An overview of RF superconductivity research

RF superconductivity has become an important technology for particle accelerators. Structures providing more than 100 million volts (MV) have been installed in accelerators for heavy ions and operated at gradients between 2.5-5 MV/m for greater than 10/sup 5/ hours. More than 1300 MV have been installed in electron accelerators and operated at gradients between 3-10 MV/m in excess of 3/spl times/10/sup 4/ hours. Beam currents up to 40 mA are supported in continuous operation. New applications are forthcoming, some demanding higher accelerating gradient, others the capability to support high beam currents. Substantial progress has been made in understanding gradient limitations and inventing techniques are now in hand to reach 25 MV/m. For the next linear collider in the TeV energy range, there are many compelling attractions to use superconducting cavities. For high current application, the beam-cavity interaction can be reduced by using a few high gradient cavities with large beam apertures. Low impedance structures are being developed. In a breakthrough, one of these was successfully tested with a beam current of 220 mA.>