Taleyarkhan theorized a form of this process involving sonoluminescence in bubbles of acetone. In the "indirect drive" method of inducing this process, lasers heat the inner walls of a gold cavity called a hohlraum. The NIF experiment uses inertial confinement to attempt this process, while ITER uses a tokamak to achieve it. Hydrogen bombs use the thermonuclear type of this process. This process is central to the proton-proton chain and powers the Sun. For 10 points, name this process in which two nuclei join together into a single heavier atom.
a. Nuclear fission
b. Nuclear fusion
c. Radioactive decay
d. Nuclear transmutation