Science Made Simple: How Do Particle Accelerators Work?

Particle accelerators are crucial machines that propel elementary particles, such as electrons or protons, to achieve high energy levels. These remarkable devices have far-reaching impacts on scientific research, product development, medical treatments, and national security.

In today’s interconnected world, particle accelerators have become integral to various sectors, including science, product development, healthcare, and national security. With over 30,000 operational accelerators worldwide, they have revolutionized our understanding of particle and nuclear physics and play a vital role in industrial processes, medical treatments, and national security operations.

An illustration depicting the workings of a particle accelerator. Credit: Sarah Gerrity, Energy Department.

Since their inception in the late 19th century with the cathode ray tube, particle accelerators have made significant contributions to scientific and technological advancements. These accelerators have become indispensable tools across a wide range of fields, and their presence can be felt in almost every aspect of our daily lives. Today, there are more than 30,000 particle accelerators operating worldwide.

What exactly is a particle accelerator?

A particle accelerator is a machine designed to accelerate elementary particles, such as electrons or protons, to incredibly high energies. At its core, a particle accelerator generates beams of charged particles that serve various research purposes. There are two main types of particle accelerators: linear accelerators and circular accelerators. Linear accelerators propel particles along a straight beam line, while circular accelerators accelerate particles around a circular track. Linear accelerators are used for fixed-target experiments, whereas circular accelerators can facilitate both colliding beam and fixed target experiments.

How does a particle accelerator function?

Particle accelerators employ electric fields to increase the speed and energy of a particle beam, while magnetic fields help steer and focus the particles. The particle source provides the particles, such as protons or electrons, which are to be accelerated. These particles travel inside a vacuum within a metal beam pipe, ensuring an obstruction-free path in an air and dust-free environment. Electromagnets guide and concentrate the particle beam as it traverses the vacuum tube.

Electric fields positioned throughout the accelerator switch polarity at specific frequencies, creating radio waves that accelerate particles in groups. The particles can be directed at a fixed target, like a thin metal foil, or two particle beams can be collided. Particle detectors record and analyze the particles and radiation resulting from the collision between the beam and the target.

What contributions have accelerators made to basic science?

Particle accelerators are indispensable tools for advancing particle and nuclear physics, as well as other fields that utilize x-rays and neutrons—neutral subatomic particles. Particle physics, also known as high-energy physics, tackles fundamental questions about the universe. By employing particle accelerators as their primary scientific instruments, physicists have achieved a profound understanding of the fundamental particles and physical laws governing matter, energy, space, and time.

Over the past four decades, light sources—accelerators that produce photons, the subatomic particles responsible for electromagnetic radiation—and the sciences relying on them have made remarkable breakthroughs across various research fields. In the United States alone, around 10,000 scientists employ x-ray beams to conduct research in physics, chemistry, biology, medicine, Earth sciences, materials science, and numerous other disciplines.

How have particle accelerators influenced consumer products?

Across the globe, hundreds of industrial processes depend on particle accelerators, ranging from computer chip manufacturing to plastic cross-linking and beyond. Electron-beam applications focus on altering material properties, such as modifying plastics for surface treatment or sterilizing medical equipment and food. Ion-beam accelerators, which accelerate heavier particles, find extensive use in the semiconductor industry for chip manufacturing and in enhancing material surfaces, like those used in artificial joints.

How are particle accelerators utilized in medical applications?

Every year, tens of millions of patients receive accelerator-based diagnoses and therapies in hospitals and clinics worldwide. Particle accelerators serve two primary roles in medical applications: producing radioisotopes for medical diagnosis and therapy, and generating beams of electrons, protons, and other charged particles for medical treatment.

Radioisotopes, with their varying half-lives and radiation types, can be optimized for specific applications. Isotopes emitting x-rays, gamma rays, or positrons can be used as diagnostic probes, allowing radiation distribution to be imaged from outside the patient, revealing biological structures, fluid motion, or constrictions (such as blood flow). Emitters of beta rays (electrons) and alpha particles (helium nuclei) deposit most of their energy near the emitting nucleus, making them effective therapeutic agents for destroying cancerous tissue.

External beam radiation therapy has become a highly effective method for treating cancer patients. The majority of these treatments now utilize microwave linear accelerators that produce electron beams and x-rays. Advancements in accelerator technology, diagnostics, and treatment techniques over the past 50 years have dramatically improved clinical outcomes. Currently, there are 30 proton treatment centers and three carbon-ion-beam treatment centers operating worldwide, with several new centers under development.

The Department of Energy’s National Labs played a crucial role in the early development of these technologies. For instance, Los Alamos National Laboratory contributed to the development of linear accelerators for electron therapy, which have become the primary treatment method. Oak Ridge and Brookhaven National Laboratories have made significant contributions to the expertise in radioisotopes for diagnosis and therapy. Lawrence Berkeley National Laboratory has been at the forefront of utilizing protons, alpha particles, and other light ions for therapy and radiobiology.

How have particle accelerators advanced national security?

Particle accelerators play a vital role in national security, encompassing applications such as cargo inspection, stockpile stewardship, and materials characterization.

Early applications of accelerators involved inspecting nuclear fuels using low-energy electron linear accelerators to induce photo-fission reactions. These inspection technologies expanded to investigate waste drums in the 1980s and eventually led to cargo inspections. The invention of the free electron laser in the 1970s enabled the production of high-power electromagnetic radiation using high-energy electrons. This development has direct implications for security and defense applications, including the proposed use of free-electron laser technology by the Navy for shipboard defense.

Frequently Asked Questions (FAQs) about Particle accelerator applications

More about Particle accelerator applications

• Particle Accelerators – Fermilab
• How Particle Accelerators Work – Jefferson Lab
• Applications of Particle Accelerators – CERN
• Particle Therapy – American Society for Radiation Oncology
• National Security Applications of Particle Accelerators – Stanford University
• Consumer Products and Industrial Applications – International Atomic Energy Agency