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.
The CLIC Positron Source Based on Compton Schemes
The CLIC polarized positron source is based on a positron production scheme in which polarized photons are produced by Compton process. Compton backscattering happens in a so-called "Compton ring" where an electron beam of 1.06 GeV interacts with a powerful laser beam amplified in an optical resonator. The circularly-polarized gamma rays are sent on to a target, producing pairs of longitudinally polarized electrons and positrons. An Adiabatic Matching Device maximizes the capture of the positrons. A normal-conducting 2 GHz Linac accelerates the beam up to 2.424 GeV before injection into the Pre-Damping Ring (PDR). The nominal CLIC bunch population is 4.4x10⁹ particles per bunch. Since the photon flux coming out from a "Compton ring" is not sufficient to obtain the requested charge, a stacking process is required in the PDR. Another option is to use a "Compton Energy Recovery Linac" where a quasi-continual stacking in the PDR could be achieved. A third option is to use a "Compton Linac" which would not require stacking. We describe the overall scheme as well as advantages and constraints of the three different options.
Mean field model of a game for power
Abstract Our aim is to model a game for power (equivalent to total energy) as a dynamical process, where an excess of power possessed by a player allows him to gain even more power. Such a positive feedback is often termed as the Matthew effect. Analytical and numerical methods allow to identify a set of stationary states, i.e. fixed points of the model dynamics. The positions of the unstable fixed points give an insight on the basins of attraction of the stable fixed points. The results are interpreted in terms of modeling of coercive power.