Before 1932, when particle accelerators were first used for nuclear research, scientists relied on naturally radioactive substances to advance their understanding of the atomic nucleus.

Particle accelerators propel matter toward small targets at high speed

Devices like cathode-ray tube televisions were once basic particle accelerators, but modern ones, such as the Large Hadron Collider, use massive magnetic fields and circular tunnels to achieve energies high enough to recreate the conditions just after the big bang.

Learn about five of the largest particle accelerators on Earth, which, as of 2026, are led by the Large Hadron Collider at the European Organization for Nuclear Research.

The first circular particle accelerator was narrower than the average cereal bowl

The 1939 Nobel Prize in physics was awarded to Ernest Lawrence for inventing the cyclotron. By comparison, the Large Hadron Collider is 5 miles in diameter and is the largest cryogenic system in the world, cooling its electromagnets to temperatures colder than those found in outer space.

Although built from 1996 to 2008, the Large Hadron Collider relies on accelerators built starting in 1954 to help bring protons to 99.9999991% the speed of light—about 2.73 million football fields per second.

The most common type of particle accelerator is a linear electron accelerator, which fires particles in a straight line, making them useful for the intense, targeted beams needed in cancer treatment.

The discovery of the neutron paved the way for nuclear weapons

In 1932, James Chadwick discovered the subatomic particle when trying to explain the radiation emitted by beryllium after it was bombarded with alpha particles. The radiation’s ability to eject protons from a target suggested a chargeless particle with slightly more mass than a proton.

More than 97% of the world's particle accelerators are used for commercial purposes

Only a few hundred of the over 30,000 particle accelerators worldwide are used for research. Most are involved in medical imaging and treatment, food sterilization, semiconductor processing, cargo screening, and radioisotope production. They're also used to modify the properties of polymers.

The first nuclear reactor was built three years after nuclear fission was discovered

After learning that large atomic nuclei release energy upon being split apart, scientists quickly researched how to control the reaction to make electricity. Fusion—combining small atomic nuclei—generates massive energy in stars and hydrogen bombs.

If particle accelerators did create black holes by packing tremendous energy into a small volume, then trillions would be created in Earth's atmosphere daily by cosmic rays.

How radioactive isotopes are created and used for medical diagnostics

In particle accelerators, protons can be accelerated into other atoms to create radioactive isotopes, which can be attached to specific molecules to create radiotracers that are taken up by specific cells. Radiotracers can emit particles that produce light once they collide with an electron, and this light can be captured by a PET scanner to diagnose specific ailments.

At CERN's Antimatter Factory, researchers create and guide antiprotons and antielectrons together to form antihydrogen, and all these antiparticles are analyzed to help scientists study the behavior of antimatter.

Ernest Rutherford's gold foil and nitrogen experiments revealed nuclear structure

Observing high-angle deflections when alpha particles were fired at gold foil led to an atomic model with a dense, positively charged nucleus. Firing those particles at nitrogen resulted in the emission of hydrogen nuclei—protons—leading to the discovery of the subatomic particle.

Cyclotrons move particles in spiral paths of increasing radius

After particles are injected into the center of the device, an alternating electric field and a constant magnetic field energize the particles as they spiral outward toward a target. Cyclotrons are common in hospitals that perform molecular imaging, which relies on radioactive components that decay within hours.

At the Large Hadron Collider, protons are accelerated so close to the speed of light that they would lag behind a laser by just 10 feet after 14 minutes of travel.

As of 2023, the world's smallest particle accelerator is smaller than a penny

The prototype is an example of a photonic accelerator, which utilizes tiny lasers to accelerate electrons rather than relying on oscillating electromagnetic fields to move them. It can deliver about 1 electron per second with energies equivalent to those found in cathode-ray tube televisions.

A beam of neutrinos can be created by firing a beam of high-energy protons at a target to produce unstable particles that decay into neutrinos.

The discovery of nuclear fission was facilitated by the discovery of the neutron

The discovery of the neutron provided scientists with a particle that could penetrate the nucleus and advance atomic physics. Otto Hahn was the sole Nobel recipient for the discovery of fission, despite collaborating with Lise Meitner and Fritz Strassmann.

Explore the components of the linear particle accelerator at Los Alamos

Located at the site of bomb design and development for the Manhattan Project, LANSCE features an injector system for hydrogen ions, a series of tanks with alternating electric fields for proton acceleration, and an isotope production facility that creates radioisotopes for medical treatments.

Particle beams can be used to alter the surface properties of artificial joints

Surface hardening and embedding specific elements or coatings can improve the biocompatibility and bone tissue integration of these implants. Particle accelerators are significant sources of the radioisotopes needed in medical diagnostics, and microwave linear accelerators are used in the majority of cancer irradiation treatments.

Scientists can create movies of atomic and molecular phenomena using X-ray free-electron lasers, in which images are produced by matter being struck by high-intensity light created by accelerating electrons.

In an X-ray free-electron laser, electromagnetic fields are used to accelerate and move electrons in wiggling patterns, causing them to emit synchronized, high-energy X-rays. This resulting light beam can strike targets up to 120 times per second to create movies of changing molecular structures and phenomena.

Build atomic nuclei to explore their instability and resulting radioactive decay

In this simulation, users can add protons and neutrons to create an atomic nucleus, view its half-life and decay options, and identify patterns in how specific combinations of particles create extremely stable nuclei, from which the nuclear shell model of stability emerged.

The Curies developed a way to measure radioactivity in an old medical dissecting room

Despite lacking proper laboratory conditions, Marie and Pierre built an ionization chamber and a piezoelectric quartz electrometer to measure the amount of charged particles released by radiation, with a sensitivity of ten-trillionth of an ampere. Substances with different emission rates indicated different elements.

An overview of radioactivity, which can spontaneously change one element into another

Unstable atomic nuclei can transmute into a new element—an atom with a different number of protons—by emitting an alpha particle (two protons and two neutrons) or a beta particle (an electron). The electron can emerge from the nucleus when a neutron, which has no charge, suddenly transforms into a proton and an electron, thereby maintaining zero charge before and after the transformation, but altering the original element.

Particle accelerators detect subatomic particles using millions of sensors

Calorimeters measure the energy of particles. Tracking devices can measure momentum and charge from the trajectory of particles, which is determined by recording tiny electrical signals. Time-of-flight detectors provide particle velocities directly and particle mass indirectly, giving physicists a suite of properties to compare with those of known matter.

While atoms are normally made of protons, neutrons, and electrons, exotic ones have been built with antimatter—alternate versions of normal matter that live for fractions of a second.

The High Luminosity Large Hadron Collider will provide a tenfold increase in particle collisions compared with the initial LHC infrastructure by increasing the number of ions in collision bundles and by concentrating the ion beams.

At the Large Hadron Collider, scientists have transformed lead into gold—a process known as chrysopoeia, which alchemists sought for centuries.

Antimatter was discovered by examining debris from collisions between atmospheric gases and cosmic rays—high-energy matter particles from space.

Nuclear fusion, where the nuclei of two atoms are combined, can produce near-limitless clean energy, but requires extreme conditions to kickstart because of the natural repulsion of atomic nuclei.

View the evolution of atomic models, with four successively overturned between 1900 and 1926

Originally thought to be indivisible spheres unique to each element, the discovery of the electron by J.J. Thomson revealed them to be made of smaller particles. Ernest Rutherford's gold foil experiment uncovered the existence of nuclei, which Niels Bohr suggested were surrounded by electrons in fixed orbits. By applying quantum mechanics, Erwin Schrödinger replaced orbits with probability clouds.

By measuring them in hot-air balloons during a partial solar eclipse and at night, Victor Hess discovered cosmic rays and concluded they came from beyond the solar system.

In 2026, researchers successfully transported antimatter in a truck using a portable trap that employed electromagnetic fields to hold 92 antiprotons.

It may be possible to create dark matter in particle accelerators

In high-energy collisions, exotic forms of matter can be produced by directly converting energy into mass according to *E = mc*². Even though a dark matter particle would not be directly observable, its creation would result in unaccounted-for mass, which can be compared to potential dark matter candidates for indirect detection.

View summaries of the most common types of radioactive decay and their associated particles

The alpha particle has the strongest ability to ionize other atoms it strikes, but it also does not travel very far before colliding with something and being absorbed. Gamma particles—high-energy photons—do not interact with matter as easily and therefore possess the greatest penetrating power, though this also makes their ionizing potential the smallest.

View the most expensive materials on Earth, led by antimatter and other elements forged in particle accelerators.

Cathode-ray tube televisions are examples of electron accelerators

CRT TVs work by converting electricity into heat, which causes electrons to be emitted from the rear of the device in three beams responsible for the colors red, green, and blue. Electromagnets direct electrons to phosphor molecules on the screen, which emit light and illuminate the pixels.

Each year, the Large Hadron Collider undergoes a winter shutdown—when electricity costs are highest—and bringing it back online requires weeks of tests, including some involving high-energy particles from outer space.

Building the first atomic bomb required unprecedented coordination

Creating the first atomic bombs demanded breakthroughs in physics, engineering, and logistics—uniting elite scientists with tens of thousands of workers across the US. This in-depth history explains how the Manhattan Project overcame those challenges.

A particle accelerator allowed researchers to noninvasively examine a mummy

The mummy hailed from the Faiyum oasis, where Egyptian and Roman cultures intersected, and was analyzed using the Advanced Photon Source at Argonne National Laboratory. The device used high-energy X-rays to probe the material composition of numerous objects embedded deep inside the mummy without damaging its remains.

Antimatter particles possess the same mass and spin as their normal particle counterparts, but possess an opposite charge and transform into pure energy upon colliding with normal matter.

Visualize what happens to atoms during nuclear fission and how the process produces energy

Nuclear fission occurs when an unstable, often massive, atomic nucleus splits into smaller ones—daughter atoms—and releases energy. Within a nuclear reactor, these daughter atoms can collide and combine with neighboring atoms, destabilizing them and triggering a chain reaction of atomic splitting.

While both are nuclear weapons, atomic bombs release nuclear energy by splitting large atomic nuclei, whereas hydrogen bombs derive most of their energy from fusing heavy hydrogen isotopes.

Nuclear batteries generate electrical currents using radioactive materials

Rather than using electrochemical reactions to produce the electrons that flow through a circuit, isotopes like nickel-63 undergo beta decay—emitting electrons—which a semiconducting material can absorb to establish a charge imbalance that generates current. Such batteries could provide low-power energy for decades.

If they could be built, antimatter drives, which run on energy released from the collision of matter and antimatter particles, would be the most efficient engines in existence.

X-rays earned the very first Nobel Prize in physics for revealing hidden worlds

In 1895, Wilhelm Conrad Röntgen discovered X-rays, which could pass through solid objects and make unseen structures visible. Today’s X-ray tools continue to advance science and medicine, including capturing real-time images of proteins.

Radioactivity was accidentally discovered when uranium left marks on photographic plates

In 1896, Henri Becquerel had been exploring phosphorescence—the emission of light of one color after an object is exposed to another color. He expected these emissions to come from objects exposed to sunlight, but he observed emissions after an overcast day.

Antimatter was predicted to exist four years before it was observed, though the mathematics responsible for the prediction described it as matter with negative energy.

Cosmic rays can be detected using cloud chambers—containers where alcohol vapor condenses around trails of ions created by these high-speed particles from space.

Cosmic rays are thought to be accelerated to near the speed of light by repeatedly bouncing across shockwaves produced by high-energy cosmic events, such as supernovae.

The oldest nuclear fission reactor on Earth formed naturally in West Africa about 2 billion years ago, where groundwater enabled atoms in uranium deposits to split, releasing energy.