The Bevatron began operation in 1954.
Physicists had to wait until they had succeeded in designing particle accelerators that would produce enough energy to allow the creation of proton-antiproton pairs. This came about in the early 1950s when a device called the “Cosmotron” was built at Brookhaven National Laboratory in Long Island in 1952 and another called the “Bevatron” at the University of California in Berkeley in 1954.
Using the Bevatron in 1956, Segrè (the discoverer of technetium who had, by that time, emigrated to the United States), the American physicist Owen Chamberlain (1920- ), and others succeeded in detecting the antiproton.
The antiproton was as unlikely to last as long as the positron was. It was surrounded by myriads of proton-containing nuclei and in a tiny fraction of a second it would encounter one. The antiproton and the proton also underwent mutual annihilation, but having 1836 times the mass, they produced 1836 times the energy that was produced in the case of an electron and a positron.
There was even an “antineutron”, a particle reported in 1956 by the Italian-American physicist Oreste Piccioni (1915- ) and his co-workers. Since the neutron has no charge, the antineutron has no charge either, and one might wonder how the antineutron would differ from the neutron then. Actually, both have a small magnetic field. In the neutron the magnetic field is pointed in one direction with reference to the neutron’s spin; in the antineutron it is pointed in the other.
Bubble chamber photograph of an antiproton annihilation.
In 1965 the American physicist Leon Max Lederman (1922- ) and his co-workers produced a combination of an antiproton and an antineutron that together formed an “antideuteron”, which is the nucleus of antihydrogen-2.
This is good enough to demonstrate that if antiparticles existed by themselves without the interfering presence of ordinary particles, they could form “antimatter”, which would be precisely identical with ordinary matter in every way except for the fact that electric charges and magnetic fields would be turned around.
If antimatter were available to us, and if we could control the manner in which it united with matter, we would have a source of energy much greater and, perhaps, simpler to produce than would be involved in hydrogen fusion.