Thomson's discovery of the electron 100 years ago, using a simple particle accelerator (a cathode-ray tube), launched modern elementary-particle physics.

Until World War II, research in particle physics was usually carried out at universities, funded by university grants or by gifts and grants from corporations and wealthy individuals. Many early developments in the field originated in Europe. The invention of the cyclotron accelerator by E.O. Lawrence and M.S. Livingston in 1931 at Berkeley signaled the beginning of major U.S. participation in nuclear and particle physics. In the years leading up to the war, the United States. gradually achieved world leadership in these areas of physics, which were energized by the influx of physicists fleeing Europe and by the Manhattan Project, the nationally critical race with Germany to build the first bomb using nuclear fission.

It was during these years that the U.S. physics community began several major research and development programs funded by the federal government. The era of large science projects was born at laboratories such as Los Alamos and Oak Ridge, as well as at large nonnuclear facilities such as the MIT Radiation Laboratory. Projects were no longer accomplished by one or two senior collaborators assisted by graduate students and skilled technicians. Rather, a larger group of senior and junior physicists, together with professional engineers, developed and used large research facilities.

Particle Physics After World War II (the Second 50 Years)

Based on the success of controlling and using nuclear fission, a series of government agencies continued the wartime pattern of federal funding at U.S. universities. These have included the Office of Naval Research, the Atomic Energy Commission, the National Science Foundation (NSF), the Energy Research and Development Administration, and the Department of Energy (DOE). With the discovery of new particles such as pions and kaons in the late 1940s and the invention of new, more powerful accelerators, a dozen or so major universities built accelerators with energies above 100 MeV (1 MeV = 106 electron volts) to study new phenomena. The physicists who executed these projects applied the methodology of wartime laboratories: The machines were large, sophisticated engineering undertakings, compared to the tabletop experimental equipment of prewar research. During the 1950s, as the complexities of particle interactions and the rich spectra of meson and nucleon states began to unfold, elementary-particle physics diverged from nuclear physics and became a distinct field.

The need for higher particle beam energies required larger accelerators and correspondingly larger detectors and experimental facilities. Accompanying this increased size and complexity was an increase in the costs of construction and operation, eventually to an extent that outstripped the resources of a single university. In response, and again modeled on the wartime experience, large facili-

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