DELTA, A STATUS-REPORT OF THE STORAGE-RING FEL FACILITY AT THE UNIVERSITY-OF-DORTMUND

The storage ring FEL facility DELTA, under construction at the Univers ity of Dortmund since the beginning of 1990, has reached the stage of assembling the accelerator components, now starting the setup of the i njection linac. DELTA is a low emittance 1.5 GeV storage ring optimize d for FEL operation. Two straight sections are available for insertion devices up to 14 m length. To achieve the design goal of extremely hi gh 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 instru mentation. Furthermore, the vacuum chamber was optimized for low imped ance. Even in the kicker magnets there is no change of the cross secti on. This yields optimized operation with respect to bunch lengthening and other wakefield effects. Due to the integrated pumping using NEG a nd ion getter pumps in a continuous antechamber, only negligible lifet ime degradations due to vacuum pressure have to be expected. Thus, DEL TA represents an optimum accelerator to operate FELs in the extremely short wavelength regime down to about 20 nm.