Particle Accelerators
Early Particle Accelerators
As physicists examine smaller and smaller objects, they need bigger and bigger toys to do the job. While Galileo was content dropping balls off the Leaning Tower of Pisa and Joule built a pulley system in his basement, modern physicists need things like the Large Hadron Collider, a "27-kilometre ring of superconducting magnets"5 buried 500 feet below Geneva, Switzerland. The LHC is, at its core, a particle accelerator—a device whose sole job is to accelerate charged particles to speeds so fast and so preposterous that no object was ever meant to achieve them. (The LHC is actually no less than two particle accelerators that fire charged particles in opposite directions in order to crash them together and figure out what the basic building blocks of matter—protons, neutrons, etc.—are themselves made of.)
Particle accelerators have much more humble beginnings, though. One of the first accelerators was a device called
Cathode ray tubes, or CRTs, use a cathode—an electron source, such as a heated wire—to create a steady stream of electrons when turned on. The electrons immediately experience a high voltage that accelerates them towards the front of the tube, turning electric potential energy into kinetic energy. Towards the front of the tube are deflecting coils, electromagnets that can be used to determine where on the screen each electron hits. CRTs were the fundamental technology behind old color TVs: each television had thousands of CRTs and each CRT could send electrons into red, blue, or green regions that would light up when struck. Taken together, these created color pictures of everything from "Gilligan's Island" to "Family Guy."
But science wouldn't stop there. Why only accelerate electrons to ridiculous speeds when you could use electromagnetism to accelerate them to LUDICROUS SPEED?
Physicists realized that there was no reason electrons had to be accelerated in a straight line, and so began a drive to design cyclical accelerators that spun electrons around in faster and faster circles. With this design, electrons could be sped up very quickly in a relatively small footprint compared to a linear accelerator—imagine running a mile by going around a quarter-mile track four times, as opposed to one straight mile-long track once.
Early cyclical accelerators, such as betatrons or cyclotrons, used a magnetic field to spin electrons around a circular path, and an electric field that turned off and on to push electrons out into larger and larger radius circles until they finally shot out the exit of the machine.
Electrons would enter the magnetic field, move in a 180º arc (right hand rule—check it), be accelerated by the electric field, and repeat the process on a larger radius arc.
These machines could accelerate electrons to relativistic speeds, which is to say speeds at which Einstein's theory of relativity starts kicking in and everything we think we know about mechanics kind of goes out the window. These particles move so fast that they give off x-rays or gamma rays, and so cyclical accelerators are very useful in medical physics—they make things that see through skin or fight cancer cells7.
Today's LHC is a byproduct of bigger and bigger cyclical particle accelerators...and shorter and shorter names. When it was first designed, one of the proposed names for the betatron was the "Ausserordentlichhochgeschwindigkeitelektronenentwickelndenschwerarbeitsbeigollitron."8 This proposed name was scrapped when the scientists realized the name was longer than the linear accelerators the betatron was replacing.