Laser assisted electron beam conditioning for free electron lasers

A new method for electron beam conditioning in free electron lasers is proposed. It uses the electron beam interaction with a laser light in two wiggler magnets separated by a strong-focusing channel. The effect of the conditioning is illustrated by the example of a hypothetical single-pass, high-gain free electron laser operating in the self-amplified spontaneous emission mode with the x-ray emission at ${\lambda }_x=1.5\AA$. The proposed conditioner is relatively compact and can be used as a practical add-on device to short x-ray wavelength free electron lasers.

Figure 1

A schematic of the Vinokurov’s conditioner.

Figure 2

A schematic of the laser assisted conditioner.

Figure 3

The electron beam energy distribution before (a) and after (b) the wiggler. Color coded are equal length regions centered at $z=\pm n{\lambda }_L$ (red) and $z=\pm (n+0.5){\lambda }_L$ (black). Only a short section of the electron beam is actually shown.

Figure 4

The FODO channel with ${\xi }_r=-5.3$ (only 12 out 16 FODO cells are actually shown): (a) beta functions, (b) chromatic functions.

Figure 5

A distribution of the electron longitudinal velocities for unconditioned (a) and conditioned (b) electron beams. An uncorrelated energy spread is ignored. Color coded sections within the electron beam are the same as in Fig. 3.

Figure 6

Conditioning $\Delta \gamma$ versus $(J_x+J_y)/{\epsilon }_r$: (a) zero relative phase between two laser waves, (b) relative phase shift is 0.09 rad. The blue line corresponds to $\Delta \gamma =6(J_x+J_y)/{\epsilon }_r$.

Figure 7

A distribution of the electron longitudinal velocities in the case of the nonzero $\Delta \varphi$ (see text): (a) $\Delta \varphi =0.09\mathrm{rad}$, (b) $\Delta \varphi =-0.03\mathrm{rad}$.

Figure 8

The average x-ray power versus distance for an electron beam with 1.2 mm-mrad normalized emittance: 1 is the standard case without conditioning, 2 is the case of an ideal conditioning (see text for explanation), and 3 is the case of a practical conditioning with a proposed conditioner.

Figure 9

The average x-ray power versus distance for an electron beam with 2.4 mm-mrad normalized emittance: 1 is the case without conditioning, 2 is the case of an ideal conditioning, and 3 is the case of a practical conditioning with a proposed conditioner.