A particle accelerator is a device that creates a beam of atomic or subatomic particles that move quickly and are electrically charged. Accelerators are used by physicists for basic research on the elements of nuclei, the nature of nuclear forces, and the characteristics of nuclei that are not present in nature. Accelerators were first built in the 1930s, to give researchers energetic particles for studying the structure of the atomic nucleus. They are now utilized to study a wide range of topics in particle physics. By forming magnetic fields to direct, focus and accelerate the particles and electric fields, they work to raise the energy and speed of a particle beam. Particle accelerators are remarkable devices that changed the trends in business, research, and medicine. These devices give significant information of the basic properties of matter, energy, and space by rapidly accelerating charged particles.
What is a Particle Accelerator?
A device used to accelerate charged particles—such as protons, electrons, or ions—to very high speeds (nearly the speed of light) is called a particle accelerator. These accelerated particles are further sent to interact with other particles. The high energies released after the collision approximate with the energy released after the big bang. Hence, fundamental forces and particles during the period of formation of the universe can be studied with the help of particle accelerators.
The particle accelerators differ in a number of sizes and structural functions. However, the smallest accelerators also contain components similar to the bigger ones. A source is a primarily required apparatus in all accelerators that produces electrically charged particles, such as protons, electrons, and their antiparticles in the case of bigger accelerators. All accelerators equally require magnetic fields to track the particles and electric fields to accelerate them. Also, the particles should travel in a vacuum with a possible little air left as a residue. Lastly, the accelerator must be able to detect, measure and count the particles after being accelerated.
From small devices used in hospitals for treatment purposes to complex structures like the Large Hadron Collider (LHC), accelerators are available in various forms. However, all of them aim to explore basic aspects of the composition of the universe.
How do Particle Accelerators Work?
In order to accelerate and guide charged particles in a desired path, a particle accelerator uses a combination of electric and magnetic fields. The process can be studied by classifying into various steps:
- Generation of Particles
Electrons and protons are the most common particles used in an accelerator. They must be in separated form to be injected in the device. An Electron gun (which is a cathode) is heated and used to separate electrons from an atom and inject in an accelerator.
Similarly for proton accelerators Hydrogen gas serves as the source as it is the only nuclei containing a single proton. Here, the gas is ionized, the electrons and protons differ in their electric field and the protons left through a hole. Protons are primarily created as negative hydrogen ions in massive high-energy particle accelerators. Before the protons go to the final phase of acceleration, they first pass through thin foils to get separated from the electrons.
- Acceleration of Particles
Particles are accelerated by the energy of electric fields. An electron with a negative charge experiences a force that pulls it in the direction of the positive potential. The electron is accelerated by this force, and its velocity and energy will rise if there are not any disturbances. If electrons are traveling through a vacuum, they will speed up as they approach the positive potential, but if they are traveling down a wire or even in air, they will hit with atoms and drop energy.
The energy of an electron is determined by the difference in electric potential between the origin where it starts to move through the field and the point where it quits the field. In linear accelerators, particles are accelerated in a straight line, whereas in circular accelerators particles are accelerated again and again as they circulate.
- Guiding the Track of the Particles
Magnetic fields are important aspects in particle accelerators to focus them in a desired direction. Because they have the ability to alter the direction of charged particles, magnetic fields are used to “bend” the beam of particles around a circle so that they repeatedly travel over the same areas of acceleration. In most common processes a charged particle traveling in a path perpendicular to that of a uniform magnetic field experiences a force perpendicular to both the field and the particle’s direction. This force causes the particle to travel in a circle perpendicular to the field until it quits the region of magnetic field or goes through the effect of another force.
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- Collision
For many years, the researchers only used the particles once and then removed them from the accelerators. But in the 1970s, rings were created, with two particle beams moving in opposing directions and colliding on each machine circuit. One significant benefit of these devices is that the energy of the particles directly contributes to the energy of the interactions between two beams when they meet head-on. Particles collide with a target or another particle beam after obtaining the energy needed. Advanced detectors record the data given by the following incidents.
Different Types of Particle Accelerators
Particle accelerators can be classified into different types according to their design and functioning:
Linear Accelerators
Particles are accelerated in a straight line by linear accelerators. The principle of phase stability must be used in an efficient linear accelerator for heavy particles like protons. There are two types of linear accelerators: traveling-wave linear accelerators, which accelerate electrons, and standing-wave linear accelerators, which accelerate heavier particles. The reason for the variance is that electrons have speeds that are quite near to that of light after being accelerated to a few megaelectron volts in the first few meters of a normal accelerator. The particles do not become out of phase because their speeds remain constant if the accelerating wave similarly travels at the speed of light. The design should be such that it must meet an extra increase in speed since protons need to achieve considerably higher energy before their speeds can be considered constant.
Linear electron accelerators are mostly used for business purposes and companies.They are used in radiography, and in cancer therapy. Linear proton accelerators are mostly used in labs to generate neutron beams for the research on neutrons.
Cyclotrons
Cyclotrons accelerate particles in a loop by combining electric and magnetic fields. They are used frequently in the production and study of medical isotopes because they are portable and effective. The first harmonic accelerator and periodic accelerator to create particles with sufficient energy for nuclear research was Cyclotron. For many years, cyclotrons were the source of the highest particle energy. These devices are known as traditional cyclotrons because the driving magnetic field has a constant strength, and the accelerating electric field oscillates at a given frequency.
Synchrotrons
Synchrotrons use magnetic fields that change as particle energy rises to accelerate particles in a circular motion. These accelerators, which create high-energy collisions for particle physics experiments, are essential to massive centers of research. A synchrotron’s orbital radius is kept nearly constant by increasing the magnetic field’s strength as the particles accelerate. The benefit of this method is that a comparatively much smaller magnet is needed to generate the particle orbits than is necessary in a cyclotron to produce the same particle energy.
Betatrons
Betatrons are specially designed circular accelerators designed for electrons. They are used in industries, such as producing X-rays for analysis of different materials. As the name indicates, a betatron is a particular kind of accelerator that works only with electrons, also known as beta particles. Under the effect of a magnetic field that gets stronger as the electrons’ energy increases, the electrons in a betatron travel in a circle. In addition to creating a field on the electron orbit, the magnet also creates a field inside the orbit. The electrons are accelerated by the electric field created as this field’s strength increases over time.
Storage Rings
Storage rings maintain high-energy particle beams for quite longer periods, allowing detailed studies of collisions and synchrotron radiation.
Applications of Particle Accelerators in Medicine and Industry
Above research labs, particle accelerators are having an incredible effect on industry and medicine.
- Medical Applications
- Radiation Therapy: Radiation levels are precisely sent to diseased areas of cancer, tumor and other deadly diseases by linear accelerators to reduce harm to healthy cells.
- Medical Imaging: Cyclotrons produce isotopes like fluorine-18, that are important for PET scans.
- Proton Therapy: High-energy protons are an effective alternative for traditional radiation therapy as their precision levels are outstanding in targeting infected areas.
- Industrial Applications
- Material Analysis: In order to test materials safely, find defects in the structure and evaluate strength, accelerators produce X-rays and neutrons.
- Semiconductor Manufacturing: Particle accelerators are necessary for ion implantation which is an important phase in the production of microchips.
- Sterilization: Food products and medical equipment are sterilized by electron beams, increasing their safety and lifespan.
The Role of Particle Accelerators in Scientific Research
Particle accelerators are necessary instruments for developing both pure and applied science. Some important roles are listed below:
- Understanding Fundamental Physics
Scientists can study the basic forces of nature controlling the universe and the smallest components of matter, such as quarks and leptons, through particle accelerators. The discovery of the Higgs boson at CERN’s LHC is the best proven example of particle accelerators.
- Astrophysics and Cosmology
Accelerators provide information about the origins of dark matter, the universe, and other processes of physics by modeling high-energy cosmological events.
- Material Science
Synchrotron radiation provides intense X-rays for studying characteristics of a material at the atomic and molecular level. This supports the further developments in chemistry and nanotechnology.
- Biology and Life Sciences
Accelerators make it possible to study the structures of biomolecules, which leads to advances in drug design and better understanding of the roots of a disease.
Real-World Examples of Particle Accelerators
- The Large Hadron Collider (LHC)
It is the biggest and most powerful accelerator in the world which is operated by CERN near Geneva, Switzerland. Its rings are spread 27 kilometers and accelerate protons nearly the speed of light. Significant discoveries are being made in particle physics by the use of LHC.
- SLAC National Accelerator Laboratory
It is a linear accelerator which is situated in California, USA. This accelerator is aiding research on particle physics, photon science, and astrophysics.
- Spallation Neutron Source (SNS)
The SNS is Situated in Tennessee, USA which generates neutrons for studying the structures and behaviour of particles.
- Diamond Light Source
It is a synchrotron reactor located in the UK. It generates X-rays for their usage in medical purposes and archaeological research.
Advancements in Particle Accelerator Technology
Current developments in technology are trying to increase effectiveness of the accelerators with low cost and increased applications:
- Compact Accelerators
Improvements in laser plasma acceleration and dielectric laser acceleration provide smaller and cheaper accelerators. This increases the availability of accelerators also in remote areas.
- Energy Efficiency
Superconducting magnets increase operational efficiency of accelerators by reducing power consumption.
- High-Intensity Beams
Higher particle densities are made possible because of developments in beam dynamics, which improves experimental sensitivity and output of the accelerators.
Safety Measures in Operating Particle Accelerators
Safety measures are the first and foremost requirements before handling particle accelerators.
- Radiation Shielding
Thick barriers of concrete, lead, or other materials can protect operators and the environment from harmful radiation.
- Access Control
Strict protocols should be regulated for the access to accelerator facilities during operation which may prevent accidental exposure.
- Monitoring Systems
Continuous radiation tracking provides conformation to safety rules and can quickly detect defects.
- Emergency Preparedness
Organizations must establish complete plans to deal with any incidents, avoiding hazards to staff and equipment.
Conclusion
Particle accelerators uplifted the standard of the human mind being the most powerful invention of their kind. They are significantly contributing to different aspects in science such as health, and industry. Their impact is wide and beneficial which lies from the origin of the universe to cancer treatments. As technology is developing, particle accelerators will probably have a more important role in enhancing daily life and modern discoveries. (Also read about Nuclear Reactors)
References
Wilson, E. (2001). An introduction to particle accelerators (p. 267). Oxford University Press.
Wille, K. (2000). The physics of particle accelerators: an introduction. Clarendon Press.
Kutsaev, S. V. (2021). Advanced technologies for applied particle accelerators and examples of their use. Technical Physics, 66(2), 161-195.
Conte, M., & MacKay, W. W. (2008). Introduction To The Physics Of Particle Accelerators, An. World Scientific Publishing Company.
https://www.britannica.com/technology/particle-accelerator
