Annealing of irradiated silicon strip detectors for the ATLAS experiment at CERN

ATLAS prototype n–in–n and p–in–n silicon strip detectors from several manufacturers were irradiated with 24 GeV protons at the CERN PS to a total fluence of 3×1014 p/cm2. This is equivalent to the maximum fluence expected in the strip detector part of the silicon tracker after 10 yr of operation. The ATLAS semiconductor tracker will be operated at −7°C. Yearly warm-up periods of 2 days at 20°C and 2 weeks at 17°C are foreseen for maintenance purposes (ATLAS Inner Detector Technical Design Rep., 1997). To study the long-term effects of radiation damage and warm-up the detectors underwent controlled thermal annealing. The Ziock parameterisation was used to simulate the warm-up effects of 10 yr on a shortened time scale (H.J. Ziock et al., Nucl. Instr. and Meth. A 342 (1994) 96). Using this parameterisation the same amount of anti-annealing gained during 10 yr of warm-ups can be reached by storing the detectors for 21 days at 25°C. During the annealing period current–voltage and capacitance–voltage measurements were carried out at regular intervals. The full depletion voltage was then determined from the capacitance measurements and showed a clear dependency on the measurement frequency and temperature. The evolution of the full depletion voltage as a function of annealing time is compared to the Ziock parameterisation.