Pair production by photons in a dense pinch

Electron-positron pair production by photons in the electromagnetic field of a strongly compressed current channel is investigated. The dependence of the cross section on the pinch radius is mainly due to the necessity of transfer of momentum to the electromagnetic field. With increase of the channel radius the cross section rapidly decreases since momentum cannot be transferred. For high energy γ quanta the main contribution is from the region located at far distances from the axis. In this case the cross section is determined by the logarithmic asymptotic value of the field of the current regarded as a charged current-carrying filament and is independent of the radius. The principle possibility of resolving the spatial structure of the pinch in the angstrem range by employing pair production is demonstrated. Hence it should be possible to ascertain experimentally whether the strong compression to the state of a linear atom predicted by the theory of equilibrium and radiation of the plasma of a strong current actually occurs