ERL PARAMETERS FOR COMPTON POLARIZED POSITRON SOURCES
One of the main challenges for also future linear colliders projects (ILC and CLIC) is to provide an efficient positron source that takes into account the constraint imposed by the target heating in the pair production. At present, different schemes have been proposed to produce high energy gammas to be converted in e-e pairs into an amorphous target [1,2,3]. One of them considers the possibility to boost the energy of the backscattered photons of a laser pulse by Compton effect [4]. This method is particularly attractive since the source is independent of the main Linac and since the photon and consequently the produced pair helicities are conserved in the scattering event. This implies that physics will have at its disposal both positron and electron polarized sources. Different solutions have been proposed to provide the electron beam for the Compton collision. They have to take into account one of the main constraints of this proposal that is the relative low value of the Thomson cross section. One of the possibilities is to design an ERL with relatively low repetition frequency and high charge per pulse and then to stack the produced positrons in an accumulation ring. Different considerations on this scheme will be illustrated and the main constraints discussed.
CLIC 2008 Parameters
This note presents the CLIC parameter set as of beginning 2008 and describes the different subsystems,pointing out how the design of the different components is driven. This design emerged from an updated understanding of limitations for normal conducting accelerating structures, which led to a new optimised design for the CLIC 12 GHz accelerating structure. The structure parameters and improvements in other sub-systems have resulted in a major revision of the parameters. The overall layout and efficiencies for CLIC with this updated parameter-set are presented.
Long Ceramic Beam Tubes for Accelerator Magnets
The ceramic beam tubes for the fast and abort kickers and the bucker and pinger magnets used at Fermilab must meet a number of exacting requirements. The tubes must be long and sufficiently straight so as not to limit magnet design. They must have wall strength capable of withstanding the atmospheric and mechanical forces encountered during construction and operation. Vacuum tight ceramic to stainless steel transitions must be of reasonable cost; they must also withstand high temperature processing and remain vacuum tight to the 10/sup -9/ Torr range. To remove the possibility of static charge buildup each tube must have a surface coating of indium oxide applied to the inner wall. This thin coating is difficult to achieve and requires the most careful attention to detail. The methods used at Fermilab to achieve these goals are presented in this paper.