Results of the tests of a CMS tracker inner barrel sub-structure with a 25 ns beam

A beam test was performed in May 2003 to validate with an LHC-like beam all the CMS tracker final components assembled together, including detectors, mechanical structure, fully optical readout, DAQ, power supplies and cables and to test the stability of the overall system. A sector of the third layer cylinder mechanical support was produced according to the final design and was equipped with services. Six modules from a pre-production and their corresponding optical hybrids were also installed in this sub-structure. This system was brought to CERN X5 beam area and connected to the power supplies and DAQ. After a relatively short period of commissioning, the system worked successfully and a very large number of events was taken. Data were carefully analysed and several results about charge collection, noise, detector performance under different bias voltages, timing structure of the signal, and detector uniformity were obtained from these studies. The main system aspects as well as the DAQ and experimental setup are described and the main results about detector performance are discussed.