- A particle accelerator is a device that propels subatomic particles to high speeds, using electromagnetic fields.
- It generates a beam of charged particles that is used for numerous research purposes.
The history of particle accelerator dates back to 1930 when scientists developed a 200,000-volt transformer and accelerated protons along a straight path. Although the machine didn’t fill its purpose, it began the quest for higher energy particle accelerators, which continues to this day.
A particle accelerator is a large device that propels subatomic particles to high speeds, using electric and magnetic fields. For more technically-inclined minds, it’s a machine that accelerates electrically charged particles close to the speed of light and contains them in well-defined beams, using electromagnetic fields.
In the 20th century, particle accelerators were referred to as atom smashers. The name persists despite the fact that present-day accelerators make collisions between two subatomic particles, instead of atoms’ nuclei.
Collisions of such particles can help scientists understand how the universe works. High-energy particle accelerators are extremely useful for fundamental and applied research in various fields, ranging from electronics and medicine to international security.
We have covered some of the most intriguing facts and statistics about modern particle accelerators that will spark your interest in particle physics. Let’s start with the basic one.
Types of Particle Accelerators
There are two basic types of accelerators:
1) Electrostatic Accelerators: use static electric fields to increase the speed of charged particles. A positive particle is attracted to a negatively-charged plate, while a negative particle is attracted to a positively-charged plate.
They are simple, less-expensive, and have limited energy output, which means they cannot accelerate particles to extremely high speeds. The maximum kinetic energy of particles depends on accelerating voltage, which is limited by a phenomenon called electrical breakdown.
Van de Graaff generator and Cockcroft-Walton generator are the most common example of electrostatic accelerators. The cathode-ray tube of any old computer monitor is a small-scale example of this type of accelerator.
2) Electrodynamic Accelerators: use altering electromagnetic fields (either oscillating radiofrequency fields or magnetic induction) to accelerate particles.
In these devices, particles are passed through the same electromagnetic field multiple times, so they can achieve much higher speeds than those in electrostatic accelerators. The maximum kinetic energy of particles isn’t limited by the intensity of the accelerating field.
These accelerators can be further subdivided into two classes:
- Linear, in which particles accelerate in a straight line
- Circular, in which particles are bent in a roughly circular orbit using magnetic fields. Particles move this orbit until they reach sufficient energy.
Operation of a Linear accelerators | Wikimedia
How Does It Work?
On a basic level, particle accelerators generate a beam of charged particles that is used for numerous research purposes. Usually, the beam is comprised of charged subatomic particles (such as protons and electrons) but in some cases, whole atoms of heavier elements (like uranium and gold) are used.
In circular accelerators, for instance, the particles are continuously accelerated in a circular tube. The intensity of the electric field increases with each pass, raising the energy level of the particle beam.
When particles achieve the required speed, a target (such as a thin piece of metal sheet) is placed into their track, where a particle detector analyzes the collision.
Overall, there are 6 key components in the particle accelerators:
A) Particle Source: provides particles (such as electrons or protons) to be accelerated. A single bottle of hydrogen gas, for example, could be particle source. One atom of hydrogen contains one electron and one proton.
B) Metal Pipe: contains a vacuum in which the beam of particles travels. The vacuum maintains the dust-free environment for electrically charged particles to move unobstructed.
C) Electromagnets: control the movement of particles while they travel through the metal pipe.
D) Electric Fields: are regularly switched from positive to negative. This generates radio waves that speed up the charged particles.
E) Targets: When particles achieve the desired speed, they are collided with a fixed target. Sometimes, two beams of particles are collided.
F) Detectors: record the collision of particles and reveal the radiation or subatomic particles generated in the process.
The Largest Particle Accelerators In the World
More than 30,000 particle accelerators are currently operating across the world. Of these, 44% are used for radiotherapy, 41% for ion implantation, 9% for industrial processing, and 4% for low-energy and biomedical research. Only 1% of existing accelerators are capable of producing energies above one billion electron Volts or 1 GeV.
At present, the Large Hadron Collider is the most powerful particle accelerator in the world. It is capable of accelerating two beams of protons to an energy of 6.5 tera electron Volts. When these two powerful beams collide, they create center-of-mass energies of 13 tera electron Volts (TeV).
A map of large hadron collider| CERN
The machine lies in a 175-meter deep tunnel. It is 27 kilometers in circumference and its ring of magnets can produce a magnetic field of 8.36 Tesla.
The structure contains over 1,000 dipole magnets end-to-end, which keep particles racing along almost at the speed of light: one particle travels the 27-kilometer-ring 11,000 times per second.
It was developed by the European Organization for Nuclear Research in collaboration with more than 10,000 researchers and hundreds of laboratories and universities from over 100 countries.
The Higgs boson particle, sometimes referred to as ‘God Particle’, was discovered in the Large Hadron Collider in 2012. In the same year, physicists formed a quark-gluon plasma that could have reached 5.5 trillion degrees Celsius — the highest temperature recorded by a man-made machine.
The Higgs boson was first observed during experiments at the Large Hadron Collider | Image Credit: Designua/Shutterstock
In the coming years, this giant machine will allow physicists to test various theories of particle physics, including analyzing the properties of Higgs bosons, searching for new elementary particles suggested by supersymmetric theories, as well as other mysteries in the universe.
From industry to energy supply, health to security, there are several fields beyond pure research in which particle accelerated-related technology impacts people’s lives in a positive way.
Medical Applications: Every year, millions of patients receive accelerator-based diagnoses and treatment in clinics and hospitals across the world. Accelerated particles (such as protons, electrons, or heavier charged particles) are used to kill cancer cells and generate a detailed image from inside the body.
Consumer Products: Particle accelerators are currently used in various industrial processes, ranging from cross-linking of plastic for shrink wrap to the manufacturing of computer chips.
Ion-beam accelerators, in particular, are used to manufacture electronic chips and harden the material surfaces like those used in artificial joints. Electron-beam accelerators, on the other hand, are generally used for altering material properties such as plastic modifications for surface treatment.
National Security: Accelerators play a crucial role in stockpile stewardship, cargo inspection, and material characterization. They are mostly used to scan containers and items and help identify weapons and other dangerous materials.
What Else Can They Do?
The analysis of high-energy particle collisions could be beneficial for fundamental and applied research in the sciences. It can help physicists solve some of the fundamental problems in physics, including the deep structure of spacetime, and the relationship between general relativity and quantum mechanics.
A collision of two protons produces a shower of particle debris | CERN
Here are the four main questions that scientists hope to answer in the next few decades:
- Are there extra dimensions, as predicted by string theory models?
- What is the nature of dark matter?
- What did the early universe look like?
- Why do we see asymmetry between matter and antimatter in the universe?
In fact, particle accelerator-based technology is the closest thing we have to time machines, according to Stephen Hawking. He wrote a paper in 2010, explaining how it might be possible to travel through time.