Low Energy Plasma Focus Research Articles

Correlation of pinch voltage with ion angular emission characteristics at varying D2 gas filling pressures in a low energy plasma focus device

Acceleration of deuterium ions to high energies and their anisotropic emission has been tried to be understood from pinch voltage (Vp) perspectives using 3.1 kJ plasma focus device. The D2 gas filling pressure was varied from 2 to 4 mbar at an operating energy of 1.1 kJ (10 μF, 15 kV). The pinch voltage was seen to be varying with filling pressure and it was found to be maximum 16.26 ± 0.56 kV at 3 mbar. The most probable energy (MPE) of deuterium ions followed the pinch voltage and maximum 11.36 ± 0.68 keV and 6.82 ± 0.41 keV were measured in the axial and the radial direction respectively at 3 mbar. Maximum energies of deuterium ions were observed to be in the range from 700 to 1000 keV. Correspondence between MPE and the pinch voltage as well as higher measured maximum energy of ions than the value eVp suggested m = 0 sausage instability might be the principal mechanism of ion acceleration coexisting with other acceleration mechanism. The energy spectrum suggested that the number of high energetic deuterium ions decreases faster in the axial direction than in the radial direction. This report discusses in details about the experimental observations and various other aspects of the measurements.

Synthesis of multi-phase steel thin films by a low energy plasma focus device

Pure iron bulk is directly transformed into multi-phase steel thin film in methane atmosphere using a plasma focus (PF) device. The thin films were deposited on pure iron substrates through various number of fired shots (10, 20, 30 and 40 shots). Ferrite, retained austenite and martensite structures were identified in multi-phase steel films. The multi-phase steel thin films contain both block-type and lamellar-type retained austenite, as well as martensite structures. The performed analyses demonstrated that low content of amorphous carbide exists in the films. Moreover, the chemisorption of N2 molecules on the film surface is higher than iron substrate. Corrosion and mechanical properties of pure iron substrate improved after deposition of multi-phase steel thin film. Magnetic measurements revealed that this type of steel is non-magnetic. The samples were characterized by measuring thin film parameters such as hardness, friction coefficient, charge transfer resistance, magnetization, and elemental composition.

Deposition of tungsten in methane atmosphere using a low energy plasma focus device

Deposition of tungsten in methane atmosphere was performed using a low energy plasma focus device. The resulting compounds were synthesized and investigated during the deposition process. Carbon-rich contamination was identified as an organic viscous liquid crystal defect. Tungsten carbide (W2C) and dark-black oxygen-deficient tungsten trioxide (WO3-x) thin films were synthesized by plasma focus device using different number of focused shots. The synthesis of each thin film, which was dependent upon operation of plasma focus device was verified and discussed. Tungsten carbide W2C was synthesized during the deposition process while the dark-black WO3-x was created after the deposition process in atmosphere. All compounds were investigated by spectroscopy, crystalline, and microscopy methods. Nano indentation test disclosed higher value of hardness for the film containing tungsten carbide compound (10.01 GPa) compared to both pure tungsten (5.72 GPa) and the dark-black WO3-x thin film (6.83 GPa). The verified band gap energy of dark-black WO3-x was around 1.475 eV.

Decomposition of SF6 by a plasma focus device

Decomposition of SF6 by a low energy plasma focus (PF) device has been investigated. The PF device performance in SF6 atmosphere was weaker than other gases such as argon, methane and nitrogen. Tungsten and vanadium anode tips were employed to generate thin layers of deposited products on substrates with different number of focused shots in SF6 atmosphere. The proper choice of the anode tip and substrate material has a direct effect on SF6 decomposition and generation of desire products. Free fluorine atoms and ions are produced during discharges that react with housing chamber and corrode the device materials such as Pyrex insulator, 304 stainless steel chamber and many more. Field emission scanning electron microscope (FESEM), energy dispersive X-ray (EDX), grazing incidence X-ray diffraction (GIXRD) and X-ray photoelectron spectroscopy (XPS) were utilized to identify the deposited solid film products.

High energy ion beams from the plasma focus

Instability development in the pinch induces a locally enhanced electric field that accelerates the charged particles to extraordinary high energies. Rapid discharge is the singular state of the ion source confirming high plasma impedance. High energy ion beam is correlated to the electrical discharge parameters and consequently the ion acceleration potential is directly related to the mean ion energy. Multi−MeV ions have been measured by magnetic spectrometry and nuclear activation yield-ratio to obtain the ion energy spectra and critically analyze the ion spectrum. A set of magnetic lens arranged in an optimized coil configuration results in medical grade radioactivity of 0.5GBq for a low energy plasma focus. High energy proton beams enables evaluating the sensitivity of link-board components and the error structure identification, with a significant probability of 0.1perproton.

Synthesis of hydrocarbon-vanadium thin films by a low energy plasma focus device

Synthesis of hydrocarbon-vanadium thin films by a low energy plasma focus device is reported. The thin films have organometallic structure and organometallic trovacenyl carboxylic acid anhydride (C26H22O3V2) is formed. The vanadium deposition process was achieved in methane atmosphere using different number (10, 20, and 30) of focused shots. Prior to deposition process, surface of pure vanadium substrate and the anode tip were exposed to atmosphere to allow the formation of vanadium trioxide (V2O3) and hydrogen vanadium bronze (HxV2O5) structures. During deposition process, HxV2O5 reacts with methane molecules and C26H22O3V2 molecular structure in nano-grain scale is created. The findings of present study indicates that C26H22O3V2 can be categorized as a semiconductor with band gap energy in the range of 1.20–1.35 eV. Furthermore, it is demonstrated that C26H22O3V2 molecular structure is not Raman active. Characteristics of the V2O3, HxV2O5 and C26H22O3V2 structures are investigated by crystalline, spectroscopy and microscopy methods. The average crystallite size of C26H22O3V2 was roughly 6 nm with almost 16% carbon deposited in the thin films. The Raman results are independent of the number of focused shots.

Comparison of formation of carbon on aluminum and graphite substrates by a low energy plasma focus device

Characterization of carbon structure was studied through deposition of carbon films on three different substrates at various angular positions. The thin films were prepared by a low energy plasma focus device and placed on graphite, aluminum, and magnesium substrates. The deposition process performed in presence of an active, as well as a noble gas, namely nitrogen and argon. The synthesis of thin films deposited at lower angular position shows nano-crystalline graphite and amorphous carbon structures. A carbon crystal has been detected for deposition at higher angular positions. The characterization of the crystal was investigated and it was revealed that the deposited thin film has hexagonal crystal structure. Further study of crystal led to the conclusion that it can be categorized under crystalline aromatic network. The surface of all synthesized films containing crystalline aromatic network was yellowish orange color (golden). The characterization of each structure was verified by x-ray diffraction (XRD), Raman spectroscopy, field emission scanning electron microscopy (FESEM), nano-indentation, Fourier transform infrared spectroscopy (FTIR), and transmission electron microscopy (TEM) analyses. Raman spectroscopy was used as a base analysis to classify carbon structures. Raman parameters of natural graphite structure, such as G peak position and ID/IG ratio, as well as, those of carbon crystal, nano-crystalline graphite, and amorphous carbon were identified.

High yield (⩾108/pulse) DD neutron generator based on a compact, transportable and low energy plasma focus device

A pulsed DD neutron generator based on the plasma focus (PF) device has been developed. The PF device was assembled using a single energy storage capacitor (10 µF) and a triggerable spark gap switch in a compact geometry. The anode of the PF device was made of SS304 material with its tip modified using a high purity tungsten insert. Excluding the power supply, the size of the overall system was 0.6 × 0.6 × 1.0 m and the weight was less than 100 kg. A maximum DD neutron yield of (3.1 ± 0.2) × 108 neutrons/pulse and average DD neutron yield of (2.24 ± 0.16) × 108 neutrons/pulse (pulse duration = 35 ± 4 ns) into 4π sr were observed at a capacitor bank energy of 3.1 kJ (25 kV) and at 4.5 mbar D2 gas filling pressure. The experimentally observed average neutron yield was found to be around 30% more than the estimated yield obtained using scaling laws for neutrons (Y n ≈ 1.7 × 10−10 I 0 3.3; I 0 is the peak discharge current in A). For a peak discharge current of 258 kA at 3.1 kJ, the neutron yield was estimated to be 1.23 × 108 neutrons/pulse. The higher neutron production was attributed to the efficient design of the PF device as well as to the low erosion of the anode tip because of the tungsten insert. Using the time-of-flight method, maximum neutron energy was calculated to be 3.91 ± 0.16 MeV in the radial direction at 4.5 mbar filling pressure. Numerical parametrization using the five-phase Lee model code was performed and found to be similar to PF devices developed across the world.

Effect of successive plasma shots on the dielectric constant of the CdS:Mn thin films exposed to the helium electron beam of plasma focus device

This paper investigated the emission of plasma concerning electron beam in a low energy Plasma Focus Device. Helium is utilized as a working gas with a pressure of 1.1 Torr. The effects of the voltage, working gas pressure, and parameters of the beam of electron applied were calculated. At the charging voltage of 12 kV, the maximum discharge current is 92kA, the maximum discharge voltage is 2.7 kV, the maximum dI/dt is -37 in.(A.U) and the maximum PMT signal is -4 in.(A.U). To estimate the electron beam energy and calculate the beam current at the side-on location, the Faraday cup was used. Using the electron beam evaporation method with coating unit from Edward 306 Auto under high vacuum conditions at room temperature, CdS1-xMnx (0 ≤ x ≤ 0.1) thin films were successfully deposited on glass substrates. The AC electrical conductivity of the (CdS) and (CdS doped with Mn) are measured. The dielectric constant of the (CdS doped with Mn) reveals that the conduction depends on the frequency. The Ac conductivity (σac) was obtained from the values of ε'. The experimental work and parameters ε' and σac at room temperature were studied as a function of frequency in the range of 100 Hz to 5 MHz. Mechanical studies of the CdS doped with Mn are investigated at different Mn concentrations and different charging voltage.

Characterization of carbonized magnesium formed in a low energy plasma focus device

Carbon-ion deposition on magnesium substrate was performed using a low energy Mather-type plasma focus device. Deposition process was carried out at 0, 15, 30 and 45° angular position with respect to the device anode axis. X-ray diffraction (XRD) confirmed presence of Mg2C3, Mg (OH)2 and graphite crystals on the produced films. Field emission scanning electron microscope (FE-SEM) coupled to elemental mapping analysis from surface and cross section of the samples was performed. The analysis showed the formation of a multi-layer thin film, in which carbon nano particles (CNPs) covered the composite layer. The CNPs were formed by graphite crystals while the composite layer formed by combination of Mg2C3 and Mg (OH)2 crystals. The band gap energy of indirect transition (⁓1.75 eV) of Mg2C3 was extracted from optical measurements of UV–Visible spectrum. XRD and Raman spectroscopy were used to investigate the graphite crystal structure of CNPs at each deposition angle. The study indicates that the graphite crystal structure of the samples is consisted of nano-crystalline and reduced nano-crystalline graphite structures. X-ray photoelectron spectroscopy (XPS) was used to characterize the elemental composition of the surface structure. The presence of Mg2C3 and Mg (OH)2 in composite layer, nano-crystalline, and reduced nano-crystalline graphite in CNPs was identified by high resolution transmission electron microscopy (HR-TEM). Potentio-dynamic polarization test was used to analyze the corrosion resistance of the prepared thin films with respect to un-deposited substrate. The findings indicate that the thickness and the size of Mg2C3 crystals have direct effect on corrosion resistance parameters.

Plasma Current Sheath Dynamics and Energy Dissipation in a Low-Energy Plasma Focus Device

This paper reports the measurements of plasma current sheath (PCS) dynamics, the energy dissipation processes, and the plasma focus (PF) electrical characteristics, particularly during the axial phase discharge in a Mather-type PF device (EAEA-PF1) energized with a 30 µF capacitor bank charged with 8, 10 and 12 kV. All these works are carried out under discharge conditions where the optimal PF action is achieved. At each charging voltage (Vch), 8 kV, 10 kV and 12 kV, the optimal PF action is studied for different Argon gas pressures (P) ranging from 0.4 to 1.2 Torr. The results show that the best PF is formed at Vch = 8 kV and P = 0.6 Torr, Vch = 10 kV and P = 0.8 Torr, and Vch = 12 kV and P = 0.8 Torr. The implosion velocity (Vz) results of PCS show that the maximum value of Vz (4.48 cm/µs) occurs at the end of the axial phase (i.e., at the coaxial electrode muzzle), which is detected at Vch = 12 kV and P = 0.8 Torr. Moreover, a less inefficient snowplow action is observed under these discharge conditions. The energy dissipation process data indicate that at Vch = 12 kV and P = 0.8 Torr, the ratio between the total energy dissipation and the input energy has a maximum value of ≅ 90%, and the minimum residual energy left on the condenser bank (175.39 J) is also achieved under these discharge conditions.

Deposition of molybdenum nitride thin layers on substrates of stainless steel AISI304 using a Mather-type of plasma focus device

This study focuses on effects of number of shots and the distance from the top of anode on Mo–N deposition process on the surfaces of AISI304 samples using a low energy (2.8 kJ) plasma focus device (AECS PF-1) at room temperature. The structural, morphological, elemental composition, surface roughness and micro-hardness properties of treated surfaces were investigated versus the number of shots and the axial distance from the anode. The obtained XRD spectra show that some of the treated surfaces were in crystalline phase with [Formula: see text]-Mo2N (FCC) structure (at 3 cm with 10–40 shots and at 5 cm with 30 and 40 shots) and some others had amorphous structure at 5 cm with 10 and 20 shots and at 7 cm with 10–40 shots. SEM images indicate that the thermal effect occurred at 3 cm and the deposition process of Mo–N at 5 cm and 7 cm from the anode with an increase in number of shots. The atomic ratio for nitrogen was 10.62%, 12.88%, and for molybdenum it was 0.23%, 3.36% at 3 cm, respectively. The atomic ratio for nitrogen has achieved 14.95% and 22.17%, however, the atomic ratio for molybdenum was 2.11% and 7.17 % at 5 cm, respectively. The surface roughness and size of grains on the surface of deposited layers were investigated by AFM analysis. Furthermore, the variation in the micro-hardness of the Mo–N thin layers deposited by different number of shots at different distances from the tip of anode was explained, qualitatively, on the basis of morphological characteristics of the thin layers. The decreasing rates of hardness in the case of 10 shots were 146%, 117% and 112%, and at 40 shots were 237%, 149% and 141% with the increasing of distances 3, 5 and 7 cm, respectively.

Ion-beam Investigation in a 1.5-kJ Dense Plasma Focus Device

An investigation of energetic ion beam emission from a low-energy (1.5 kJ) Mather-type plasma focus (PF) device operating with argon gas is studied with an operating pressure ranging from 2 × 10−2 to 1 Torr. The device has been energized by 30.84-μF capacitors charged up to 10 kV, giving a peak discharge current up to 120 kA with a rise time of 3 μs. A Faraday cup (FC) and its operation has been studied. This device is utilized to perform time-of-flight (TOF) measurements in order to characterize the beams of charged particles. The FC is placed at 20 cm from the tip of anode electrode at 0° with respect to anode axis to detect the ions. The FC operating in bias ion collector mode has been developed for measuring and characterizing pulsed ion beam. Energy and velocity of ions are determined with the TOF method, taking into account distance from the center electrode to the detection plane. The surface morphology of the pristine and irradiated ZnOCo0.04 samples is investigated as imaged by scanning electron microscope (SEM). The untreated sample showed rather relatively smooth surface; meanwhile, the SEM micrographs of bombarded samples display numerous small voids on the surface of the ZnOCo0.04 samples as a result of ion beam emission from PF device. X-ray fluorescence analysis showed that there are some new elements appeared on the surface of the sample after exposed to the ion beam; these elements and their concentrations are recorded. The surface roughness values for the pristine and the irradiated ZnOCo0.04 sample with Ar ion beam at different plasma shots are measured. A Vickers microhardness tester is used to measure the surface hardness, and the results demonstrate a significant increase in the hardness depending on the ion dose and decreases by increasing the applied load at 0° angular position.

Damage study of irradiated tungsten and copper using proton and argon ions of a plasma focus device

The destructive effects of proton and argon ions produced in a low energy plasma focus device on the surface of tungsten and copper were investigated. Optical microscopy, SEM, EDX, XRD and ERD analysis were performed for initial and irradiated samples. The results showed that total thermal impact under the irradiation by argon is much more significant than that by hydrogen. Sub-micrometer blisters, clusters of joined bubbles and rupture patterns were observed on the surface of copper after irradiation by argon. Micro-cracks were observed on the tungsten samples irradiated by argon, which indicate fast annealing of the molten surface. Many dense blisters and evidence of ion sputtering were observed on the surfaces irradiated by protons. Results of ERD analysis showed that the highest concentration of hydrogen is 24% in the second layer and at a depth of 20–55 nm from the tungsten surface. In the copper sample, the highest density of hydrogen was found to be 23% in the second layer and at a depth of 28–68 nm. Also, the highest penetration depth of protons into the tungsten and copper samples was 118 nm and 160 nm, respectively.

Growth and characterization of TiAlN nanoparticles using low-energy plasma focus device

In this experimental study, a 1.5-kJ plasma focus device of Mather type was employed to grow titanium aluminum nitride (TiAlN) coatings at room temperature on 316 stainless steel sub-layer. The anode of the device was made of Titanium and Aluminium. A mixture of N2 and Ar gases was used as the work gas for TiAlN deposition. TiAlN nanoparticles were formed on stainless steel with 0° of the degree with respect to the anode axis by different shots at 5 cm above the anode. X-ray diffraction results indicated the formation of the TiAlN structure on stainless steel. Scanning electron microscopy images demonstrated the approximately uniform growth of TiAlN nanoparticles on the surface. EDX analysis results showed that an increase in the number of the shots increased the deposition of TiAlN on the sub-layer. According to the atomic force microscopy images, the mean thickness of the surface increased as the shots increased in number. Microhardness test results of the thin layers showed that an increase in the number of the shots increased the hardness of the samples.

Characteristics of tungsten layer deposited on graphite substrate by a low energy plasma focus device at different angular position

Layers of tungsten were deposited on two types of graphite substrates at three different angular position by a low energy plasma focus device. First series of substrates included only raw graphite while carbon interlayers were used for the second type. Tungsten deposition process was carried out at 0°, 15°, and 30° angular location with respect to the device anode axis during 40 focus shots at optimum argon gas pressure. The characterization of the deposited tungsten coatings was verified by X-ray diffraction (XRD), scanning electron microscopy, energy-dispersive X-ray spectroscopy, Raman spectroscopy and Nanoindentation analyses. Tungsten-carbon structures such as WC1-X, W2C, WC, and W2(C, O) were detected by XRD analysis. Compounds such as WC1-X, W2C and W2(C, O) were identified on raw graphite substrate while WC1-X, WC, W2C were formed on the graphite substrates with carbon interlayer. For both types of samples positioned at 30 degrees with respect to device axis, the WC1-X phase, which is a high temperature structure with high melting point, was detected more than other tungsten-carbon structures. The coating of carbon interlayer on substrates changes surface morphologies and leads to homogenous deposition of tungsten layer on the surface. The increase in angular position of substrates led to creation of flat and smooth surfaces. Raman spectroscopy shows the presence of WO3 and amorphous carbon structures in both types of prepared samples. Nanoindentation analysis indicates that the hardness of samples increases after tungsten deposition process. The substrate angular position with respect to anode axis is an effective parameter in deposition process of tungsten layers.

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.

Enhancement of Mechanical and Structural Traits of Aluminum Using Low Energy Plasma Focus Device

AbstractOwing to good machinability, low weight and high specific strength, aluminum is widely used in aerospace and automotive industries. However, low mechanical strength limits its wide spread use in mainstream industries. In this study, nitriding of aluminum was performed with a stream of low energy ions in 1.8 kJ Mather type dense plasma focus (DPF) device. The axial distance from the anode tip was varied in steps to study the effect of the stream length on structural and mechanical properties of the nitrided samples. XRD and Raman analysis confirmed the formation of aluminum nitride (AlN) on the plasma exposed surface. Williamson‐Hall (W−H) study revealed significant improvement in crystallinity and strain of the nitride samples. The most favorable results on mechanical and structural properties of the nitrided samples were obtained at an axial distance of 10 cm. The improved texture and maximum dislocation density for typical AlN (311) is obtained at the optimum distance. The micro‐hardness of the nitrided samples was measured ∼4.5 times higher than the base material.

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.

Fabrication, characterization and hydrogen gas sensing performance of nanostructured V2O5 thin films prepared by plasma focus method

Nanocrystalline V2O5 thin films were deposited on glass substrates at room temperature using a low energy (1.3 kJ) plasma focus device. The argon:oxygen gas mixture (in 7:3 ratio) was utilized as a working gas and metallic vanadium was used as the anode tip material. The V2O5 thin films were synthesized with different number of shots (10, 20 and 30 shots), at 0° angular position with respect to the anode axis and at same axial position from the tip of anode (10 cm). The structural properties and phase composition of the thin films were studied by means of X-ray diffraction (XRD) and Raman scattering analysis. The results obtained from scanning electron microscopy (SEM), and atomic force microscopy (AFM) analyzes revealed that the size of nanoparticles/agglomerates and surface roughness of V2O5 thin films strongly depend on number of shots. The variation in the gas response of the V2O5 thin films for 1000 ppm concentration of hydrogen gas at different operating temperatures (150–350 °C) revealed an optimal operating temperature of 275 °C. Moreover, among all the V2O5 thin films studied, the sample deposited with ten shots showed the maximum gas response to various H2 concentrations at optimal operating temperature.