Scientists often call this impressive device a linac for short. It uses powerful microwave electromagnetic waves to push charged particles down a long, straight vacuum pipe. Inside this empty pipe is a series of hollow metal cylinders called drift tubes.
The machine creates an oscillating electric field across the open gaps between these tubes. This means the electric voltage flips back and forth at exactly the right moment. When a particle reaches a gap, the electric field strongly pulls it forward.
The particle gains more speed and more kinetic energy at every single gap. The metal tubes get progressively longer as the particles move faster to keep the electrical timing perfect. These machines can be a few meters long in a hospital or miles long in a national lab.
In physical chemistry, researchers use linear accelerators to study extremely fast chemical reactions. They shoot a rapid burst of fast electrons into a chemical sample to start a reaction. This fast process creates highly reactive pieces of molecules for a tiny fraction of a second.
Doctors also use smaller versions of these machines in modern hospitals. They use them to make special radioactive elements for medical scans and cancer treatments.