Jyotsna Sharma

Excitation of electrostatic ion-cyclotron waves by an ion beam in a two-ion component plasma

An ion beam propagating through a magnetized plasma cylinder containing electrons, light positive potassium ions (K+), and heavy positive cesium ions (Cs+) drives electrostatic ion cyclotron (EIC) waves to instability via Cerenkov interaction. Two EIC wave modes are present, the K+ and Cs+ modes. The unstable wave frequencies and the growth rate of both the light positive ion and heavy positive ion modes increase with an increase in their relative ion concentrations. The growth rate of both the unstable modes (K+ and Cs+) scales one-third power of the beam density. The real part of the frequency of both the unstable modes (K+ and Cs+) increases with the beam energy and scales as almost one-half power of the beam energy. Numerical calculations of the growth rate and mode frequencies have been carried out for the parameters of the experiment of Suszcynsky et al. [J. Geophys. Res. 94, 8966 (1989)]. It is found that the unstable wave frequencies of both the light positive ion and heavy positive ion modes incr...

Excitation of ion cyclotron waves by a spiraling ion beam in a magnetized dusty plasma cylinder

A spiraling ion beam propagating through a magnetized dusty plasma cylinder drives electrostatic ion cyclotron waves to instability via cyclotron interaction. Numerical calculations of the growth rate and unstable mode frequencies have been carried out for the typical parameters of dusty plasma experiments in the two limits, namely, long parallel wavelength and short parallel wavelength. It is found that as the density ratio of negatively charged dust grains to electrons increases, the unstable mode frequency and the growth rate of the instability of the ion cyclotron waves increase in both the limits. The growth rate of the instability increases by a factor of ∼2.5 when the density ratio of negatively charged dust grains changes from 1.0 to 4.0 in the limit of short parallel wavelengths. Moreover, the growth rate increases with the density ratio of negatively charged dust at higher values in the present case in the limit of long parallel wavelengths. The growth rate of the unstable mode has the largest v...

Excitation of lower hybrid waves by a gyrating ion beam in a negative ion plasma

A gyrating ion beam propagating through a magnetized plasma cylinder containing K+ positive ions, electrons, and SF6− negative ions drives electrostatic lower hybrid waves to instability via Cyclotron interaction. Numerical calculations of the unstable mode frequencies and growth rates of both the unstable positive ion and negative ion modes have been carried out for the existing negative ion plasma parameters. It is found that the unstable mode frequencies of both the modes increase, with the relative density of negative ions. In addition, the growth rates of both the unstable modes also increases with relative density of negative ions. Moreover, the growth rates of both the unstable modes scale as the one-third power of the beam density. The frequencies of both the unstable modes also increase with the magnetic fields. The real part of the unstable wave frequency increases as almost the square root of the beam energy.

Instability of Ion Beam Driven Electrostatic Ion-Cyclotron Waves in Collisional Magnetized Two-Ion Component Plasma

We have studied the instability of electrostatic ion-cyclotron waves in collisional magnetized two-ion component plasma (light positive K + ions and heavy positive Cs + ions). An ion beam propagating through collisional magnetized plasma containing electrons and two positive ion components drives electrostatic ion cyclotron (EIC) waves to instability via Cerenkov interaction. Analytical expressions & numerical calculations have been carried out for the frequency and growth rate of ion cyclotron waves for two EIC wave modes for existing experimental parameters, and it is found that the unstable mode frequency does not depend on electron collision frequency, while the growth rate is increased linearly with the electron collision frequency. Moreover, as the light ion concentration is increased, the frequency of the heavy ion mode moves closer to its gyrofrequency. Similarly, the frequency of the light ion mode approaches the light ion cyclotron frequency as the heavy ion concentration is increased. It is also found that the normalized unstable mode frequencies remains unchanged with electron collision frequencies, while the growth rate is increased linearly with the electron collision frequencies. In addition, the unstable mode frequencies are found to be dependent on the magnetic field strengths.

Effect of dust charge fluctuations on upper hybrid wave instabilities in magnetized dusty plasma

The decay instability of an upper hybrid electrostatic wave into an upper hybrid sideband wave and lower hybrid wave is studied in magnetized dusty plasma. A local theory of this process has been developed. The growth rate and mode frequencies of the unstable wave were evaluated based on existing dusty plasma parameters and it is found that the unstable mode frequency and growth rate increases with δ (ion-to-electron density ratio) in the presence and absence of dust charge fluctuations in addition to dust dynamics.

Experimental investigation of plasma instabilities by Fourier analysis in an electron cyclotron resonance ion source

Sarvesh Kumar, Jyotsna Sharma, Prashant Sharma, Shatendra Sharma, Yaduvansh Mathur, Devendra Sharma, and Manish K. Kashyap Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110067, India Amity School of Applied Sciences, Amity University, Gurgaon 122413, Haryana, India USIC, Jawaharlal Nehru University, New Delhi 110067, India Institute for Plasma Research, HBNI, Bhat, Gandhinagar 382428, Gujarat, India Department of Physics, Kurukshetra University, Kurukshetra 136119, Haryana, India

Synthesis and characterization of ZnO flower-like structures

Abstract The flower-like ZnO nanorods have been successfully synthesized by a surfactant-assisted hydrothermal method. The nanostructures formed by ZnO nanorods were synthesized and deposited without seeding in glass flask by a hexamethylenetetramine (HMTA)-assisted hydrothermal method at low temperature with NaOH as surfactant and catalyst. The synthesized ZnO flowers comprise of several spike structures that have hexagonal cross section and taper toward the end. The structures are investigated using X-ray diffraction, scanning electron microscope and transmission microscope. The optical properties are studied with UV-VIS, FTIR, and Raman spectroscopy. The process of synthesis is simple and highly reproducible. The synthesized flower-like structures are suitable for use as sensors applications.

DFT calculations of electronic and optical properties of SrS with LDA, GGA and mGGA functionals

The theoretical investigations of electronic and optical properties of SrS are made using the first principle DFT calculations. The calculations are performed for the local-density approximation (LDA), generalized gradient approximation (GGA) and for an alternative form of GGA i.e. metaGGA for both rock salt type (B1, Fm3m) and cesium chloride (B2, Pm3m) structures. The band structure, density of states and optical spectra are calculated under various available functional. The calculations with LDA and GGA functional underestimate the values of band gaps with all functional, however the values with mGGA show reasonably good agreement with experimental and those calculated by using other methods.

Excitation of dust acoustic waves by an ion beam in a plasma cylinder with negatively charged dust grains

An ion beam propagating through a plasma cylinder having negatively charged dust grains drives a low frequency electrostatic dust acoustic wave (DAW) to instability via Cerenkov interaction. The unstable wave frequencies and the growth rate increase with the relative density of negatively charged dust grains. The growth rate of the unstable mode scales to the one-third power of the beam density. The real part of the frequency of the unstable mode increases with the beam energy and scales to almost one-half power of the beam energy. The phase velocity, frequency, and wavelength results of the unstable mode are in compliance with the experimental observations.

Spiraling ion beam driven electrostatic ion cyclotron wave instabilities in collisionless dusty plasma

The numerical calculations of the growth rate in long parallel wavelength are made for a spiraling ion beam propagating through a collision less magnetized dusty plasma cylinder that drives electrostatic ion cyclotron waves to instability via cyclotron interaction. It is found that the growth rate of the instability of the electrostatic ion cyclotron waves increase in the long parallel limit with the density ratio of negatively charged dust grains to electrons. The growth rate of the unstable mode has the maximum value for the modes whose Eigen functions peak at the location of the beam and varies as the one-third power of the beam current in both the limits.