#z-pinch

[wikipediapictures]

Plasma-filaments

“Z-pinches constrain the plasma filaments in an electrical discharge from a Tesla coil.” - via Wikimedia Commons

[krismur]

Toughtober - Firefly

https://projectrho.com/public_html/rocket/slowerlight2.php#id--Go_Slow--Sublight_Starships--Project_Icarus--Firefly_Starship

Interstellar Z-pinch fusion rocket with a Saturn V for scale

[literallymechanical]

Zap Energy says that they’ve solved Z-pinch by “shear stabilization”, where they have different sections of the plasma moving at different velocities (faster outside, slower inside). Doesn’t shear like that cause instability, not suppress it? Or are plasmas not subject to that law of fluid dynamics

You’re thinking of instabilities in flowing plasma like it’s turbulence in flowing fluid. This is partially correct, but like... okay. So, the field of physics that governs the movement of plasma is called magnetohydrodynamics, where you introduce Maxwell’s equations into Navier-Stokes. It is horrible. I am but a humble mechanical engineer, and I leave the physics to physicists.

The physicists tell me that Zap Energy's science is solid.

Bit of context: Zap Energy is taking an old fusion energy concept from the 1950's called a Z-pinch, and revamping it with modern plasma physics.

A Z-pinch works on the principle that passing an electric current through a conductor generates a magnetic field, which in turn crushes (or "pinches") the conductor. The first observations of the pinch effect were in hollow metal tubes that were used as lightning rods, like this one from a factory in 1905:

Image by Brian James, CC BY-SA 3.0, Wikimedia Commons

Plasma is electrically conductive, and is subject to the same compressive pinch effect as metal. Lightning itself is a plasma pinch, actually.

When you pinch a plasma, it heats up. The fast-moving, charged plasma particles repel each other and push back against the magnetic field until the system reaches equilibrium. The stronger the plasma current, the harder the pinch, the more pressure, and the more heat. With sufficient plasma current and the right hydrogen isotopes, you can create a pinch strong enough to induce nuclear fusion.

The pinch effect was first utilized by a class of fusion machines called Z-pinches in the early 1950's. However, those Z-pinches were extremely unstable. The most common analogy is that compressing plasma with a Z-pinch is like trying to squeeze jello with rubber bands.

UK Atomic Energy Authority, Public domain, via Wikimedia Commons

Both linear and toroidal Z-pinches have been built. The toroidal Z-pinch above shows some of the characteristic kink instabilities of a pinched plasma – it goes all squiggly. Researchers started adding external magnets to Z-pinches to help reduce instabilities (which eventually led to the development of the tokamak), but could never get a truly stable plasma. Z-pinch fusion research was largely abandoned in favor of the tokamak and stellarator.

However, the external magnets of a tokamak or stellarator are massive, complex, and use incredible amounts of power. The University of Washington and Zap Energy went back to the old concept of a magnet-less linear Z-pinch, but with a more modern understanding of plasma physics. They discovered that by using a flowing plasma rather than a stationary one, with a faster flow rate on the outer layers (a "sheared-flow" Z-pinch), they were able to achieve great stability with no magnets.

Credit: Zap Energy

Rather than filling a chamber with stationary hydrogen and then pinching it, they blow a "smoke ring" of plasma around a cylinder into their chamber. An electrode at the tip of the cylinder then fires a pulse into the plasma, which creates a pinch with a complex velocity profile.

Credit: Zap Energy

Zap Energy’s physics basis is good. They’ve pretty convincingly demonstrated that sheared-flow does indeed stabilize a pinched plasma, and if they can pull off magnetic confinement fusion with no magnets, it will be massively cheaper than any other method. The uncertainty that Zap is facing comes from mechanical considerations (in particular, electrode erosion is a tricky problem to solve), and the relatively thin margins for efficiency that are inherent to any pulsed fusion technique.

[krismur]

HOPE Z-Pinch

[cavenewstimestoday]

Stabilized Z-Pinch Fusion Driven Electromagnetic Propulsion

Loura Hall Apr 18, 2025 ECF 2024 Quadchart Underwood.pdf Thomas Underwood University of Texas, Austin This project will demonstrate a fusion propulsion system based on z-pinch which is a method of compressing plasma by running electrical current though it. The z-pinch will compress and heat the plasma to produce fusion reactions, and the system will be paired with an electromagnetic accelerator…

Stabilized Z-Pinch Fusion Driven Electromagnetic Propulsion

[truphysics]

Z-Pinch

Introduction Z-Pinch, also known as zeta pinch, is a type of plasma confinement system that uses an electric current in the plasma to generate a magnetic field that compresses it. This physical principle is applied in various scientific fields, notably in fusion power and astrophysics research. Basic Principle: Lorentz Force The core principle of the Z-Pinch method lies in the magnetic fields…

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[zeitvox]

In science, if you do something once that's never been done before, it's considered a mistake. Do it twice, and it's simply a mirage. But the third time . . . you can't deny or refute the third time. The third time is the truth. With Z's new, seemingly impossible results came the first flickering sign that some deep, unknowable power resided in the Machine. And so today, the Z Machine is considered one of the world's best hopes for achieving fusion.

Michael Paterniti, A Voyage to the Sun

[spaceplasma]

Z-pinch in action

The plasma universe consists of swirling streams of electrons and ions flowing in filaments. There is a tendency for these filaments to repel at close range, and attract at greater distances. Within the shell of a planetary nebula are one or more plasma sheaths, or “double layers,” that act like capacitors, alternately storing and releasing electrical energy. The current flow alternately increases and decreases within the sheaths inside and outside the shell.

Charged particles in motion constitute an electric current. An electric current is accompanied by a magnetic field that wraps around the current and diminishes with the distance from it. The magnetic field gets stronger when more charged particles move in the same direction or when they move faster. Ions moving through the magnetic field are squeezed toward the axis. Plasma physicists refer to this as the “Bennett pinch", Z-pinch. For example; the planetary nebula M2-9 (above) shows the classic hourglass, Z-pinch shape.

The electric discharge in a plasma cloud creates a double layer along its axis. Positive charge builds up on one side and negative charge on the other. A strong e-field exists between the sides and if enough current is applied the double layer glows, otherwise it is invisible and is described as “dark mode”.

Double layers and current filaments also respond to the interstellar electric currents in the circuit that threads through the galaxy. They are mostly dark mode phenomena because of their low current density, but the magnetic fields they produce are apparent and detectable in the z-pinch (Bennett pinch) zones that arise.

Credit: Stephen Smith