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The expected particle fluence in the inner part of the CMS Preshower is calculated to be 1.6×1014 cm-2 for neutrons and 0.4×1014 cm-2 for charged hadrons. Since the error of the calculation is high and/or unexpected accidental beam misalignments might happen we have irradiated Preshower silicon sensors to fluences up to 5×1014 n/cm2 to verify that they hold voltages necessary to reach the full charge collection efficiency. All irradiated sensors showed no signs of breakdown up to 1000 V, the maximum voltage applied. All but one display a sufficiently stable charge collection efficiency up to 1000 V. No noisy channels were observed at the extreme voltages.The measured charge collection efficiency was 71±12% and 59±12% for sensors irradiated to 3×1014 and 5×1014 n/cm2, respectively. These values are consistent with the extrapolation from previous measurements made on sensors irradiated to 2.3×1014 n/cm2.The work presents the results of static and dynamic measurements and shows that our design and the technology are very robust. [Copyright &y& Elsevier]

This paper is a summary of a research and development programme, conducted during the past 3 years on the CMS Preshower silicon sensors to define the specifications. The main purpose was to study the radiation hardness of these devices resulting from the specific design (metal lines wider than the p+ implants) and the production technology, a deep n+ layer on the ohmic side. An acceptable noise and a uniform charge collection were guaranteed by an appropriate choice of the interstrip region width. About 65 sensors, of different designs and produced by six manufacturers, were irradiated with neutrons and protons and thoroughly tested before and after irradiation. The results of the tests and the final specifications are presented. [Copyright &y& Elsevier]

Developing silicon strip sensors for the CMS Preshower detector we have noticed that some strips have a noise higher than the average and not correlated to a high leakage current. In order to investigate this effect we have developed a set-up for noise measurement on wafers and diced sensors that does not require bonding. The set-up is based on the DeltaStream chip coupled to a probe card. We have tested 45 sensors and found that the strips with an above average noise have a higher relative current increase as a function of voltage, ΔI/(IΔV). We also observed that, on these strips, the breakdown occurs within about 60 V from the voltage at which the noise is observed. We describe our measurement method and present the results. [Copyright &y& Elsevier]