Pulsed Power Plasmas

Pulsed power is simply the compression of electrical energy into short, high power bursts. This typically uses capacitive storage charged slowly from a wall outlet, which is then discharged in timescales from nanoseconds to milliseconds through a target. This method can be used to initialize and drive plasmas in solids, liquids and gases, and has found applications in areas from water sanitation to x-ray lasers and inertial confinement fusion.

 

 

Wire-based Z-Pinches use fine metallic wires (e.g. Al, Cu or W) which can be loaded in various geometries depending on the experiment of interest. The peak of the current pulse 100 kA to several MA and rises to a maximum in around 100 - 1500 ns. The total power delivered to the load is often measured in terawatts.

For a single wire, this axial current initially ohmically heats the material which expands outwards at the sound speed. At the current rises the self-generated azimuthal magnetic field increases rapidly and pinches the plasma back onto its axis through the Lorentz (j x B) force. In this geometry the process is refered to as a z-pinch, since the current flows along the axial, or z, axis. As pinching occurs, the interface of the plasma and the B-field is highly unstable to magneto-hydrodynamics (MHD) and a classical classical m=0 structure is observed.

For different applications, the geometry of the wires can be altered very simply, which changes the geometry of the driving B-fields. Inclining the wires into a cone generates a central plasma column with axial momentum, which is then launched out of the array as a jet relevant to astrophysical jets. Inverting the electrode geometry causes a radially outward Lorentz force, and the plasma ejected can be used for studying shock formation in radiatively cooled flows (see Shocks project on the Projects page).

Pulsed power driven wire plasmas provide a versatile system to examine issues in laboratory astrophysics, basic plasma science and high energy density physics.

 

Gorgon 3D MHD Simulation

Liners for Inertial Confinement Fusion form the basis for the pulsed power approach to fusion energy. Instead of wires, a solid metallic liner filled with DT fusion fuel is mounted in the driver. The liner is pre-heated using a laser and then rapidly compressed using the fast-rising magnetic field from a pulsed power machine.

 

 

 

 

 

 

 

 

 

 

 

 

 

This experiment is called Magnetized Liner Inertial Fusion (MagLIF) and is a main focus of the Z machine at Sandia Laboratories. Z is largest pulsed power generator in the world,  producing 26MA in 100ns. It is the most powerful laboratory x-ray source, generating 1.8 MJ of x-ray energy at a power of 280 TW, and is a potential driver for both Inertial Confinement Fusion (ICF) and Inertial Fusion Energy (IFE).

For more information on pulsed power IFE, see the talk by Simon Bott-Suzuki here