Abstract
The upgrade of the LHC to the High Luminosity LHC will challenge the silicon strip detector performance with high fluence and long operation time. Sensors have been designed and tests on charge collection and electrical performance have been carried out in order to evaluate their behaviour. Besides that, it is important to understand and predict the long-term evolution of the sensor properties. In this work, detailed studies on the annealing behaviour of ATLAS12 strip sensors designed by the ITK Strip Sensor Working Group and irradiated from 5×1013neqcm−2 to 2×1015neqcm−2 are presented. Systematic charge collection and leakage current measurements have been carried out during the annealing process until break-down or the appearance of charge multiplication. The annealing was carried out, separating the sensors into two groups being either annealed at 23°C or 60°C. Sensors showing charge multiplication have been then kept at high voltage for a long time in order to monitor their stability. The difference in the annealing behaviour between the two temperatures has been analysed and compared to similar measurements on n-type sensors and with a theoretical model. From the impedance measurements for the samples irradiated to low fluences it was possible to extract the effective doping concentration. This was compared to similar measurements on n-type sensors and with a theoretical model.
Highlights
The high-luminosity LHC (HL-LHC) [1] will commence data-taking in 2025
The Hamburg model is derived from measurements of n-bulk silicon, whereas p-bulk silicon sensors are mandatory at the HL-LHC, due to their superior radiation hardness [5, 6, 7]
This study presents the annealing behaviour of ATLAS12 [12] sensors designed by the ATLAS Collaboration and manufactured by Hamamatsu Photonics [13]
Summary
The high-luminosity LHC (HL-LHC) [1] will commence data-taking in 2025. With a total integrated luminosity of 4000 fb−1 it will lead to unprecedented radiation fluences in the tracking layers, posing enormous challenges to the silicon detectors and their operation. The run schedule of the HL-LHC foresees shutdown periods on a yearly basis for machine maintenance During part of these periods the silicon detectors can not be cooled. Hadron radiation leads to significant changes of the electrical properties of silicon sensors. These are caused by defects to the silicon bulk, which are subject to a complex migration process, called annealing and have a strong time and temperature dependence. Some sensors showed charge multiplication.They were further investigated in a long term stability measurement, applying a constant high bias voltage. A detailed investigation on the difference in the annealing behaviour of sensors annealed at room-temperature and at 60 ◦C are presented and a comparison to the Hamburg Model is given
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