SRF cavities for future applications

Superconducting cavities are under operation or construction for acceleration of electrons and heavy ions at several laboratories. At present gradients around 5 MV/m, beam current up to 10 mA and operating experience exceeding 10,000 h are typical values. The advantage of superconducting RF is the high cw accelerating gradient, the low operating cost to establish RF voltage and the favourable cavity shape for a low loss factor. Ongoing progress in improving the niobium material, simplifying design and fabrication, understanding of performance limitations and investing cures against field emission promise to increase the operating gradient at reduced investment, costs. High beam current applications are investigated to take advantage of the small higher order mode impedance. The most challenging development is the use of superconducting cavities for a TeV Linear Collider (TESLA)