The LHC superconducting cavities

Abstract

The LHC RF system, which must handle high intensity (0.5 A d.c.) beams, makes use of superconducting singlecell cavities, best suited to minimizing the effects of periodic transient beam loading. There will be eight cavities per beam, each capable of delivering 2 MV (5 MV/m accelerating field) at 400 MHz. The cavities themselves are now being manufactured by industry, using niobium-on-copper technology which gives full satisfaction at LEP. A cavity unit includes a helium tank (4.5 K operating temperature) built around a cavity cell, RF and HOM couplers and a mechanical tuner, all housed in a modular cryostat. Four-unit modules are ultimately foreseen for the LHC (two per beam), while at present a prototype version with two complete units is being extensively tested. In addition to a detailed description of the cavity and its ancillary equipment, the first test results of the prototype will be reported.

RF system models for the CERN Large Hadron Collider with application to longitudinal dynamics

“…Various studies have been conducted to evaluate the longitudinal coupled-bunch instabilities at the LHC [18,19]. These studies do not include the cavity fundamental impedance nor consider the effect of the LLRF impedance reduction feedback system though.…”

Comparison of higher order modes damping techniques for 800 MHz single cell superconducting cavities

“…The LHC cryogenic system provides the possibility to place four cavities in one cryomodule [24], which excludes the installation of the load between the resonators but admits its placement outside of the cryostat. HOMs extraction from each superconducting resonator is provided by using two broadband and two narrowband couplers.…”

Summary of the Mini BNL/LARP/CARE-HHH workshop on Crab Cavities for the LHC

“…An impedance budget was not presented to the meeting and this is critical to assessing all the various schemes that have been proposed. A reference was made to a paper by Daniel Boussard at PAC 99 [1], that contains a few relevant numbers, and the subject is discussed in the LHC conceptual design report [2], but this references other papers for the details of the mode damping requirements. Other references include [3,4].…”