Accelerator Concepts Workshops have included a

A précis is given of a critical review of a few advanced acceleration concepts that involve neither plasma nor periodic metallic slow-wave structures. These so-called “vacuum accelerators ” are either externally driven using powerful rf or laser sources, or internally driven using strong wake fields set up by a train of drive bunches. Merits and limitations of each concept are given, and speculations are advanced on the potential of each to mature into a practical accelerator for use as a tool in high-energy physics or other scientific applications