This is explaining fusion.

Fusion reactions are inhibited by the electrical repulsive force that acts between two positively charged nuclei. For fusion to occur, the two nuclei must approach each other at high speed to overcome the electrical repulsion and attain a sufficiently small separation (less than one-trillionth of a centimeter) that the short-range strong nuclear force dominates. For the production of useful amounts of energy, a large number of nuclei must under go fusion: that is to say, …

…of producing beams of high-energy electrons or ions. Lasers that produce more than 100,000 joules in pulses on the order of one nanosecond (10-9 second) have been developed, and the power available in short bursts exceeds 1014 watts. Best estimates are that practical inertial confinement for fusion energy will require either laser or particle-beam drivers with an energy of 5,000,000 to 10,000,000 joules capable of delivering more than 1014 watts of power to a small target of deuterium and tritium .