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A pinch (or: Bennett pinch [2] (after Willard Harrison Bennett), electromagnetic pinch, [3] magnetic pinch, [4] pinch effect, [5] or plasma pinch. [6]) is the compression of an electrically conducting filament by magnetic forces, or a device that does such. The conductor is usually a plasma, but could also be a solid or liquid metal.
The Z-pinch is an application of the Lorentz force, in which a current-carrying conductor in a magnetic field experiences a force.One example of the Lorentz force is that, if two parallel wires are carrying current in the same direction, the wires will be pulled toward each other.
When a field-reversed configuration is formed using the theta-pinch (or inductive electric field) method, a cylindrical coil first produces an axial magnetic field. Then the gas is pre-ionized, which "freezes in" the bias field from a magnetohydrodynamic standpoint, finally the axial field is reversed, hence "field-reversed configuration."
A reversed-field pinch (RFP) is a device used to produce and contain near-thermonuclear plasmas. It is a toroidal pinch that uses a unique magnetic field configuration as a scheme to magnetically confine a plasma, primarily to study magnetic confinement fusion. Its magnetic geometry is somewhat different from that of a tokamak.
Birkeland currents are also one of a class of plasma phenomena called a z-pinch, so named because the azimuthal magnetic fields produced by the current pinches the current into a filamentary cable. This can also twist, producing a helical pinch that spirals like a twisted or braided rope, and this most closely corresponds to a Birkeland current.
The current induces an intense Z-pinch magnetic field that crushes the liner and fuel. The compression does work to the fuel, heating it to tens of millions of degrees Celsius. Normally the electrons in the plasma would be free to escape, and the ions to a lesser extent, carrying away energy and cooling the plasma.
The magnetic mirror and pinch effect devices were dramatically simpler, the former consisting of a modified solenoid and the latter is effectively a high-power version of a fluorescent lamp. Pinch, in particular, seemed like an extremely simple solution to the confinement problem, and was being actively studied at labs in the US, UK and USSR. [11]
A magnetic mirror, also known as a magnetic trap or sometimes as a pyrotron, is a type of magnetic confinement fusion device used in fusion power to trap high temperature plasma using magnetic fields. The mirror was one of the earliest major approaches to fusion power, along with the stellarator and z-pinch machines.