Fast polycrystalline-CdTe detectors for LHC luminosity measurements

Beam diagnostics in future high-energy accelerators will require long lived instrumentation in highly hostile radiation environments. A research program aiming at individuating new solutions and testing them under extreme operational conditions has been launched at CERN in the framework of developments for LHC instrumentation. Its outcome might be used in future accelerator projects, in industry or in physics applications. The detectors which will be adopted for the LHC luminosity monitoring and optimization will be installed close to or inside copper absorbers specifically designed for radiation protection of the accelerator magnetic elements in the interaction regions. These detectors will have to withstand extreme radiation levels and their long-term operation has to be assured without requiring human intervention. Polycrystalline-CdTe detectors have demonstrated their radiation hardness against extreme doses of X-ray exposure in the LEP collider and are considered as good candidates for LHC luminosity monitoring applications. After recalling a series of measurements obtained on CdTe samples exposed to different sources to study their time response and sensitivity we present results on their performance after irradiation at doses of 10¹⁶ neutrons/cm². This is a preliminary step in the program intended to test the samples during and after irradiation up to levels of 10¹⁸ neutrons/cm ² and 10¹⁶ protons/cm² comparable to those anticipated at the detector locations over ten years of operation of the accelerator