what is nuclear fusion?

Answer 1

Nuclear fusion is the process by which multiple atomic particles join together to create a heavier nucleus. The process results in the release and absorption of thermal energy.

Answer 2

Fusion means to come together and form one. In nuclear fusion, multiple nuclei (atom cores) come together and form one nucleus.

In a fusion bomb, lithium deuteride (LiD) is fused under the initial heat and pressure caused by fission and that fusion adds to the yield of the bomb. In general, the fusion reaction looks like n + n + q --> N + Q; where n is a nucleus, N is the fused product, q is endothermic energy added to cause the fusion, and Q is exothermic energy (e.g., heat). Naturally, q < Q; othewise it'd make no sense to do the fusion.

Turns out the sum of masses for the two n's (m + m) is greater than the mass (M) of the resulting nucleus N. That is 2m > M; so that delm = 2m - M > 0; where delm is the mass difference before and after the fusion.

Then E = delm c^2 = Q, which says that, under fusion, the mass difference delm is converted to exothermic energy Q. And that's the big bang of the fusion bomb.