Lekha Nath Mishra | Patan Multiple Campus, Patan, Nepal (original) (raw)

Papers by Lekha Nath Mishra

Eastern-European Journal of Enterprise Technologies

Plasma technology stands at the forefront of numerous industrial applications, offering versatile... more Plasma technology stands at the forefront of numerous industrial applications, offering versatile solutions from materials processing to aerospace engineering. This study employs a single Langmuir probe technique operating at atmospheric pressure to scrutinize the transformative impact of silica seeding on low-temperature arc plasma. The investigation unveils a dynamic interplay of electrons and ions within the plasma, unveiling key electrical properties. The I–V electrical properties of the arcs plasma before seeding, having a floating voltage of –39 V, demonstrate electron and ion currents for varied probe voltages. The electrons’ density is calculated to be 2.11×1013 m–3, and the electrons’ temperature is at 6.25 eV. The I–V characteristics show a floating potential of about –35 V and –37 V after seeding an arc plasma using silica in the presence of aluminum oxide (2 % by weight) powder and grain, respectively. After seeding, it is discovered that the electron temperature falls t...

APS, Nov 1, 2002

The dispersion relation for plasma oscillations in a thin layered film is calculated in the SCF a... more The dispersion relation for plasma oscillations in a thin layered film is calculated in the SCF approximation for a model in which the electron motion along the film thickness is described like a tunnelling process between adjacent planes. For a semi-infinite medium the linear term in the dispersion relation of the surface plasmon is obtained. This is done using an appropriate expansion technique and in the limit of a 'greate' separation between adjacent planes.

Patan Pragya

Due to its numerous health advantages, coriander is one of the most used cooking ingredients. Thi... more Due to its numerous health advantages, coriander is one of the most used cooking ingredients. This paper describes the coriander plant's germination and growth after plasma treatment. The seeds are treated using the gliding arc for periods ranging from one minute to ten minutes. It is discovered that as treatment time is extended, the temperature of the seed rises while its weight continues to fall. The sixth and ninth days are used to calculate the germination rate. The study shows that the treatment time of plasma on seeds increases the hydrophilicity of coriander seeds. It is found that roots and shoots of seeds treated for ten minutes and eight minutes were significantly longer than the other seeds.

Meeting Abstracts of the Physical Society of Japan (Nihon Butsuri Gakkai koen gaiyoshu), 2003

The generation of the plasma by electron cyclotron resonance (ECR), a well known techniques, has ... more The generation of the plasma by electron cyclotron resonance (ECR), a well known techniques, has been increasingly used as an important tools in various purposes. The ECR plasma has high potential due to its wide range of field from nuclear fusion to plasma ...

Journal of Nepal Physical Society, 2021

This article deals about the experimental measurement of plasma potential, ion saturation current... more This article deals about the experimental measurement of plasma potential, ion saturation current and Mach number obtained with the variation of power, operating gas pressure and radial position using retarding field energy analyzer. We employed a retarding field energy analyzer by rotating with different angles such as 0° (facing toward source), 90° (facing side walls) and 180° (facing opposite the source). The coil current is varied from 0 to 15 A to produce the magnetic field which is used to confine the plasma. The flow of plasma has been characterized which was found to be subsonic. The low-temperature plasma is produced by means of a 13.56 MHz helicon plasma source at 300-1000 kW radio frequency power. The plasma is expanding from 13.8 cm diameter source into a 150 cm long diffusion chamber of 60 cm diameter.

Plasma parameters like electron temperature (Te), electron density (ne), Debye length (D) and pl... more Plasma parameters like electron temperature (Te), electron density (ne), Debye length (D) and plasma frequency (fp) were measured using Langmuir probes in air seeded arc-plasma at low pressure range of 0.10 mbar to 0.16 mbar. Double slope method, Dote method and Interception method were used to calculate the electron temperature (Te) and mean value of electron temperatures obtained from these three methods was used to calculate the electron density, Debye length and plasma frequency. To investigate the effect of pressure and discharge voltage on the plasma parameters at low voltage and low pressure is the main objective of the study. It was observed that Te, ne and fp gradually increased respectively but D decreased on increasing the voltage from 500 V to 600 V. It was also observed that on increasing the pressure there was decrease in Te and D but increase in ne and fe.

Journal of Nepal Physical Society, 2020

Arc plasma is generated using low voltage dc power supply for the measurement of plasma parameter... more Arc plasma is generated using low voltage dc power supply for the measurement of plasma parameters such as floating potential and ion-concentration in the plasma seeded with molybdenum. Langmuir moving probe is used in order to measure the probe current at different values of the dc potential applied on the probe. A graph is plotted between the probe current and the probe potential, based on data at the atmospheric pressure, using the experimental set up in the gas discharge chamber for the single probe method. The floating potential is calculated to be 32V, and the average ion-concentration to be 1.43 - 10e16m3.

Journal of Nepal Physical Society, 2016

Plasma expanding in the space along the magnetic filed is well known phenomenon. This plasma devi... more Plasma expanding in the space along the magnetic filed is well known phenomenon. This plasma device was constructed to investigate the space plasma in laboratory in connection with plasma flows, electron distribution, ion distribution, instability and turbulence. For this purpose, the low-temperature plasma is produced by means of a 13.56 MHz Helicon plasma source at 300-1000 W rf power. The plasma is expanding from the 13.5 cm diameter source into a 150 cm long chamber of 60 cm diameter. Ion energy and its velocity distribution produced by a current-free double layer at the expansion region have been studied by means of retarding field energy analyzers. Furthermore, the effects due to the geometrical shape of the expanding magnetic field in plasma flows have also been investigated.

IEEE Transactions on Plasma Science, 2004

AbstractExperiments are performed to develop a pulsed corona plasma system for the production of... more AbstractExperiments are performed to develop a pulsed corona plasma system for the production of hydrogen and carbon nanotubes (CNTs), directly by methane decomposition, at atmo-spheric pressure ( 760 torr). The corona discharge is energized by a pulse voltage ( 7 kV) with ...

Applied Physics Letters, 2010

The importance of an acceptance angle in the plasma diagnostics with ion energy analyzers is inve... more The importance of an acceptance angle in the plasma diagnostics with ion energy analyzers is investigated by means of numerical simulations. It is shown that wide acceptance angles result in low energy tails in measured ion distribution functions (IDFx). For flowing plasmas or plasmas with beams, the orientation of the analyzer’s orifice gives different results due to bending of ion trajectories in the vicinity of the analyzer. It is demonstrated that the maximum in the IDFx is at energies lower than the plasma potential. Simulations are done with DIP3D, a three-dimensional particle-in-cell code.

Publications de l' …, 2010

The Njord device is an inductively coupled plasma device with 13.56 Mhz and 400-900 W RF power in... more The Njord device is an inductively coupled plasma device with 13.56 Mhz and 400-900 W RF power inserted into the working gas by means of a saddle antenna through a 13.8 cm ID pyrex tube. The source plasma expands through a 10 cm long port into a 0.6m diameter and ...

Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, 1989

Electron cyclotron resonance plasmas were excited at a frequency of 2.45 GHz in chambers with dia... more Electron cyclotron resonance plasmas were excited at a frequency of 2.45 GHz in chambers with diameters smaller and larger than cutoff ones for fundamental TE and TM modes. Microwaves were introduced in the plasma chambers from the cw generator via a vacuum window and the microwave transmission line. It was found that microwave breakdowns at pressures 10−5–10−1 Torr (argon, nitrogen, oxygen) occurred at sites where the static magnetic field was 875 G (or close). In chambers with diameter smaller than cutoff, the breakdown occurred only near the vacuum window. A high absorption level of microwave power (>95%) was achieved in all explored chambers at microwave power P=300–1000 W. It occurred at areas where the static magnetic field was ∼875 G and the plasma density was Ncr=7.4×1010 cm−3. A high microwave power absorption level resulted in high plasma density up to Ne=1012 cm−3 at P=1000 W. No saturation in Ne=f(P) was observed. The shape and location of the high plasma density area...

Journal of Physics: Conference Series, 2010

View the article online for updates and enhancements. You may also like Ion energy distribution m... more View the article online for updates and enhancements. You may also like Ion energy distribution measurements in rf and pulsed dc plasma discharges D Gahan, S Daniels, C Hayden et al.

Surface and Coatings Technology, 2007

Experiments are performed to improve a pulsed corona discharge system for methane destruction at ... more Experiments are performed to improve a pulsed corona discharge system for methane destruction at atmospheric pressure. The corona discharge is energized by 6-12 µs wide voltage pulses (0.3-7 kV) at a repetition frequency of 1.050 kHz. The characteristic of methane destruction is observed by a mass spectrometer. We have found that methane destruction depends on the parameters such as: pulse width, input pulse voltage, repetition frequency, discharge current and discharge time. The effects of argon gas on methane destruction were also observed. The structural geometry of the soot, resulting from discharge process, is observed by transmission electron microscope. The main aim of this study is to show that the discharge could help as for the production of hydrogen and carbon nanotubes.

Submitted for the GEC10 Meeting of The American Physical Society Numerical simulations of the inf... more Submitted for the GEC10 Meeting of The American Physical Society Numerical simulations of the influence of an ion beam on the plasma analyzer performance in Njord helicon device WOJCIECH MILOCH, LEKHA MISHRA, NJAL GULBRANDSEN, ASHILD FREDRIKSEN, Department of Physics and Technology, University of Tromso, Norway — Recent experiments in Njord helicon plasma device confirmed the presence of an ion beam in a weakly magnetized plasma downstream from the double layer region [1]. The measurements were carried out with the retarding-field energy analyzer (RFEA). Since the housing of RFEA is biased with respect to the plasma, the plasma current to the orifice can depend on the sheath structure in its vicinity, and on its orientation with respect to the flow. Throughout understanding of the problem is needed for the analysis of data from such measurements. Numerical simulations allow to address this problem self-consistently. We simulate weakly magnetized plasmas with an additional ion beam f...

BIBECHANA

In this piece of study, the design and development of a low cost vacuum chamber with different po... more In this piece of study, the design and development of a low cost vacuum chamber with different ports are mentioned. I-V characteristic of Langmuir Probe is obtained using the primary data of the experimental set up for 'single probe method' in nitrogen seeded arc plasma at atmospheric pressure The floating potential was found to be 36V and the electron density to be 1.24 × 10 4 K. Variation in electron density of the arc plasma with probe potential is also studied at low pressure range from 10 Nm −2 (0.10 mbar) to 20 Nm −2 .

Journal of Natural Gas Chemistry

Abstract: Experiments are performed to develop a pulsed corona discharge system for the conversio... more Abstract: Experiments are performed to develop a pulsed corona discharge system for the conversion of methane to hydrogen at atmospheric pressure (≃760 Torr) without using a catalyst. The corona discharge was energized by 1012 µs wide voltage pulses (≤7 kV) at a repetition rate of ...

2011 XXXth URSI General Assembly and Scientific Symposium, 2011

Measurements of plasma flow are of key interest in a number of plasma environments and applicatio... more Measurements of plasma flow are of key interest in a number of plasma environments and applications. In laboratory magnetized plasmas, the directional Langmuir or Mach probe is a well-proven "in-situ" diagnostic tool to obtain the flow velocity. However, in non-magnetized or weakly magnetized plasmas, this method does not readily yield reliable velocity measurements, as it has been shown by numerical and experimental studies that the collection of upstream ions to the rearward probe surface can be significant. In this study, we utilize the analysis of data from 3D PIC simulations of ion velocity distributions in the vicinity of a negatively biased object embedded in a collision-less, source-free plasma with and without flow. The simulations allow us to study how the grounded probe housing of a retarding field ion energy analyzer (RFEA) affects the distribution of ions and their collection at different angles with a flowing, electropositive plasma. Comparisons are carried out with RFEA measurements in an inductively coupled helicon plasma.

Experiments are performrd to generate the hydrogen and carbon nanotubes from the decomposition of... more Experiments are performrd to generate the hydrogen and carbon nanotubes from the decomposition of methane using ultra short pulses under the atmospheric pressure. The results of discharge of methane obtained by the Mass Spectrometer are presented. Specially, the spectrum of hydrogen is presented under the different conditions. Carbon nanotube is observed by Scaning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). The results of morphology of the carbon nanotubes are also presented. The results from this experiment could be useful for the industry in future.

Plasma Sources Science and Technology, 2010

The Njord device was constructed with the aim of investigating instabilities and turbulence in pl... more The Njord device was constructed with the aim of investigating instabilities and turbulence in plasmas with flows and beams, which are common also in space plasmas. Njord is an inductively coupled helicon plasma device with 13.56 MHz RF power inserted into the working gas by means of a saddle antenna through a 13.8 cm inner diameter Pyrex tube. The source plasma expands through a 7 cm long and 20 cm wide port into a 0.6 m diameter and 1.2 m long chamber. Two magnetic field coils around the source and one additional downstream coil produce a magnetic field of about 25 mT at maximum. We have characterized current-free double layers in argon plasmas, and we find that they are generated at the position where the plasma expands into the main chamber. Further, the effect of shaping the magnetic field from an expanding one to a mirror shaped field by means of the downstream coil has been investigated. The downstream density and the plasma potential increase significantly when all the magnetic field lines in the source are passing also through the port-dome intersection without intersecting the port walls. The ion beam disappears when the plasma potential increases up to a potential similar to that in the source.