The Princeton MRI experiment: an overview

The Princeton MRI experiment is used to study the magnetorotational instability (MRI), the instability believed to be responsible for the transport of angular momentum in accretion disks. The MRI is excited when a background magnetic field causes a radially-decreasing angular velocity field to become a source of free energy. The experiment consists of a Taylor-Couette apparatus with independently-rotating split endcaps filled with the gallium eutectic GaInSn. When operated in the stable regime the flow has an outwardly-decreasing angular velocity profile and is hydrodynamically stable up to a Reynolds number on the order of one million, as determined during the water stage of the experiment. An axial magnetic field, up to 5 kG, is applied to the experiment. Magnetic perturbations are measured using an array of Mirnov Coils and the velocity field is measured using a new ultrasonic velocimetry (UDV) system. Initial UDV measurements will be presented. When turbulent flows are generated, and a magnetic field is applied, evidence for magneto-Coriolis waves is found. The hydrodynamically stable flows are expected to become unstable due to the MRI. The latest results of the search for the MRI will be presented.