Imagine that you’re an automobile engineer that builds cars. The most recent car you made,
let’s call it “the cool car”, broke the world record as the fastest car ever made. However, a
year later, an automobile manufacturer made a new remote-controlled vehicle called the “wonder car”,
which bested your car’s top speed. It's only natural that you would want to see
what unique parts the wonder car used and how it’s built differently from your cool car.
The problem is, the wonder car is put together using special,
proprietary tools that you can't access. So,
given that you are unconventionally adventurous, you buy two wonder cars and put them on a race
track in opposite directions so that they travel towards each other. Using their remote controls,
you accelerate both cars to their top speeds, which is when you make them crash into each other.
There’s a deafening bang, and the internal parts of both wonder cars fly out in every direction.
That is the basic working principle of the world’s largest particle accelerator.
In the most basic terms, a particle accelerator is a machine that accelerates particles.
More specifically, it accelerates elementary particles, like protons and electrons,
at extremely high speeds—almost 99.99% of the speed of light. These particles are then smashed
against a stationary target or against other particles traveling in the opposite direction.
These collisions produce massive particles, such as the top quark or the Higgs boson,
which last for only a fraction of a second. Then, almost immediately, these particles
convert into smaller, lighter particles, which, in turn, decay almost instantly. These collisions
not only help us understand the composition of the elementary particles in question, but also
supplement our knowledge of our universe’s origin immediately following the Big Bang.
Particle accelerators can be broadly classified into two categories—linear
accelerators (also called LINACs) and circular accelerators.
A linear accelerator accelerates ions or subatomic particles to a very high speed
using a strong electric field along a linear path, hence the name linear accelerators. A
circular accelerator, in contrast, accelerates elementary particles along a circular path
to finally smash into a target or other incoming particles from the opposite direction.
The largest circular accelerator in the world is called the Large Hadron Collider or LHC,
and is located at CERN near the French-Swiss border. The circumference of the accelerator
is nearly 17 miles or 27 kilometers, greater than the length of Manhattan!
Circular particle accelerators are sometimes also referred to as
“atom smashers”, as they smash subatomic particles into each other.
The basic working principle of all particle accelerators remains the same:
they contain a particle source that provides elementary particles. Although a particle
accelerator commonly accelerates protons or electrons, it can also accelerate other
particles. The LHC, for example, can accelerate the nuclei of argon, xenon, or lead atoms.
This beam of elementary particles travels inside a metal beam pipe, which maintains a vacuum inside.
It is critical to ensure that the whole beam setup is devoid of air and dust particles,
so that accelerated particles can travel unimpeded and achieve speeds close to the speed of light.
There is special equipment placed around the accelerator that produces strong electric fields.
It is these electric fields that allow the particle to achieve such high speeds.
They switch from positive to negative at a given frequency,
creating radio waves that “push” and accelerate particles.
There are also numerous electromagnets placed along the length of the accelerator;
their primary job is to focus the beam of particles as they accelerate
and keep them “locked” in a circular path within the metal beam.
As the particle races extremely fast around the accelerator, it gains more and more energy
with each turn. In the LHC, for example, accelerated protons attain the energy of
6.5 trillion electron volts. This is the highest magnitude of energy reached by the accelerator,
and when protons carrying this much energy collide with other protons, the energy of those collisions
is transformed into matter, following Einstein’s energy-mass equivalence equation, which states
that mass and energy are interchangeable, since matter is just a concentrated form of energy.
This is why particles like the Higgs boson are produced by these collisions. Studying
their properties provides us with insight into the composition of matter and the universe's origins.
Contrary to popular belief, particle accelerators are not all highly complicated machines that ONLY
exist in huge laboratories or movies; a particle accelerator can be as small as a few inches!
In fact, the first accelerator ever built was less than 5 inches across.
There are currently more than 30,000 particle accelerators in the world. Although they’re
often associated with particle research and understanding our universe's origins,
accelerators are also used in medicinal sciences. Millions of patients around the
world are diagnosed using medical appliances that are essentially particle accelerators.
Linear accelerators can generate X-rays and high-energy electrons, which can be
used in medical diagnostics and radiation therapy for cancer patients. Furthermore,
accelerators are also used in ion implantation to manufacture semiconductors. This process is
critical to introduce a specific type of ion at a desired depth to create semiconductors.
Hundreds of industrial processes involve accelerators,
ranging from manufacturing computer chips that power our computers to the sterilization
of culinary processed food items that can be stored at room temperature for months.
Although you shouldn’t smash two wonder cars together to see what’s inside,
you can rest assured that particle accelerators are, and will forever be,
an integral part of modern civilization.