Scientists have long been attempting to harness fusion, the process that powers the Sun, as it could provide an unlimited and cheap source of energy. For fusion plants to be viable, they would need to produce more energy than they consume. The scientists at the National Ignition Facility (NIF) used 192 beams to deliver 1.7 megajoules of ultraviolet light at 350 terawatts of peak power focused through holes in a target container called a hohlraum, to heat and compress a tiny deuterium-tritium filled capsule to the point where nuclear fusion reactions took place. In the nanoseconds that followed, the capsule imploded and released a neutron yield of nearly 3 x 1015, or approximately 8,000 joules of neutron energy. This amount of energy exceeded the amount of energy consumed for the first time ever.
Nuclear fusion is vastly different from current nuclear power. Nuclear power works through the splitting of atoms, called fission. The nucleus of a particle splits into smaller parts and often produces free neutrons and photons and releases a very large amount of energy. Nuclear fusion is where two or more atoms collide at a very high speed and join to form a new type of atomic nucleus. Matter is not conserved as some of the mass of the fusing nuclei is converted to energy.
This recent result is just short of the NIF’s goal of "ignition", which is where nuclear fusion generates as much energy as the lasers supply. Inefficiencies in different parts of the system result in not all of the energy supplied through the laser reaching the fuel.
Within the hohlraum is a tiny pellet which contains an extremely cold and solid mixture of hydrogen isotopes. When the lasers hit the hohlraum's walls, they radiate x-rays which then strip material from the outer shell of the fuel pellet. This heats the fuel pellet up to million of degrees Celsius. If the fuel compression is high enough and uniform enough, nuclear fusion can result.
Controlled nuclear fusion has been sought after for nearly fifty years, and this latest result has been described by some as the single most meaningful step for fusion in recent years. NIF officials aimed to demonstrate nuclear fusion producing net energy by 30 September 2012, but unexpected technical problems saw the deadline come and go. The facility then shifted focus and cut the amount of time spent on fusion versus nuclear weapons research.
