Channeling 2012

Is it Possible to Produse Circularly Polarized γ-beam via Coherent Bremsstrahlung Process?

24 Sept 2012, 12:20

15m

Hotel Calabona (Hotel Calabona)

Coherent Bremsstrahlung S1.2 Coherent Bremsstrahlung

Speaker

Mr Konstantin Kruchinin (Tomsk Polytechnic University)

Description

Beams of polarized electrons and positrons play an important role in experiments for discovering physics beyond the standard model [1]. Circularly polarized $\gamma$-beams are used for longitudinally-polarized positrons producing. Nowadays, there are experimentally improved methods for generation circularly polarized $\gamma$-beams based on electron radiation in the helical undulators [2] and Compton backscattering process where circularly polarized laser photons are scattered on electron beam [3]. In such a case, it seems very important to analyze new possibilities for circularly polarized photon beams generation. We investigate the method for obtaining the circularly polarized photon beam based on the fact that superposition of two linearly-polarized beams can give a circularly polarized beam as a result. As a source of linearly-polarized photons we propose to use two crystals oriented in such a way that coherent bremsstrahlung (CBS) beams, which planes of polarization are rotated by 90 degrees, are generated in these crystals. In the first approximation, the CBS process of electrons passing through a set of crystalline chains can be described by the formulas for undulator radiation [4]. In this approximation, we investigate the dependence of circular polarization degree on emitted photons energy and the distance between crystals. We have shown that with beam energy of 10 GeV and for emitted photon energy 50 MeV it is possible to achieve a circular polarization of the beam above 50 percent at the distance between crystals comparable with the formation length.