ИСТИНА

Test masses of future laser interferometric GW detectors will be fabricated from high purity silicon and cooled, in particular to 123 K in the LIGO Voyager project. Electrostatic actuators are supposed to use in order to tune their position. Capacitive coupling of the actuator electrodes with the silicon test mass results in the additional mechanical loss introduced into the test mass oscillation caused by electric currents flowing in silicon having a finite resistivity. This loss is a cause of additional thermal noise. We have carried out a study of this loss in silicon disk mechanical resonators at room temperature. A model that relates the electric field induced mechanical loss in disk resonators to the resistivity of the material was proposed. It follows from the model that, under certain conditions that are satisfied for the silicon resonators under study, the electric field induced loss is directly proportional to the resistivity of silicon. We present results of study of temperature dependence of the electric field induced loss of the bending mode of commercial disk-shaped undoped silicon wafers (UniversityWafer, Inc., resistivity more than 10 kOhm*cm) in the temperature range of 100 – 295 K.