Nuclear Particle Detection (Cloud Chambers and Bubble Chambers)

Abstract

The first photographs of the tracks of nuclear particles in a cloud chamber were obtained by C.T.R. Wilson (1) in 1911. A year later (2) Wilson pub­ lished photographs of tracks of a-particles, j3-particles, and the electrons produced by a beam of x-rays passing through his chamber. In these pictures, Wilson set a standard of quality for cloud-chamber photographs that has not often been excelled and described techniques of measurement that are still of great importance. The development of cloud chambers has made possible many discoveries in nuclear physics and has provided visual proof of the existence of various types of nuclear particles. A collection of some of the most important and beautiful cloud chamber pictures has been made by Gentner, Maier-Leibnitz & Bothe (3) and by Rochester & J. G. Wilson (4) in which they trace the growth of knowledge of nuclear physics through the years since 1911, demonstrating clearly the importance of the cloud chamber technique. Cloud chambers, when operated under suitable conditions, can provide information on the charge, momentum, velocity, lifetime, direction of motion, and interaction properties of nuclear particles, as well as the t otal number of such particles existing at a given time within the useful volume of the chamber. Cloud chambers have been operated at low, atmospheric, and high pressure, in balloons 100,000 ft. above the earth, in mines hundreds of feet below the surface of the earth, on mountain tops for cosmic ray re­ search, and in the beams of particles created by accelerators. They are versatile and adaptable, but inevitably have their limitations. The invention in 1952 of the bubble chamber by Glaser makes available stilI another in­ strument for the detection of nuclear particles. Bubble chambers have im­ portant applications in connection with high-energy accelerators. They can be operated on a cycle of a few seconds, can be made with various liquids, in­ cluding liquid hydrogen, and have many detection properties in common with cloud chambers. This article will review the developments in cloud-chamber and bubble­ chamber technique that have been made since 1951. The excellent book by J. G. Wilson (5) and the article by Das Gupta & Ghosh (6) describe the classi­ cal work on expansion cloud chambers in some detail. Snowden has written a review article (7) on diffusion cloud chambers that contains much valuable material , and Glaser has published several articles on bubble chambers that will be referred to in the latter part of this paper.