Coherent Thomson backscattering from laser-driven relativistic ultra-thin electron layers

Abstract

The generation of laser-driven dense relativistic electron layers from ultra-thin foils and their use for coherent Thomson backscattering is discussed, applying analytic theory and one-dimensional particlein-cell simulation. The blow-out regime is explored in which all foil electrons are separated from ions by direct laser action. The electrons follow the light wave close to its leading front. Single electron solutions are applied to initial acceleration, phase switching, and second-stage boosting. Coherently reflected light shows Doppler-shifted spectra, chirped over several octaves. The Doppler shift is found ∝ γ 2 x = 1/(1 − β 2 x ), where βx is the electron velocity component in normal direction of the electron layer which is also the direction of the driving laser pulse. Due to transverse electron momentum py, the Doppler shift by 4γ 2 x = 4γ 2 /(1 + (py/mc) 2 ) ≈ 2γ is significantly smaller than full shift of 4γ 2 . Methods to turn py → 0 and to recover the full Doppler shift are proposed and verified by 1D-PIC simulation. These methods open new ways to design intense single attosecond pulses.PACS. 41.75.Jv Laser-driven acceleration, -52.38.-f Intense particle beams and radiation sources in physics of plasmas, -52.59.Ye Plasma devices for generation of coherent radiation

Attosecond electron sheets and attosecond light pulses from relativistic laser wakefields in underdense plasmas

“…The attosecond feature does not derive from solid surfaces [3] or thin foils [4], but arises from intrinsic features of nonlinear plasma waves, namely steepening and breaking. It makes use of quasi-1D wavebreaking, allowing to trap an ultrathin electron sheet into the wakefield using an up-ramp density transition.…”

“…Single attosecond light pulse can also be produced from relativistic electron sheets extracted from thin foils. These sheets can be used for coherent backscattering or selfemit single attosecond pulses [4].…”

Nanocontrol of single dense energetic electron sheet in a chirped pulse with critical relativistic intensity

“…To begin with, the chirp effect on the electron acceleration potential needs to be investigated to find a proper chirp parameter. In this case, an analytical treatment for a free electron motion in a electromagnetic field is applied [4]. The transverse momentum of electron sheet is dominated by the transverse laser field,…”

“…The interaction of matter with such fields is capable of producing high energy electrons, ions, as well as photons. In particular, the wave reflected at a laser driven relativistic electron bunch can be a very potential compact x-ray source [2][3][4], which attracts more and more attention due to its application on the detection of matter [5]. Electron bunches with GeV energy can be generated by bubble formation in plasma [6][7][8][9][10].…”

“…is the longitudinal relativistic factor of a DEES and x ¼ v x =c is the corresponding velocity [4]. Except for the application of the DEES on the coherent Thomson backscattering, the nanocontrolled DEES is also capable of generating giant half-cycle attosecond pulses [11].…”