The purpose of the optical system, which we call the dump line, is not simply the transport of the beam to the beam dump. It is an essential part of the beam switchyard whichprovidesthepossibilitytodistributeelectronbunches of one beam pulse to different FEL beam lines, allowing a flexible selection of the bunch pattern at each FEL experi- ment. In this paper we describe the final layout of this opti- cal system as it is now under construction.

The European X-Ray Free Electron Laser (E-XFEL) [1] will have a fast transverse intra-bunch train feedback (IBFB) system [2] to stabilize the beam position in the SASE undulators. E-XFEL bunch trains consist of up to 2700 bunches with a minimum bunch spacing of 222ns and typ. 10Hz train repetition rate. The IBFB will measure the positions of each bunch in the bunch train, and apply intra-train feedback corrections with fast kickers, in addition to a feed-forward correction for reproducible trajectory perturbations. By achieving a feedback loop latency in the order of one microsecond, the IBFB will allow the beam position to converge quickly to the nominal orbit as required for stable SASE operation. The latest conceptual design of the IBFB and the status of IBFB components will be presented.

PETRA III is a 6GeV positron light source with a design horizontal beam emittance of 1nm.rad and 1% emittance coupling. This low emittance is achieved with proper correction of horizontal dispersion to its theoretical values in the arcs as well as dispersion free sections. The spurious vertical dispersion, arising due to misalignment and rotational errors of the magnets is also duly corrected as this contributes to the vertical beam size of the photon beam. Here we discuss the method taken to correct the horizontal dispersion using a combined orbit and dispersion correction scheme. In the vertical plane the same procedure can be used as that of horizontal plane or only the dispersion can be corrected using dedicated skew quadrupoles to millimeter level after orbit correction has been done. In this paper we present the methods used and results obtained in correction of dispersions in transverse planes.

A 4-cavity 3.9 GHz cryomodule has been constructed at Fermilab and delivered to DESY. Its intended use is to linearize the non-linear beam energy-time profile produced by the 1.3 GHz accelerating gradient and thus improve the operating characteristics of FLASH for its users. First cold testing of the module is expected in the near future prior to its installation. We will report on the performance of the cavities, assembly and transport of the module as well as anticipated testing, installation, and commissioning plans.

The spurious vertical dispersion, arising due to the misalignment and rotational errors of the magnets in the storage rings dedicated for synchrotron radiation sources are highly undesirable in the low emittance machines, as this contributes to the vertical beam size of the photon beam. This is a matter of concern in PETRA III, a 6GeV positron storage ring with a horizontal beam emittance of 1nm.rad and 1% emittance coupling. In this paper the local and/or global vertical dispersion correction in the ring after getting a corrected orbit with combined horizontal dispersion correction of the perturbed lattice are discussed. The global vertical dispersion is corrected using the vertical corrector magnets used for orbit correction and 12 skew quadrupole magnets are used at three locations viz. two damping wiggler sections and the new octant with DBA cells, with a pair of skew quadrupoles on either side to correct locally without disturbing the dispersion out side. A SVD method can also be used considering the BPMs (Beam Position Monitors) on either side of insertion devices using skew quadrupoles to minimize the vertical dispersion in those locations so that the vertical emittance can be maintained at a desired value.

PETRA III is a low-emittance storage ring dedicated to synchrotron radiation. For efficient injection in the top-up mode, the dynamic aperture has to be larger than 30 mm- mrad in the horizontal plane. This paper presents the choice of tunes and the optimization of the sextupole configuration. Tracking simulations have been performed, including the non-linear effects of 20 four-meters-long damping wigglers and a representative set of undulators. Misalignment and multipole errors are considered as well, leading to specifications for the magnet design and alignment procedure.

PETRA III is a 6 GeV synchrotron light source being reconstructed out of the existing storage ring PETRA II. It will have a horizontal beam emittance of 1nm.rad and a 1% emittance ratio. Since the vertical beam sizes are ~5- 10 micron in the low gap undulators sections the beam position stability requirement in the vertical plane is between 0.5 and 1 micron whereas the stability requirement in the horizontal plane is more relaxed. In this paper determination of golden orbit in the presence of magnetic field errors and magnet misalignments and correction of vertical spurious dispersion is discussed. A scheme of slow and fast orbit correction using the SVD algorithm has been developed. The distribution of monitors and the location of slow and fast correctors are reported. Estimations of the parameters of the fast orbit feedback have been derived from present measurements on PETRA II. Figure 1: The horizontal and vertical RMS COD produced by 600 sets of random errors before correction. Table-1: Magnet, BPM alignment & magnet field errors.

Vertical emittance is a critical issue for future linear collider damping rings. Both NLC and TESLA specify vertical emittance of the order of a few picometers, below values currently achieved in any storage ring. Simulations show that algorithms based on correcting the closed orbit and the vertical dispersion can be effective in reducing the vertical emittance to the required levels, in the presence of a limited subset of alignment errors.

The international TESLA collaboration proposes a 500-800 GeV center-of-mass linear collider based on super-conducting 1.3 GHz cavities. This technology promises a luminosity of 3.4×10 34 cm -2 s -1 . Results from the cavity R&D program at the TESLA test facility and details of the collider design will be presented.