Physics: Lawrence Livermore National Lab in Livermore, California. Nova Laser. The Nova laser is the worlds most powerful, and is being used to initiate nuclear fusion reactions. Nuclear fusion is the joining of the nuclei of deuterium and tritium (heavy isotopes of hydrogen). The reaction produces vast amounts of energy, but requires an initial temperature of 100 million Celsius. To achieve this, a pinhead-sized pellet of fuel is placed in the chamber. The Nova laser is focused onto the pellet before a full- power burst is fired. This lasts only 50 picoseconds (trillionths of a second), but gives sufficient energy for fusion to occur.