Interstrip capacitance stabilization at low humidity

A long-term stabilisation of the interstrip capacitance after bias application is investigated with emphasis on low ambient humidity conditions. The measurements are made with ATLAS SCT microstrip detectors produced by Hamamatsu. It is shown that after the application of 150 V bias the interstrip capacitance is higher by 25–30% than its stable value. It is demonstrated that at low absolute humidity, mandatory for the SCT operation at subzero temperatures, the stabilisation time may be of order of months. Since the interstrip capacitance is one of the major sources of front-end electronics noise the results are important for the optimisation of operating conditions for the ATLAS SCT.