Target for inertial fusion — capsule filled with frozen mixture of deuterium and tritium. (Source: Wikipedia.org)

A peppercorn-sized sphere filled with frozen hydrogen that lasers focus on during inertial fusion, squeeze it and ignite fusion inside. The surface of the target, called an ablator, can be plastic, glass or even beryllium. Inside is a mixture of deuterium and tritium, which is frozen to make the fuel as smooth and evenly distributed as possible. The lasers can be aimed directly at the target (direct drive) or the target is placed in a cavity called the hohlraum (indirect drive) and the sphere is then uniformly compressed by the X-rays produced when the lasers hit the inner wall of the hohlraum.