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Plasma Science, IEEE Transactions on

Issue 7  Part 2 • Date July 2009

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Displaying Results 1 - 25 of 31
  • Table of contents

    Page(s): C1 - 1189
    Save to Project icon | Request Permissions | PDF file iconPDF (45 KB)  
    Freely Available from IEEE
  • IEEE Transactions on Plasma Science publication information

    Page(s): C2
    Save to Project icon | Request Permissions | PDF file iconPDF (38 KB)  
    Freely Available from IEEE
  • Pulsed Atmospheric-Pressure Cold Plasma for Endodontic Disinfection ^{\ast }

    Page(s): 1190 - 1195
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (652 KB) |  | HTML iconHTML  

    A new plasma dental probe (PDP), powered with 4-6-kV ~100-ns electric pulses at repetition rates of up to 2 kHz, generates a room-temperature > 2-cm-long ~2-mm-diameter plasma plume at ambient atmospheric pressure. The shape of the plasma plume depends on the gas flow rate and the pulse voltage. Growth of Bacillus atrophaeus on nutrient agar plates is completely inhibited by exposure to both He and He/(1%)O2 plasmas for 60 s. A 300-s treatment with the He/(1%)O2 plasma disinfected a human tooth root canal colonized with saliva-derived biofilms, demonstrating the potential of the PDP as a simple, safe, and effective tool or adjunct for the disinfection of root canals during endodontic therapy. He/(1%)O2 plasma is more effective than He alone for B. atrophaeus growth inhibition, and the emission spectrum of the He-O2 plasma supports the identification of atomic oxygen as the likely primary reactive chemical species contributing to bacterial inactivation. View full abstract»

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  • Evolution of a Two-Temperature Plasma Expanding With Metal Vapor Generated by Electron-Beam Heating

    Page(s): 1196 - 1202
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (204 KB) |  | HTML iconHTML  

    During the electron-beam evaporation of metals, a weakly ionized plasma is formed, which consists of two different groups of electrons characterized by different energy spreads (or temperature). While this plasma expands along with the metal vapor, a thermodynamic equilibrium between these two groups of electrons is gradually established by electron-electron Coulomb collisions and electron-atom inelastic collisions. The evolution of this two-temperature plasma was experimentally observed by a Langmuir probe during an electron-beam evaporation of zirconium. Mathematical expressions for the effect of different interactions on the evolution of the electron temperatures of the plasma were derived and applied to our experimental observations. Taking the initial temperature of the plasma at the source of vapor, the total cross section for electron-atom inelastic collisions was calculated, the order of which agreed well with the reported values. Finally, the contributions of each type of interaction (electron-electron and electron-atom) on the cooling of the high-temperature group of electrons in the plasma are quantified. View full abstract»

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  • Development of a Transformable Plasma Device for Materials Processing

    Page(s): 1203 - 1207
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (344 KB) |  | HTML iconHTML  

    In this paper, we have developed transformable-sheet electrodes for a capacitively coupled microwave plasma (CCMP) and diagnosed parameters of the CCMP in air, such as the rotational temperature of N2 (400-600 K at 80-230 torr) and the electron density (approximately 1013/cm3 at 300 torr). We applied the CCMP to surface modification of polycarbonate to improve the hydrophilic property of the surface. We also performed generation of a homogeneous plasma, which could be of various shapes, developing different transformable-sheet electrodes in air by ac (1.6 kV) at 10 kHz at 3 torr. These results suggested that on-demand plasma processing without an operating gas could be achieved by utilizing transformable-sheet electrode technology. View full abstract»

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  • Fluid Modeling and Analysis of the Constriction of the DC Positive Column in Argon

    Page(s): 1208 - 1218
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (296 KB) |  | HTML iconHTML  

    The glow-to-arc transition of the positive column of a dc discharge in argon in the course of constriction has been investigated on the basis of a self-consistent 1-D axisymmetric fluid model. The model adopts the nonlocal moment method, i.e., the system of balance equations resulting from the moments of the radially dependent Boltzmann equation is solved. The electron transport and rate coefficients are applied in dependence on the mean energy of the electrons, the gas temperature, and the ionization degree. Investigations have been performed for currents from 0.6 to 70 mA and pressures from 100 to 500 torr. The model predictions are compared with experimental and other available modeling results, and they show good agreement with these data in general. The pronounced nonlocal features of the mean electron energy balance are found, and their influence on the constricted argon positive column is analyzed. Different assumptions concerning the electron velocity distribution function have been considered in the present model. In particular, the impact of using a Maxwellian distribution instead of solutions of the steady-state spatially homogeneous electron Boltzmann equation is discussed where the assumption of a Maxwellian distribution for the electrons was found to be inappropriate for describing the constriction effect. View full abstract»

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  • Observation and Study of Low-Frequency Oscillations in a 1.5-MW 110-GHz Gyrotron

    Page(s): 1219 - 1224
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (398 KB) |  | HTML iconHTML  

    We report the observation of low-frequency oscillations (LFOs) in the range 165-180 MHz in a 1.5-MW 110-GHz gyrotron operating in 3-mus pulses. The oscillations have been measured by a capacitive probe located just before the entrance to the cavity. The LFOs are observed only in a narrow region of beam parameter space, at voltages between 45 and 60 kV, where no microwave emission occurs. When the gyrotron operates near 96 kV, with high output power, they are not seen. The variation of the frequency of the oscillations with electron beam voltage and magnetic compression was measured, and the results are reported. Time-domain analysis of the probe signal shows the influence of the beam current and cathode voltage on the time of onset of the oscillations. The amplitude of the time-domain signal indicates that the trapped electron current associated with the LFOs represents a few percent of the total electron current. View full abstract»

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  • The Arletron: A New Buncher for High-Repetition-Rate HPM Operation

    Page(s): 1225 - 1232
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1140 KB) |  | HTML iconHTML  

    In this paper, I present simulations of a new buncher that can be used in a compact high-repetition-rate high-power microwave device. The bunching mechanism involves the growth of the II-mode of two coupled cavities traversed by a medium-power annular electron beam (200 keV, 1 kA). The cavities are simple pillboxes, and frequency tuning can be obtained by using plungers to vary the internal radius of the cavities. Since the magnetic field needed to ensure beam transport is small enough to be provided by permanent magnets, no external source is required. View full abstract»

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  • Effects of Different Cathode Materials on Submicrosecond Double-Gap Vircator Operation

    Page(s): 1233 - 1241
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (971 KB) |  | HTML iconHTML  

    The operation of a double-gap S-band vircator has been investigated at submicrosecond duration of a high-current electron beam generated in a planar diode. The experiments were performed at accelerating voltages of les550 kV and diode currents of up to 17 kA using a radio-frequency cavity with a wide coupling window between its two sections. Three types of cathodes have been studied, namely, metal-dielectric, carbon fiber, and velvet cathodes. The main features of the operation of the vircator using each cathode are analyzed. The microwave pulse duration with the metal-dielectric and carbon fiber cathodes reached ~250 ns at the peak power level of ~100 MW; with the velvet cathode, a duration of ~400 ns was achieved. It has been found that, in addition to the common limitations of the microwave pulse duration related to the dynamics of the diode impedance governed by the cathode plasma expansion, there is another factor, namely, the anode-cathode gap, which determines the delay at the beginning of the microwave generation. The latter effect is explained by the role of electrons oscillating between the virtual and real cathodes in the generation process. The issue of radiated microwave frequency behavior is discussed as well. View full abstract»

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  • Relativistic Cherenkov Microwave Oscillator Without a Guiding Magnetic Field

    Page(s): 1242 - 1245
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (404 KB) |  | HTML iconHTML  

    In this paper, microwave oscillation in which an electromagnetic wave and a continuous cylindrical relativistic electron beam (REB) with no magnetic field are in Cherenkov synchronism was studied. Analytical estimates of the beam-transport length were given, and analysis of the effect of electron-beam premodulation on the oscillator starting current and linear efficiency was made. Using numerical simulation, the oscillator geometry with a slow wave structure of length about three times the wavelength and with an efficiency of 30%-44% was determined. In experiment, the transport of a continuous cylindrical high-current REB over a distance about two times greater than the drift-tube diameter was demonstrated. Stable oscillation with ap 10% efficiency was obtained, taking into account the total current of a planar diode producing the electron beam. The microwave peak power for the operating TM01 mode was 1.3 plusmn 0.3 GW at 4.03 GHz. View full abstract»

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  • Numerical Studies on a Novel Coaxial Single-Pass Superradiance Relativistic Backward-Wave Oscillator

    Page(s): 1246 - 1250
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (207 KB) |  | HTML iconHTML  

    In this paper, a novel coaxial single-pass superradiance relativistic backward-wave oscillator (SR-RBWO) is proposed and studied by simulation. In the proposed SR-RBWO, a coaxial structure is used in the beam-wave interaction region. The outer conductor is a corrugated waveguide, and the inner conductor is hollow inside and forms a circular waveguide. The circular waveguide is then used as the output waveguide. Instead of being reflected, microwaves will be coupled to the output waveguide by the coupling hole at the electron-injector (left) end. Cutoff neck is not required. Strongly nonuniform corrugation depth is used near the collector edge to increase the power-conversion efficiency. For an electron beam having a 3.25-GW power in 4.9-ns pulse, in the proposed SR-RBWO with optimized parameters, the SR pulses of a 7-GW power and 450-ps pulse duration are obtained by simulation at an 8.2-GHz center frequency that corresponds to the power-conversion efficiency of 215%. The applied magnetic field is about 2.7 T. View full abstract»

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  • Resonant Transmission of Electromagnetic Waves in Multilayer Dense-Plasma Structures

    Page(s): 1251 - 1260
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (237 KB) |  | HTML iconHTML  

    An analysis of electromagnetic-wave propagation in dense plasmas when the wave frequency is below the cutoff frequency is presented. Under such conditions, the wave amplitude is usually exponentially attenuated due to collisionless skin effect. It is shown that combining multiple plasma layers of various densities induces a surface-wave resonance, which greatly enhances electromagnetic-wave transmission. Absolute transmission can be achieved even for plasma thickness of many skin depths. Resonant conditions are investigated analytically and numerically. View full abstract»

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  • Energetic Particles and Radiation Intense Emission During Ferroelectric Surface Discharge

    Page(s): 1261 - 1266
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (360 KB) |  | HTML iconHTML  

    In this paper, the operation of ferroelectric plasma sources (FPSs) under the application of driving pulses with different amplitudes (4-40 kV) was studied. It was found that, in addition to the electron/ion flows studied in earlier research, the dense plasma formation during the fast fall (a few tens of nanoseconds) of the driving pulse is accompanied by the generation of a highly diverging ~180deg neutral flow with velocity of ~7ldr107 cm/s as well as by charged microparticles and intense extreme ultraviolet radiation. It was shown that the velocity and intensity of the generated neutral flow remained the same for different parameters of the driving pulse. A model for the neutrals and microparticles emission based on Coulomb microexplosions of ferroelectric ceramics is suggested. The application of the FPS as a promising micro thruster is also discussed. View full abstract»

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  • Proposed High Energy Density Physics Research Using Intense Particle Beams at FAIR: The HEDgeHOB Collaboration

    Page(s): 1267 - 1275
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (597 KB) |  | HTML iconHTML  

    Physics of high energy density (HED) matter is an ever-expanding field of research with very wide applications to basic and applied physics and with great potential for revolutionary technological and industrial applications. Over the past decades, static as well as dynamic configurations have been widely used to research this interesting field of science. Recent technological advances in the development of high-quality well-focused strongly bunched intense particle beams have led to the idea of generating samples of HED matter using isochoric and uniform heating of solid targets by such intense beams. Theoretical work reported in this paper explores the possibility of carrying out novel experiments using the future Facility for Antiprotons and Ion Research at Darmstadt. View full abstract»

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  • Optimizing UNU/ICTP PFF Plasma Focus for Neon Soft X-ray Operation

    Page(s): 1276 - 1282
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (223 KB) |  | HTML iconHTML  

    The United Nations University/International Centre for Theoretical Physics Plasma Focus Facility (UNU/ICTP PFF), a 3.3-kJ plasma focus, was designed for operation in deuterium with a speed factor S such that the axial run-down time matches the current rise time at an end axial speed of nearly 10 cm/mus. For operation in neon, we first consider that a focus pinch temperature between 200 and 500 eV may be suitable for a good yield of neon soft X-rays, which corresponds to an end axial speed of 6-7 cm/mus. On this basis, for operation in neon, the standard UNU/ICTP PFF needs to have its anode length z0 reduced by some 30%-40% to maintain the time matching. Numerical experiments using the Lee model code are carried out to determine the optimum configuration of the electrodes for the UNU/ICTP PFF capacitor system. The results show that an even more drastic shortening of anode length z0 is required, from the original 16 to 7 cm, at the same time, increasing the anode radius ldquoardquo from 0.95 to 1.2 cm, to obtain an optimum yield of Y sxr = 9.5 J. This represents a two- to threefold increase in the Y sxr from that computed for the standard UNU/ICTP PFF. View full abstract»

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  • Advances in Novel Plasma Devices Based on the Plasma Lens

    Page(s): 1283 - 1288
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (490 KB) |  | HTML iconHTML  

    We review some new results in the development of novel cylindrical plasma devices based on the electrostatic plasma lens configuration and the concepts of electron magnetic insulation and magnetic field line equipotentialization. The plasma lens configuration of crossed electric and magnetic fields provides an attractive method for establishing a stable plasma discharge at low pressure. Use of the plasma lens configuration in this way has been explored, and a number of easily maintained low-cost plasma devices for ion treatment and deposition of exotic coatings have been developed. These devices make use of permanent magnets and possess considerable flexibility with respect to spatial configuration. They can be operated as a stand-alone tool for ion treatment of substrates, or as part of an integrated processing system together with cylindrical magnetron sputtering, for coating and deposition. Here, we describe the operation and features of some cylindrical plasma devices based on the plasma lens configuration, the results of theoretical investigations of the plasma discharge characteristics, and experimental investigations of the physical mechanisms determining optimal operating conditions for these devices. View full abstract»

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  • From Submicrosecond- to Nanosecond-Pulsed Atmospheric-Pressure Plasmas

    Page(s): 1289 - 1296
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (769 KB) |  | HTML iconHTML  

    We have developed a time-hybrid computational model to study pulsed atmospheric-pressure discharges and compared simulation results with experimental data. Experimental and computational results indicate that increasing the applied voltage results in faster ignition of the discharge and an increase in the mean electron energy, opening the door to tunable plasma chemistry by means of pulse shaping. Above a critical electric field of ~2 kV/mm for ~1-mm discharges, pulsed plasmas ignite right after the application of an externally applied voltage pulse. Despite the large pd value (30-300 torr ldr cm) and the high applied electric field, the discharges are found to be streamer free in a desirable glow like mode. The comparison of the time evolution of the mean electron kinetic energy as a function of the pulse rise time suggests that a fast rise time is not necessarily the best way of achieving high mean electron energy. View full abstract»

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  • Atmospheric-Pressure Air Glow Discharge in a Three-Electrode Configuration

    Page(s): 1297 - 1304
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (830 KB) |  | HTML iconHTML  

    Nonthermal non-self-sustained dc glow discharge in atmospheric-pressure air was developed in a three-electrode configuration. A self-sustained normal dc atmospheric-pressure glow discharge in helium served as a ldquoplasma cathoderdquo for the main discharge in ambient air. Conditions of discharge transfer from helium volume to atmospheric air are under investigation. It is shown that a smooth transfer between the discharges in both volumes takes place only at small gaps between the ldquoplasma cathoderdquo and the third electrode (less than 5 mm) as the voltage applied to the air gap is increased. For larger gaps, this transfer is accompanied by discontinuous changes in both the voltage and current. After the jump, the discharge is contracted. But if the interelectrode gap is increased (more than 10 mm), then two forms of the discharge exist in one discharge space: diffuse and contracted. View full abstract»

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  • An Improved Adaptive Subfield Coding Method for Driving AC PDPs

    Page(s): 1305 - 1310
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (931 KB) |  | HTML iconHTML  

    An improved adaptive subfield coding driving method was proposed to reduce the static false contours when the simple-accumulation lighting mode is applied to alternating current plasma display panels (ac PDPs). In the proposed method, when the weighted ratio of the subgrayscale interval to the main grayscale interval is smaller, the gray cumulative probability densities in the subgrayscale interval are sampled in order to locate the sampling gray levels at which the gray probability densities are larger. When the weighted ratio of the subgrayscale interval to the main grayscale interval is larger, the gray levels in the subgrayscale interval are sampled directly so as not to generate larger quantization error brought by the excessive convergence of the sampling gray levels. The simulation results show that the proposed method can eliminate the dynamic false contours in the AC PDPs and has better grayscale expression capability than the existing similar method appearing in the literature. The method proposed in this paper can reproduce the original image information more faithfully. View full abstract»

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  • The Estimation of the Current-Density Distribution in a Moving Arc Root Using the ART Algorithm

    Page(s): 1311 - 1317
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (718 KB) |  | HTML iconHTML  

    This paper mainly contributes to the estimation of 2-D current-density distribution in a moving arc root. For this purpose, the multiple-split-cathode-with-different-slit-angle method is used to perform measurements of the linear current distribution of the arc root in seven different directions. On the basis of the measurement results, a large system of linear algebraic equations is treated with the algebraic-reconstruction-technique algorithm to obtain the 2-D current density. The calculation results indicate that the transverse profile of current density in a moving arc root can be characterized by a high-current core with two low-current hysteretic wings and that the maximum current density tends to the fore part of it. View full abstract»

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  • Experimental Study on Multigap Multichannel Gas Spark Closing Switch for LTD

    Page(s): 1318 - 1323
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (865 KB) |  | HTML iconHTML  

    In this paper, a multigap multichannel gas spark closing switch (MMCS) has been modified to improve the synchronous closing characteristics of ten switches designed for linear transformer driver (LTD). Convexo-convex discal electrodes have been used instead of the plane toroidal electrodes to improve the electric field across the gaps. A new endo-grooved plane bracing structure has been designed for fixing the electrodes instead of the small ball anchoring method to ensure the length of the gap uniformity. In order to observe the discharge process of the MMCS, the transparent lucite insulation chambers instead of the nylon ones have been used. A test circuit comprising a single discharge circuit called LTD brick has been established to investigate the self-breakdown and triggered breakdown characteristics of ten switches. The results show that when switches are filled with pure nitrogen of 0.14 MPa and charged to plusmn60 kV, the synchronous discharge of ten MMCSs has output a current pulse with an amplitude of about 100 kA and a rise time of 100 ns. View full abstract»

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  • Design of the Plasma Position and Shape Control in the ITER Tokamak Using In-Vessel Coils

    Page(s): 1324 - 1331
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (693 KB) |  | HTML iconHTML  

    The International Thermonuclear Experimental Reactor (ITER) is the next step toward the realization of electricity-producing fusion power plants, and it is planned to be in operation in 2016. ITER has been designed so as to reach the plasma burning condition and to operate with high-elongated unstable plasmas. However, due to the constraints that affect the machine realization, these open-loop unstable high-performance plasmas can hardly be stabilized using the poloidal field coils placed outside the tokamak vessel. For this reason, during the ITER design review phase, it has been proposed to investigate the possibility of using in-vessel coils in order to improve the best achievable performance of the vertical stabilization (VS) system. This paper proposes a new approach for the plasma current, position, and shape control design in the presence of in-vessel coils. Two control loops are designed: a first loop that guarantees the VS driving the voltage applied to in-vessel coils, and a second loop that controls the plasma current and up to 32 geometrical shape descriptors as close as possible to the reference values. The performance of the proposed control system is shown by means of simulations of some cases of interest. View full abstract»

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  • Measurement of the Vacuum Arc Plasma Force

    Page(s): 1332 - 1337
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (668 KB) |  | HTML iconHTML  

    The axial force carried by the expanding plasma plume from 50-250-A copper and aluminum vacuum arcs was measured using a pendulum whose axle was equipped with a rotary optical encoder. It was found that the force was a linear function of current. The electrode geometry was varied to find the maximum force. At maximum, the average forces per unit current were 21.4 dyn/A for aluminum cathodes and 36.1 dyn/A for copper cathodes. The Cu ion current fraction was measured to be 8.6%. View full abstract»

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  • Special issue on numerical simulation of plasmas

    Page(s): 1338
    Save to Project icon | Request Permissions | PDF file iconPDF (143 KB)  
    Freely Available from IEEE
  • Special issue for invited papers from the 36th International Conference on Plasma Science 2009

    Page(s): 1339
    Save to Project icon | Request Permissions | PDF file iconPDF (455 KB)  
    Freely Available from IEEE

Aims & Scope

IEEE Transactions on Plasma Sciences focuses on plasma science and engineering, including: magnetofluid dynamics and thermionics; plasma dynamics; gaseous electronics and arc technology.

 

 

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Steven J. Gitomer, Ph.D.
Senior Scientist, US Civilian Research & Development Foundation
Guest Scientist, Los Alamos National Laboratory
1428 Miracerros Loop South
Santa Fe, NM  87505  87505  USA
tps-editor@ieee.org
Phone:505-988-5751
Fax:505-988-5751 (call first)