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Concept
Pinch (plasma physics)
Summary
A pinch (or: Bennett pinch (after Willard Harrison Bennett), electromagnetic pinch, magnetic pinch, pinch effect, or plasma pinch.) 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. Pinches were the first type of device used for experiments in controlled nuclear fusion power.
Pinches occur naturally in electrical discharges such as lightning bolts, planetary auroras, current sheets, and solar flares.
Pinches exist in nature and in laboratories. Pinches differ in their geometry and operating forces. These include:
Uncontrolled – Any time an electric current moves in large amounts (e.g., lightning, arcs, sparks, discharges) a magnetic force can pull together plasma. This can be insufficient for fusion.
Sheet pinch – An astrophysical effect, this arises from vast sheets of charged particles.
Z-pinch – The current runs down the axis, or walls, of a cylinder while the magnetic field is azimuthal
Theta pinch – The magnetic field runs down the axis of a cylinder, while the electric field is in the azimuthal direction (also called a thetatron)
Screw pinch – A combination of a Z-pinch and theta pinch (also called a stabilized Z-pinch, or θ-Z pinch)
Reversed field pinch or toroidal pinch – This is a Z-pinch arranged in the shape of a torus. The plasma has an internal magnetic field. As distance increases from the center of this ring, the magnetic field reverses direction.
Inverse pinch – An early fusion concept, this device consisted of a rod surrounded by plasma. Current traveled through the plasma and returned along the center rod. This geometry was slightly different than a z-pinch in that the conductor was in the center, not the sides.
Cylindrical pinch
Orthogonal pinch effect
Ware pinch – A pinch that occurs inside a Tokamak plasma, when particles inside the banana orbit condense together.
Official source
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Plasma (physics)
Plasma () is one of four fundamental states of matter, characterized by the presence of a significant portion of charged particles in any combination of ions or electrons. It is the most abundant form of ordinary matter in the universe, being mostly associated with stars, including the Sun. Extending to the rarefied intracluster medium and possibly to intergalactic regions, plasma can be artificially generated by heating a neutral gas or subjecting it to a strong electromagnetic field.
Reversed field pinch
A reversed-field pinch (RFP) is a device used to produce and contain near-thermonuclear plasmas. It is a toroidal pinch which 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 the more common tokamak. As one moves out radially, the portion of the magnetic field pointing toroidally reverses its direction, giving rise to the term reversed field.
Magnetic confinement fusion
Magnetic confinement fusion is an approach to generate thermonuclear fusion power that uses magnetic fields to confine fusion fuel in the form of a plasma. Magnetic confinement is one of two major branches of fusion energy research, along with inertial confinement fusion. The magnetic approach began in the 1940s and absorbed the majority of subsequent development. Fusion reactions combine light atomic nuclei such as hydrogen to form heavier ones such as helium, producing energy.
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