Particle accelerators, machines that accelerate elementary particles, are critical in various industries, including science, product development, health care, and national security. Used in more than 30,000 operations worldwide, these accelerators have profoundly shaped our understanding of particle and nuclear physics and are an integral part of many industrial processes, medical treatments and national security operations.
Whether it is medical or scientific research, consumer product development or national security, particle accelerators touch almost every part of our daily lives. Since the early days of the cathode ray tube in the 1890s, particle accelerators have made major contributions to scientific and technological innovation. Today there are more than 30,000 particle accelerators in operation around the world.
What is a particle accelerator?
A particle accelerator is a machine that accelerates elementary particles, such as electrons or protons, to very high energies. At a basic level, particle accelerators produce beams of charged particles that can be used for a variety of research purposes. There are two basic types of particle accelerators: linear accelerators and circular accelerators. Linear accelerators propel particles along a linear or straight line of radius. Circular accelerators propel particles along a circular track. Linear accelerators are used for fixed target experiments, while circular accelerators can be used for both colliding beam experiments and fixed target experiments.
How does a particle accelerator work?
Particle accelerators use electric fields to accelerate and increase the energy of a beam of particles, which are guided and focused by magnetic fields. The particle source supplies the particles, such as protons or electrons, that need to be accelerated. The particle beam travels within a vacuum in the metal beam tube. The vacuum is essential to maintain an air and dust free environment for the particle beam to travel unhindered. Electromagnets guide and focus the particle beam as it travels through the vacuum tube.
The electric fields spaced around the accelerator switch from positive to negative at a given frequency, creating radio waves that accelerate particles into groups. The particles can be directed at a fixed target, such as a thin piece of metal foil, or they can cause two beams of particles to collide. Particle detectors record and detect particles and radiation produced by the collision between a beam of particles and the target.
How have accelerators contributed to basic science?
Particle accelerators are essential discovery tools for particle and nuclear physics and sciences using X-rays and neutrons, a type of neutral subatomic particle.
Particle physics, also called high-energy physics, poses fundamental questions about the universe. With particle accelerators as their primary scientific tools, particle physicists have achieved a deep understanding of fundamental particles and the physical laws that govern matter, energy, space and time.
Over the past forty years, accelerators of light sources that produce photons, the subatomic particle responsible for electromagnetic radiation, and the sciences that use them, have made enormous progress that cuts across many fields of research. Today there are approximately 10,000 scientists in the United States who use X-rays for research in physics and chemistry, biology and medicine, earth sciences, and many other aspects of materials science and development.
How have particle accelerators improved consumer products?
Around the world, hundreds of industrial processes use particle accelerators from making computer chips to curing plastic for shrink wrap and beyond.
Electron beam applications focus on the modification of material properties, such as the alteration of plastics, for surface treatment and for the destruction of pathogens in medical sterilization and food irradiation. Ion beam accelerators, which accelerate heavier particles, find extensive use in the semiconductor industry in chip manufacturing and surface hardening of materials such as those used in artificial joints.
How are particle accelerators used in medical applications?
Tens of millions of patients receive accelerator-based diagnoses and therapies each year in hospitals and clinics around the world. There are two main roles for particle accelerators in medical applications: the production of radioisotopes for medical diagnosis and therapy, and as sources of electron beams, protons and heavier charged particles for medical treatment.
The wide range of half-lives of radioisotopes and their different types of radiation allow optimization for specific applications. Isotopes emitting X-rays, gamma rays or positrons can serve as diagnostic probes, with instruments located outside the patient to visualize the distribution of radiation and thus biological structures and the movement or constriction of fluids (blood flow, for example ). Emitters of beta rays (electrons) and alpha particles (helium nuclei) deposit most of their energy near the site of the emitting nucleus and act as therapeutic agents to destroy cancerous tissue.
External beam radiation therapy has developed into a highly effective method of treating cancer patients. The vast majority of these irradiations are now performed with microwave linear accelerators that produce electron beams and X-rays. Accelerator technology, diagnostics and treatment technique developments over the past 50 years have greatly improved clinical outcomes. Today, 30 proton beam and three carbon ion beam treatment centers are in operation worldwide, with many new centers on the way.
The Departments of Energy National Laboratories played a crucial role in the early development of these technologies. Los Alamos National Laboratory helped develop linear accelerators for electrons, now the workhorses of external-beam therapy. Oak Ridge and Brookhaven National Laboratories have contributed much of the current expertise in isotopes for diagnosis and therapy. Lawrence Berkeley National Laboratory pioneered the use of protons, alpha particles (helium nuclei), and other light ions for therapy and radiobiology.
How have particle accelerators benefited national security?
Particle accelerators play an important role in national security, including cargo inspection, inventory management, and material characterization.
Early applications of accelerators to inspect nuclear fuels used commercial low-energy linear electron accelerators to induce photofission reactions. These inspection technologies extended to waste drum investigations in the 1980s and eventually to cargo inspections. The invention of the free electron laser in the 1970s resulted in electromagnetic radiation of ever increasing power using high energy electrons, of direct interest to security and defense applications, including the Navy’s proposed application of electron laser technology free to defense on board.
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