thermonuclear bomb

[Lanell]

a nuclear weapon that releases atomic energy by union of light (hydrogen) nuclei at high temperatures to form helium

[Thomassew]

A thermonuclear bomb is a weapon of mass destruction that generates explosive energy through the nuclear fusion of hydrogen isotopes. This process involves the fusion of light atomic nuclei, typically isotopes of hydrogen like deuterium and tritium, subjected under extremely high temperatures, in the millions of degrees, to initiate the fusion reaction. Such a bomb is also known as a hydrogen bomb or an H-bomb, and it is hundreds of times more powerful than an atomic bomb. It was first developed and tested in the mid-20th century.