Electrodynamics of helical wigglers for free-electron lasers

Abstract EN

The exact expressions for the magnetic field and vector potential inside a bi-helical wiggler, used in Free-Electron laser, are obtained by solving the differential equations for the magnetic field using the helical currents as the boundary conditions.

This approach of the problem is original.

Next, the trajectory of an electron entering the helical wiggler with relativistic initial velocity in the axial direction and any arbitrary initial velocity and initial coordinates in the transverse direction is obtained.

Finally Finally, the average power radiated by an electron having such a trajectory is obtained.

The results indicate that the radiated power increases with the magnetic field magnitude and the axial speed, as expected.

However, for a large range of values of the axial speed, the slope of the power is rather flat until the speed reaches approximately 0.85 times the speed of light Then, to obtain better perforrnance, the condition "l>2 becomes almost compulsory