Low Energy Dense Plasma Focus Research Articles

Numerical Experiments to Optimize Argon Soft X-Ray Yield in a Low-Energy Plasma Focus

Numerical experiments are carried out on a low-energy (2.2 kJ) Mather-type Egyptian Atomic Energy Authority-Plasma Focus (EAEA-PF1) to investigate the optimum combination of all electrode system dimensions and gas pressure for maximum argon soft X-ray (SXR) yield, $Y_{\mathrm {SXR}}$ , using Lee Model RADPF5.15. This paper aims to finalize the first step prior to building an automated method of optimization that could be applied when a low-energy dense plasma focus is designed or need to be reconfigured, for this purpose, and to assist further research efforts in this field. The second part of the study deals with the investigation of the role of changing outer electrode radius “b” and the outer to inner radii ratio “c” on plasma focus (PF) parameters such as ion density, pinch duration, and column length and how are these, consequently, related to the maximum SXR yield. It is shown that lower radius ratio values (typically less than 2) are favored over higher ones, for argon SXR yield, and unlike most of the low-energy PF devices that are designed for this purpose. It is also shown that inductance and pinch current are only affected by the dimension of inner electrode radius, while the ion density, pinch duration, and focus volume are also affected by the change of outer electrode radius.

Optimization of neon soft X-ray yield in a low-energy dense plasma focus device

The modified version of Lee model code is used in numerical experiments for characterizing and optimizing neon soft X-ray yield ([Formula: see text]) of the United Nations University/International Center for Theoretical Physics Plasma Focus Facility (UNU/ICTP PFF) device operated at 14 kV and 30 [Formula: see text]. In our present work, the neon yield [Formula: see text] is improved with an optimized UNU/ICTP PFF device by computing the optimum combination of static inductance ([Formula: see text]), anode length ([Formula: see text]), anode radius ([Formula: see text]) and cathode radius ([Formula: see text]), keeping fixed their ratio ([Formula: see text]) at 3.368, through a lot of numerical experiments at six operating pressures ([Formula: see text]). At lower [Formula: see text] (e.g. 2.0, 2.5 and 3.3 Torr), the optimum [Formula: see text] value, together with the corresponding optimum combination of [Formula: see text], [Formula: see text] and [Formula: see text], is found to be 15 nH, whereas at higher [Formula: see text] (e.g. 4.0, 5.0 and 6.0 Torr), it is obtained as 10 nH. Though the computed maximum neon yield [Formula: see text] (57.2 J with the corresponding efficiency of 1.94%) is found at [Formula: see text], assuming an achievable range of incorporating low-inductance technology, the best optimum combination of [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text] is found to be at [Formula: see text], resulting in the computed optimum neon yield [Formula: see text] of 54.60 J with a corresponding efficiency of 1.9%. This computed neon yield [Formula: see text] is about 11 times higher than the measured value [Formula: see text] at optimum [Formula: see text] of UNU/ICTP PFF. It is also observed that our computed neon yield [Formula: see text] is improved by around six times from the previously computed value, which was 9.5 J at the optimum [Formula: see text] Torr for optimum anode configuration of this machine. In addition, neon yield [Formula: see text] is obtained with our optimized combination of [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text] at 11.5 kV and compared with the measured neon yield [Formula: see text] of the NX2 machine.

Simultaneous Ultra-Fast Imaging and Neutron Emission from a Compact Dense Plasma Focus Fusion Device

Recently, there has been intense interest in small dense plasma focus (DPF) devices for use as pulsed neutron and X-ray sources. Although DPFs have been studied for decades and scaling laws for neutron yield versus system discharge current and energy have been established (Milanese, M. et al., Eur. Phys. J. D 2003, 27, 77–81), there are notable deviations at low energies due to contributions from both thermonuclear and beam-target interactions (Schmidt, A. et al., Phys. Rev. Lett. 2012, 109, 1–4). For low energy DPFs (100 s of Joules), other empirical scaling laws have been found (Bures, B.L. et al., Phys. Plasmas 2012, 112702, 1–9). Although theoretical mechanisms to explain this change have been proposed, the cause of this reduced efficiency is not well understood. A new apparatus with advanced diagnostic capabilities allows us to probe this regime, including variants in which a piston gas is employed. Several complementary diagnostics of the pinch dynamics and resulting X-ray neutron production are employed to understand the underlying mechanisms involved. This apparatus is unique in its employment of a 50 fs laser-based shadowgraphy system that possesses unprecedented spatio-temporal resolution.

Common features of particle beams and x-rays generated in a low energy dense plasma focus device

Features of energetic charged particle beams and x-ray emission in a low energy (1–2 kJ) plasma focus (DPF) device are described and the possible mechanism are explained based on circuit analyses and energy balance in the DPF system. In particular, the resistance and the voltage across the plasma column are estimated to explain the mechanisms of the generation of particle beams and hard x-ray. The analysis shows that the total inductance of a DPF might have played a role for enhancement of the particle beams and x-ray emissions during the phase of anomalous resistance.

The first stages of the discharge in a low-energy dense plasma focus

The very beginning of the discharge has been studied in the PACO dense plasma focus (DPF) device. Electrical and optical diagnostics (ultra-fast photographs of emitting light) have been employed to describe the plasma in the breakdown and also when the plasma sheath (or current sheath) did part of its coaxial travel. The plasma shape in its earliest stage and in more advanced stages are related between them for characteristic working pressure regimes. Using other diagnostics such as neutron emission detection, the breakdown features and the apparatus performance were correlated.

Comparative study of soft x-ray emission characteristics in a low energy dense plasma focus device

An investigation on the soft x rays emitted in a 2.2 kJ Mather-type dense plasma focus device using a multichannel diode spectrometer and a simple pinhole camera is reported. Emitted x rays associated with different shapes (hollow, solid, and hemispherical) of anode and in hydrogen/nitrogen gas medium are compared. The structure of x-ray emitting sites as well as x-ray yields were found to be strongly influenced by the shape of the anode and the filling gas pressure. The maximum yield of 2.2 J into 4π sr was obtained in the case of hemispherical anode in hydrogen gas medium. The x-ray pinhole images of the collapsed plasma with the hemispherical anode indicated spot-like structure having 500–800 μm in diameter. On the contrary, other anode shapes showed columnar pinched structure of 8–10 mm in length and 1–2 mm in diameter. Results indicated that an appropriate design of the anode could enhance the x-ray yield by more than tenfold in a conventional low energy dense plasma focus device.

New efficient low-energy dense plasma focus in IPPLM

The paper describes a new Dense Plasma Focus 6 kJ device, assembled in IPPLM and design to work in a repetition mode of operation (up to 10 Hz). An important part of the device is one of four exchangeable chambers of a special geometry, each designed as an efficient source of pulse hard and soft X-rays, neutrons or fast ions. The experiment has been performed in single-shot mode, limited by the charger. The projectible lifetime of all elements except the chmbers is about 106 shots, which seems to be very promising from scientific, medical and industrial applications.

Magnetic probe measurements of current sheet dynamics in a coaxial plasmaaccelerator

A high-frequency multiple magnetic probe assembly has been specificallyfabricated for the study of current sheet dynamics in the axial acceleration phaseof a low-energy dense plasma focus (DPF) device operated in a nitrogen gasmedium. The response time of each probe is of the order of 1 ns and the tinystructure of the probe is well suited to sense the magnetic field associated with apulsed plasma without perturbing the plasma unduly. The magnetic probes werecalibrated using a simple, novel and reliable calibration technique and thecalibration factor is found to be 0.34 ± 0.028 T V−1.Our study reveals that the parabolic current sheet accelerates asit propagates through the electrode assembly, reaching a rundownvelocity of ∼6.1 cm µs−1.The average current sheet thickness in the axial acceleration phase is found to be∼3 cm. In our case, the current shedding and mass loss factors are estimated to be32% and 40% respectively. Our approach of using a high-frequency multiplemagnetic probe assembly for the study of current sheet dynamics in a DPF deviceis highly effective in obtaining precise and accurate measurements.