Laser Fusion experiment

BBC News: Giant laser experiment powers up.

The US has finished constructing a huge physics experiment aimed at recreating conditions at the heart of our Sun.  The US National Ignition Facility is designed to demonstrate the feasibility of nuclear fusion, a process that could offer abundant clean energy.  The lab will kick-start the reaction by focusing 192 giant laser beams on a tiny pellet of hydrogen fuel.  To work, it must show that more energy can be extracted from the process than is required to initiate it.

Professor Mike Dunne, who leads a European venture that is also pursuing nuclear fusion with lasers, told BBC News that if NIF was successful, it would be a  "seismic event ".  "It would mark the transition for laser fusion from 'physics' to 'engineering reality', " he said. The California-based NIF is the largest experimental science facility in the US and contains the world's most powerful laser.  It has taken 12 years to build.

If this works, the lasers shove hydrogen isotopes together, making them into helium and getting energy out.  Fission works by splitting a big atom into smaller ones and using the heat to boil water to turn a turbine, but you have radioactive by-products  and it's a chore to deal with the waste.  Fusion is clean, the by-product is clean, deuterium is readily available (unlike uranium 235), if this works, you have clean energy.

The hard part of these experiments is getting more energy out than you put in, because it takes a lot of energy to initiate fusion.  At the heart of the Sun, the intense gravitational field helps the fusion take place at 'cooler' temperatures, on Earth, cooler being a relative term. We need to make the fuel much hotter than the Sun to compensate for the lowered gravity.  Think about that, hotter than the Sun.