Observation of redshifting and harmonic radiation in inverse Compton scattering

Journal Article · Wed Jun 17 00:00:00 EDT 2015 · Physical Review Special Topics. Accelerators and Beams

DOI:https://doi.org/10.1103/PhysRevSTAB.18.060702· OSTI ID:1186730

Sakai, Y.; Pogorelsky, I.; Williams, O.; O’Shea, F.; Barber, S.; Gadjev, I.; Duris, J.; Musumeci, P.; Fedurin, M.; Korostyshevsky, A.; Malone, B.; Swinson, C.; Stenby, G.; Kusche, K.; Babzien, M.; Montemagno, M.; Jacob, P.; Zhong, Z.; Polyanskiy, M.; Yakimenko, V. ; Rosenzweig, J.

Inverse Compton scattering of laser photons by ultrarelativistic electron beam provides polarized x- to γ-ray pulses due to the Doppler blueshifting. Nonlinear electrodynamics in the relativistically intense linearly polarized laser field changes the radiation kinetics established during the Compton interaction. These are due to the induced figure-8 motion, which introduces an overall redshift in the radiation spectrum, with the concomitant emission of higher order harmonics. To experimentally analyze the strong field physics associated with the nonlinear electron-laser interaction, clear modifications to the angular and wavelength distributions of x rays are observed. The relativistic photon wave field is provided by the ps CO₂ laser of peak normalized vector potential of 0.5_L<0.7, which due to the quadratic dependence of the strength of nonlinear phenomena on aL permits sufficient effects not observed in past 2^nd harmonic study with a_L ≈ 0.3 laser [M. Babzien et al., Phys. Rev. Lett. 96, 054802 (2006)]. The angular spectral characteristics are revealed using K-, L-edge, and high energy attenuation filters. The observation indicates existence of the electrons’ longitudinal motion through frequency redshifting understood as the mass shift effect. The 3^rd harmonic radiation has been observed containing on-axis x-ray component that is directly associated with the induced figure-8 motion. These are further supported by an initial evidence of off-axis 2^nd harmonic radiation produced in a circularly polarized laser wave field. Total x-ray photon number per pulse, scattered by 65 MeV electron beam of 0.3 nC, at the interaction point is measured to be approximately 10⁹.

• Research Organization: Brookhaven National Laboratory (BNL), Upton, NY (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Nuclear Physics (NP)
• Grant/Contract Number: FG02-07ER46272; FG03-92ER40693; AC02-98CH10886; 2014-DN-077-ARI084-01; SC00112704
• OSTI ID: 1186730
• Alternate ID(s): OSTI ID: 1224188
• Report Number(s): BNL-108404-2015-JA; PRABFM; 060702
• Journal Information: Physical Review Special Topics. Accelerators and Beams, Journal Name: Physical Review Special Topics. Accelerators and Beams Vol. 18 Journal Issue: 6; ISSN 1098-4402
• Publisher: American Physical Society
• Country of Publication: United States
• Language: English

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