Figure 4: View along the undulator installed in the tunnel of the TTF
The undulator system for the SASE FEL at the TTF and its magnetic performance has been described. It has been demonstrated that the tolerances on magnetic performance and mechanical alignment could well be met. As a summary Fig. 4 shows the undulator system installed in the TTF tunnel. Fig. 4 is dominated by the mechanical support structures. The magnetic structures are embedded in the girders made of low carbon steel. They also act as efficient screen for perturbing ambient fields. Cables and connectors for beam position monitors and correction coils can be seen. These components are integrated into the vacuum chamber which fits inside the 12 mm gap of the undulator. The chambers are described in References.
An extension of the existing FEL to a VUV-FEL [note: now named FLASH] user facility called TTF Phase 2 is already under construction. It is based on the experience made in TTF Phase 1. Its wavelength will be as low as 6.4 nm at an electron energy of 1 GeV. The total length of the undulator system will have to be tripled to reach this goal.
