An Abnormal Vibrational Mode of Torsion Pendulum

In the experiment for the determination of the gravitational constant G, we found an abnormal vibrational mode of the torsion pendulum. The abnormal mode disappeared as a magnetic damper was introduced to the torsion pendulum system. Our experimental results also show that the magnetic damper can be used to suppress the high frequency vibrational noises to torsion pendulums effectively.