Neutrons, X-Rays and Charged Particle Beams Emission in a 65 kV Plasma Focus

Abstract

The correlation between the dynamic behaviour of a focused plasma and the bursts of neutrons, X-rays and charged particle beams have been investigated experimentally using a 65 kV plasma focus device. The dynamic bahaviour has been observed with a Mach-Zehnder interferometric system operating in the framing mode. The ion- and the electron beams are detected by a Thomson parabola analyzer and a Čerenkov detector, respectively. Neutrons, X-rays and charged particle beams are produced when a voltage spike appears. The generation of the electron- and the ion beam occur in an interval of 20 ns around the peak of the voltage spike. The m=0 type instabilities are observed even if the voltage spike does not appear. The plasma inductance increases monotonically but rather slowly during the process of the m=0 type instability growth. The neutron yield is ascribed to a generation of the anomalous resistivity in the plasma.

Experimental study of neutron emission characteristics in a compact sub-kilojoule range miniature plasma focus device

“…According to the beam-target hypothesis, the production of accelerated deuterons produced by spatial charge separation in plasma diodes generated by a rapid change in plasma inductance along with abrupt increase in the plasma resistance (with the onset of m = 0 instability followed by disruption of the pinched plasma column) plays a crucial role in neutron production [10,11] and hence the factors affecting instability/stabilization of the pinched plasma column play an important role in the beam-target contribution [45,46]. The growth time (t i ) of the Rayleigh-Taylor (RT) instability in accelerated dynamic pinches is given by t i = √ 2π λ/a, where a is the sheath acceleration and λ is the dominant wavelength of perturbation [47].…”

“…These findings pointed to the existence of non-thermal processes in which the D-D reactions are produced by accelerated (suprathermal) deuterons, colliding with the thermal deuterons in the plasma bulk and the neutral gas atoms outside the plasma (beam-target effect) [9]. The conventional explanation of the ion acceleration involves production of strong localized electric fields which result from the destruction of the plasma column due to the development of MHD instabilities, especially the m = 0 sausage instability [10][11][12]. Bernstein and Hai [13] postulated that the high energy deuterons are generated by an acceleration mechanism, in which the ion velocities are randomly oriented because of curved motion in the magnetic field of the pinch.…”

Observation of Two Phases of Neutron Emission in a Low Energy Plasma Focus

“…2,3) Both thermonuclear and nonthermonuclear mechanisms are believed to be responsible for the production of the neutrons. [4][5][6][7][8] Potter attributed the neutron emission to thermonuclear reactions based on the two-dimensional fluid model numerical simulation. 9) The non-thermonuclear mechanism involves a beam-target effect where accelerated deuterons collide with the thermal deuterons in the plasma or with the background deuterium molecules.…”

“…The correlation between the dynamic behaviour of a focussed plasma and the emission of neutron, X-ray and charge particle was investigated using a 65 kV plasma focus device. 8) The particle beams were found to be generated in an interval of 20 ns around the peak of the voltage spike while the neutron yield was ascribed to the generation of the anomalous resistivity in the plasma.…”

Time-resolved hard X-ray emission from a small plasma focus

“…It is now generally agreed that the hard X rays are produced at the anode region by the interaction of energetic electrons generated in the focus with the anode and with the material evaporated from the anode by intense electron beam heating (Bernstein et al 1969;Jalufka & Lee 1972;Harries et al 1978). Although more direct methods of studying the energetic electrons have been reported in recent years (Stygar et al 1982;Yamamoto et al 1985;Choi et al 1990), the simpler method of hard X-ray measurement continues to provide useful information on the energetic electrons produced in the plasma focus. Although more direct methods of studying the energetic electrons have been reported in recent years (Stygar et al 1982;Yamamoto et al 1985;Choi et al 1990), the simpler method of hard X-ray measurement continues to provide useful information on the energetic electrons produced in the plasma focus.…”