An improved experiment for the investigation of the helical magnetorotational instability

The magnetorotational instability (MRI) is widely believed to play an essential role in the formation of stars and black holes. Destabilizing hydrodynamically stable Keplerian flows, the MRI triggers turbulence and enables outward transport of angular momentum in accretion discs which is necessary to explain the mass accumulation rates of central objects. The Potsdam Rossendorf Magnetic InStability Experiment (PROMISE) is intended to study the helical version of MRI which works already at Reynolds numbers of the order of 1000 and Hartmann numbers of the order 10. We focus on the results of an improved experiment in which split end caps are used to minimize the effect of Ekman pumping.