A couple of days ago, physicists at the National Ignition Facility in California pointed 192 powerful laser beams at a tiny capsule containing deuterium and tritium, heating it to temperatures more than 1 million degrees centigrade -- thus briefly simulating the conditions of a star (i.e., nuclear fusion in the star core). Prior, this exact experiment was carried out hundreds of times, but had never successfully produced more energy than was consumed. For the first time, they witnessed a net energy gain from heating/fusion (about 2.05MJ in and approx 3.15MJ out).

Really high temperatures are needed so that the tritium and deuterium can get close enough to enter the regime where the strong nuclear force dominates over electrostatic repulsion (caused by the proton in each atom). You can think of this as giving a ball enough energy to roll over a massive hill. When this reaction happens, the products have less mass than what you started with. The mass deficit (Δm) is explained by a release of energy, related by E=Δmc². 

The Sun and all other stars on the main sequence are powered by nuclear fusion. The 'nuclear energy' we use nowadays refers to nuclear fission, which is where an atom is split up to produce energy. Sadly, fission is not as safe as fusion (which is completely harmless) and is much less efficient. To put it simply, the ability to harness fusion is the holy grail of energy physics. 

Despite the groundbreaking news, fusion power stations are still a distant dream. NIF was never designed to produce power commercially; its primary function is to create miniature thermonuclear explosions and provide data to ensure the US arsenal of nuclear weapons is safe and reliable. Many researchers believe furnace-like tokamaks are a better design for commercial fusion power because they can sustain longer fusion 'burns'. In a tokamak, microwaves and particle beams do the heating and magnetic fields do the trapping. Unfortunately, building one of these tokamaks seems to be a real challenge, so we'll have to wait a little longer to fully utilise the power of the stars.

published: 16/12/22 by kaan evcimen