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 manu facturers were irradiated with 24 GeV protons at the CERN PS to a total flu ence of 3 x 10(14) p/cm(2). This is equivalent to the maximum fluence expec ted in the strip detector part of the silicon tracker after 10yr of operati on. The ATLAS semiconductor tracker will be operated at -7 degrees C. Yearl y warm-up periods of 2 days at 20 degrees C and 2 weeks at 17 degrees C are foreseen for maintenance purposes (ATLAS inner Detector Technical Design R ep., 1997). To study the long-term effects of radiation damage and warm-up the detectors underwent controlled thermal annealing. The Ziock parameteris ation was used to simulate the warm-up effects of 10yr on a shortened time scale (H.J. Ziock et al., Nucl. Instr. and Meth. A 342 (1994) 96), Using th is parameterisation the same amount of anti-annealing gained during 10 yr o f warm-ups can be reached by storing the detectors for 21 days at 25 degree s C. During the annealing period current-voltage and capacitance-voltage me asurements were carried out at regular intervals. The full depletion voltag e was then determined from the capacitance measurements and showed a clear dependency on the measurement frequency and temperature. The evolution of t he full depletion voltage as a function of annealing time is compared to th e Ziock parameterisation. (C) 1999 Elsevier Science B.V. All rights reserve d.