DESY, Hamburg
Uni HH, Hamburg
The free-electron laser facility FLASH at DESY, Germany finished its very successful 2nd user period late summer 2009. Recently FLASH has been upgraded. The 3rd user period is scheduled to start late summer 2010. In many aspects the upgraded FLASH is an FEL with a new quality of performance. It can provide thousands of FEL pulses per second with wavelengths approaching the carbon 1s absorption edge and the water window. The extension of the photon wavelength range is realized by increasing the electron beam energy up to 1.2 GeV by adding a 7th superconducting accelerating module. The dynamics behavior of the electron beam is improved by installing 3rd harmonic superconducting RF cavities. In addition, an experiment for seeded FEL radiation, sFLASH, is integrated to the FLASH linac. Recently, FLASH achieved a beam energy above 1.2 GeV and lasing below 5 nm with a remarkably improved performance.
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.