Vicente Valenzuela Villaseca (Imperial): High Energy Density Rotating Plasmas: Why and How to Stir Plasmas in Pulsed-Power Experiments
Rotating plasmas in the shape of accretion disks orbiting a central object are common throughout the universe. One of the outstanding questions about these disks is the mechanism allowing material to spiral inwards. Turbulence is the best candidate to enhance the transport of angular momentum. However, in keplerian disks its efficiency decreases as the magnetic Prandtl number (Pm), i.e. ratio of viscosity to magnetic diffusivity, is much smaller than unity.
In this talk I will present a new experimental platform being developed at Imperial College London aiming at simulating the key physics of accretion disks. A 1.4 MA, 500 ns duration electrical discharge drives the oblique collision of 8 plasma jets carrying a finite amount of angular momentum, forming a rotating elongated plasma column, simulating an accretion disk. Optical Thomson scattering indicates the rotating flow is quasi-keplerian with a characteristic velocity ~10 km/s. Laser interferometry used to determine the radial density profile provides measurements of the plasma density. These measurements combined indicate that Pm ~ 10-3, in the regime of applicability for stellar and protoplanetary disks.