USTRAT/SUPA, Glasgow
An unaveraged 3D model of the FEL has been developed which can model variably polarised undulators. The radiation field polarisation is self-consistently driven by the electron dynamics and is completely variable. This paper describes both physical model and computational code.
USTRAT/SUPA, Glasgow
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
The method of Echo Enabled Harmonic Generation is a possible method of achieving coherent short wavelengths in an FEL amplifier. In this paper the effects of noise variations is some of the important parameters affecting the stability of the final harmonic bunching of the electron beam are investigated numerically.
USTRAT/SUPA, Glasgow
This tutorial will give an introduction to the physics of how FELs work and will be targeted at a 1st/2nd year post-graduate level audience. I will try to give the audience a conceptual understanding of the basic electron-field interactions that allow the electrons to bunch and emit coherently. Some of the physics that tends to inhibit the FEL interaction will also be described.
USTRAT/SUPA, Glasgow
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
Chicanes placed between undulator modules in a high-gain FEL amplifier have been shown to generate a set of axial modes that may be locked to generate attosecond pulse trains in the x-ray [1]. Using numerical simulations, it is shown in this paper that a similar system of undulator/chicane modules may be used in a low-gain FEL cavity resonator to generate a equally spaced set of frequency modes with a spacing much greater than those of the cavity. As with the high-gain FEL amplifier case, these mode can lock to generate a pulse train.
[1] N.R. Thompson & B.W.J. McNeil, Phys. Rev. Lett. 100, 203901 (2008)
USTRAT/SUPA, Glasgow
DESY, Hamburg
So far, short wavelength Free Electron Laser amplifiers have produced linearly polarised radiation. For several important classes of experiment, variable polarisation is required. For example, in the wavelength range from 1.5 to 2.5 nm, light polarisation is important in characterising magnetic materials where measurements depend critically upon the handedness of the polarisation. It is therefore important that the polarisation does not fluctuate between measurements. In this paper, we study possible methods to generate variably polarised light and consider its shot-to-shot stability.
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
USTRAT/SUPA, Glasgow
The effects of pre-conditioned electron beams on free electron laser (FEL) behaviour are considered in simulations. Under consideration is modulation of the electron beam energy, using long-scale modulation period relative to the resonant FEL wavelength. Structure can be generated in the radiation field and electron beam with extent of significantly less than the FEL co-operation length, without applying spatio-temporal shifts between the radiation and electron beam*.
* N.R. Thompson and B.W.J. McNeil, Phys. Rev. Lett. 100, 203901 (2008).