Research supported by

1. National Science Foundation 
2. David and Lucille Packard Foundation
3. Alfred P. Sloan Foundation

This new experimental device and specialized infrastructure will be used to investigate dynamo action and the related physics issues in two primary configurations defined by propeller geometries. 

The first, a stretch-twist-fold dynamo, is a dynamo geometry which uses two large-scale helical vortices (the Double Vortex Dynamo) that couple kinetic energy to a large scale magnetic eigenmode. 

The second is a turbulent alpha-omega dynamo which relies upon differential rotation and helical  turbulence for the self-generation of magnetic fields. Small-scale turbulent velocity fields are expected to contribute to the growth of magnetic fields at a large scale. 

Both geometries are feasible in the sodium device, and water experiments have been carried out which show the necessary flows can be achieved.

For both the Double Vortex Dynamo and the alpha omega configurations, several common physics questions emerge which  are the focus of our proposed research: 

1. What are the growth-rates (or damping rates) of magnetic 
eigenmodes and how do they compare with theoretical predictions? 
2. Are there mean-field modifications to Ohm's law in a turbulent conducting fluid (such as a turbulent conductivity, or generation of current)? 
3. What is that nature of the  back-reaction in which a self-generated magnetic field modifies the flow to bring about saturation?

All three of these issues are fundamentally part of a larger goal, which is to test the fundamental tenets of MHD turbulence at large Rm: including observation of equipartition of magnetic energy and kinetic energy at small scales and an nverse cascade of magnetic helicity from small scales to large scales.