Near-wall wakefields for optimized geometry of TTF 2 collimator

Wakefields excited in the small aperture collimators may damage the beam. As pointed out by K. Bane and P. Morton the wakefields can be reduced considerably by tapering the steps and using the “step+taper” collimator geometry. The optimisation of this kind of geometry for TTF 2 collimators with different apertures is carried out in the paper. For the optimal geometries the non-linear near-wall wakefields are calculated. The numerical results are confirmed by comparison with analytical estimations for the fully tapered collimator in inductive regime

Studies of the collimation system for the TTF FEL at DESY

A collimation scheme for the protection of the undulators at the TESLA Test Facility phase 2 (TTF2) is discussed. The transverse and energy collimation, and the protection against off-energy and mis-steered bunches are proposed in a beam line which, besides the collimation elements, integrates the fast feedback system and matches the beam to the undulator entrance

Studies of the collimation system for the TTF FEL at DESY

A collimation scheme for the protection of the undulators at the TESLA Test Facility phase 2 (TTF2) is discussed. The transverse and energy collimation, and the protection against off-energy and mis-steered bunches are proposed in a beam line which, besides the collimation elements, integrates the fast feedback system and matches the beam to the undulator entrance

Preliminary trials with optical fiber dosimeters at TTF

Ionizing radiation leads to a degradation of the light transmitting properties of fiber optic cables. These effects usually place restrictions on where they can be used in a particle accelerator facility. These effects can also be used to our advantage, the losses from a particle beam create wavelength dependant increases of attenuation by absorption and scattering which can be measured using Optical Time Domain Reflectometry (OTDR). From these measurements a measure of the radiation dose received can be inferred

Scheme for time-resolved experiments based on the use of statistical properties of the third harmonic of the SASE FEL radiation

A closer inspection of the statistical properties of the third-harmonic radiation from the SASE FEL reveals that it is possible to select single, temporary coherent radiation spikes by using a simple intensity trigger. A carefully designed optical system for splitting, delaying, filtering, and recombining the radiation would then allow time-resolved measurements with resolution down to the coherence time of the FEL, i.e. a few femtoseconds in the case of the TTF FEL

The structural examination of myocardial samples from patients with end-stage heart failure supported by ventricular assist devices using electron-microscopy and amino acid analysis reveals low degree of reverse remodeling

Milting H, Jacob M, Kassner A, et al. The structural examination of myocardial samples from patients with end-stage heart failure supported by ventricular assist devices using electron-microscopy and amino acid analysis reveals low degree of reverse remodeling. JOURNAL OF HEART AND LUNG TRANSPLANTATION. 2004;23(4):396-404.Background: Chronic heart failure is a multifactorial, progressive disease of many causes and is associated with complex ventricular remodeling. Deposition of extracellular matrix proteins and sarcomeric disarray of the myocytes occur in end-stage heart failure. Ventricular assist devices (VAD), implanted as bridge to transplantation, may reverse ventricular remodeling. Although successfully weaning patients from VAD support has been reported, it is not clear to what degree reversal of remodeling,occurs in unloaded failing hearts. Because collagen deposition, and ultrastructural disarray are hallmarks of myocardial remodeling, we analyzed the myocardial ultrastructure and collagen content of VAD-supported hearts before and after mechanical unloading. Methods: We used amino acid analysis to measure collagen content (4-hydroxyproline content) in 24 transplant candidates receiving VAD support. We used transmission electron microscopy to examine the ultrastructure in 6 patients receiving VAD support. Results: The 4-hydroxyprohne content increased significantly at VAD implantation and was not altered by mechanical unloading. The ultrastructure showed signs of persisting. cardiomyopathy. Conclusion: Mechanical unloading does not alter the total collagen content of the supported, failing heart. Thus, structural reversal of the remodeling process associated with heart failure is not a general phenomenon in mechanically unloaded hearts