Controlled Thermonuclear Fusion

13.7.3 Controlled Thermonuclear Fusion

The energy that powers stars, including our Sun, comes from nuclear fusion — the process in which very light nuclei combine to form a heavier nucleus. In a star, the enormous gravitational pressure creates the extreme temperatures and densities needed for fusion to occur naturally. On Earth, we attempt to replicate this process in a controlled manner to generate power.

In a controlled thermonuclear fusion reactor, the goal is to produce steady power by heating nuclear fuel to temperatures on the order of $10^8$ K. At such temperatures, matter exists in a state called plasma — a mixture of positive ions and free electrons. No physical container can withstand these temperatures, so confining the plasma is the central technical challenge. Research into controlled fusion is ongoing in many countries, including India. If successful, fusion reactors could provide humanity with a nearly limitless source of energy.

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Summary of Key Ideas

• Controlled thermonuclear fusion requires heating fuel to about $10^8$ K, creating a plasma of ions and electrons.
• The plasma must be confined without physical contact — magnetic confinement and inertial confinement are the main approaches being developed.
• Nuclear reaction equations are balanced by conservation of proton number and neutron number (and more fundamentally, by conservation of charge and baryon number). …