Evolution of the rf systems layout for the SSC collider rings

摘要

This note contains information on the results of ongoing reviews concerning the basic design of the 360-MHz rf systems for the 2 (times) 20 TeV Superconducting Super Collider (SSC). For generation of 20-MV peak voltage per ring, with proton beams of 2 (times) 70 mA, several versions have been investigated: Version A (baseline design and modified baseline): 2 (times) 8 five-cell normalconducting cavities; Version B: 2 (times) 24 single-cell normalconducting cavities; and Version C: 2 (times) 8 or 2 (times) 10 single-cell superconducting cavities. For reasons of easier High Order Mode (HOM) damping, multicell cavities have been found inferior in performance when compared to single cells. Superconducting cavities have been found superior in handling transient beam loading when compared to normalconducting cavities. A threefold higher voltage, and a reduced R/Q value of superconducting cells lead to a ninefold increase in stored electromagnetic energy which, by the same factor, reduces the speed of phase changes originating from notches in the circulating beams. The theoretical possibility to operate superconducting cavities half-detuned in order to supply reactive power to the beam may also lead to considerable savings in overall power consumption. On the other hand, many challenges are involved with the use of superconducting cavities, such as the delicacy of the superconductive state, the complexity of cryostat design and operation, tuning requirements, sensitivity to vibration, and other issues.