Mather-type Plasma Focus Research Articles

EFFECT OF INNER ELECTRODE LENGTH OF 2.2 KJ MATHER TYPE PLASMA FOCUS ON FOCUS ACTION

This paper presents results of experimental studies carried out with a Mather type plasma focus device of 2.2 kJ energy. A critical effect of plasma focus inner electrode, IE length on the plasma focus action is detected for IE length has been changed to 9.5, 10.5 and 11.5 cm respectively; also for different Argon gas pressure ranging from 0.2 to 1.8 Torr. To verify this effect, it is important to investigate the plasma focus characteristics such as, a focusing time, voltage spike amplitude, focus action intensity, focus duration time, plasma focus inductance, and radius of plasma focus column as well as pinching ratio.The diagnostics used in the experiments include a Rogowski coil and resistive high voltage probe to measure the discharge current and voltage signals respectively. All the results illustrated that, the best focus action has been achieved for IE length of 10.5 cm and at filling Argon gas pressures varied from 0.8 to 1.2 Torr.

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.

Introduction to Numerical Experiment on Plasma Focus using Lee Model Code

A dense plasma focus is table top machine producing short-lived very hot plasma and can cause nuclear fusion. Lee Model Code is a computer simulation package, which was successfully used in Mather and Fillipov type plasma focus. Lee Model couples the electrical circuit with the plasma focus dynamics, radiation and thermodynamics to simplify the complicated dynamics of plasma focus. This package enables us to simulate and analyze all of the gross properties. In this paper we present the importance of current fitting and the relation of it with other plasma focus parameter and overview of Lee Model Code together with physical basis, scope and the results obtained from the Lee Model Code. The Himalayan Physics Year 5, Vol. 5, Kartik 2071 (Nov 2014)Page: 137-141

Synthesis of nano-structure tungsten nitride thin films on silicon using Mather-type plasma focus

Nano-structure thin film of tungsten nitride was deposited onto Si-substrate at room temperature using Mather-type plasma focus (3.3 kJ) machine. Substrate was exposed against 10, 20, 30, and 40 deposition shots and its corresponding effect on structure, morphology, conductivity and nano-hardness has been systematically studied. The X-ray diffractormeter spectra of the exposed samples show the presence of various phases of WN and WN2 that depends on number of deposition shots. Surface morphological study revealed the uniform distribution of nano-sized grains on deposited film surface. Hardness and conductivity of exposed substrate improved with higher deposition shots. X-ray photo-electron spectroscopy survey scan of 40 deposition shots confirmed the elemental presence of W and N on Si-substrate.

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.

A study of structural and mechanical properties of nano-crystalline tungsten nitride film synthesis by plasma focus

Nano-crystalline tungsten nitride thin films are synthesized on AISI-304 steel at room temperature using Mather-type plasma focus system. The surface properties of the exposed substrate against different deposition shots are examined for crystal structure, surface morphology and mechanical properties using X-ray diffraction (XRD), atomic force microscope, field emission scanning electron microscope and nano-indenter. The XRD results show the growth of WN and WN2 phases and the development of strain/stress in the deposited films by varying the number of deposition shots. Morphology of deposited films shows the significant change in the surface structure with different ion energy doses (number of deposition shots). Due to the effect of different ion energy doses, the strain/stress developed in the deposited film leads to an improvement of hardness of deposited films.

Numerical Experiments to Obtain the Scaling Laws for Neutron Yield on Mather-Type Plasma Focus Machines Below 500 Joules

Numerical Experiments to Obtain the Scaling Laws for Neutron Yield on Mather-Type Plasma Focus Machines Below 500 Joules

Determination of Ion Beam Properties In Nitrogen and Helium Using Mather Type Plasma Focus Device

Some of ion beam properties have been investigated by using Lee model code on plasma focus devices which is operated with nitrogen and helium gases. The operation of plasma focus in different pressure regime gives a consistent ion beam properties which can make the plasma focus a reliable ion beam source .These ion beam properties such as ion beam flux, ion beam fluence, ion beam energy, ion beam current, and beam ion number corresponding to gas pressure have been studied for Mather type plasma focus device. The result shows the differences between helium as lighter gas and nitrogen as heavier gas in term of ion beam properties. The fluence and flux are decrease for nitrogen while increase for helium.

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.

English

A Mather-type plasma focus device is used in this work which is prefilled with helium at 0.8 Torr. The total ion current density of the plasma stream is measured to be 750 mA/cm2. From time-resolved measurements (Faraday cup), the ion beam energy was distributed with energy ranging from 0.3 to 540 keV. The ion flux density of ion beam is estimated to be 4.47 × 1011 ion/steradian using track etching technique (LR-115A). Key words: Energetic ions, plasma focus, charging voltage.

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)

Global parameter optimization of a Mather-type plasma focus in the framework of the Gratton–Vargas two-dimensional snowplow model

Dense plasma focus (DPF) is known to produce highly energetic ions, electrons and plasma environment which can be used for breeding short-lived isotopes, plasma nanotechnology and other material processing applications. Commercial utilization of DPF in such areas would need a design tool that can be deployed in an automatic search for the best possible device configuration for a given application. The recently revisited (Auluck 2013 Phys. Plasmas 20 112501) Gratton–Vargas (GV) two-dimensional analytical snowplow model of plasma focus provides a numerical formula for dynamic inductance of a Mather-type plasma focus fitted to thousands of automated computations, which enables the construction of such a design tool. This inductance formula is utilized in the present work to explore global optimization, based on first-principles optimality criteria, in a four-dimensional parameter-subspace of the zero-resistance GV model. The optimization process is shown to reproduce the empirically observed constancy of the drive parameter over eight decades in capacitor bank energy. The optimized geometry of plasma focus normalized to the anode radius is shown to be independent of voltage, while the optimized anode radius is shown to be related to capacitor bank inductance.

Deposition of magnesium nitride thin films on stainless steel-304 substrates by using a plasma focus device

In this research, for the first time, we synthesize magnesium nitride thin films on 304-type stainless steel substrates using a Mather-type (2 kJ) plasma focus (PF) device. The films of magnesium nitride are coated with different number of focus shots (like 15, 25 and 35) at a distance of 8 cm from the anode tip and at 0° angular position with respect to the anode axis. For investigation of the structural properties and surface morphology of magnesium nitride films, we utilized the X-ray diffractometer (XRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM) analysis, respectively. Also, the elemental composition is characterized by energy-dispersive X-ray (EDX) analysis. Furthermore, Vicker’s microhardness is used to study the mechanical properties of the deposited films. The results show that the degree of crystallinity of deposited thin films (from XRD), the average size of particles and surface roughness (from AFM), crystalline growth of structures (from SEM) and the hardness values of the films depend on the number of focus shots. The EDX analysis demonstrates the existence of the elemental composition of magnesium in the deposited samples.

Comparison the Results of Numerical Simulation And Experimental Results for Amirkabir Plasma Focus Facility

In this paper the results of the numerical simulation for Amirkabir Mather-type Plasma Focus Facility (16 kV, 36μF and 115 nH) in several experiments with Argon as working gas at different working conditions (different discharge voltages and gas pressures) have been presented and compared with the experimental results. Two different models have been used for simulation: five-phase model of Lee and lumped parameter model of Gonzalez. It is seen that the results (optimum pressures and current signals) of the Lee model at different working conditions show better agreement than lumped parameter model with experimental values.

Investigation of the ion beam emission from a pulsed power plasma device

Plasma Focus (PF) devices are well known as ion beam sources with characteristic energy among the hundreds of keV to tens of MeV. The information on ion beam energy, ion distribution and composition is essential from the viewpoint of understanding fundamental physics behind their production and acceleration and also their applications in various fields, such as surface properties modification, ion implantation, thin film deposition, semiconductor doping and ion assisted coating. An investigation from a low energy, 1.8 kJ 160 kA, Mather type plasma focus device operating with nitrogen using CR-39 detectors was conducted to study the emission of ions at different angular positions. Tracks on CR-39 detectors at different angular positions reveal the existence of angular ion anisotropy. The results obtained are comparable with the time integrated measurements using FC. Preliminary results of this work are presented.

Energy spectrum of multi-radiation of X-rays in a low energy Mather-type plasma focus device

The multi-radiation of X-rays was investigated with special attention to their energy spectrum in a Mather-type plasma focus device (operated with argon gas). The analysis is based on the effect of anomalous resistances. To study the energy spectrum, a four-channel diode X-ray spectrometer was used along with a special set of filters. The filters were suitable for detection of medium range X-rays as well as hard X-rays with energy exceeding 30 keV. The results indicate that the anomalous resistivity effect during the post pinch phase may cause multi-radiation of X-rays with a total duration of 300 ± 50 ns. The significant contribution of Cu—Kα was due to the medium range X-rays, nonetheless, hard X-rays with energies greater than 15 keV also participate in the process. The total emitted X-ray energy in the forms of Cu—Kα and Cu—Kβ was around 0.14 ± 0.02 (J/Sr) and 0.04 ± 0.01 (J/Sr), respectively. The total energy of the emitted hard X-ray (> 15 keV) was around 0.12 ± 0.02 (J/Sr).

Plasma Focus Radiative Model: Review of the Lee Model Code

The code couples the electrical circuit with plasma focus (PF) dynamics, thermodynamics and radiation. It is energy-, charge- and mass-consistent and accounts for the effects of transit times of small disturbances and plasma self-absorption. It has been used in design and interpretation of Mather-type PF experiments and as a complementary facility to provide diagnostic reference numbers in all gases. Information computed includes axial and radial dynamics, SXR emission characteristics and yield for various applications including microelectronics lithography and optimization of machines. Plasma focus neutron yield calculations, current and neutron yield limitations, deterioration of neutron scaling (neutron saturation), radiative collapse, speed-enhanced PF, current-stepped PF and extraction of diagnostic and anomalous resistance data from current signals have been studied using the code; which also produces reference numbers for fluence, flux and energy of deuteron beams and ion beams for all gases. There has been no pause in its continuous evolution in three decades so much so that the model code has no formal source reference except www.plasmafocus.net. This review presents, for the first time a comprehensive up-to-date version of the 5-phase model code. The equations of each phase are derived. Those of the first two phases are normalized to reveal important scaling parameters. The focus pinch phase is discussed with radiation-coupled dynamics necessitating the computation of radiation terms moderated by plasma self-absorption. Neutron and ion beam yields are computed. The 5-phase model code appears to be adequate for all Mather-type PF, lacking only in one aspect that for high inductance PF (termed Type 2) the measured current waveform contains an extended dip which cannot be fitted by the 5-phase code; necessitating an extended 6-phase code. This sixth phase (termed phase 4a) is dominated by anomalous resistance, providing a way to extract valuable data on anomalous resistivity from the current trace.

Synthesis of composite TiN/Ni3N/a-Si3N4 thin films using the plasma focus device

Composite films of TiN/Ni3N/a-Si3N4 were synthesized using the Mather-type plasma focus device with varying numbers of focus deposition shots (5, 15, and 25) at 0° and 10° angular positions. The composition and structural analysis of these films were analyzed by using Rutherford backscattering (RBS) and X-ray diffraction (XRD). Scanning electron microscope and atomic force microscope were used to study the surface morphology of films. XRD patterns confirm the formation of composite TiN/Ni3N/a-Si3N4 films. The crystallite size of TiN (200) plane is 11 and 22 nm, respectively, at 0° and 10° angular positions for same 25 focus deposition shots. Impurity levels and thickness were measured using RBS. Scanning electron microscopy results show the formation of net-like structures for multiple focus shots (5, 15, and 25) at angular positions of 0° and 10°. The average surface roughness of the deposited films increases with increasing focus shots. The roughness of the film decreases at higher angle 10° and the films obtained are smoother as compared with the films deposited at 0° angular positions.

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.