Stability of the LIPAc beam dump to vibrations induced bythe cooling flow

Abstract

The beam dump of the LIPAc consists of a long and thin copper cone where the ions are stopped, cooled by water flowing along its outer surface. The high water velocity (between 4 and 8 m/s) and the turbulent regimes involved may compromise the mechanical stability of the slender beam dump structure and cause damages due to flow induced vibrations. Since the system is too complex to be studied theoretically, some tests have been carried out to evaluate its behavior in normal operating conditions. These tests, performed on a model built at 1:1 scale and replicating exactly the final version, have been focused on finding experimentally the main vibration modes and the responses to the different working flowrates. This modal analysis, together with the results of the measurements of the vibration characteristics obtained at several positions of the cone, is presented here. With amplitudes not greater than 500 mg rms in any case, the structure has proved its practical immunity to flow induced vibrations, thus validating its design and construction methodology.