Bevatron: The Particle Accelerator That Discovered Antimatter
The Bevatron was a particle accelerator that operated at Lawrence Berkeley National Laboratory in the United States from 1954 to 1993. It was one of the largest and most powerful accelerators of its time, capable of accelerating protons to energies of billions of electron volts (GeV). The Bevatron was instrumental in the discovery of the antiproton, the antimatter counterpart of the proton, in 1955, which earned Emilio SegrÃ¨ and Owen Chamberlain the Nobel Prize in Physics in 1959. The Bevatron also contributed to many other discoveries and advances in particle physics, nuclear physics, and medical physics.
What is a particle accelerator?
A particle accelerator is a device that uses electric and magnetic fields to accelerate charged particles, such as protons or electrons, to very high speeds and energies. By colliding these particles with other particles or targets, scientists can study the structure and interactions of matter and energy at the smallest scales. Particle accelerators are also used for various applications in industry, medicine, and research.
How did the Bevatron work?
The Bevatron was a type of particle accelerator called a synchrotron, which uses a circular ring of magnets to bend and focus a beam of particles. The particles are injected into the ring by a smaller accelerator, called an injector, and then accelerated by an alternating electric field. As the particles gain speed, they also gain mass according to Einstein’s theory of relativity, which means they need stronger magnetic fields to keep them on track. The Bevatron used a huge iron magnet that weighed 10,000 tons and had a diameter of 65 feet (20 meters). The magnet could produce a magnetic field of up to 18,000 gauss (1.8 tesla), which is about 360 times stronger than the Earth’s magnetic field. The Bevatron also had a large vacuum system to remove any air molecules that could interfere with the beam.
What did the Bevatron discover?
The Bevatron’s most famous discovery was the antiproton, which was predicted by quantum theory but had never been observed before. The antiproton is identical to the proton in mass and spin, but has the opposite electric charge. To create antiprotons, the Bevatron accelerated protons to about 6.2 GeV and smashed them into a copper target. The collision produced many particles, some of which were antiprotons. The antiprotons were detected by a special device called an emulsion chamber, which recorded their tracks as they passed through layers of photographic film. The discovery of the antiproton confirmed the existence of antimatter and opened up new possibilities for studying matter-antimatter interactions.
The Bevatron also discovered the antineutron, the antimatter counterpart of the neutron, in 1956. The antineutron has no electric charge but has the opposite magnetic moment and baryon number as the neutron. The antineutron was produced by colliding antiprotons with protons in a liquid hydrogen target.
In addition to antimatter, the Bevatron also explored other aspects of particle physics, such as parity violation, strangeness conservation, meson production, and resonance states. The Bevatron also helped develop new techniques and technologies for particle detection and measurement.
What happened to the Bevatron?
The Bevatron continued to operate until 1993, when it was decommissioned due to budget cuts and environmental concerns. In 1971, it was joined to another accelerator called the SuperHILAC (Super Heavy Ion Linear Accelerator) as an injector for heavy ions. The combination was called the Bevalac (Bevatron-SuperHILAC), and it could accelerate a wide range of stable nuclei to relativistic energies. The Bevalac was used for research in nuclear physics, astrophysics, biology, and medicine.
In 2021, the site of the Bevatron was recognized by the American Physical Society as a historic physics site for its contributions to physics and society.