Physical Review Special Topics - Accelerators and Beams (PRST-AB) is a peer-reviewed, purely electronic journal, distributed without charge to readers and funded by sponsors from national and international laboratories and other partners. The articles are published by the American Physical Society under the terms of the Creative Commons Attribution 3.0 License.It covers the full range of accelerator science and technology; subsystem and component technologies; beam dynamics; accelerator applications; and design, operation, and improvement of accelerators used in science and industry. This includes accelerators for high-energy and nuclear physics, synchrotron-radiation production, spallation neutron sources, medical therapy, and intense-beam applications.