میرمحمدرضا سیدحبشی

In studying the interaction of hydrogen ions emitted from a plasma focus device with selected materials for the first wall of a tokamak, characterizing the ion beam is crucial. For this purpose, a Faraday-cup detector was designed and built for the MTPF plasma focus device, and its electrical parameters were extracted. The signals obtained from the Faraday-cup exhibited two peaks: the first peak corresponds to radiation impact, and the second peak is due to the impact of the hydrogen ion beam on the graphite electrode of the Faraday-cup. Using the time-of-flight (TOF) method, the average energy of the hydrogen ion beam was determined to be 46 keV. The flux parameters of the beam at the aperture of the Faraday-cup were 2.37×10^24 ions.m^-2.s^-1 and 1.45×10^16 ions.m^-2, respectively. The specifications of the MTPF plasma focus device were incorporated into the Lee model code, and the resulting ion beam specifications from the code showed good agreement with the experimental results obtained from the Faraday-cup signal. Additionally, other characteristics of the hydrogen ion beam were extracted.

In this study, the effects of high-energy hydrogen ion irradiation, generated by the MTPF-2 type modern plasma focus device, on the surface and structural properties of graphite were investigated. High-energy protons produced by the plasma focus device were used to irradiate graphite samples in various shots. The radiation-induced changes on the graphite surface were examined using optical microscope and scanning electron microscopy. The modifications on the irradiated samples' surface were clearly observed in the scanning electron microscopyand optical microscope images. The microscopic images of the irradiated samples revealed point sputtering as well as pores on the sample surface, along with point melting, which are dependent on the ion fluence (number of shots). X-ray diffraction analysis was employed to study the structural changes in the graphite caused by the high-energy proton irradiation. The X-ray diffraction spectra of the irradiated samples showed shifts in the peak positions, changes in the peak intensities, and an increase in the crystallite size compared to the X-ray diffractionspectra of the reference sample. Additionally, a Faraday cup detector was used to characterize the hydrogen ion spectrum produced in the plasma focus device. The results indicated that the average energy of the generated ions was ~ 46 keV.

In this research, the effects of high-energy proton bombardment produced by the plasma focus device on the surface morphology and structural parameters of tungsten and molybdenum were investigated. Tungsten and molybdenum samples, placed at a distance of 6 cm from the anode head, were irradiated with hydrogen ions in 20 discharges. The samples were examined before and after irradiation using a scanning electron microscope (SEM). The SEM results revealed the formation of blisters, cracks, and surface melting on both tungsten and molybdenum samples due to the high-energy proton irradiation. To characterize the ion beam of the plasma focus device, Lee's code was employed. The results from Lee's code indicated that approximately 7.9 × 1014 ions are emitted from the plasma column in each discharge. Additionally, the SRIM code was utilized to calculate the damage created in tungsten and molybdenum, as well as the hydrogen density at various depths within the materials. According to the SRIM code results, the maximum value of displacements per atom (dpa) per shot for tungsten and molybdenum samples irradiated with hydrogen ions was estimated to be 0.025 and 0.014, respectively, at depths of 150 nm and 250 nm. Moreover, the maximum concentration of hydrogen ions in the irradiated samples of tungsten and molybdenum at depths of 150 nm and 250 nm was found to be 0.4% and 0.035%, respectively.

In this research, the effect of nitrogen ion radiation on the surface properties and structure of titanium metal was investigated. For this purpose, titanium samples were subjected to 2.7 kJ focal plasma device with nitrogen ions emitted from it in 5, 10 and 20 shots of the plasma device. The focus was irradiated. SEM, EDX and XRD analyzes were taken from titanium samples before and after irradiation. The results of SEM show that with the irradiation of ions on the surface of titanium, rough blisters are created on the surface of the specimens; the density and size of these blisters increase with the number of shots. Also, on the surface of the irradiated samples, sputtered areas were observed, owing to the increase in the temperature of the titanium surface by the impact of high-energy nitrogen ions. The X-ray diffraction results showed that with the irradiation of nitrogen ions onto titanium, the diffraction pattern has undergone changes in the peak locations; the peaks shifted to smaller angles, due to the stress and strains created in the surface layers as a result of high heat transfer to titanium during the irradiation of nitrogen ions. In addition, the irradiation of nitrogen ions on titanium caused a decrease in the height of the peaks. The results obtained from EDX also revealed that by irradiating nitrogen ions on the titanium, a small amount of copper has been deposited on the titanium surface due to evaporation from the anode head of the focal plasma device.

The main features of damages that occurred on surface morphology as well as the structural parameters of Cu and Mo materials when irradiated to high-energy protons produced in the dense plasma focus device was investigated. The samples placed 6 cm from the anode head were irradiated in 20 shots with hydrogen ions. The samples examined with Scanning Electron Microscopy (SEM) before and after irradiation. SEM results showed that the radiation of high-energy protons on the surface of Mo and Cu has caused blisters, cracks, and melts on the surface of the specimens. X-ray diffraction analysis used to investigate changes in the structure of the specimens due to the radiation of high-energy protons. The Lee code was used to characterize the ionic beam of the plasma focus device. The results showed that 7.9 x 1014 ions are emitted from the plasma column in each shot. The SRIM code used to calculate the damage created in Mo and Cu, as well as the concentration of hydrogen at different depths of them. The results of SRIM revealed that the maximum of displacement per atom (DPA) for Mo and Cu samples irradiated with hydrogen ions at depths of 500 and 580 nm was estimated to be 0.024 and 0.009 dpa per shot, respectively. The maximum concentrations of hydrogen ions in the irradiated samples at depths of 550 nm, and 750 nm are 0.5%, and 0.11%, respectively.

Due to the importance of Teflon in the military industries, especially the missile and aerospace industries, the study of the effect of different nuclear radiation on the physical properties of this polymer can greatly assist the fabrication and engineering process of the components used in its manufacture. In this study, Teflon tape was cut into six bands, and then five bands were irradiated with different absorbed doses of gamma radiation up to 12 kGy. Moreover, the tensile test to evaluate the mechanical properties, and the FTIR spectra to investigate the changes in the structural properties, were obtained from Teflon samples. Through the structural studies, variations such as the formation of double bond in the structure of irradiated Teflon strips were observed. Also, the reduction of the stress and the strain values ​​at the final strength and rupture point were observed by studying the mechanical parameters of the Teflon strips. It was concluded that in the irradiated Teflon strip structure, double bonds are formed which is a sign of major chain failure. Furthermore, no improvement in mechanical properties was observed.

Damage of tungsten due to helium and argon ions of a PF device was studied. Tungsten samples were irradiated by 20 shots of the plasma focus device with argon and helium as working gases, separately. The tungsten surface was analyzed by SEM, before and after irradiation. SEM revealed dense blisters with diameters of a few hundred nanometers, on the samples which were irradiated by helium ions, while on the samples irradiated by argon, cracks were developed on the surface. XRD analysis was used for crystallography of tungsten, before and after irradiation. Irradiation by helium and argon affects peak location, peak intensity, FWHM, and spacing of planes, which shows that the crystalline structure of tungsten is affected by irradiation.Characteristics of ion beam of the plasma focus device were calculated by the Lee code. The depth profiles of dpa/shot and ion concentration were calculated using the SRIM code. Using the Lee code, the average fluencies of helium and argon ion beams of the PF device were calculated about 7.9×1014 cm-2 and 0.25×1014 cm2 per shot, respectively. SRIM revealed that the maximum DPA was about 1.7 and 0.17 and occur in the depth of 7 nm and 30 nm for argon and helium, respectively. Also, the maximum concentration occurs in the depth of 20 nm and 40 nm for argon and helium, respectively.

In the present work, the results of using a low energy plasma focus device MTPF-2, in order to investigate the destructive effects of shockwave and high-energy ions on tungsten and copper surfaces, are presented. Tungsten and copper were selected as a relatively hard and soft metals, respectively. The samples were placed at a distance of 8 cm from the upper anode surface at zero degrees relative to the symmetry axis and were exposed to ions and a shockwave from 20 electrical discharges. The discharge voltages were 12 kV and carried out in hydrogen gas at a pressure of 1mbar. By using the optical microscopy images, scanning electron microscopy images, x-ray diffraction spectroscopy, and x-ray diffraction analysis, the reference and irradiated samples were analyzed. The results, in addition to confirming the performance of the MTPF-2 device to be used in such studies, showed that the collision of ions and the shockwave creates, cracks and blister at the surface of the tungsten, lead to the creation of cracks, blisters, and melting of the copper surface, and changing the crystalline parameters such as the Bragg angles, the intensity of the peaks of the diffraction spectrum, and the distance between the crystalline plates. The calculations, which were performed by using the Scherrer’s formula also show a change in the average grain size of both metal surfaces.

One way of detecting ships or submarines is the observation of magnetic field signature around the object. Ships or submarines can be assumed as a collection of closed circuit of electrical currents. The electrical current of each close circuit must be properly regulated. The main purpose is production of a magnetic field equal to the magnetic field around the ship but with the opposite direction. By using this method, the magnetic field can be effectively reduced. This simulator is designed in C# language and it was named General Magnetic Compensation. The inputs of this software are geometry, location and magnetic field and the output is electrical currents of each closed loop, thus making the magnetic field reduced around the submarine. Accuracy and validity of the new software was investigated by analytical relation of magnetic field for proper geometry. Then a submarine was simulated in COMSOL and data of this simulation were used in General Magnetic Compensation software. The results were in great agreement with the results of the COMSOL software and could predict the magnetic field well.