Z-Pinch physics: Axial current Jz →
azimuthal field Bθ → inward Lorentz force
J × B compresses plasma. Sausage (m=0):
symmetric squeezing. Kink (m=1): column bends
sideways. β = 2μ₀nkT / B².
🌀 Z-Pinch
About this simulation
A Z-pinch confines plasma by passing a strong axial electric current
through it: the current generates its own azimuthal magnetic field,
and the resulting Lorentz force squeezes the plasma column inward.
This was one of the earliest approaches to controlled nuclear fusion
and still powers facilities like the Z Machine at Sandia, which
drives radiation experiments and inertial-confinement research. It is
fascinating because the same self-pinching that compresses the plasma
also makes it violently unstable.
How it works
An axial current Jz flows through the plasma column.
It creates an azimuthal magnetic field Bθ wrapping the column.
The inward J × B Lorentz force compresses the plasma toward the axis.
Thermal pressure pushes outward; equilibrium sets the pinch radius — until instabilities (sausage or kink) break it apart.
Key equations
I² = 8π N k T — the Bennett pinch relation, balancing
magnetic compression against thermal pressure (I = current, N = line
density, T = temperature). Plasma beta:
β = 2μ₀ n k T / B² compares plasma pressure to magnetic
pressure.
Current I (MA) — stronger current means tighter, faster compression.
Temperature (keV) — higher thermal pressure widens the equilibrium radius.
Perturbation — sets the seed amplitude that instabilities grow from.
Pause / Reset — freeze the animation or restart the column.
Did you know?
The Z-pinch sausage instability is the same physics that pinches off
a stream of water into droplets — a current-carrying plasma "necks"
wherever it is slightly thinner, because the magnetic field is
stronger there, accelerating the squeeze.