Speaker
Description
See the full abstract here:
http://ocs.ciemat.es/EPS2019ABS/pdf/P1.2012.pdf
The laser plasma undulator is a tunable device which utilizes laser plasma interaction to function as a short period undulator. Such an undulator could provide a table top solution for the production of X-ray beams which could be utilized in laboratories and medicine. In the regime of linear laser plasma interaction, the propagation of a beam in plasma can be modeled using the wave equation applied to the beam's vector potential function.. An underdense, parabolic plasma channel can essentially function as a waveguide for the injected beam, however, the propagation of the beam is highly dependent on the injection conditions. If the beam is injected off of the channel's axis of symmetry, the beam's centroid will oscillate about the channel's central axis. In this case, the amplitude and other characteristics of the beam are conserved during propagation. Through utilizing the solutions of an electron under the influence of a plane wave, one can model the trajectories of electrons copropagating with the beam in the plasma channel. The electron velocities follow the vector potential and subsequently the electrons also oscillate about the plasma channel's axis of symmetry producing undulator motion[1]. From the motion of the electron in such a channel, one can calculate the spectrum of the emitted radiation through Lienard-Wiechert potentials.
In this work, we utilized Crank-Nicolson schemes to model the propagation of the beam within the channel. This vector potential is then used to compute the trajectories of electrons. We then numerically integrate the intensity equation. We also analytically solved the intensity integral for this synchrotron motion. We found that the emitted spectrum of this device displays interesting features as shown in figure 1.
First, the short undulator wavelength results in a strong fundamental harmonic of 10keV X-rays. Second, off-axis, we find integer spaced harmonics corresponding to angular momentum quanta as indicated by the analytical solution of the intensity integral. The solution describes a helically distributed field similar to optical vortices.
References
[1] S. G. Rykovanov et al, Phys. Rev. Accel. Beams strong fundamental and harmonics in the 19,090703 (2016)
