DELTA, a status report of the storage ring FEL facility at the University of Dortmund

Abstract

The storage ring FEL facility DELTA, under construction at the University of Dortmund since the beginning of 1990, has reached the stage of assembling the accelerator components, now starting the setup of the injection linac. DELTA is a low emittance 1.5 GeV storage ring optimized for FEL operation. Two straight sections are available for insertion devices up to 14 m length. To achieve the design goal of extremely high brilliance of the electron beam a triplet lattice is chosen, giving low emittance values comparable to FODO designs. This lattice has the advantage of more space between the elements, allowing further instrumentation. Furthermore, the vacuum chamber was optimized for low impedance. Even in the kicker magnets there is no change of the cross section. This yields optimized operation with respect to bunch lengthening and other wakefield effects. Due to the integrated pumping using NEG and ion getter pumps in a continuous antechamber, only negligible lifetime degradations due to vacuum pressure have to be expected. Thus, DELTA represents an optinum accelerator to operate FELs in the extremely short wavelength regime down to about 20 nm.