Present Status of RFQS

Since its introduction and during its recent development, the radio-frequency quadrupole (RFQ) has had a significant impact on the design, construction, and operation of ion accelerators. Characteristics of operating RFQs, those under construction and those in a preliminary design phase, will be highlighted with reference to the overall historical development. Advances in related technologies that have assisted development and establishment of the RFQ worldwide will be reviewed, including novel characteristics that could be incorporated in future devices. Predictions on where the technology is leading and what aspects require further development will be presented.