Mehboob Sadiq

Enhanced and reproducible neutron emission from a plasma focus with pre-ionization induced by depleted uranium (U238)

The effect of pre-ionization induced by depleted uranium (92U238) around the insulator sleeve on the neutron emission of (1.8?3.3?kJ) plasma focus device is investigated by employing time resolved and time integrated neutron detectors. The maximum average neutron yield of 2.5 ? 108 is recorded at 3.5?mbar without pre-ionization, which increases up to 3.85 ? 108 with pre-ionization. It is found that the pre-ionization enhances neutron yield, about (50 ? 5)%, broadens the neutron emission pressure range and improves shot-to-shot reproducibility of plasma focus operation for neutron emission. The pinhole images of charged particles emitting zones indicate that the pre-ionization increases the high temperature plasma volume.

The effect of pre-ionization by a shunt resistor on the reproducibility of plasma focus x-ray emission

The effect of pre-ionization by means of a shunt resistor on the x-ray emission of a low energy (1.8?kJ) plasma focus device powered by a 9??F capacitor bank, charged at 20?kV and giving a peak discharge current of about 175?kA is investigated. Quantrad Si pin-diodes along with a suitable filter are employed as time-resolved x-ray detectors, whereas a multipinhole camera with absorption filters is used for time-integrated analysis. X-ray flux in 4?-geometry is measured as a function of argon filling pressure with and without pre-ionization. It is found that appropriate selection of the shunt resistor increases shot-to-shot reproducibility of the x-ray emission as well as the stability of the pinch filament and broadens the x-ray pulse width. The x-ray emission is also enhanced by (45 ? 5)% at the optimum pressure.

Catalytic action of β source on x-ray emission from plasma focus

The influence of preionization around the insulator sleeve by a mesh-type β source (Ni6328) for the x-ray emission from a (2.3-3.9 kJ) plasma focus device is investigated. Quantrad Si p-i-n diodes along with suitable filters are employed as time-resolved x-ray detectors and a multipinhole camera with absorption filters is used for time-integrated analysis. X-ray emission in 4π geometry is measured as a function of argon and hydrogen gas filling pressures with and without β source at different charging voltages. It is found that the pressure range for the x-ray emission is broadened, x-ray emission is enhanced, and shot to shot reproducibility is improved with the β source. With argon, the CuKα emission is estimated to be 27.14 J with an efficiency of 0.7% for β source and 21.5 J with an efficiency of 0.55% without β source. The maximum x-ray yield in 4π geometry is found to be about 68.90 J with an efficiency of 1.8% for β source and 54.58 J with an efficiency of 1.4% without β source. With hydrogen, CuKα...

Reactive sputter-deposition of AlN films by dense plasma focus

A low energy (1.45kJ) dense plasma focus device is used to deposit thin films of aluminum nitride (AlN) at room temperature on silicon substrates. For deposition of films, a conventional hollow copper anode is replaced with a solid aluminum anode and nitrogen is used as fill gas. The films are deposited using a multiple number of focus shots by placing the substrate in front of the anode. The deposited films are characterized using x-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy, and a microhardness test. The XRD analysis of the films shows that the deposited films show strong c-axis alignment. The Raman spectra of the films indicate that the deposited films are under compressive stress and crystalline quality decreases with increasing number of focus shots. The microhardness results point toward the uniform deposition of hard AlN layers on silicon substrates.

Dense plasma focus-assisted nitriding of AISI-304

Nitrogen ion implantation into AISI-304 stainless steel is carried out using a dense plasma focus device, operated at a charging voltage of 18 kV (discharge energy=1.45 kJ) with nitrogen filling at optimum pressure of 0.75 mbar. AISI-304 stainless steel samples placed axially above the anode tip are exposed to the ions for 10, 20 and 30 focus shots. X-ray diffraction (XRD), Vickerss micro hardness tester, scanning electron microscopy, and energy dispersive X-ray spectroscopy are used to explore the ion induced changes in the crystallographic structures, surface morphology, elemental composition and surface hardness of the ion irradiated samples. The XRD pattern confirms the formation of an expanded austenite phase, owing to nitrogen incorporated into the existing iron lattice. The results of micro hardness tester show that the hardness is increased about three times at an axial distance of 5 cm for 20 shots.

Characterization of carbon film by Raman spectroscopy

The deposition of amorphous carbon films is made on silicon substrates, using a low energy (1.4 kJ) dense plasma focus. The silicon substrates are placed in front of the graphite inserted anode at a 5 cm distance for different angular positions (0°, 8°, and 12°) with respect to the anode axis. The films are deposited using 25 focus shots at an optimum pressure of 0.75 mbar by using argon as working gas. The structural information of the deposited films is obtained by using Raman spectroscopy at room temperature with 785 nm line of a solid-state diode laser at an operating power of 100 mW. The analyses show the deposition of both graphite-type trigonal sp2 and diamond-type tetragonal sp3 films. The surface morphology is studied by using a scanning electron microscope. The irradiation by energetic high-fluence ions results in surface swelling of the substrate, increasing its roughness. With higher fluence, the surface damage is significant as a consequence of the excessive energy deposited on the substrate.