Transformation of the Pinched Column at a Period of the Neutron Production

Abstract

A PF-1000 device working with a deuterium gas filling and a current on the order of 1 MA was used for studies of the pinch-column structure by means of a laser interferometric system at a period of hard X-ray (HXR) and neutron production. Three different phases of the plasma-column evolution, corresponding to the intense HXR and neutron emission, were studied for discharges with neutron yields equal to about 10 11 neutrons/shot. First, the start of the stagnation of a pinch column was considered; as the second phase, the development and disruption of constrictions was studied, and as the third phase, the decrease of the plasma density in a part of the plasma column during its stagnation was considered. Regions of the probable electron and ion acceleration and possible neutron production were identified.

Deuterium gas puff Z-pinch at currents of 2 to 3 mega-ampere

“…It was the case of the shots with a 3 kA/ns as well as with a 20 kA/ns current rise rate even though there was a difference in the width of radial neutron spectra. On the basis of previous plasma focus experiments, 10,15,47 we believe that these neutrons were produced by the beam-target mechanism after the disruptive development of instabilities. Therefore, we may ask if conditions convenient for a high x-ray yield are also optimal for a high neutron yield.…”

“…Subsequently, neutron yields are lower than those in PFs where a large number of neutrons are produced in a dense structure at the heel of the current sheath. 47 In order to achieve higher neutron yields in megaampere deuterium Z-pinches, it seems convenient to "simulate" a plasma focus-like geometry. Such a geometry has been tried on the Angara-5-1 Z-pinch in Troitsk where a strong axial gradient of a linear density was achieved with a short delay between the initiation of the current generator and the breakdown pin pulse.…”

Spatially resolved high-resolution x-ray spectroscopy of high-current plasma-focus discharges

“…This value corresponds to the maximum electron density observed in the interferometry measurements performed for a pure deuterium. 12 We believe that in the case of the argon and deuterium mixture, the average electron density should be in this range ͑or slightly higher͒. The increase in the superthermal electrons' fractions significantly shifts the He-␣ to Li-like intensity ratios toward higher values, especially for low electron temperatures.…”

Energy Transformations in Column of Plasma-Focus Discharges With Megaampere Currents

“…The acceleration of fast deuterons, observed to be mainly directed along the motion of the current sheath, must be taking place in the region between the anode and the plasmoid. In this region, a fast decrease of plasma density is observed [13], [14]. In [15], the total number (about 10 17 ) of fast deuterons producing observed neutrons in intense pulses was estimated to have total energy of 3-5 kJ.…”

“…The neutron sources can be identified with dense plasmoids. They correspond to the spherical source of fusion protons registered with a pinhole camera [12] as to the densest region of the plasma column registered in the time of neutron production, in which the highest probability of D-D fusion reaction occurs [13], [14]. The acceleration of fast deuterons, observed to be mainly directed along the motion of the current sheath, must be taking place in the region between the anode and the plasmoid.…”