Plasma dynamics in the PF-1000 device under full-scale energy storage: II. Fast electron and ion characteristics versus neutron emission parameters and gun optimization perspectives

Abstract

Electron and ion beam dynamics of the PF-1000 facility were investigated for the first time at its upper energy limit (≈1 MJ) in relation to neutron emission, the pinch's plasma ('target') characteristics and some other parameters with the help of a number of diagnostics with ns temporal resolution. Special attention was paid to the temporal and the spatial cross correlations of different phenomena. Results of these experiments are in favour of a neutron emission model based on ion beam-plasma interaction with three important features: (1) the plasma target is hot and confined during a few 'inertial confinement times'; (2) the ions of the main part of the beam are magnetized and entrapped around the pinch plasma target for a period longer than the characteristic time of the plasma inductive storage system and (3) ion-ion collisions (both fusion collisions, due to head-on impacts and Coulomb collisions) are responsible for neutron emission. Analysis has shown that one of the ways for achieving a future improvement in the neutron yield of the PF-1000 facility may by changing the geometry of the device. It may ensure an increase in both the discharge current and the initial working gas pressure, eventually resulting in the neutron yield boost.

Recent ion measurements within the modified DPF-1000U facility

“…Studies of the fast ion emission from various Plasma--Focus (PF) facilities were performed in many laboratories all over the world, and their results were published in numerous papers which can be found as references in some review papers [1][2][3][4][5]. Such studies have also been carried out within different PF-type facilities in Poland [6][7][8][9][10][11][12][13][14][15].…”

The experimental and theoretical investigations of damage development and distribution in double-forged tungsten under plasma irradiation-initiated extreme heat loads

“…It is known that changing the distance between the anode and the sample (see Fig. 1) allows one to change plasma parameters on the sample surface [16,17] (see also [18,19] for an overview of PF-1000 and [10] for PF-12).…”

“…Thus, the power fl ux density of slow plasma is almost the same for all the samples those were placed at the same distance from the anode. The power fl ux density of slow plasma (E ~ 0.1-1 keV) and fast ions (E ~ 100 keV) was calculated considering initial conditions and plasma properties (velocity of a plasma shock wave and the current rise time) for working PF devices [16,18,19]. The power fl ux density of non-homogeneous slow plasma (E ~ 0.1-1 keV) varied from 5 × 10 7 to 5 × 10 9 W/cm 2 with interaction time equal to 50-100 ns depended on samples' positions.…”

“…Plasma and ion fl ux parameters generated at the PF-1000 were measured by different direct methods (see e.g. [18,19]). It was estimated that hot plasma power fl ux density was 10 9 to 10 10 W/cm 2 at the pulse duration 100 ns.…”

Role of static inductance on ion beam emission in plasma focus devices

“…Using Lee's analysis, the effect of change in static inductance on ion beam emission has been investigated. Lee's model which is based on the coupling between plasma and current sheath dynamics, as well as plasma thermodynamics, and radiation processes along with device circuit parameters has been extensively and successfully applied to different plasma focus devices from low-to high-energy machines such as UNU/ICTP PFF [12,13], NX1 and NX2 [14], Stuttgart DPF [15], and PF1000 [12,16]. This model assumes that the plasma focus current trace is the fundamental signal from which all of the occurring phenomena can be extracted.…”