When high-intensity lasers became available around 1970, people like Ray Kidder at Livermore and Keith Brueckner at the University of California, San Diego, began to think about inertial fusion. If it’s so hard to hold a plasma with a magnetic field, what about heating a plasma so fast with a laser that it fuses before it can fly apart? The idea was to fill a very small glass sphere with deuterium or DT fuel and zap it with lasers from all sides. The glass would evaporate and expand outwards, and the reaction would push the fuel inwards into a small hotspot where it would fuse before it could turn around and blow out. They worked out the numbers and made a proposal to the Atomic Energy Commission to start a laser-fusion program at Livermore. This proposal was reviewed by a committee, chaired by Lawrence Hafstad, which included the author. The proposal was accepted, and the rest is history.

Starting with a budget much smaller than that for magnetic fusion, the laser program was very successful, and a series of larger and larger lasers was built, with names like Janus, Argus, Shiva, Nova, and now NIF, the National Ignition Facility. The success depended in large part on an intricate computer program by John Nuckolls, the first of its kind, which could predict what would happen in the implosions. At $458M, the budget for inertial confinement has overtaken that for magnetic confinement ($426M) [29]. However, inertial fusion is not primarily funded for energy. Although some scientific support comes from Fusion Energy Sciences, the main support is from the National Nuclear Security Administration. That’s because the miniexplosions that lasers can create are powerful enough to mimic the effects of hydrogen bombs on materials. Data needed to maintain the nuclear stockpile and develop new weapons can be obtained without underground testing with real explosions. In addition, the study of the behavior of matter under extreme pressure and temperature conditions is vital to our understanding of astrophysical objects in our universe.

One might object to spending more money on the military part of fusion rather than on the energy part, but that expenditure is essential. National security must come first. Without freedom, we can’t do anything. Laser fusion is sold to the public as an energy source because of its glamorous achievements. It will reach ignition decades before ITER can. However, it is a pulsed system like the pinches in the previous section and is difficult to make into a steady power source.

The main problem is the lack of a suitable driver. The term inertial confinement fusion was coined to include drivers that are not lasers. To have a steady power output, a laser-fusion power plant has to implode a pellet at least ten times a second. A car runs smoothly with 3,200 explosions a second (four cylinders at 800 rpm), but 10 explosions per second would be enough for a power plant. However, lasers can’t pulse that fast. The most powerful ones use neodymium-doped glass disks a couple of feet in diameter. As much light as possible is passed through the glass for amplification. This heats up the glass almost to the point of cracking. It takes hours for the glass to cool. With earlier lasers, two shots a day were all that could be expected. There are thousands of these disks in a megajoule laser. If one of them cracks, the whole system shuts down.

The main task, then, is to find a better driver. Ion beams have been tried, but they are hard to focus down to a small target and also have to be pulsed. Krypton — fluoride (KrF) lasers use no glass and can be pulsed more rapidly. They have some promise, but pulsing at five times a second has been proved possible only at low power. Systems based on pulsed power (discussed later) are also pulsed infre­quently. Laser fusion should be considered as the fantastic technological achieve­ment that it is, but not as a promising base-load energy source.