A   B   C   D   E   F   G   H   I   J   K   L   M   N   O   P   Q   R   S   T   U   V   W   X   Y   Z  

Kot, Y.A.

Paper Title Page
TUP032 Simulations on Impact of the 3.9 GHz RF Section on the Multi Bunch Emittance at FLASH 465
 
  • Y.A. Kot
    DESY, Hamburg
 
 

In order to compensate nonlinear distortions of the longitudinal phase space a rf section operated at three times the 1.3 GHz frequency of the existing TTF cavities is foreseen in the next phase of FLASH. Four modules of a nine-cell 3.9 GHz cavities will be installed right after the first accelerating module ACC1. These cavities could cause additional long-range wake fields which would affect the multi bunch (mb) beam dynamics leading to increase of the mb emittance. The mb emittance at the end of the linac is determined by the strength of the transverse wake fields in the rf system. These higher order modes appear after any off-crest moving bunch, which could happen either due to the cavity misalignment, or by transverse position fluctuations of the injected bunches. It is intended to damp them by means of the HOM couplers, which may reduce the damping time by factor of 105. The misalignment of the cavities offsets is expected to be by 0.5 mm rms. The paper describes the results of the simulations on the dependence of the mb emittance on cavities misalignment offsets and damping strength of the HOM couplers in the planned 3.9 GHz rf section.

 
TUP033 Lattice Studies for the XFEL-Injector 468
 
  • Y.A. Kot, V. Balandin, W. Decking, C. Gerth, N. Golubeva, T. Limberg
    DESY, Hamburg
 
 

The XFEL injector building has a length of 74.3 metres and is divided by 2.5 m long concrete shielding wall. The section upstream the shielding wall will have a length of 42.3 m and give place for the gun, accelerating module, 3rd harmonic section, laser heater and the beam diagnostics section. At its end the possibility for the beam dump is foreseen so that the tuning of the beam in the injector would become possible without any impact on the subsequent parts of the XFEL. Each of these components sets certain requirements on beam optics which may compete with each other. Downstream the shielding the beam will be vertically displaced by 2.75 m over the distance of 20 m by means of the so called dogleg - a combination of two four cell arcs (8 cell system). Since the vertical displacement takes place there it is important to optimize cells in such an order that the chromatic effects don't impact the beam quality noticeably. In this paper we describe the solution for the beam optics at the XFEL injector.