The motivation to conceive and build accelerators comes from a most fundamental need of man - to understand and control the world around us. With beams and their associated accelerators, scientists and engineers can gain understanding of the nature of matter and modify matter, which is not possible by other means. The areas already influenced by the developments in accelerator technology are high energy and nuclear physics, atomic and molecular physics, condensed matter physics and the biological sciences. There are also a growing number of applications in medicine and industry. This book summarizes all the currently available knowledge on the rf technology driving the development of particle beams for science, medicine and industry. It is a unique collection of information on this technology.