VIBRATION ISOLATION SCHEME BASED ON ELECTROMAGNETIC SPRING

Sensitive measurements require a vibration isolation system to safeguard against detrimental tremble. Two types of vibration isolation systems - passive and active - are currently implemented. The spring-based passive designs usually accompany with ineffective low-frequency response. Therefore, the active designs, consisting of sensors, feedback control systems, and actuators, are consolidated to improve the total effectiveness of the cancellation performance. In this work, we focus on developing the actuator founded on electromagnetic spring to be incorporated into our compact quantum gravimeter. Each spring-actuated part comprises two repelling Nd magnets positioned face to face inside a solenoid. With this configuration, the spring can also work in the passive mode via repulsive magnetic force. In the active mode, the exerted force is a result of magnetic fields formed by the magnets and the current-controlled solenoid coils. By changing the coil current, the stiffness of the spring can be modified, and thus the displacement can be controlled.  Different sizes of magnets are explored, and their force behaviors in passive and active modes are characterized. The implementation scheme of the actuator in the quantum gravimeter is also discussed.