kJ Mather-type Plasma Focus Research Articles

Experimental investigation and simulation of penetration depth of nitrogen ions emitted by plasma focus device inside titanium samples

The plasma focus device is a simple, inexpensive, and precious device that can be considered as a source of high-energy ions for researches relevant to interactions of ions with widely used materials such as titanium. Regarding exclusive properties such as a high degree of hardness and resistance to corrosion, titanium nitride alloy is considered to be one of the most essential materials with a wide range of industrial applications. In the present study, the characteristics of titanium nitride alloys were studied using a 1.5 kJ Mather-type plasma focus device. To do this, a Faraday cup detector is used to measure the current density of the ion beam in order to determine the energy spectrum of nitrogen ions using time of flight approach. The optimal operational condition of the device for nitrogen ions emission, in terms of gas pressure and voltage of discharge were also determined. Titanium samples were situated on the top of the anode of the device and were exposed to nitrogen ion radiation considering 5, 10, and 20 shots of the device. To simulate the penetration depth of nitrogen ions inside the titanium samples, the SRIM code is used. The obtained energy of ions from the time of flight technique was set as input of the SRIM code, and it was found that nitrogen ions, with an average energy of 50 keV can penetrate about 110 nm inside the titanium sample. It was understood that the finding results of the penetration depth are in good agreement with the SEM micrographs of the titanium samples. The sputtering yield of titanium atoms was determined using the SRIM simulation code, and it was found that the yield of the surface of the samples is less than 0.2 atoms per individual nitrogen atom.

Hard X-ray dosimetry of a plasma focus suitable for industrial radiography

Dosimetric measurements of the hard X-ray emission by a small-chamber 4.7kJ Mather-type plasma focus device capable of producing neat radiographs of metallic objects, were carried out with a set of thermoluminescent detectors TLD 700 (LiF:Mg,Ti). Measurements of the hard X-ray dose dependence with the angular position relative to the electrodes axis, are presented. The source-detector distance was changed in the range from 50 to 100cm, and the angular positions were explored between ± 70°, relative to the symmetry axis of the electrodes. On-axis measurements show that the X-ray intensity is uniform within a half aperture angle of 6°, in which the source delivers an average dose of (1.5 ± 0.1)mGy/sr per shot. Monte Carlo calculations suggest that the energy of the electron beam responsible for the X-ray emission ranges 100–600keV.

Time-to-Pinch Investigation of 5 kJ Mather-Type Plasma Focus Device

The Egyptian Atomic Energy Authority-Plasma focus (EAEA-PF2) has been upgraded to a 5 kJ plasma focus device. Its characteristics have been investigated at various pressures and different voltages in a 5 kJ Mather-type plasma focus device for Ar gas. Its time-to-pinch has been measured, simulated and analyzed at different operating conditions. It is observed from the results that, the time-to-pinch decreased when either the charging voltage increased or the gas pressure decreased. In addition, the time-to-pinch is estimated theoretically using Lee model RADPF5.15. A comparison between the experimental and theoretical time-to-pinch is discussed. Also, the drive factor of plasma focus is analyzed at different pressures and charging voltages. It is noticed that, the mass and current factors are affected by changing the pressure and voltage. Finally, it is observed that, the drive factor is proportional inversely to the pressure and directly to the charging voltage.

Characteristics of X-ray Hot Spots in a 3.5 kJ Plasma Focus Device at Different Pressures of Argon and Air

The present study examined the formation of hot spots in the plasma column of a 3.5 kJ Mather-type plasma focus device. Experiments were performed with air and argon as operating gases at 0.2–1.5 mbar of pressures. X-ray source images were obtained using a pinhole camera with dental X-ray film as X-ray detector. The objective was to investigate the effect of the operating conditions and gas type on formation and characteristics of the hot spots. Results showed that when using air in comparison to argon, the total X-ray emission is increased and therefore, the hot spots are covered by this high intensity emission and would be observed less frequently in the image. Using metal filters to attenuate the low-energy X-rays revealed that the most energetic or the most intense radiation was emitted from the hot spots region. The images of the X-ray source obtained using argon at the middle pressures (0.4–0.6 mbar) showed both the plasma column and the photons emitted from the anode surface. A pressure of 0.8–1.5 mbar using argon was most likely to observe the hot spots. For argon gas, the 0.9 mbar was the pressure in which the hot spots were more frequently observed with high reproducibility of location and number. Measurements revealed that the typical size of a hot spot was 10–300 µm and the distance from the anode surface was 0.5–20 mm.

Studying Soft X-Rays Emitted by SUT-PF Using a Cylindrical Bent Crystal Spectrometer

Plasma focus is a copious source of electrons, ions, neutrons, and X-rays. SUT-PF is a 7 kJ Mather type plasma focus device. In order to study soft X-rays emitted by this device a bent crystal spectrometer has been designed and constructed based on Johann method. Before recording spectral lines, using a photodiode detector and a pinhole camera, optimum parameters for maximum emission of soft X-rays have been studied and registered. Results show that ionized Argon atomic lines mostly have wavelengths between 3 and 4 A. Among them 1s2–1s2p transition with a wavelength of 3.943 A represents the most intense line.

Argon ion beam interaction on polyethylene terephthalate surface by a 4 kJ plasma focus device

Polyethylene terephthalate (PET) has a wide variety of applications ranging from making regular bottles to biosensors. However, for many of these applications, surface treatment is needed to improve its surface characteristics such as adhesion to other materials. In this study, we focussed on treating PET foils by dense Ar pulsed plasma produced by a 4.5 kJ Mather-type plasma focus device (20 kV, 40 µf, 115 nH) to examine its ability to make the PET surface hydrophilic. The most common method to examine this characteristic is measuring the water contact angle on a polymer surface. The results show that while the energy and density of plasma in our device are higher compared to other devices, as the exposure time is very low, the device can enhance the wettability of PET film surfaces.

Preliminary Results of 1.5 kJ Mather-Type Plasma Focus with Stainless Steel Anode

A new low energy (1.5 kJ) Mather-type dense plasma focus, called Sahand University of Technology Dense Plasma Focus (SUT-DPF) device has been designed, constructed and operated. The paper reports on the preliminary results with argon as filling gas. A Rogowski coil has been used to measure the experimental discharge current. The current signal contains a set of data from physical processes in the device as well as discharge current characteristics. The device circuit parameters were calculated using the short-circuit test. In a typical discharge experiment, these values were obtained: the discharge period was 15.4 ± 0.1 μs, the discharge current 100.8 ± 0.7 kA, the total inductance of the device 197 ± 3 nH and electrical resistance of circuit 11.3 ± 1 mΩ. The Rogowski coil sensitivity was obtained 49.65 ± 0.3 kA/V. A resistive voltage divider was also used to measure the transient voltage across the plasma. The experimental results showed that the pinch time at a constant pressure of the argon gas, decreased by increasing the charging voltage. The optimum pressure for 5, 6.5 and 7.5 kV obtained 0.75, 1 and 1.5 mbar, respectively.

Deposition of AlN on Nimonic 75 by PFD device

In this study, thin films of aluminium nitride (AlN) are deposited on Nimonic 75 substrates using a 4 kJ Mather type plasma focus device (PFD) for 5, 10 and 15 focus shots. For the deposition of AlN films, a solid aluminium fitted anode was used instead of a copper anode. The PFD was operated with nitrogen gas at a pressure of 2 torr. X-ray diffraction results reveal the formation of a nanocrystalline AlN coating on the surface of the substrate. The crystallite size is dependent on the number of focus shots. The density of grains increased with an increase in the number of focus deposition shots, as illustrated by field emission scanning electron microscopy (FESEM). The FESEM images confirm the distribution of spherical grains for 15 focus shots. Energy dispersive X-ray spectroscopy spectra indicate the presence of expected constituent elements such as N and Al.

MCNP Dose Analysis for the Iranian Plasma Focus Neutron Source

The equivalent and effective doses from the first Iranian 115 kJ Mather type Plasma Focus machine (IR-MPF-100) have been calculated for the analytical ORNL modified adult phantom in 12 body organs using MCNP4C Monte Carlo code. The largest doses are related to spleen in PA other than lungs, and testes in AP orientation. The largest values in RLAT and LLAT orientations are related to right and left lung, respectively. AP orientation appears with the largest effective doses stemming from the contribution due to exposure of the testes. It is demonstrated that the effective dose due to neutrons for people working with the PF is well within the relevant dose limits. Differences of approximately 10 % are observed in the obtained results for the effective dose between a bare source of neutrons and the realistic situation in which electrodes, chamber wall and concrete floor are included in the MCNP simulation.

Three Dimensional Angular Distributions of X‐Rays in a 4 kJ Plasma Focus Device for Different Anode Tips Using TLD‐100 Dosimeters

AbstractTime and energy integrated measurements of the 3‐D angular distribution of X‐rays emission within the chamber of a 4 kJ Mather‐type plasma focus is investigated employing four different anode shapes and using nitrogen as the filling gas by the TLD‐100 thermoluminescence dosimeters. The distributions of X‐ray radiation in the energy range of 5 keV to several hundred keV were bimodal for all of the anode tips, peaked approximately at ±15°. The intensity of X‐rays decreased abruptly along the central axis of the device where the quasi cylindrical plasma pinch was formed. High intensity of X‐ray was observed in the case of a tapered ?at‐end anode, whereas less was obtained with the cylindrical hollow‐end anode. The maximum nitrogen X‐rays were for the tapered flat‐end anode at 4.5 mbar and 13 kV. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Estimation of electron temperature and radiation emission of a low energy (2.2 kJ) plasma focus device

Radiation emission in a 2.2 kJ Mather-type plasma focus device is investigated using a five channel BPX65 PIN diode spectrometer. At optimum condition, radiation emission from the system is found to be strongly influenced in hollow anode and filling gas pressure. Maximum X-ray yield in 4p sr has been obtained in case of hollow anode in argon gas medium due to interaction of electron beam. Results indicate that an appropriate design of anode can enhance radiation emission by more intense interaction of expected electron beam with hollow anode. The outcome is helpful to design a plasma focus with enhanced X-ray generation with improved shot-to-shot reproducibility in plasma focus device.

Preliminary Results of the 115 kJ Dense Plasma Focus Device IR-MPF-100

This work summarizes the design and construction of the first Iranian 115 kJ Mather type plasma focus (PF) machine (IR-MPF-100). This machine consists of a 6.25 cm radius and 22 cm height brass made anode with a 50 mm height insulator which separates the anode and cathode electrodes. Twelve copper made 22 cm height rods play the role of cathode with 10.2 cm radius. Twenty four 6 μF capacitors were used with the maximum charging voltage of 40 kV (maximum energy of 115 kJ) as the capacitor bank and maximum theoretical current around 1.224 MA. The total inductance of the system is 120 nH. By using NE-102 plastic Scintillator, Rogowski coil, current and voltage probes, hard X-ray, current derivative, current and voltage signals of IR-MPF-100 were measured. The primary result of neutron detection by neutron activation counter represents approximately 109 neutrons per shot at 65 kJ discharge energy while using deuterium filling gas. Also IR-MPF-100 PF has been tested successfully at 90 kJ by using the argon gas.

Deuteron Beam Source Based on Mather Type Plasma Focus

A 3 kJ Mather type plasma focus system filled with deuterium gas is operated at pressure lower than 1 mbar. Operating the plasma focus in a low pressure regime gives a consistent ion beam which can make the plasma focus a reliable ion beam source. In our case, this makes a good deuteron beam source, which can be utilized for neutron generation by coupling a suitable target. This paper reports ion beam measurements obtained at the filling pressure of 0.05–0.5 mbar. Deuteron beam energy is measured by time of flight technique using three biased ion collectors. The ion beam energy variation with the filling pressure is investigated. Deuteron beam of up to 170 keV are obtained with the strongest deuteron beam measured at 0.1 mbar, with an average energy of 80 keV. The total number of deuterons per shot is in the order of 1018 cm−2.

Improvement of corrosion and electrical conductivity of 316L stainless steel as bipolar plate by TiN nanoparticle implantation using plasma focus

The present work reports the results of TiN-ions implantation into the SS316L samples as bipolar plates by a 4 kJ Mather type Plasma Focus (PF) device operated with nitrogen gas for 10, 20, and 30 shots in order to improve the corrosion resistance and electrical conductivity of samples. The PF can generate short lived (10–100 ns) but high temperature (0.1–2.0 keV) and high density (1018–1020 cm−3) plasma, and the whole process of PF lasts just a few microseconds. X-ray diffraction (XRD) results reveal the formation of a nanocrystalline titanium nitride coating on the surface of substrate. The interfacial contact resistance (ICR) of samples is measured, and the results show that the conductivity of samples increase after coating because of high electrical conductivity of TiN coating. The electrochemical results show that the corrosion resistances are significantly improved when TiN films are deposited into SS316L substrate. The corrosion potential of the TiN coated samples increases compared with that of the bare SSI316L and corrosion currents decrease in TiN implanted samples. Scanning Electron Microscopy (SEM) indicates changes in surface morphology before and after potentiostatic test. The thickness of coated layer which is obtained by cross sectional SEM is about 19 μm.

Preparation of Titanium Carbide Thin Film Using Plasma Focus Device

In this work, we report titanium carbide (TiC) formation on the stainless steel—304 substrates by using a low energy (2 kJ) Mather-type plasma focus (PF) device. The argon–acetylene admixture (in 3:1 ratio) was used as the filling gas at a pressure of 1 torr. The thin films were deposited with different number of focus deposition shots (5, 15 and 25 shots), at 0° angular position with respect to the anode axis and at constant distance from the anode tip (10 cm). Deposited thin films have been investigated for their structure by X-Ray diffractometry (XRD) and surface morphology by scanning electron microscopy (SEM) and atomic force microscopy (AFM) analysis. The average size of crystallites (from XRD), crystalline growth of structures (from SEM), and size of grains and surface roughness (from AFM) were investigated, which increase by increasing the number of focus deposition shots.

Deposition of tungsten nitride on stainless steel substrates using plasma focus device

Tungsten nitride (WN) films were deposited on the stainless steel-304 substrate by a 2 kJ Mather-type plasma focus device. The preparation method and characterization data are presented. X-ray diffractometer (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM) were employed for the characterization of the samples obtained with different number of focus shots, respectively. The average size of crystallites (from XRD), sub-micro-structures (from SEM) and particles (from AFM images) increase when the number of shots increase from 10 to 20 then 30, then they decrease when the substrate is exposed to 40 shots.

Structural and Morphological Investigations of Deposited Tungsten Nitride Thin Films Using Plasma Focus Device

Tungsten nitride thin films were deposited on the stainless steel-304 substrates by a 2 kJ Mather-type plasma focus device. The preparation method and characterization data are presented. The average size of crystallites, sub-micro structures and size of grains were characterized by X-ray diffractometer (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM) respectively, which increases by increasing the number of focus shots from 10 to 20 then 30 shots.

Effect of insulator sleeve material on the x-ray emission from a plasma focus device

The effect of insulator sleeve material on x-ray emission from a 2.3 kJ Mather type plasma focus device operated in argon-hydrogen mixture is investigated. The time and space resolved x-ray emission characteristics are studied by using a three channel p-i-n diode x-ray spectrometer and a multipinhole camera. The x-ray emission depends on the volumetric ratio of argon-hydrogen mixture as well as the filling pressure and the highest x-ray emission is observed for a volumetric ratio 40% Ar to 60% H2 at 2.5 mbar filling pressure. The fused silica insulator sleeve produces the highest x-ray emission whereas nonceramic insulator sleeves such as nylon, Perspex, or Teflon does not produce focus or x-rays. The pinhole images of the x-ray emitting zones reveal that the contribution of the Cu Kα line is weak and plasma x-rays are intense. The highest plasma electron temperature is estimated to be 3.3 and 3.6 keV for Pyrex glass and fused silica insulator sleeves, respectively. It is speculated that the higher surface resistivity of fused silica is responsible for enhanced x-ray emission and plasma electron temperature.

Radiation Emission Correlated with the Evolution of Current Sheath from a Deuterium Plasma Focus

The time resolved emission of neutrons and X-rays (both soft and hard) is correlated with the current sheath evolution during the radial phase of a 3.2 kJ Mather-type plasma focus device operated in deuterium at an optimised pressure of 4 mbar. A three-frame computer-controlled laser shadowgraphy system was incorporated in the experiment to investigate the time evolution of the radial phase of the plasma focus. The dynamics of the sheath was then correlated with the time resolved X-rays and neutron emission. The time-resolved neuron and hard X-ray emission was detected by a Scintillator-photomultiplier system while the time resolved soft X-rays were detected employing filtered PIN photo diodes. The observations were recorded with a temporal accuracy of a few ns. For the reference, the total neutron yield was also monitored by an Indium Foil activation detector. The correlation with the High Voltage Probe signal of the discharge, together with the X-ray and neutron emission regimes enabled to identify the important periods of the sheath evolution i.e. the radial compression (pre focus), minimum pinch radius (focus) and the post focus phenomena. During the initial stage of the radial phase, velocities of 10–23 cm/μs, while at the later stage of the radial phase (up till the compression), velocities up to 32–42 cm/μs were measured in our experiment. For the discharges with the lower neutron yield (lower than the average value ~1 × 108 n/discharge), the current sheath appears to be disturbed and neutron and hard X-ray signal profiles do not carry much information whereas the soft X-ray emission is significant. For the discharges with high neutron yield (higher than the average value), the current sheath has a smooth structure until the maximum compression occurs. Hard X-ray emission is maximum for the discharges with high neutron yield, especially whenever there is development of m = 0 instability compressing the column to very high densities. The neutron are emitted long after the maximum compression supporting the beam target fusion. For the discharges with High neutron yield, the soft X-ray production is less as compared to the discharges with low neutron yield.

Soft X-ray emission from preionized He plasma in a 3.3 kJ Mather type plasma focus device

Soft X-ray emission from He plasma in a 3.3 kJ plasma focus system is investigated without and with preionization by α particles. Silicon PIN diodes and a multi-pinhole camera with absorption filters are employed for time-resolved and time-integrated X-ray analyzes, respectively. X-ray emission in 4π geometry is measured as a function of He gas filling pressures. The highest soft X-ray yield, of 0.25±0.01 J, is obtained at a filling pressure of 125 Pa without preionization, which increases to 0.50±0.02 J with preionization at a filling pressure of 150 Pa. The total X-ray yield without preionization, 1.50±0.07 J, is observed at a filling pressure of 125 Pa and this is enhanced to 2.44±0.11 J with preionization at a filling pressure of 150 Pa. The preionization makes the focus filament symmetric and enhances its volume.