Deanna Brennan, age 14, of Pocatello, Ida., for her question:
WHO INVENTED THE SPARK CHAMBER?
A spark chamber is a device that makes visible the paths followed by electrically charged atomic particles. It is a rather recent scientific development. The first particle spark chamber was invented and built in 1959 by two Japanese physicists, S. Kukui and S. Miyamsdoto.
Nuclear physicists use spark chambers to study electrically charged atomic particles that are too small and travel too fast to be seen by the naked eye. Since 1960, the spark chamber has become a very important research tool for high energy nuclear physicists.
Physicists use the spark chamber because with it a particle can be made sensitive for the short time that is necessary for a physicist to study it.
A spark chamber is made up of a series of thin metal plates that are set parallel in an airtight box. The box is filled with neon gas. A gap of from 300 to 400 millimeters separates the plates, depending upon the design of the chamber.
A typical spark chamber is about 3 feet long and has 150 plates spaced 6 millimeters apart. Electrical equipment powers the chamber.
The spark chamber is used most often with a device called a particle accelerator. This device produces high energy particles that can be studied by the scientist in a chamber.
When a charged atomic particle enters the chamber, it ionizes or electrically charges the neon gas atoms in its path. The particle penetrates the thin metal plates. The ionized gas atoms will conduct electricity but the atoms that have been ionized will not.
An electrical field of 1,000 volts per millimeter of plate separation is applied to alternate plates immediately after the particle ionizes the neon. This field causes a lightning like spark to jump from plate to plate along the particle's ionized path, the spark can easily be seen and photographed. In a spark chamber, scientists trace the paths atomic particles follow.
Special electronic circuits apply high voltage to the plates after a selected particle enters the spark chamber. Physicists can select the particle they wish to study in the chamber. By eliminating unwanted particle tracks, the physicist can spend more time studying the important paths.
Physicists learn much more about the nucleus of the atom and atomic particles by studying the tracks or paths made by such particles. They have discovered several previously unknown particles with the help of spark chambers.
During the late 1960s and 1970s, physicists developed two devices similar to the spark chamber: the magnetostrictive chamber and the proportional wire chamber. The construction of both of these devices is very much like that of the spark chamber, but wires instead of metal plates are used.
As particles pass through the airtight box of each device, they create electric impulses on the wires. These impulses are then read by a computer to determine the paths taken by the particles.