Using a Bessel light beam as an ultrashort period helical undulator

An undulator is a critical component to produce synchrotron radiation and a free electron laser. When a Bessel light beam carrying the orbit angular momentum copropagates with an electron beam bunch, a net transverse deflection force will be subjected to the latter one. As a result of dephasing effect, the deflection force will oscillate and act as an undulator. For such a laser based undulator, the period length can reach submillimeter level, which will greatly reduce the electron energy for the required x-ray production.

Figure 1

Sketch of Bessel light beam (red-orange vortex) interaction with electron beam (blue dot).

Figure 2

Tracking result of electron trajectory (a), and the defocus effect (b), with the zoomed beam trajectory for a clear view, and with the electrical field rotating counterclockwise in the bottom.

Figure 3

Radiation phase errors for electrons with different initial $x-x^{\prime }$ conditions.