New solid state detectors

Abstract

Contemporary particle accelerators for fundamental research in particle physics like Fermilab’s Tevatron and CERN’s Large Hadron Collider (LHC) provide researchers with higher and higher luminosities. This sets the pace for the need for radiation-hard detector materials for both beamline instrumentation and the physics experiments themselves. Silicon pixel and silicon microstrip detectors are well-developed devices for tracking applications in these high-energy physics experiments. However, these detectors are expected to reach the end of their lifetime within a few years due to their exposure to harsh radiation, of which the yearly level amounts to up to several 1014 hadrons/cm2 during the foreseen 10 years of operation in the case of LHC experiments. In order to protect sensitive experimental devices from adverse beam conditions, chemical vapor deposition (CVD) diamond, an artificially generated diamond material, is more and more being used in systems called Beam Condition Monitors (BCM). The radiation level these sensors are exposed to is even higher than in the case of position-sensitive tracking detectors. An example are the CVD diamond sensors of the BCM of the LHCb experiment at CERN, which is meant to withstand 1015 hadrons/cm2 during 10 years. Preparation of CVD diamond sensors for BCM applications is discussed in detail, together with the properties of this new material as a candidate for position-sensitive devices in high-energy physics experiments, addressing also operational questions like the appearance of erratic dark currents in polycrystalline diamond bulks. Other new materials for position-sensitive devices such as CdZnTe and CdTe are discussed as well and compared to the well-established silicon, together with a compilation of their properties relevant to particle detection. Recent advances in the field of passive radiation monitors, where thermoluminescent sensors made from lithium fluoride now cover a dynamic range from several fvGy up to 105 Gy, are also discussed briefly.