High gradient superconducting RF

All currently proposed methods of building a TeV linear collider at an affordable cost entail significant technological challenges. The use of superconducting accelerating cavities reduces the technological challenges to two parameters: the accelerating gradient and the Q/sub o/. Pulsing the RF at about 30 Hz with a duty cycle of around 0.01 relaxes the requirement on Q/sub o/ and makes Q/sub o/ values presently achieved at lower gradients (--3 . 10/sup 9/) acceptable. All other technical challenges are equal to or less difficult than those of the SLC. One key reason for the attractiveness of RF superconductivity for use in colliding linacs in the high Q/sub o/, which permits the cavity to be filled with RF energy slowly. This keeps the RF sources from being at their peak power limit. If the sources were peak power limited, a larger number of sources and modulators would be required to obtain the same average power, thereby adding to the cost. A second key advantage of RF superconductivity is the high achievable ratio of fundamental Q/sub o/ to higher-order-mode Q. This properly permits many bunches to be passed through the accelerator during each RF pulse without encountering cumulative wakefield build-up, without dissipation of excessive power between beam bunches, without dumping excessive stored RF energy due to a high RF pulse rate, and without having wrong bunches collide near the interaction point. By using SLC values as practical limits for certain parameters, optimization of the accelerator design becomes straightforward. Details of this optimization are presented