A coil of wire, or solenoid, consists of a wire coiled up into a spiral shape. When an electric current flows, the shape of the magnetic field is very similar to the field of a bar magnet.

Earlier this week, the company successfully tested the Central Solenoid Model Coil (CSMC), a crucial component of its SPARC tokamak reactor design that could one day help produce carbon-free energy.

Solenoids, electromagnets formed by a coil of wire wrapped around a magnetic core, are a fundamental building block of many electronics, from dialysis machines and respirators to washing machines ...