Micropinch in a high-current diode

The basic data on the micropinch in a high-current, low-inductance spark are reviewed. This phenomenon was discovered by Cohen et al. in 1968. A theory for the equilibrium and collisionless emission of a plasma compressed to a degenerate state by the magnetic field of the high current yields a natural explanation for several properties of the micropinch which are unexpected at first glance: the hard x-ray burst, the time evolution and directional pattern of this burst, the power-law spectrum above 150 keV, the confinement of the emission sources to certain spatial regions, and the highly ionized atoms, among others. (Similar effects are observed in $z$ pinches, the plasma focus, and the explosion of wires.) At maximum compression, the micropinch seems to be similar to the Thomas–Fermi “linear atom”, which consists of ions which are at rest on the whole and drifting electrons which carry the current. The micropinch has potential applications (in the fusion problem and in developing sources of induced synchrotron radiation for the x-ray range), but it is also of much physical interest in itself, since it allows laboratory research on a supercontracted hot plasma, i.e., matter in a state approaching that in stars. In order to prove unmistakably that supercontracted matter is present in a micropinch, however, it would be necessary to carry out direct experiments to observe the strong electromagnetic fields and the high density of matter in regions with dimensions measured in angstroms.