ACCELERATOR COMPONENT VIBRATION STUDIES AND TOOLS

Mechanical design of the ILC (International Linear Collider) cryomodules is presently under development (1). The design under consideration is a further evolution of the cryomodules built in several units, and with several revisions, for the linac of the TESLA project (2). Nevertheless, except for the proposed new location of the quadrupole package at the center of the module, the main features and the layout of the components inside the main cryogenic vessel, with the Helium gas return pipe (GRP) as the main structural element, are preserved (1). Therefore, a detailed study of the mechanical behavior of the TESLA modules is useful to provide a reliable input for the ILC cryomodule design. In this work, we have focused our investigation on the support structure of the quadrupole, as designed for TESLA Type II cryomodules. We have measured the displacement power spectral density (PSD) at different positions and integrated the spectra to obtain root mean square (rms) displacement for these positions. We have also calculated the mechanical transfer function from the vacuum vessel to the quadrupole package and have checked for internal resonances (3). The measurements, performed at room temperature with inertial sensors, confirm reliability of the TESLA cryomodule design, in terms of vibrational stability, with the quadrupole, supported by the GRP, located at the end of the cryomodule.