is far over budget and behind schedule, and appears to verify a wit's observation that "fusion power is 30 years in the future, and always will be."
To keep global warming to no more than 1.5 degrees Celsius (2.7 degrees Fahrenheit) as called for in the Paris Agreement, emissions must reach net zero by 2050. Nuclear fission power can help us achieve this goal and is, in my opinion, essential to accomplishing this goal. Nuclear fusion power cannot help us meet this goal because it cannot be ready for widespread use until at least late in this century, and more probably sometime in the next century.
The world today is threatened by never-ending wars of all sorts, global warming, overpopulation, militarization, poverty, hunger, income inequality and government breakdown in all nations including the three nuclear superpowers. The biggest immediate threats are nuclear war and global warming. For the next several decades, additional investments in energy should go to renewable energies, energy efficiency and power from nuclear fission rather than from nuclear fusion.
Humankind is capable of doing much better and being much happier than we are today. Science has made great gains in global health, food production, communication, psychology, sociology and other essentials for human happiness. Young people are increasingly turning away from tribal beliefs and toward reliance on evidence and reason as guides to social behavior and public policy.
Fusion power is a worthy dream for the far future, provided civilization gets there.