Thermonuclearizing the plasma focus—converting plasma focus fusion mechanism from beam-gas target to thermonuclear

Abstract

It has been reported that over a range of 3–280 kJ, neutron-optimized deuterium plasma focus machines operate with a near constant speed factor S = 89 ± 8 kA cm−1 per (torr)0.5. This near-constant value of S is consistent with a narrow range of peak axial speeds approximately 10 cm μs−1 and peak radial speeds 20–30 cm μs−1, resulting in focus pinch temperatures less than 0.5 keV and inductively generated high voltages, producing deuteron beams with energies from high tens to hundreds keV. The low pinch temperatures and high beam-deuteron energies result in fusion neutrons predominantly from a beam-target mechanism. A converging taper ending in radius a e, is added to the end of the standard cylindrical anode of radius ‘a’. This taper converts the pinch from one with starting radius ‘a’ to one with a reduced starting radius a e. This increases the value of S and consequently the pinch temperature. This study examines the scaling of the end taper and finds that a taper ending in a radius, which is 1/20 that of the before-taper section increases the pinch temperature by a factor approximately 200, to above 20 keV. This increases the thermonuclear cross-sections by up to 14 orders of magnitude. Numerical experiments using the Lee code confirm that the thermonuclear component of the fusion yield becomes predominant. Such a taper may be considered as a thermonuclear converter.

Study of the plasma pinch and ion beam properties versus the nitrogen gas pressure using the Lee model code

“…The code was used to determine current and neutron yield limitation, investigate neutron saturation effect, investigate radiative collapse and obtain anomalous resistance data. The model then has been also enhanced and used to study ion beams emitted from plasma focus devices [16][17][18][19][20][21][22]. Using the Lee model code, numerical experiments for two devices: APF [23,24] and PF400 [25,26] operated with nitrogen gas were simulated by entering several parameters including: Bank parameters (capacitor bank C0, inductance L0, stray circuit resistance r0), Tube parameters (length z0 and radius a of the anode, the radius of the cathode b) and Operational parameters (operator charging voltage V0 and pressure P0 of the gas, the energy storage in the capacitor bank E0).…”

Pushing the limits of existing plasma focus towards 1016 fusion neutrons with Q = 0.01

“…Recent use of the code includes developing the concept of thermalization of the plasma focus using a tapered anode which, by increasing the value of (I/a) in the tapered pinch, increases the temperature of the focus pinch, for the pinch to transition from a beam-target fusion source to one of a thermonuclear fusion source [40,41]. By adjusting the taper ratio, the pinch temperature is tunable up to 200 keV, sufficient for aneutronic fusion applications [27,42].…”