Fundamental Measurements in Gravitational Physics Using Precision Rotations: I. Motivations and Unprotected-Rotor Results

Decay time constants for magnetically-suspended rotors undergoing inertial spin-down have been measured at room temperature. Bearing-rotor interactions have been studied and evidence found that there is a driving mechanism capable of accelerating or decelerating a rotor with a moment of inertia of ≈1100 g cm 2 at the 10 -14 W level. The complicated rotor decay structure suggests that there exist unfavorable rotational frequencies at which mode coupling exists and leads to unavoidably large levels of angular momentum dissipation. The length of the rotors (≈20 cm) also produces a pendulum motion which at times results in ambiguities in the spin-down data due to interference with the normal operation of the optical-lever timing system.