Measuring Spatial Profiles of Velocity in a Plasma Dynamo

Keefe Mitman with John Wallace, David Weisberg, Jason Milhone, and Dr. Cary Forest

UW Department of Plasma Physics

Astrophysical dynamos convert kinetic energy from flowing plasma into magnetic energy.  A novel experiment in the UW Department of Physics is attempting to create a dynamo in the lab.  This requires a hot (>500,000 degrees) plasma that is stirred in a specific manner.  Our research was concerned with measuring the velocity of flowing plasma in the Madison Plasma Dynamo, a basic plasma research device designed to investigate flow-driven magnetohydrodynamic instabilities and other high-β phenomena.  To accomplish this, we constructed a prototype velocity probe capable of withstanding the harsh plasma conditions and able to be automatically moved using stepper motors and computer controls.  The design of this probe will be presented.  The probe was then used for measuring the plasma flow speed and to spatially scan the plasma.  Plasma flow speeds of >5 km/s were observed and the flow profile was consistent with inward momentum transport due to velocity.  Future work will involve replicating this probe in 15 more locations so that the entire velocity field will be measurable.