A proposal for the surface roughness wake field measurement at the TESLA Test Facility

The wake fields due to the rough surface of the vacuum chamber have a major influence on the beam dynamics in linear colliders and free electron lasers. These wake fields mainly consists of the fundamental tube mode, modified by the rough boundary condition, which decreases its phase velocity to the speed of light. Its wavelength is proportional to the square root of the tube radius and the roughness depth and is comparable to the FEL bunch length, i.e. in the order of 10-30 micron. To study this effect with the beam available at the TESLA Test Facility (TTF) the use of tubes with an artificially increased roughness is suggested. The expected pulse power of these wakes, caused by the 250 micron bunch carrying a charge of 1 nC, can reach up to several MW. In this paper a preliminary design of an installation of a surface roughness wake field experiment at the TESLA Test Facility is presented