Pinch (plasma physics)

A pinch is the compression of an electrically conducting filament by magnetic forces. The conductor is usually a plasma, but could also be a solid or liquid metal. Pinches were the first device used by humankind for controlled nuclear fusion.

The phenomenon may also be referred to as a Bennett pinch (after Willard Harrison Bennett), electromagnetic pinch,magnetic pinch,pinch effect or plasma pinch.

Pinches occur naturally in electrical discharges such as lightning bolts, the aurora,current sheets, and solar flares.

Pinches exist in laboratories and in nature. Pinches differ in their geometry and operating forces. These include:

Pinches may become unstable. They radiate energy as light across the whole electromagnetic spectrum including radio waves, x-rays,gamma rays,synchrotron radiation, and visible light. They also produce neutrons, as a product of fusion.

Pinches are used to generate X-rays and the intense magnetic fields generated are used in electromagnetic forming of metals. They also have applications in particle beams including particle beam weapons, astrophysics studies and it has been proposed to use them in space propulsion. A number of large pinch machines have been built to study fusion power; here are several:

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