M.P. Srivastava

Thin carbon film deposition using energetic ions of a dense plasma focus

Abstract We report the first ever application of the dense plasma focus (DPF) device for thin film deposition. Thin films of carbon have been deposited on glass, silicon and quartz substrates by ablation of the graphite target using highly energetic argon ions of DPF. These films have been analysed for their surface profiles, structure and chemical composition using a surface profilometer, X-ray diffractometer (XRD), Raman spectrometer, and electron spectroscopic composition analyser (ESCA), respectively.

Dense plasma focus energetic ions based fullerene films on a Si(111) substrate

Abstract The highly energetic and high fluence argon ions emitted in a dense plasma focus device have been used for the first time to get fullerene films by ablating the graphite target such that the ablated material is deposited on a Si(111) substrate. These films have been studied using XRD, high resolution transmission electron microscopy (HRTEM), Raman spectroscopy, FTIR spectroscopy and SEM microscopy. The XRD, Raman and FTIR spectra show peaks corresponding to fullerenes, mainly C 60 and C 70 . Moreover, prominent peaks of C 60 have been observed in XRD spectra. The TEM micrograph shows crystalline fullerene structures and the selected area diffraction (SAD) pattern shows single crystalline spot patterns exhibiting the (110) and (006) planes of the hcp C 60 clusters. The SEM micrographs also show spherical clusters of fullerenes.

Carbon ion implantation on titanium for TiC formation using a dense plasma focus device

In this paper, we report titanium carbide formation on a titanium metal substrate by using a 3.3 kJ Mather-type dense plasma focus (DPF) device equipped with a graphite carbon source. The titanium substrate is inserted from the top of the plasma chamber and is irradiated by argon and carbon ions produced in multiple shots of DPF. X-ray diffraction spectra of the layer formed on the titanium substrate with 10, 15, 20, 25 and 30 shots at a typical distance of 2.5 cm from the top of the anode show peaks corresponding mostly to titanium carbide. The surface morphology and hardness of the layer formed have been investigated using a scanning electron microscope and a Knoop microhardness tester, respectively.

Magnetite phase due to energetic argon ion irradiation from a dense plasma focus on hematite thin film

Abstract Highly energetic pulsed argon ions that are generated during the focus phase of a dense plasma focus (DPF) device, are used for the first time to achieve a complete phase of magnetite from hematite thin films. The films are exposed to the ions of the DPF device axially above the anode at various distances. XRD spectra of the ion irradiated films show the change from α-Fe2O3 to Fe3O4 phase in the film which is irradiated at a particular distance from the anode. SEM micrographs of Fe3O4 films indicate the presence of columnar grains of the order of 50 to 90 nm. The magnetization curves confirm the change from non-magnetic α-Fe2O3 to magnetic Fe3O4 phase.

Deposition of nanosized grains of ferroelectric lead zirconate titanate on thin films using dense plasma focus

Pb(Zr0.53Ti0.47)O3 (PZT) thin films have been successfully deposited on glass, silicon and ITO coated glass substrates by a 3.3?kJ Mather type dense plasma focus device. The x-ray diffraction spectra of the films deposited on glass substrates kept at a distance of 4.2?cm from the top of the anode with 10, 15 and 25 shots show peaks at 2? = 31.3? corresponding to the perovskite phase of PZT. Transmission electron microscopy shows the presence of 0.5?nm grains of PZT. The leakage current density is found to be 10?6?A?cm?2 at a reverse voltage of 1?V, from current density?voltage (J?V) characteristics. The capacitance?voltage (C?V) characteristics show a counter-clockwise hysteresis loop with a memory window of 1.2?V. The ferroelectric characteristic has been confirmed using the polarization?field hysteresis loop. The resistance of the film is about 1?G?. The spontaneous polarization, remanent polarization and coercive field values are found to be 20.1??C?cm?2, 8.6??C?cm?2 and 79.9?kV?cm?1, respectively.

Enhancement in Tc of superconducting BPSCCO thick films due to irradiation of energetic argon ions of dense plasma focus

Abstract The highly energetic high fluence argon ions that are generated in dense plasma focus (DPF) device are used for the first time for the enhancement in Tc of superconducting BPSCCO thick films. These films are in mixed phase 2212 (Tc=85 K) and 2223 (Tc=110 K) prepared by screen printing technique. They are exposed to the ions of DPF axially above the anode at various distances. Tc of the films irradiated at a particular distance have been found to increase with maximum of 15 K. XRD peaks also confirm the presence of high Tc (2223) phase of BPSCCO only, for the films for which increase in Tc is 15 K.

STUDY OF X-RAY EMISSION OF DENSE PLASMA FOCUS DEVICE IN THE PRESENCE OF EXTERNAL MAGNETIC FIELD

Abstract The X-ray emission from a 3.3 kJ dense plasma focus device filled with argon in the presence of an external axial magnetic field has been quantitatively measured for the first time with the help of a diode X-ray spectrometer. The X-ray energy and electron temperature estimated from signals are found to be lower with application of the external axial magnetic field. The variation of the electron temperature with pressure shows a maximum at 80 Pa and a decrease both with increase or decrease of the filling gas pressure.

Current sheath dynamics and X-ray emission studies from sequential dense plasma focus device

A conventional dense plasma focus (DPF) device shows one or two compression phases. In the present paper, we report on a sequential DPF device with modified central electrode design to obtain more than two compression phases (i.e., multiple focusing). The sequential focusing was optimized by taking six different electrode designs for different filling gas pressures of argon. The optimization was inferred on the basis of intensity of spikes of voltage probe signals. The optimized central electrode design has then been used to study current sheath dynamics and X-ray emission using nitrogen laser shadowgraphy and diode X-ray spectrometer, respectively. Shadowgraphs show the breaking of current sheath during first focus as one part of it goes into radial collapse phase, and the other remains in axial acceleration phase. The one that remains in axial phase moves axially ahead in comparison to the other part of the current sheath. A bubble formation is observed after first focus phase. Shadowgraphs also show the formation of weak off-axis second focus. Finally, an on-axis third radial collapse is observed shadowgraphically (X-ray signals depict a multispike structure indicating hereby a sequential X-ray bursts from the sequential DPF device). The plasma electron temperatures have also been estimated using these X-ray signals.

STIMULATED RAMAN SCATTERING OF A TRANSVERSE MAGNETIC (TM) MODE IN A STRONGLY MAGNETISED PLASMA

Abstract A strongly magnetized plasma, e.g., the one encountered in a plasma filled backward wave oscillator (BWO), supports an obliquely propagating electromagnetic (EM) mode, k 0 ⊥ 2 = (k 0z 2 − ω 0 2 c 2 )( ω p 2 ω 0 2 − 1) where ωp2 ⪡ ωc2, ωp2 ⪡ ω02, ω0 and k0 are the pump wave frequency and pump wave vector, ωp and ωc are electron plasma and cyclotron frequencies, c is the speed of light in vacuum and z and ⊥ refer to the static magnetic field. As this mode acquires large amplitude it becomes susceptible to decay into a Trivelpiece-Gould (TG) mode and a sideband electromagnetic mode. The growth rate of the instability scales as γ ⋍ 1 4 υ osc k z ( k z k ⊥ ) 1 2 ( ω p k 1 c ) 3 2 , where υosc is the electron oscillatory velocity, k and k1 are the wave vectors of the low frequency electrostatic (ES) Trivelpiece-Gould mode and EM sideband wave. For typical BWO parameters the growth rate is of the order of the 109 s−1 range.