arXiv subjects

G. Veda Prakash

Publications and source records attributed to G. Veda Prakash.

4 recordsLinked to original sources

arXiv2022

Influence of pulse modulation frequency on helium RF atmospheric pressure plasma jet characteristics

This work investigates the influence of pulse modulation frequency ranging from 50 Hz- 10 kHz on the helium RF atmospheric pressure plasma jet's fundamental characteristics. The impact of modulation frequency on plasma jet discharge behavior, geometrical variation, reactive species emission, and plasma parameters (gas temperature Tg, electron excitation temperature Texc, and electron density (ne) are studied using various diagnostics such as optical imaging, emission spectra, and thermal diagnostics. From the experiments, it is observed that operating the plasma jet at low pulse modulation frequencies (around 50 Hz) provides enhanced plasma dimensions, higher electron densities and greater optical emission from reactive species (viz., He I, O, OH, N2+, etc.) as compared to the higher modulation frequencies. Besides the low power consumption, the three times less gas temperature of the modulated plasma jet than the continuous wave mode makes it more advantageous for the applications. Moreover, the influence of duty cycle (D) and applied RF power (P) on the plasma jet characteristics are also discussed. It is found that 10- 40% duty cycle operation provides the most favorable attributes. More importantly, the concern of shorter plasma length in RF plasma jets is overcome by operating at 10- 20% duty cycle with increased applied power. This work thoroughly characterizes helium atmospheric pressure RF plasma jet with a wide range of pulse mode operating parameters, which could help select appropriate operating conditions for various industrial and biomedical applications.

physics.plasm-ph↗

arXiv2020

Characterization of atmospheric pressure plasma plume

In order to optimize the parameters of the plasma plume for atmospheric pressure plasma applications such as biological and industrial applications, it is highly necessary to thoroughly understand its characteristics. In this paper, various diagnostic techniques are discussed to characterize the atmospheric pressure plasma plume. The major emphasis of this work is to utilize possibly simple methods, low complexity in post data analysis and obtain in-situ information. The parameters of the plasma plume such as spatial variation of gas temperature, electron excitation temperature, plume velocity, plume current, electron density are experimentally measured. In addition, plasma discharge behavior and plume formation with various gas flow rates and applied voltage are studied. The characterization of the above parameters is carried out by using electrical diagnostics (voltage probe and a current sensor), Optical diagnostics (optical emission spectroscopy (OES), fast imaging method using ICCD camera), and thermocouple. The plasma plume/gas temperature along the plume length is measured by using a simple K-type thermocouple and is found to be in the range of (42.5 - 24.5) deg C. The OES is used to estimate the electron excitation temperature of plasma plume and to identify the key reactive species (OH, NO, N2+, O, etc.) present in the plume. ICCD camera is utilized to capture the temporal evolution of plasma and to estimate the plume velocity along the plume length. The current transformer is utilized to measure the plume current along the plume length. By using the velocity and current information, the plasma density is evaluated, and the obtained values are in the range of (0.069-5.96)x 10^12 cm^-3. The above range of parameters and tunable nature of our designed plasma source will be useful for the development and optimization of plasma sources for various applications.

physics.plasm-ph↗

arXiv2019

Study of diamagnetism in laser-produced plasma using B-dot probe

Time-varying diamagnetism in laser-produced plasma moving across the transverse magnetic field with different field strengths has been studied using fast imaging and magnetic probe. The emphasis of the present work is on the development of suitable B-dot probe and quantitative analysis of induced diamagnetic field in an expanding plasma plume. A Helmholtz coil associated with pulsed power system is used to produce uniform magnetic field of different strengths. Helmholtz coil allowed the plume imaging along the magnetic field lines, which gives the direct structural information of the induced diamagnetic cavity. A high frequency three-axis B-dot probe has been developed to measure the transient magnetic field. Different experimental approaches have been used to test the response, sensitivity and calibration of the developed probe. Findings indicate that plasma plume shows the perfect diamagnetic behaviour for the external field varying from 0.13 T to 0.57 T where the induced magnetic field almost completely displaced the external magnetic field.

physics.plasm-ph↗

arXiv2018

Study of plume dynamics and plasma density during its expansion

The electron density is one of the crucial parameters in plasma plume, which plays a major role in producing the key reactive species required for biological and industrial applications. In this work, experiments are performed to estimate the spatial variation of plasma density in a steady plume. The time-resolved images obtained from the ICCD camera, plume current measurements are utilized for estimating the plasma density. We observed the plasma density increases from the glass nozzle to the plume tip. This increase in plasma density is due to the combined effect of reduction of drift velocity, charge, and area confinement of plume. Further, the intensity plots of the ICCD camera images obtained with larger exposure time validate the increased density at the plume tip. The plasma density along the plume gives information about the approximation to the plume exposure time desired and the impact it creates on the very sensitive targets. The spatial variation of plasma density in a plume is a futuristic requirement for several biological and industrial applications considering a single plasma device.

physics.plasm-ph↗