The shape of the plasma at the National Ignition Facility (NIF) is primarily spherical, as it is generated within a fuel capsule that is a hollow sphere approximately 2 mm in diameter. This capsule contains a deuterium-tritium layer and is subjected to 192 pulsed laser beams, delivering around 1.8 MJ of energy. The rapid implosion of the capsule creates extreme temperatures and pressures, leading to fusion reactions in a central "hot spot." The discussion also considers alternative shapes, such as spindle or fusiform, but the established fact remains that the plasma is predominantly spherical.
PREREQUISITESPhysicists, fusion energy researchers, and students studying plasma physics or laser technology will benefit from this discussion, particularly those interested in the mechanics of plasma formation and fusion processes at NIF.
The $3.5bn NIF trains 192 pulsed laser beams on to the inner surface of a centimetre-long hollow metal cylinder known as a hohlraum. Inside is a fuel capsule, which is a roughly 2 mm-diameter hollow sphere containing a thin deuterium-tritium layer. Each pulse lasts just a few nanoseconds and the lasers can deliver about 1.8 MJ of energy. This powerful blast causes the capsule to implode rapidly, creating immense temperatures and pressures inside a central “hot spot”, where fusion reactions occur.