Spark chamber was a device invented to study electrically charged subatomic particles. Such particles are too small to be seen with the naked eye. The chamber produced sparks along the path that a particle took through it. The sparks made the path visible, enabling physicists to study the particle. The particles studied in spark chambers usually came from a machine called a particle accelerator.
A spark chamber consisted of a series of thin metal plates set parallel in an airtight box filled with a noble gas such as neon. When a charged particle entered the chamber and passed through the plates, the particle ionized (electrically charged) the gas atoms in its path. The ionized gas atoms could conduct electric current, but the nonionized atoms could not.
An electronic circuit determined whether to record the path of a particular particle. When triggered by the circuit, the spark chamber applied a high voltage to alternate plates. The voltage caused sparks to jump like lightning from plate to plate along the particle’s ionized, electrically conducting path. The sparks were easy to see and photograph. The spark pattern also could be recorded electronically for analysis by computer.
Japanese physicists Shuji Fukui and Sigenori Miyamoto built the first practical spark chamber in 1959. It represented a major advance over earlier particle detectors, the Wilson cloud chamber and the bubble chamber. Unlike the earlier devices, the spark chamber was continuously sensitive to all particles entering it. Physicists could set it to operate only when a particle they wanted to study entered it.
A spark chamber revealed the first evidence of a subatomic particle known as the mu-neutrino. For this experiment, the American physicists Leon M. Lederman, Melvin Schwartz, and Jack Steinberger won the 1988 Nobel Prize for physics. Spark chambers also were used to show that laws regarding fundamental symmetries in nature could be violated. James W. Cronin and Val L. Fitch, two American physicists, won the 1980 Nobel Prize for this research.
From 1991 to 2000, a spark chamber known as EGRET orbited the earth aboard a scientific satellite called the Compton Gamma Ray Observatory. EGRET made many valuable discoveries about gamma rays, a high-energy form of radiation given off by supernovae, quasars, and other astronomical objects.
Physicists have developed advanced devices based on the spark chamber. These include two tracking chambers called the multiwire proportional chamber and the drift chamber. Instead of plates, these instruments have sheets of parallel wires. Pulses of electric current in the wires reveal the paths of the charged particles. Tracking chambers often form part of the thousand-ton detectors used with advanced particle accelerators.
