Harishankar Ramachandran

Hari Ramachandran received his B.Tech. from IIT Bombay in 1982 and his Ph.D. from the University of California at Berkeley, both in Electrical Engineering. He was a research scientist in the Physics Department at the University of California, Los Angeles for five years before returning to India. He was a scientist at the Institute for Plasma Research, Gandhinagar, from 1993 till 2001 and joined IIT Madras in Nov 2001.

Teaching

EC 301: Electromagnetic Fields (once a year)
EC 541: Introduction to Fiber Optic Technology (even semesters)
EC 205: CAD Laboratory (odd semesters)
Microwave Lab in charge.

Research Interests

Optical Link Design and Planning

The tenet group has a great deal of experience in the development of Access level networking systems. This strength lies in the group's expertise in all the related areas of the technology, including the optical layer, the electronic subsystems, network management systems and protocols. My own interests are in the area of the optical physical layer, including both access links and backbone link design.

Nonlinear Optics

Modern optical systems exhibit a variety of interesting phenomena, many of these nonlinear in nature. My interests are mainly in the areas of

Optical beam propagation in turbulent media, as occurs in terrestrial optical links.
The interaction between nonlinearity and dispersion.
Solitary wave propagation (ie, solitons) in optical fibres.

Computational Optics

We are in the process of developing inhouse a full set of numerical tools for the investigation of optical communication problems. These include

A Beam Propagation Method code to simulate the propataion of waves in complex geometries.
A Finite Difference Time Domain code to simulate the transient effects on optical pulses when they encounter opto-electronic devices.
A Physical Layer Design tool, to study the interaction between different aspects of link design. This is intended to become a pedagogical tool for introducing students to the complex world of the optical layer.

Edge Plasma Physics

Plasma Systems are notoriously complex, and never more so than in the edge. A large part of my work has related to understanding the behaviour of plasmas in the sheath and presheath. The goals of my research are to understand better some of the following:

The nature of the ionacoustic wave in the sheath and presheath. To identify particle and energy transport mechanisms that might be unique to this region.
The nature of the particle distribution function near the sheath region.
The proper forms of fluid equations that are valid in the sheath and presheath.
The sheath-presheath interface.

Computational Plasma Physics

I am developing a particle simulation code to focus on sheath and presheath physics. Issues that have already been investigated include the identification of the sheath and presheath about a dust particle, study of wave fluctuations in an afterglow plasma, the effect of magnetic fields on plasma accretion, etc.

Publications

Journal Articles

H. Ramachandran, A.J. Lichtenberg and M.A. Lieberman, "A collisional treatment of the trapped particle mode in multiregion mirror systems," Phys. FLuids 31 (8), August 1988.
H. Ramachandran, G.J. Morales, V.K. Decyk, "Relaxation and Self-Organization of a Nonneutral Plasma," 1992 International Conf. on Plasma Physics, Europhysics Conf. Abst. 16c, Part I, page 135.
G.J. Morales and H. Ramachandran, "Role of Alven-Wave Filaments in Tokamak Transport," 1992 International Conf. on Plasma Physics, Europhysics Conf. Abst. 16c, Part III, page 1839.
H. Ramachandran, G.J. Morales and B.D. Fried, "Model Study of H-Mode Behavior Induced by Radial Currents," Phys. Fluids B, 5(3), March 1993.
H. Ramachandran, G.J. Morales and V.K. Decyk, "Particle Simulation of Nonneutral Plasma Behavior," Phys. Fluids B, August 1993.
H. Ramachandran, G.J. Morales, and V.K. Decyk, "Formation of Extended Sheaths in Nonneutral Plasmas," Proceedings of the International Conference on Nonneutral Plasmas, San Francisco, Dec 93.
M. Goswami and H. Ramachandran, "A Self-Consistent Kinetic Treatment of an Unmagnetised Sheath," Proceedings of the Plasma Technology Conference, IIT, Kanpur, Nov 1995.
Goswami, M. and Ramachandran, H., "A Self-Consistent Analysis of a Collisional Presheath," Phys. Plasmas 6(12) p 4522 (1999).
Gupta, D.K., Ramachandran, H. and John, P.I., "Spatio-Temporal Measurements of Trichel Corona Discharge using Capacitive Probe Diagnostic," Review of Scientific Instruments, Feb 2000.
M. Goswami and H. Ramachandran, "A Self-Consistent Kinetic modeling of a 1-D, Bounded, Plasma in Equilibrium," Pramana 55(5&6), page 887 (Nov & Dec 2000).
Sharma, D. and Ramachandran, H, "Self-Consistent Analysis of a Source Driven Magnetised Presheath," will appear in the Aug 2002 issue of Physical Review E.
Sharma, D. and Ramachandran, H., "Revised Boundary Condition to the E×B drift Dominated Plasma Flow in the Scrap-off Layer," J. Plasma and Fusion Res. Series, (Proc. 14 Int. Toki Conf, Toki City, Japan) Vol. 3, Page 218 (2000).
Sharma, D. and Ramachandran, H., "Kinetic Simulation of a Source Dominated Plasma-Wall interaction in an Oblique Magnetic Field," J. Nucl. Mater. Vol 290-293, Page 725 (2001).
Rajkhowa, K.R. and Ramachandran, H., "Characteristics of gravitationally affected colloidal plasma sheath," accepted for publication in Physics of Plasmas.