Generation of circularly polarized photons for a linear collider polarized positron source

Abstract

les fichiers pdf et ps correspondent à une version modifiée de la fiche arXiv hep-ph/0409178 - Théorie, CASVarious methods of obtaining longitudinally polarized positrons for future linear colliders are reviewed. Special attention is paid to the schemes using circularly polarized high-energy photons for positron production. Most effectively such photons are obtained from electrons passing through a helical undulator or colliding with a circularly polarized laser wave. Spectrum and polarization of radiation emitted during helical motion of electrons are considered in detail. A new simple presentation of known formulas is used to account for the influence of the wave intensity, of the electron-beam angular divergence, of the collimation of radiation, and of the lateral and temporal profiles of the laser bunch on the radiation properties

Note on “discrete-like diffraction dynamics in free space”: highlighting the variety of solving procedures

“…Evidently, expression (12) reproduces that obtained in [1] [where, indeed, Qσ; ζ is replaced by the complex conjugate, Q σ; ζ], but, in our opinion, it has been more plainly deduced on account of the basic properties of the PWE [Eq. (1)].…”

“…The Volkov solution of the associated Dirac equation is, indeed, naturally expressed in terms of GBFs [12].…”

Equilibrium energy spread and emittance in a Compton ring: An alternative approach

“…The Compton backscattering effect can be also seen like the emission of radiation by the electrons oscillating in the laser field [27], as in an undulator. The angular distribution of the scattered photons is thus concentrated within the typical ∼1=γ opening angle cone around the direction of motion of the electrons.…”

“…Taking into account only the unpolarized part and imposing E e − E γ ≈ E e one obtains the following expression for the differential cross section: 27) and rearranging the terms the final expression reads:…”

Beam dynamics in a spectrometer for the polarized positron production experiment

“…While polarized electron beams have been steadily operated at SLAC [3] for some time, production of polarized positrons is in the research stage [4]. The traditional method of positron beam polarization used in HERA collider in DESY [5] via Sokolov-Ternov mechanism is not suitable for a linear collider because of the long time required for the beam polarization in a synchrotron.…”