A novel hollow active auxiliary electrode applied for the vertical calculable cross-capacitor at NIM

In order to compensate the end-effect error in the vertical calculable cross-capacitor with one fixed and one movable guard electrodes, two different methods including the nosepiece and the modified active auxiliary electrode are usually adopted in the main worldwide national measurement institutes. However, the latter electrical approach will have some difficulties in assembling the mirrors for the resonant cavity of Fabry-Perot laser interferometer. This paper describes one novel hollow active auxiliary electrode which can satisfy the optical requirements and the model experimental results show that it has similar excellent compensation effect with the modified active auxiliary electrode.