Showing papers in "IEEE Transactions on Plasma Science in 2005"

High-speed photographs of a dielectric barrier atmospheric pressure plasma jet

Abstract: The propagation of an atmospheric pressure plasma jet (APPJ) is investigated by use of an intensified charge coupled device (ICCD) camera. It is shown that the APPJ is mainly an electrical phenomenon and not a flow related one. The jet does not consist of a voluminous plasma. Much more, the presented plasma source acts like a "plasma gun" blowing small "plasma bullets" out of its mouth. Furthermore, the interaction of the jet with a surface has been investigated.

Plasma-based ion implantation and deposition: a review of physics, technology, and applications

Abstract: After pioneering work in the 1980s, plasma-based ion implantation (PBII) and plasma-based ion implantation and deposition (PBIID) can now be considered mature technologies for surface modification and thin film deposition. This review starts by looking at the historical development and recalling the basic ideas of PBII. Advantages and disadvantages are compared to conventional ion beam implantation and physical vapor deposition for PBII and PBIID, respectively, followed by a summary of the physics of sheath dynamics, plasma and pulse specifications, plasma diagnostics, and process modeling. The review moves on to technology considerations for plasma sources and process reactors. PBII surface modification and PBIID coatings are applied in a wide range of situations. They include the by-now traditional tribological applications of reducing wear and corrosion through the formation of hard, tough, smooth, low-friction, and chemically inert phases and coatings, e.g., for engine components. PBII has become viable for the formation of shallow junctions and other applications in microelectronics. More recently, the rapidly growing field of biomaterial synthesis makes use of PBII and PBIID to alter surfaces of or produce coatings on surgical implants and other biomedical devices. With limitations, also nonconducting materials such as plastic sheets can be treated. The major interest in PBII processing originates from its flexibility in ion energy (from a few electron volts up to about 100 keV), and the capability to efficiently treat, or deposit on, large areas, and (within limits) to process nonflat, three-dimensional workpieces, including forming and modifying metastable phases and nanostructures.

Physics of high-current interruption of vacuum circuit breakers

Abstract: The present state of knowledge concerning the physical phenomena of high-current interruption with vacuum interrupters (VI) is reviewed. Two arc control methods, application of externally applied axial magnetic field (AMF) or transverse magnetic field (TMF), are available to distribute the heat flux from arc to contacts homogeneously over contact surface, to avoid local overheating. AMF spreads the arc at fixed location. TMF moves the constricted arc over contact surface. Change from diffuse to constricted arcing mode results from superposition of two effects: "instability of anode sheath" and "influence of magneto-gas-dynamic", when no AMF component exists. Conditions of arc memory at current zero determine the process of current extinction and of recovery of breakdown strength to its ultimate value. Evaporation of metal vapor continues. Charge exchange between fast ions and slow vapor atoms increases the residual charge, left in the switching gap at current zero. Post arc current prolongs and increases consequently. Breakdown during recovery of dielectric strength occurs instantaneously or sporadically delayed. Behavior of breakdown is essentially determined by vapor density. Breakdown mechanism of delayed breakdown is still unresolved. Vapor density is too low to initiate breakdown alone. Lack of fundamental knowledge in combination with complexity hampers numerical treatment of arc behavior, as well as heat flux to contact during arcing and process of interruption presently, as needed for interpretation of experimental results and prediction purposes.

Spatial electron density distribution in a high-power pulsed magnetron discharge

Abstract: The spatial electron density distribution was measured as function of time in a high-power pulsed magnetron discharge. A Langmuir probe was positioned in various positions below the target and the electron density was mapped out. We recorded peak electron densities exceeding 10/sup 19/ m/sup -3/ in a close vicinity of the target. The dynamics of the discharge showed a dense plasma expanding from the "race-track" axially into the vacuum chamber. We also record electrons trapped in a magnetic bottle where the magnetron magnetic field is zero, formed due to the unbalanced magnetron.

DC microdischarges inside porous ceramics

Abstract: The hybrid plasma-catalyst system represents an effective method for the pollutant abatement from car exhaust. A problem, however, is a limited volume of the generated plasma, and a pressure drop across the catalyst layer. A new approach on the generation of microdischarges inside porous ceramic materials is reported. The results show that the stable generation of microdischarges can be observed only in ceramics with specific pore size.

Positive and negative ion sources for magnetic fusion

Abstract: The positive or negative ion sources which form the primary components of neutral beam injection systems used in controlled nuclear fusion using magnetic confinement have to meet simultaneously several demanding requirements. This paper describes the underlying physics of modern positive ion sources, which provide the required high proton fraction (>90%) and high current density (/spl ap/2 kA/m/sup 2/) at a low source pressure (0.4 Pa) with a high electrical efficiency and uniformity across the accelerator grids. The development of negative ion sources, which are required if high energy neutral beams are to be produced, is described, and the present understanding of the physics of negative ion production in sources is explained. The paper reports that negative ion sources have achieved many of the parameters required of sources for the neutral beam injectors of future fusion devices and reactors, >200 A/m/sup 2/ of D/sup -/ at low source pressure, <0.3 Pa, with a low co-extracted electron content. The development needed to meet all the requirements of future systems is briefly discussed.

Negative hydrogen ion sources for accelerators

Abstract: A variety of H/sup -/ ion sources are in use at accelerator laboratories around the world. A list of these ion sources includes surface plasma sources with magnetron, Penning and surface converter geometries as well as magnetic-multipole volume sources with and without cesium. Just as varied is the means of igniting and maintaining magnetically confined plasmas. Hot and cold cathodes, radio frequency, and microwave power are all in use, as well as electron tandem source ignition. The extraction systems of accelerator H/sup o/n sources are highly specialized utilizing magnetic and electric fields in their low energy beam transport systems to produce direct current, as well as pulsed and/or chopped beams with a variety of time structures. Within this paper, specific ion sources utilized at accelerator laboratories shall be reviewed along with the physics of surface and volume H/sup -/ production in regard to source emittance. Current research trends including aperture modeling, thermal modeling, surface conditioning, and laser diagnostics will also be discussed.

Measurements of the total ion flux from vacuum arc cathode spots

Abstract: The ion current from different cathode materials was measured for 50-500 A of arc current. The ion current normalized by the arc current was found to depend on the cathode material, with values in the range from 5% to 19%. The normalized ion current was generally greater for elements of low cohesive energy. The ion erosion rates were determined from values of ion current and ion charge states, which were previously measured in the same ion source. The absolute ion erosion rates ranged from 16-173 /spl mu/g/C.

Low-temperature direct current glow discharges at atmospheric pressure

Abstract: Low-temperature direct current (dc) glow discharges were successfully generated at one atmospheric pressure with very low-power consumption in the level of several watts up to tens of watts The glow discharges can be ignited and sustained in both continuous and pulsed modes, and can be run with several plasma gases including argon, helium, nitrogen, and air Depending on the gas flow rate ranged from tens of millimeters per minute to several liters per minute, the glow discharges can be created and sustained in between the two planar electrodes or blown out of the discharge chamber to form low-temperature plasma brushes The dc current to sustain the glow discharges is in the range of several milliamps to tens of milliamps Temperature measurements using a thermocouple thermometer showed that the gas temperatures of the plasma brushes are close to room temperature when running with relatively high gas flow rates

Novel dual Marx Generator for microplasma applications

Abstract: Micrometer size plasmas, or microplasmas, find applications in pollution control, reduction, and prevention. The required nonthermal plasmas can be generated by either an electron beam or an electric discharge. The pulse widths and voltages necessary to generate these nonthermal plasmas are 10/sup -10/-10/sup -8/ s, and 10/sup 3/-10/sup 4/ V, respectively, depending on the application. The required energy is typically in the low 10/sup -3/ J range. This paper presents a novel circuit design to generate high-voltage pulses with variable pulse widths and pulse rise and fall times in the low 10/sup -9/ s regime. The circuit employs two parallel Marx Generators utilizing bipolar junction transistors (BJTs) as closing switches. The BJTs are operated in the avalanche mode to yield fast rise times. The design allows for positive or negative polarity pulses, and can easily be changed to yield higher or lower output voltage.

Solid state Marx Generator using series-connected IGBTs

Abstract: This paper describes a newly developed novel repetitive impulse voltage generator using a boost converter array. To solve problems such as short life time, low operating frequency, and the fixed pulse width of conventional generators, the proposed generator is designed with a boost converter array that employs series-connected capacitors and insulated gate bipolar transistors. The circuit can easily obtain a high-voltage pulse without any high-voltage direct current source and pulse transformer. Thus, the proposed circuit not only allows elimination of the expensive high-frequency transformer but also allows operation at a frequency up to several kilohertz with high reliability and longer life span. To validate the proposed circuit, two pulse generators rated at 1.8 kV, 40 A and 20 kV, 300 A are implemented and tested.

Volume production negative hydrogen ion sources

Abstract: We review the evolution of volume production negative hydrogen ion sources since the discovery in 1977 of the new phenomenon, designated as volume production and attributed to dissociative electron attachment of low energy electrons to rovibrationally excited molecules. The experimental verification in 2005 of the reality of this mechanism is reported. The magnetically filtered tandem sources, using hot filaments or inductively coupled radio frequency discharges, proposed in order to make use of the volume production mechanism, are used as continuous wave sources for cyclotrons and short pulse sources for synchrotrons. The extraction physics, required to correlate the negative ion and electron densities near the extraction opening with the extracted currents, is discussed taking into account the recently measured H/sup -//D/sup -/ ion temperatures. It is also shown that the extracted negative ion current can be predicted from the directed flow velocity (measured by two laser photodetachment) and the negative ion density measured in the extraction region plasma. Progress in modeling the volume production negative hydrogen ion sources is briefly summarized. Main attention has been paid to some recent topics, such as negative ion temperature and specific for two negative species plasmas transport in a weak transverse magnetic field. A new view on the potential of volume production making use of the vibrationally excited molecules produced on surfaces (plasma electrode, walls) by recombinative desorption is presented.

Three-dimensional computation of reduction in Radar cross section using plasma shielding

Abstract: We have performed three-dimensional (3-D) finite-difference time-domain (FDTD) simulations for calculating microwave scattering from metallic objects shielded by a plasma shroud. Such simulations are of interest for plasma-based stealth technology. The simulations yield a reasonable match with experimental measurements. A physical interpretation has also been provided for these results, in terms of the flow of electromagnetic power. Such an analysis is only possible using the detailed spatio-temporal evolution of electromagnetic fields that is provided by the FDTD method. We find that apart from absorption, the bending of waves toward regions of lower plasma density plays an important role in determining the extent of backscatter. This has major implications for plasma stealth applications, which have heretofore assumed that plasma absorption is the main mechanism. Also, bending could actually enhance radar scattering in directions oblique to the incident direction. We have also identified situations where 3-D simulations become necessary, and other situations where a composite one-dimensional simulation may be enough. This has practical relevance since it could help reduce the demand for computational resources while modeling large objects like aircraft.

Experimental study of cathode spot motion and burning voltage of low-current vacuum arc in magnetic field

Abstract: This experimental study dealt with cathode spot (CS) motion and the burning voltage of a low-current vacuum arc with electrodes of HCOF Cu and with a composition of CuCr30, subjected to a magnetic field. Arcs with current of I/spl ap/30 A burned in axial and transverse fields as well as with the induction vector inclined at an angle 5/spl deg/

The fractal nature of vacuum arc cathode spots

Abstract: Cathode spot phenomena show many features of fractals, for example self-similar patterns in the emitted light and arc erosion traces. Although there have been hints on the fractal nature of cathode spots in the literature, the fractal approach to spot interpretation is underutilized. In this work, a brief review of spot properties is given, touching the differences between spot type 1 (on cathodes surfaces with dielectric layers) and spot type 2 (on metallic, clean surfaces), as well as the known spot fragment or cell structure. The basic properties of self-similarity, power laws, random colored noise, and fractals are introduced. Several points of evidence for the fractal nature of spots are provided. Specifically, power laws are identified as signature of fractal properties, such as spectral power of noisy arc parameters (ion current, arc voltage, etc.) obtained by fast Fourier transform. It is shown that fractal properties can be observed down to the cutoff by measurement resolution or occurrence of elementary steps in physical processes. Random walk models of cathode spot motion are well established: they go asymptotically to Brownian motion for infinitesimal step width. The power spectrum of the arc voltage noise falls as 1/f/sup 2/, where f is frequency, supporting a fractal spot model associated with Brownian motion.

Removal of volatile organic compounds in atmospheric pressure air by means of direct current glow discharges

Abstract: A nonthermal plasma with an electron density on the order of 10/sup 12/ cm/sup -3/ and a gas temperature of 2000 K was generated in atmospheric pressure air, using a microhollow cathode discharge as plasma cathode. The plasma was sustained in a /spl sim/1 mm/sup 3/ micro reactor, by a voltage of 470 V between the plasma cathode and a planar anode, and at currents ranging from 12 to 22 mA. This direct current glow discharge has been used to study the remediation of methane and benzene, two of the most stable volatile organic compounds (VOCs). The removal fraction for 300-ppm methane in atmospheric pressure air, flowing through the 0.5-mm thick plasma layer, with a residence time of the gas in the plasma of less than 0.5 ms, was measured at 80% with an energy density of 4 kJ/L. For benzene, the remediation rate is as high as 90%, comparable to results obtained with low pressure glow discharges. The energy efficiency for benzene remediation is 0.9 g/kWh, higher than that obtained for benzene remediation in low pressure glow discharges in noble gases. However, the VOC fraction remaining was found to be limited to values of approximately 0.1 and 0.05 for methane and benzene, respectively. In addition to experimental studies, the VOC dissociation mechanism in a VOC/dry air mixture plasma was modeled using a zero-dimensional plasma chemistry code. The modeling results have shown that atomic oxygen impact reactions are the dominant dissociation reactions for VOC destruction in this kind of glow discharge. Diffusion of atomic oxygen to the dielectric walls of the reactor is assumed to cause the observed limitation in the VOC destruction rate and efficiency.

Effect of electric fields on the liftoff of nonpremixed turbulent jet flames

Abstract: The effect of electric fields on the liftoff of nonpremixed turbulent jet flames has been investigated by applying high-voltage alternate current (ac) to the nozzle of propane fuel. Flame liftoff velocities and liftoff heights were measured as functions of applied voltage and frequency. The fuel jet velocity at flame liftoff increased and flame liftoff height decreased with increasing voltage, implying that the range of flame stability can be extended with the ac charging. Meanwhile, the effect was minimal when applying direct current (dc). This stabilization effect with ac charging was also influenced by the frequency. As the applied voltage increased, a streamer corona was generated between the flame edge and the nozzle. When the jet velocity and, thus, the liftoff height becomes large, then the ac charging effect disappeared in such a way that the flame liftoff height became comparable to that of a free jet without applying voltage. The liftoff velocity was correlated linearly with voltage in the corona-free electric field enhanced regime.

High-frequency multimegawatt polyphase resonant power conditioning

Abstract: High-frequency multimegawatt polyphase resonant power conditioning techniques have recently been realized as a result of key component developments, cooperative efforts, research and development funding contracts, and newly applied engineering techniques. The first generation 10-MW pulsed converter-modulators, implemented at Los Alamos National Laboratory, Los Alamos, NM, are now utilized for the Oak Ridge National Laboratory, Oak Ridge, TN, Spallation Neutron Source (SNS) accelerator klystron radio frequency amplifier power systems . Three different styles of polyphase resonant converter-modulators were developed for the SNS application. The various systems operate up to 140-kV, or 11-MW pulses, or up to 1.1 MW average power, all from a direct current input of +/-1.2 kV. The component improvements realized with the SNS effort coupled with new applied engineering techniques have resulted in dramatic changes in overall power conditioning topology. As an example, the 20-kHz high-voltage transformers are less than 1% the size and weight of equivalent 60-Hz versions. With resonant conversion techniques, load protective networks are not required. A shorted load de-tunes the resonance which results in limited power transfer. This provides for power conditioning systems that are inherently self-protective, with automatic fault "ride-through" capabilities. By altering and iterating the Los Alamos design, higher power and continuous wave power conditioning systems can now be realized with improved performance and flexibility. This paper will examine the SNS engineering data, briefly review the underlying theory of polyphase resonant conversion techniques, and apply this knowledge to future system topologies.

Critical component requirements for compact pulse power system architectures

Abstract: The fundamental limits on the volume and energy density of a pulse power that is to deliver a specific peak power pulse to a load depends upon the architecture of the system, the operational mode of the system, the energy storage geometries, the switching parameters employed, and the auxiliary equipment required. This paper examines these factors and develops the fundamental limits on the volume of a pulse power system for a given output pulse energy and pulse length. The fundamental limits on power density lead to the selection of an optimum architecture, which leads to critical specifications for the components involved. This paper develops and presents those specifications for the major components in a pulse power system with maximum power density. Two prototype systems, a short pulse (50 ns) system and a long pulse (1 /spl mu/s) system, are designed as examples of the optimum pulse power architecture and the resulting component requirements.

High-speed observations of arc modes and material erosion on RMF- and AMF-contact electrodes

Abstract: Vacuum interrupters, particularly with high short-circuit interruption ability, are mostly equipped with contact systems based on two different principles: the widely used radial magnetic field (RMF) contact and the axial magnetic field (AMF) contact system. In this investigation, contact electrodes performance of an improved RMF system was compared with both an unipolar and a quadrupolar AMF contact system. By using a high-speed complementary metal oxide semiconductor digital video camera, the different systems were observed during arcing under short-circuit conditions at different current levels, concentrating on arc modes development with different arcing times. Contact erosion and thermal stress of the high-current vacuum arc on the contacts was basically evaluated on the basis of contact melting depth, with the result of comparable melting depths at insignificantly higher thermal stress of the RMF versus AMF systems. The microstructure of the copper and chromium compound contact material cross section was analyzed by means of a scanning electron microscope.

Two-dimensional simulation of photon acceleration by using laser wake fields

Abstract: Two-dimensional simulations of photon acceleration by using a laser wake field are presented with a fully electromagnetic and relativistic particle-in-cell code. The frequency increase of about 10% is observed, which is saturated mainly by diffraction and dispersion of the laser pulse. Images of electron density and laser field profiles are presented.

Laser ion sources

Abstract: Laser ion sources (LIS) are capable of delivering short pulses of highly charged ions of almost any element, with high intensity. In this paper, the basic processes of the laser interaction with plasma generated from a solid target will be discussed. The application of the laser-plasma theory will be applied to the subsystems of the LIS, and some examples of ion beam properties given, with a more detailed description of the implementation of a LIS at ITEP, Moscow. Finally the parameters for a LIS for high-current, low charge-state, long pulse operation will be discussed, along with transverse magnetic confinement, and the possibilities for injecting a laser plasma into an electron cyclotron resonance ion source.

Nonthermal plasma applications to the environment: gaseous electronics and power conditioning

Abstract: For nearly two decades, interest in gas-phase pollution control has greatly increased, arising from a greater respect for the environment, more attention to the effects of pollution, and a larger body of regulations and laws. Nonthermal plasma (NTP) technology shows promise for destroying pollutants in gas streams and cleaning contaminated surfaces, using plasma-generated reactive species (e.g., free radicals). NTPs can generate both oxidative and reductive radicals, showing promise for treating a variety of pollutants, sometimes simultaneously decomposing multiple species. In this paper, some applications of NTP processing for the environment, associated discharge physics and plasma chemistry, and power conditioning systems for driving the NTP reactors will be discussed.

Decomposition of volatile organic compounds in plasma-catalytic system

Abstract: A plasma-catalytic combined reactor system was used to decompose volatile organic compounds. Metal oxide catalysts, as well as Pt-based catalyst, were employed in the studies. The plasma treatment alone leads to the formation of high concentration of byproducts. A Pt-based catalyst, combined with plasma reactor, was helpful in minimizing the byproduct formation. The plasma reactor significantly enhances the catalytic performance. Plasma reactor, combined with Pt-based catalyst, removed more than 90% of toluene. The Pt-based catalyst completely removed the CO produced by plasma reactor. In order to determine the mechanism of the plasma treatment, the plasma reactor was replaced by ozone reactor and the results were compared with plasma-catalytic reactor. It was found that ozone plays a significant role in enhancing the catalytic activity.

Nanosecond pulse Generator using fast recovery diodes for cell electromanipulation

Abstract: Design and operation of a fast recovery diode based pulse generator is presented. The generator produces 3.5-ns-wide, 1200 V amplitude unipolar pulses or +/-600-V bipolar pulses into 50-/spl Omega/ load at the maximum repetition rate of 100 kHz. Pulses shorter than 10 ns are essential for the studies of biological cell response to high electric fields while avoiding ordinary electroporation effects dominant at long pulses. Bipolar pulses are used for the studies of biological cell response to high electric fields when the net transfer of charge is undesirable. The bipolar pulse is produced from a unipolar pulse with the help of a shorted transmission line. This transmission line delays and inverts the initial pulse, so the output is the sum of the initial and the inverted and delayed pulses. The use of mass-produced fast recovery surface-mount rectifier diodes in this circuit substantially simplifies the generator and results in low cost and very small footprint. Similar diode switched pulse generators have been described in the literature using mostly custom fabricated snap-recovery diodes. Here we give an example of an ordinary low-cost diode performing similarly to the custom fabricated counterpart. The diode switched circuit relaxes the requirement on the speed of the main closing switch; in our case, a low-cost power metal-oxide semiconductor field-effect transistor (MOSFET)-saturable core transformer combination.

Branching of positive discharge streamers in air at varying pressures

Abstract: The formation of positive streamers in a 17-mm gap in air is studied at pressures varying in the range from 1010 to 100 mbar. An intensified charge coupled device camera is used to image the discharge. At high pressures, the discharge shows many branches, while at low pressure, fewer branches arise. The structure is not simply determined by the ratio of voltage over pressure.

Generation of high-power ultrasound by spark discharges in water

Abstract: It is impractical to achieve the desired combination of power and bandwidth from conventional electromechanical acoustic sources. However, these characteristics can be achieved by the use of pulsed power technology to generate high-power ultrasound (HPU). High-voltage pulses induce the electrical breakdown of water and the resulting bubble formation and collapse produce acoustic waves of high power and frequency. The dynamics of spark generated bubbles are formulated to predict the development of the bubble radius with time and an experimental system to produce a consistent source of spherically symmetric HPU acoustic waves is described. Pressure pulses due to both bubble formation and collapse were detected and, although their relative amplitudes varied, their frequency spectra did not differ significantly. The amplitude of the acoustic output rises sharply for applied pulse energies up to /spl sim/25 J but the effect saturates indicating little gain and poor efficiency by using high-energy pulses. Variation of the source topology in the form of the electrode separation was found to be the most important factor in the acoustic output. The detected HPU increased as the source became larger but as the two-thirds power of the electrode separation, thereby showing progressively diminishing enhancement. The frequency content of the acoustic signal did not appear to vary with either applied pulse energy or the electrode separation.

Dielectric barrier discharge technique in improving the wettability and adhesion properties of polymer surfaces

Abstract: A dielectric barrier discharge (DBD) in helium at atmospheric pressure was used to improve the polymer surface wettability as a first condition for ensuring a good adhesivity in particular for a subsequent immobilization of selected biological macromolecules (heparin, drugs, enzymes, etc.) on these surfaces. The DBD was analyzed by electrical measurements and optical emission spectroscopy. The polymer surface was characterized by thermodynamic parameters which may predict the adhesion properties, the adhesion work and the surface polarity, and also by its morphology. The results show that the DBD treatments improve the wettability and thus the adhesive properties due to the creation of functional groups and less due to a physical adsorption induced by an expected larger area of the treated surfaces. Dimensions of grains/crystallites are decreased on the treated surface, but a significant and systematic modification of the surface roughness was not observed.

Compact high repetition rate pseudospark pulse Generator

Abstract: A pseudospark-based high repetition rate pulse generator, together with a resonant charging power supply is presented. The pulse generator was developed for research applications that include transient plasma ignition. The design incorporates a lumped element Blumlein pulse-forming network that is switched by a commercial pseudospark into an output pulse transformer with a METGLAS core. The Blumlein is charged up to 30 kV by a resonant capacitor charger, based on a fly-back transformer and high-power insulated gate bipolar transistor (IGBT) switch module. The output voltage of the charger is controlled by the on-time of the IGBT. Pulses with duration of 50 ns can be generated at a 2.6-kHz maximum repetition rate. Pulses with amplitude up to 90 kV can be delivered into a 200-/spl Omega/ load.

Time-resolved measurements of electron number density and collision frequency for a fluorescent lamp plasma using microwave diagnostics

Abstract: Microwave interferometry is an established nonperturbing plasma diagnostic technique to measure plasma number density that is simple, accurate, robust, and reliable. This paper reports a related microwave diagnostic method that measures both the electron number density and the electron-neutral collision frequency, which are crucial to understanding the behavior and transport coefficients of plasma. This method measures the attenuation and phase shift of a microwave signal propagating through a plasma with a network analyzer. These measured quantities are related to the real and imaginary parts of the plasma index of refraction by Appleton's equations, which contain the electron number density and collision frequency. Since the electron number density and collision frequency can be obtained directly from measured quantities, one need not know the electron energy distribution function, the electron kinetic temperature, or the electron energy-dependent cross section for the collision process to determine the electron collision frequency. The experimental measurements used to illustrate the method are a paired comparison of the time-resolved electron number density and collision frequency of two types of commercial fluorescent lamps: the "standard" mercury-based lamp, and the recently introduced "green" low mercury lamp. Since the plasma properties are periodic at 60 Hz, time-resolved measurements could be made by using the external triggering feature of the network analyzer. Data were taken to illustrate the variation of electron number density and collision frequency during one 60-Hz cycle of the fluorescent lamp plasmas.