The Plasma Lab was initiated in 1980 and has been working on various scientific and technological studies on wide variety of plasma sources for the societal needs and national interest. Some of the salient works of the lab are highlighted below.
Microwave-Plasma Interaction inside Conducting Waveguides
Plasma production experiments using slow wave structures
Slow wave structures (slotted line antenna, slotted and wire helices) were used for plasma production in a magnetic mirror field configuration for improving plasma production efficiency and confinement. Plasma was initiated using 2.45 GHz microwaves at electron cyclotron resonance.
Plasma production using polarization control
RHP and LHP waves were used for plasma production giving novel insights into guided wave modes. Also, O-mode polarization was also used to excite the plasma.
Analysis of Slow wave structures for microwave coupling to plasmas
Slow wave structures (slotted line antenna, slotted and wire helices) were investigated theoretically. These were used for plasma production using CW microwaves were coupled at 2.45 GHz, 100 – 3kW power achieving for higher plasma production efficiency.
Theory of high frequency waves in magnetized, non-uniform, warm plasma loaded in waveguides
High frequency waves in magnetized, warm, non-uniform plasma, loaded inside conducting waveguides were investigated theoretically using kinetic theory. Among other features the waves exhibit polarization reversal along the radius: a RHP wave near the plasma-waveguide axis becomes LHP away from the axis and vice-versa. Propagation characteristics, electric field, polarization profiles and wave absorption by cyclotron and Landau damping were determined.
Modes of plasma waves in cold, magnetized, uniform plasma inside waveguides and helical slow wave structure
Propagation characteristics, field structures and polarization details of slow and fast waves supported by cold, uniform magnetized plasma inside waveguides and sheath helices were investigated in detail.
Arbitrary ratio Power splitter
An arbitrary ratio power splitter that can split input CW microwaves at 2.45 GHz, 100 – 3kW power, into two arms was developed, tested and used in experiments. The test results were verified theoretically using scattering matrix formulation.
High Power microwave line with Coaxial Triple Stub Tuner and Mica vacuum window
The line uses indigenously developed coaxial triple stub tuner, along with low loss mica microwave-vacuum window for high power plasma applications with arbitrary impedance matching capability.
Variable Polarizer for circular guide – LCP to RCP
A high power polarizer with capability to mix LCP and RCP in arbitrary ratio for the TE11 dominant mode of a circular guide was designed, fabricated and used in experiments.
Conventional Langmuir Probe, Electron and Ion Energy Analyzers
Standard Langmuir probes and electron and ion energy analyzers were developed and built for use in various experiments.
Wave Diagnostics at Microwave frequencies – E-probe, Wavelength measurement using interferometry
Wavelengths and electric fields of plasma waves generated by high power microwaves at 2.45 GHz were measured using interferometric techniques (using mixers) and capacitively coupled high-frequency E-probes.
Generation of complex Bessel Functions with high accuracy
Algorithms and programs were developed for generating the Bessel functions Jn(z) and Yn(z) and their derivatives, where z is complex and n an integer.
Graphical–cum-analytical program for automatic analysis of Langmuir Probe Data
A Fortran-cum-Windows based software was developed for undertaking interactive analysis of LP data as early as in 1995. Over time this software was replaced by faster MATLAB, GUI-based programs.
Program for Computation of high frequency modes and their absorption in plasma loaded conducting waveguides
Programs were developed for computing high-frequency whistler (microwaves) and helicon (MHz) modes of plasma-loaded waveguides, their absorption.
Studies on Helicon Waves in Conducting Waveguides and Development of Plasma Sources
Propagation and absorption of helicon waves in plasma loaded waveguides
Propagation characteristics of helicon waves coupled to Trivelpiece-Gold (TG) waves along with collisional and Landau absorption was investigated in detail. Absorption is accounted for exactly, which brings about drastic changes in field patterns of the modes.
Plasma production and absorption of helicon waves in conducting waveguides
Absorption mechanisms of helicon waves and the associated TG waves in helicon discharges in conducting chamber were investigated experimentally. At low pressures Landau damping is the absorption mechanism, while at high pressures it is collisional absorption. The results are compared with the theory.
Studies on double-layer structures in helicon plasmas in conducting waveguides
Different types of potential jumps (multiple) were observed along the system length at different pressures. These are investigated and analyzed in detail in a series of papers.
Compact ECR Plasma Source (CEPS)
The CEPS was conceived and developed (1995) as an ECR based compact source for high-density plasma, which can be attached to any suitable port of a chamber for filling it with plasma. Its total weight including the ring magnets is @ 14 kg and its length is about 60 cm.
Large Volume Plasma System (LVPS) using multiple CEPS
By combining multiple CEPS in a suitable manner it is possible to produce high density, uniform plasma over very large volume and large area, for industrial scale applications like, nitriding, carburizing, PIII, semiconductor processing for shallow junctions, ion beam source for ion implantation, etc. LVPS specifications: Chamber dia.: @1m, Height: @1 m, Volume: @1.6 m3, Number of CEPS: 18.
RF Compensated Langmuir Probe (CLP)
A novel RF compensated Langmuir probe (LP) was developed for LP diagnostics in helicon experiments. The probe was compensated for the fundamental and two harmonics. Similar probes were used for capacitively coupled discharges.
Wave Diagnostics at RF frequencies: B-dot probe, Wave-length Measurement
The RF wave magnetic field was sensed using a B-dot probe, built in-house. The wavelength was measured using a vector-voltmeter, with reference signal from RF power source. The signal from the B-dot probe was amplified and integrated to yield B.
Low Cost, Power Supply for 800 W, CW Microwaves for Plasma Applications
In microwave ovens, low cost, 800-Watt magnetrons are operated in short pulses (with high peak power) to save cost of power supply. Since the magnetrons are very rugged, these can be used for plasma applications in CW mode (without exceeding the average power rating of the magnetrons), by designing an appropriate power supply with continuously variable power output. Such power supplies have been built in large numbers for the Compact ECR Plasma Sources (CEPS: Patent: IIT Delhi) and operated continuously for hours without isolators in large numbers for the Large Volume Plasma System (LVPS; Patent: IIT Delhi) and other experiments.
High power Passive microwave components
Various high power, passive components have been designed and fabricated for the high power microwave experiments using the Compact ECR Plasma Sources (CEPS: Patent: IIT Delhi) and the Large Volume Plasma System (LVPS; Patent: IIT Delhi). Components include: launcher section (for coupling magnetron to waveguide), rectangular to circular waveguide converters, waveguide triple stub tuner, E-plane and H-plane bends, water loads, quartz vacuum window, waveguide sections, etc. To reduce weight most components were fabricated from aluminum.
RF Phased-Array Antenna for EM Wave Launching
A novel technique for launching m = ±1 helicon or any other EM wave in plasma was developed. The method uses two loop antennas, oriented orthogonally and energized in quadrature phase. The separation between the loops controls the wavelength and their phasing, the polarization (left or right). Above all, the technique uses only one RF power supply.
Program for Computation of helicon modes and their absorption in conducting waveguides
Programs were developed for computing high-frequency whistler (microwaves) and helicon (MHz) modes of plasma-loaded waveguides, their absorption.
Development of Plasma sources and diagnostics relevant for Industry / Nation/ Society
Characterization of the CEPS
Plasma flowing from the CEPS into small and medium sized chambers attached to it was characterized in detail. These studies have revealed some interesting and novel features of the plasma ejected from the CEPS.
Characterization of LVPS
By combining multiple CEPS in a suitable manner it is possible to produce high density, uniform plasma over very large volume and large area, for industrial scale applications like, nitriding, carburizing, PIII, semiconductor processing for shallow junctions, ion beam source for ion implantation, etc. LVPS specifications: Chamber dia.: @1m, Height: @1 m, Volume: @1.6 m3, Number of CEPS: 18.
Development of CEPS based plasma thruster
In another recent study using a CEPS connected to large expansion chamber, it was shown that the CEPS has very good thruster properties. In argon gas it can produce a thrust of @50 mN at a pressure of @5 mTorr and @600 W of microwave power. These values are highly encouraging and have been vetted by theoretical calculations.
Studies on Hydrogen ion (H+, H2+, H–) production
Detailed studies have been conducted on hydrogen plasma produced by CEPS and allowing it to flow into an expansion. The studies have relevance for semiconductor surface modification, negative hydrogen ion beam production, etc.
CEPS based High pressure discharges for waste mitigation, surface treatment, tribology
Studies have been initiated for surface treatment, tribology and waste mitigation.
Power Absorption in Capacitively Coupled Discharges (CCDs)
New and novel diagnostics have been developed for measuring accurately the harmonic power spectrum both inside and outside the CCD. Measurements have yielded new results on the harmonic spectrum and tuning theoretical models to reproduce these results would result in stronger and more accurate predictions from such models leading to better system design.Two major diagnostics for which patents have been filed are:
- RF Dual Directional Couplers (More details)
- J.E Probe (More details)
Sub-Atmospheric RF plasmas using co-planar multi-structured electrodes
A co-planar multi-structure electrode antenna array was designed and fabricated in the lab on a glass-epoxy substrate to produce high pressure rf Dielectric Barrier Discharges (DBD) discharges at pressures ≈ few 100s Torr and rf power ≈ few 10s of Watt.
Coaxial and Planar DC Discharge Systems
DC discharge sources in coaxial and planar electrode configurations have been developed for basic studies to study effect of boundaries on the discharge dynamics.
Characterization of nonlinear effects in dc discharges
DC discharges depict a rich source of nonlinear behavior, such as Negative Differential Resistance (NDR), Anode Glows and its dynamical transitions, order-to-chaos-to-order transitions fluctuation, etc. These characteristics have been analyzed using time-series and non-linear dynamical tools.
Non-thermal Atmospheric plasma jet
Two nonthermal plasma jets have been developed recently at the Plasma Lab, IIT Delhi. One is a low frequency (AC) plasma jet whereas the other is a plasma jet powered at rf frequency (27.12 MHz). It is being utilized for various environment and biomedical applications, which include Bactericidal activities, decreasing contact angle of bio-materials.
Plasma Pyrolysis for waste mitigation
The lab is in the process of installing two plasma pyrolysis plants for waste management studies. One is already being set up near to the Babarpur drain in the East Delhi Municipal Corporation (EDMC) whereas the other is planned to be setup in IIT Delhi Campus as a Central Research Facility for undertaking research activities towards improvements in plant operation in terms of energy efficiency and environment management.
RF / DC Plasma-liquid Interaction
Currently the lab is working toward developing rf and dc based atmospheric pressure plasma sources for investigating plasma-liquid interactions.
PIC & Molecular Dynamics Simulations
Fluid, Particle – In – Cell (PIC) and Molecular Dynamics simulation techniques are employed to unravel frontier problems of nonlinear and strongly coupled plasma medium and its interaction with intense laser radiation.
Modeling of electrodeless plasma thruster
The lab is currently seeking a better understanding of the plasma dynamics in electrodeless plasma thrusters using computer simulations.
Universal Langmuir probe
A universal LP has been developed for operation in normal as well as RF environment.
Special Langmuir probe and Ion energy analyzer for CEPS
The Compact ECR Plasma Source (CEPS); Patent: IIT Delhi) has a very harsh ECR zone with high plasma density and high-energy ions. To conduct LP measurements inside the CEPS and measure ion energies close to it requires special designs of the LP and RFEA.
Novel method of harmonic detection using RF Dual-Directional Couplers
Using a dual directional coupler between the plasma load and the matching network, it is possible to measure the entire harmonic spectrum produced in RF discharges like capacitively coupled plasmas, for gaining insight into the nonlinear mechanisms generating the harmonics.
J.E probe for power density measurement in RF discharges
A novel J.E probe was developed for measuring absorbed power density in RF discharges at the fundamental and its harmonics.
LabVIEW Controlled Data Acquisition and LP Power Supply
A Data Acquisition Card (DAC) from National was configured on a LabVIEW platform to acquire Langmuir probe (LP) data. The LP power supply accepts a trigger from the DAC and produces an appropriate voltage ramp. The Start and Stop voltages for the scan, the duration of the ramp, the number of data points, etc. are all controlled from the LabVIEW program. The measured LP voltage and current are sampled and displayed.
Program for Two-Zone Global model
A two-zone global model was developed for determining plasma parameters in the ECR (source) region (CEPS) and the expansion chamber into which the plasma is ejected from the source. The calculations yield the flux and energy of ions exiting the source region from which the thrust imparted by the ions is determined.