Improvement of radiation hardness of double-sided silicon strip detector for Belle SVD upgrade

We have developed a double-sided silicon strip detector for the Belle silicon vertex detector upgrade. Since a radiation-hard front-end VLSI has been successfully developed, the shot noise due to the radiation-induced leakage current of the sensor will be the dominant source or the noise after irradiation in the Belle apparatus. Test structures with various strip pitches and strip widths were fabricated to study optimum strip width. The temperature dependence of the leakage current was measured with a prototype sensor after ⁶⁰C gamma-ray irradiation. It was confirmed that the radiation-induced leakage current can be reduced by half by cooling the sensor from 25 to 15°C. A radiation test with a prototype module consisting of a prototype sensor and front-end VLSI was also performed to evaluate the radiation hardness of the whole system. The signal-to-noise ratio was found to be better than 20 up to 5 Mrd(Si).