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Fast neutrons from deuteron-deuteron fusion reactions were used for a study of fast deuterons in the PF-1000 plasma-focus device. The energy spectrum of neutrons was determined by the time-of-flight method using ten scintillation detectors positioned downstream, upstream, and side-on the experimental facility. Neutron energy-distribution functions enabled the determination of axial and radial components of energy of deuterons producing the fusion neutrons, as well as a rough evaluation of the total energy distribution of all fast deuterons in the pinch. It was found that the total deuteron energy-distribution function decreases with the deuteron energy more slowly than the tail of the Maxwellian distribution for 1-2-keV deuterons. Index Terms--Energy spectrum of fast deuterons, neutron production, plasma diagnostics, plasma focus (PF).

We present the results of a series of measurements in which an array of capacitive V-dot probes are used to determine the surface potential in a single dielectric barrier discharge plasma operated as an aerodynamic plasma actuator. From these measurements, we determine the longitudinal electric field in the plasma. The results show that the surface immediately (within the first alternating current cycle of the plasma discharge) acquires a net positive surface charge, so that the electric field in the plasma is asymmetric, the magnitude of the maximum field being more than 50% larger in the negative than the positive polarity. The measurements also show that there is a region several millimeters downstream from the exposed electrode edge over which the electric field maintains a constant positive (downstream) polarity over the course of the discharge cycle. DOI: 10.2514/1.33973

In this paper, a simply constructed magnetically insulated transmission line oscillator (MILO) is proposed and studied by simulation. The proposed C-band MILO has no choke vane and impedance discontinuity at the launch point. There are only five vanes and four cavities in it. For an electron beam of 500 kV and 20 GW, by changing from one vane to two vanes having tapered radii in the extraction region and adjusting the axial width of the first vane, the output efficiency can reach 10.5% at an output power of 2.1 GW at 3.72 GHz. Index Terms--High-power microwave, magnetically insulated transmission line oscillator (MILO), numerical simulation.

A numerical simulation utilizing a box_tree code is used to investigate the structure and vertical mode spectrum of finite two-dimensional (2-D) plasma crystals. The overall structural symmetry of the system is examined for various Debye lengths, and a transition from a predominantly hexagonal structure to a structure having concentric rings along the outer edge and hexagonal lattice symmetry in the interior is shown to develop as the Debye length increases. Both the vertical and horizontal oscillation modes for this type of system are investigated, where the horizontal mode spectra are shown to agree with the published results, whereas the vertical mode spectra obtained are shown to agree with an independent analytical method. The fundamental frequency for the vertical modes decreases as the mode number I decreases and is shown to have a maximum corresponding to that which would exist if the system acted in toto as a solid plane. For low-frequency vertical modes, the largest amplitude particle motion is concentrated within a few inner rings, with the outer rings remaining almost motionless. Both of these are in direct contrast with the data obtained for the horizontal modes, where it is shown that the largest amplitude particle motion is concentrated within the inner rings at high frequencies. Index Terms--Complex plasmas, dusty plasmas, mode spectrum, plasma crystals, structural phase transitions, three-dimensional (3-D) screened Coulomb clusters, Yukawa systems.

Circuit modeling is ubiquitous throughout the pulsed power discipline. Both plasma processes and systems can be modeled with circuits of varying complexities. Sometimes, circuit models need to be generated to match experimental waveforms. Particle swarm optimization (PSO) is a technique which can be utilized to automatically generate a circuit model to match experimental data. This paper details the PSO algorithm as well as two case studies of the implementation. Index Terms--Circuit modeling, closing switches, Marx banks, optimization, particle swarm, pulsed power.

A substantial narrowing of the plume of the cylindrical Hall thruster (CHT) was observed upon the enhancement of the electron emission from the hollow-cathode discharge, which implies the possibility for the thruster efficiency increase due to the ion-beam focusing. It is demonstrated that the miniaturized CHT can be operated in the non-self-sustained regime, with the discharge current being controlled by the cathode electron emission. The thruster operation in this mode greatly expands the range of the plasma and discharge parameters normally accessible for the CHT. The observed variation of the plasma potential, electron temperature, and plasma density with the cathode current in the non-self-sustained regime points to the fact that the cathode discharge can affect the electron cross-field transport in the CHT plasma. Index Terms--Cross-field discharge, Langmuir probe, magnetic mirror, plasma thruster.

A new technology of resist trimming in a gate etch process using organic bottom antireflective coating (BARC) for accurate and stable gate critical dimension (CD) control of sub-0.18-[micro]m node technology is presented in this paper. The new method uses an m situ C[F.sub.4] plasma treatment following an HBr/[O.sub.2] plasma treatment step as a part of the gate etch process to achieve a stable gate CD. The new method controls gate CD by trimming the photo resist masking gate lille by reducing the effect of etch by-products, the source of CD variation, after etching organic BARC with HBr/[O.sub.2] plasma. It shows the markedly improved gate CD capability over the conventional one using just an HBr/[O.sub.2] plasma treatment for the CD control. We confirm that this new method is very useful and effective for the accurate gate CD control for sub-0.18-[micro]m node metal-oxide semiconductor technology. Index Terms--C[F.sub.4] plasma treatment, critical dimension (CD), resist gate mask CD, resist trimming.

Etching of TaN gates on high-k dielectrics (Hf[O.sub.2] or HfAlO) is investigated using HBr/[Cl.sub.2] chemistry in a decoupled plasma source (DPS). The patterning sequence includes 248-nm lithography, plasma photoresist trimming, etching of a SiN-Si[O.sub.2] hard mask, and photoresist stripping, followed by TaN etching. TaN etching is studied by design of experiment (DOE) with four variables using a linear model with interactions. It is found that at a fixed substrate temperature and wafer chuck power, etch critical dimensions (CD) gain decreases with decreasing HBr/[Cl.sub.2] flow rate ratio and pressure and with increasing source power and total gas flow rate. Based on these DOE findings, subsequent optimization is performed and a three-step etching process is developed; a main feature of the process is progressively increasing HBr/[Cl.sub.2] flow rate ratio. The optimized process provides etch CD gain within 2 nm and gate profile close to vertical and reliable etch-stop on high-k dielectric. This process is successfully applied to the fabrication of the 40-nm HfAlO/TaN gate stack p-MOSFETs with good electrical parameters. Index Terms--Decoupled plasma source, hard mask, high-[kappa] dielectric, plasma etching, TaN metal gate.

Plasma etching is a key process for pattern formation in integrated circuit (IC) manufacturing. Unfortunately, pattern-dependent nonuniformities arise in plasma etching processes due to localized microloading and feature size or aspect ratio-dependent reactive ion etch lag. We propose a semi-empirical methodology for characterization and chip-scale modeling of pattern-dependent effects in plasma etching of ICs. We apply this methodology to the study of interconnect trench etching and show that an integrated model is able to predict both pattern density and feature size dependent nonuniformities in trench depth. Index Terms--Aspect ratio dependent etch (ARDE), die level variation, feature level variation, microloading, pattern density, pattern dependency, reactive ion etch (RIE).

Experimental investigations are reported on the charging of dust particles resting on conducting and insulating surfaces beneath plasma. The experiment is configured to give insight into the behavior of dust on planetary surfaces exposed to solar wind plasma. In the experiments, the surfaces are agitated so that the particles drop through a small hole into a Faraday cup that measures the charge on each dust particle. Both conducting (Ni) and insulating dusts (Si[O.sub.2], [Al.sub.2][O.sub.3] and JSC-1 lunar regolith simulant) are investigated. The conducting surface is given a bias voltage above the floating potential to create conditions in which the electron flux is dominant or a bias voltage below the floating potential for which the ion flux is dominant. The dust charges more positively in ion-flux-dominant conditions and more negatively in electron-flux-dominant conditions. The insulating dusts retain the charge for a long period of time (> 1 h) after the plasma is turned off. The charge decays more quickly if the surface is agitated, causing the dust to roll around, or if there is ultraviolet illumination. The conducting dust often has a lower level of charge than the insulating dust because the charge is conducted from the dust particle into the conducting surface. Conducting and insulating dusts on an insulating surface have approximately the same level of charge. Index Terms--Dust grain, electron flux, Faraday cup, floating potential, ion flux, plasma charging.

The mesosphere is a naturally occurring complex plasma with nanometer-sized smoke particles from the ablation of meteors that remain aloft as a consequence of their low rate of sedimentation. Methods are discussed for creating and diagnosing a relatively uniform smoky plasma in the laboratory for the purpose of investigating mesospheric physics. Metallic particles, a few nanometers in radius, are created by evaporation of metal into an inert carrier gas. The particles are transported by gas flow into a double plasma device, where they are charged by the plasma and confined by the plasma potential. Physics issues for the mesosphere that may be investigated include the origins of positively charged smoke particles and of fluctuating electric fields that have been observed by rocket-borne probes. Index Terms--Ionosphere, plasma devices, plasmas.

Measurements of the velocity space distribution function of 1.2-[micro]m-diameter alumina particles in an argon direct-current glow discharge dusty plasma are made using stereoscopic particle image velocimetry. These distribution functions are then used to determine the kinetic temperature of the dust component. These measurements show that the kinetic temperature of the dust component is significantly larger than the other plasma components, such as electrons, ions, and background neutrals. Index Terms--Complex (dusty) plasmas, kinetic temperature, particle image velocimetry (PIV).

The formation of 3-D dust clusters within a complex plasma modeled as a spatially confined Yukawa system is simulated using the box tree code. Similar to unscreened Coulomb clusters, the occurrence of concentric shells with characteristic occupation numbers was observed. Both the occupation numbers and radii were found to depend on the Debye length. Ground and low-energy metastable states of the shielded 3-D Coulomb clusters were determined for 4 < N < 20. The structure and energy of the clusters in different states was analyzed for various Debye lengths. Structural phase transitions, including intershell structural phase transitions and intrashell structural phase transitions, were observed for varying Debye length and the critical value for transitions calculated. Index Terms--Complex plasmas, dusty plasmas, structural phases, Yukawa systems, 3-D screened Coulomb clusters.

The levitation height of a dust-particle layer within an RF discharge plasma sheath is known to be related to the dc bias, the background pressure, and the Debye length. In this paper, a new experimental technique for measurement of the Debye length is introduced. This technique is based on the relationship between an externally applied dc bias and the particle levitation height and shows that under appropriate conditions, the addition of an externally applied dc bias provides a mechanism for the evaluation of the Debye length. When compared with existing techniques, this new method appears to be simpler to implement in some cases. Index Terms--Complex plasma, Debye length, diagnostic techniques, plasma sheath.

Modifications have been made to the Auburn dusty plasma experiment to create 1-D flows. These include the addition of a new segmented electrode with two sections that can be biased independently. By varying the bias of one section, 1-D flows have been created in a dusty plasma. Particle image velocimetry techniques are used to measure the transport. A preliminary analysis shows that the particles in the flowing cloud increase their speed as they approach the boundary of the stationary cloud (within 2 mm). This suggests the presence of a sheathlike layer at the cloud-plasma interface. Index Terms--DC glow discharge, dusty plasma, particle image velocimetry (PIV), plasma transport.

Experiments on the laser manipulation of dust particles in a 3-D dust cloud under microgravity conditions are presented. The experiments have been performed on two parabolic flight campaigns in 2005 and 2006 to study the formation of the dust-free region ('void') in the center of the cloud. The manipulation laser is used to drive particles from the void edge into the void. From the particle trajectories, the forces on the particles are derived. The measured forces are compared to models of the ion drag force. Index Terms--Complex plasma, dusty plasma, laser manipulation, micro gravity experiments.

PK-4 is an experiment designed to investigate complex plasmas in a combined dc/RF discharge under microgravity conditions on board of the International Space Station. The dc discharge is produced in a glass tube with a length of 35 cm and a diameter of 3 cm. In addition, an RF discharge can be applied by external RF coils. The setup is especially suited for studying the liquid phase of the complex plasmas, e.g., flow phenomena such as turbulence or nozzles, and forces acting on the microparticles. Experiments in the laboratory and in parabolic flights have been used to determine the charge of the microparticles as well as the ion drag force acting on them. Index Terms--Complex plasmas, dc/rf discharge, fluid simulation.

Addressable microcavity plasma devices with two- or three-electrode, dielectric barrier designs have been fabricated in 20 x 20 or 50 x 50 device arrays in Si(100) and characterized in the rare gases. Each device comprises a metal/Si electrode structure, a dielectric stack, and an inverted square pyramid microcavity having an emitting aperture of 50 x 50 [micro][m.sup.2] or 100 x 100 [micro][m.sup.2]. Arrays with filling factors of 11% and 25% [for [(100 [micro]m).sup.2] and [(50 [micro]m).sup.2] device arrays, respectively] and a crossed electrode (passive matrix) geometry exhibit operating voltages in Ne of ~220-300 V (RMS) when driven by a 20-kHz sinusoidal driving voltage. Displacement currents are ~50% of those for previous Si microplasma device arrays, and when exciting the array with 100-140-V pulses, the rise time of the wavelength-integrated fluorescence is observed to be < 600 ns for pure Ne or Ne/5% Xe gas mixtures at a pressure of 700 torr. A full address and sustain pulse sequence has also been demonstrated with a symmetrical three-electrode device structure. Index Terms--Addressable, displays, microdischarge, microplasma, silicon devices.

This paper summarizes observations of precursor-column formation in cylindrical wire arrays on the 1-MA MAGPIE generator at Imperial College London. Direct experimental measurements of the diameter variation during the collapse and formation phase of the precursor column taken from gated soft X-ray images are presented. Three stages in precursor-column formation are identifiable from the data: broad initial density profile, rapid contraction to small diameter, and slow expansion after formation. The variation in the minimum diameter is measured for several materials, and data show good agreement with a pressure-balance model. Stability calculations suggest that the fraction of the drive current flowing the precursor column is Index Terms--Precursor column, precursor plasma, wire-array Z-pinches.

This paper introduces the plasma-nanoscience research area and shows the way from Nature's mastery in assembling nanosized dust grains in the Universe to deterministic plasma-aided nanofabrication. The concept of deterministic nanoassembly is explained, and the multidisciplinary approach to bridge the spatial gap of nine orders of magnitude between the sizes of plasma reactors and atomic building units is discussed. Ongoing numerical simulation and experimental efforts on highly controlled synthesis of carbon nanotip and semiconducting quantum-dot structures show potential benefits of using ionized-gas environments in nanofabrication. Index Terms--Low-temperature plasma, nanofabrication, nanostructures, plasma nauoscience.

The gliding electric discharge is a source of nonthermal plasma at atmospheric pressure efficient for pollutant abatement. It was used with a wet airflow to determine the kinetics of the postdischarge oxidation process of methyl orange dye in acidic solution (i.e., an oxidation reaction occurring after switching off the discharge). A strong postdischarge degradation of the dye giving N.N dimethyl-4-nitroaniline, as the major yellow intermediate product with a relevant overall first-order kinetics, was observed. Effects of both discharge exposure time and wet airflow were studied, showing linear correlations between these parameters and the overall rate constant. Such results combined with the studies of nitrous acid occurrence and oxidation of the dye by HN[O.sub.2] and [H.sub.2][O.sub.2] suggest that nitrous and peroxonitrons acids are the main oxidizing species involved in the phenomenon. Index Terms--Azoic dye, gliding discharge, hydroxyl radical OH, methyl orange (MO), nonthermal plasma, NOx derivatives, oxidation, postdischarge effect.

A two-dimensional fluid simulation of microplasmas is used to study the ac-driven cylindrical microactivity plasma devices. The analysis reveals that an annular discharge can be easily produced by increasing the gas pressure, which in turn leads to a negative glow in the vicinity of the microcavity wall.

A novel high-sped magnetooptic (MO) modulator based on the optical excitation of surface magneto-plasmo (SMP) waves in bismuth-substituted yttrium iron garnet (Bi-YIG) has been proposed. Using practical material parameters, it was found that the modulator had an improved efficiency over MO modulation devices relying on bulk propagation for comparable driving current pulse durations, as well as the added benefits of a miniature design, multigigahertz operation and tunable bandwidth.

Pseudomorphic heterojunction-FET's with very short gates are successfully developed through the two-step dry-etching and selective growth MOMBE techniques. The use of the drying technique has reduced gate-openings with a high aspect-ratio of 3.5 in Sio(sub 2) film. While the introduction of the MOMBE growth techniques has completed the filling of the openings with refractory p+-GaAs. This fabrication technology has strong potentials for future high speed applications.

This paper reports work on the development of an automatic control system for a Helicon plasma processing source. The lack of a definitive physical model for the plasma physics of the source and the power coupling mechanism to the plasma precludes the use of traditional control algorithms. This paper develops a fuzzy model that simulates the behavior of the plasma source using the process of genetic algorithms to identify and optimize the parameters of the fuzzy model. This type of model will eventually be used to test a fuzzy control system for the plasma source. In this work, an extensive set of experimental data was acquired where the magnetic field and input power to the plasma source were varied over a wide range while the electron number density was measured. From this learning dataset, the genetic algorithm derived the values of the parameters for the difference equation that describes the system. The fuzzy model so constructed was used to predict the behavior of the source from known input parameters. Comparing the predictions with experimental observations showed that the fuzzy model was generally able to predict the behavior of the plasma as its input parameters were varied with a precision of better than 10%. Index Terms - Fuzzy control, fuzzy systems, genetic algorithms, plasma control, plasma devices, plasma material-processing applications.

This paper develops a fuzzy model to simulate the behavior of a nonlinear system, in particular a plasma source, with a view to developing a control system for processing plasmas employing a helicon source. Genetic algorithms are employed to optimize fuzzy rules related to the parameters of the fuzzy model which contain a set of variable zeros and poles of the nonlinear system as well as its time delay. A practical application of the fuzzy model is to estimate the electron number density of a low-temperature plasma. Based on the membership functions of the input and output, a set of fuzzy rules by which the variable zeros and poles are identified is derived and optimized using a genetic algorithm. The principal reason for investigating the proposed fuzzy model is the subsequent computer-aided design of a fuzzy controller to control the nonlinear system. Two experimental results are presented to validate the fuzzy model method. One shows a computer simulation and the other predicts the real-time behavior of the plasma source as its input parameters are varied. Index Terms - Fuzzy control, fuzzy systems, genetic algorithms, plasma control, plasma devices, plasma material-processing applications

Optical properties of plasma lenses strongly depend on the magnetic field distribution. Its measurement with conventional magnetic probes is quite critical for such application. In this paper the measurement of the magnetic field in z-pinch discharge, based on Faraday effect in optical fibers, is described. It is shown that it is possible, using a quite simple and relatively low cost experimental setup, to detect the field dynamics inside the discharge tube assuring low disturbance, a large bandwidth, and a high signal to noise ratio. Applications to several kinds of plasma lenses and further development are discussed.

The understanding of emission and transport in the pseudospark is complex because these are related to a transition between two fundamentally different modes of electron emission. In this paper probe, measurements of plasma parameters are presented providing evidence for oscillatory behavior of the current and potential during this transition. It is shown that these fluctuations are related to a glow-to-arc transition wherein smooth current growth is interrupted by cathode spot formation inside of the hollow cathode resulting in very rapid rise in current. These results support a view that quenching observed in the pseudospark is a double-layer phenomenon that occurs when emission cannot exceed secondary emission produced by ion bombardment.

Plasma opening switches (POS) are optimized on Gamble I in positive polarity into electron beam loads. The POS is widely used for inductive storage applications. The switch opening process is retarded by the positive polarity coaxial configuration. The optimization of the POS eliminates this configuration and enhances the wide applicability of the POS.

Several analytical simulation studies are conducted to explain the mechanisms involved in the plasma immersion ion implantation processing of the various thin wires. The impact of the substrate geometry on the sheath expansion and ion flux density of these wires is also analyzed.

The article presents a new technique, which can be employed for identifying the source of excess ionizing radiation observed during the electromagnetic breakdown of air. A 670 GHz gyrotron oscillator and a Transversely Excited Atmospheric-Pressure [CO.sub.2] laser are shown to be some of the main potential sources.

Several studies are conducted to explain the pressure, as well as the arc voltage coupling that takes place in the different dc plasma torches. The different effects of the operating parameters on its impact of the amplitude of the different modes are also analyzed.

A plasma assistance system is examined in order to operate high power impulse magnetron sputtering (HiPIMS) at lower pressure, thereby enhancing the utilization of the ballistic atoms and ions with high kinetic energy in the film growth process. The studies have shown that the method, known from medium-frequency (MF) pulse sputtering, is important at the much lower pulse repetition rates of HiPIMS.

A wave cutoff probe is used for measuring the effect of radio-frequency bias on electron density in an inductively coupled plasma reactor over a wide range of conditions in pure Ar, pure C[F.sub.4] and mixtures of Ar/C[F.sub.4]. The studies have shown a bias-induced decrease in bias voltage at high source powers and a faster, bias-induced increase in electron density at low source powers.

Thallium arc plasma was investigated in a vacuum arc ion source. As expected from previous considerations of cathode materials in the Periodic Table of Elements, thallium plasma shows leadlike behavior. Its mean ion charge state exceeds 2.0 immediately after arc triggering and diminishes to the predicted 1.60 and 1.45 after about 100 and 150 [micro]s, respectively. The most likely ion velocity is initially 8000 m/s and decays to 6500 and 6200 m/s after 100 and 150 [micro]s, respectively. Both ion charge states and ion velocities decay further toward steady-state values, which are not reached within the 300-[micro]s pulses used here. It is argued that the exceptionally high vapor pressure and charge exchange reactions are associated with the establishment of steady-state ion values. Index Terms--Cathodic vacuum arcs, ion charge states, ion velocity, thallium.

Optical emission of a XeCl excimer discharge, within a 1.2-cm diameter quartz discharge tube, excited by 2.45-GHz microwaves in an Asmussen resonant cavity, operating in the T[M.sub.012] cavity mode, has been imaged onto a two-dimensional (2-D) charge-coupled device (CCD) camera. Spatial imaging of the discharge provides information on the heating regions of the cylindrical plasma as well as the contraction of the plasma diameter with increasing pressure. This technique also provides a real-time diagnostic for production of ultra-violet (UV) emission using a UV bandpass filter. Index Terms--Cavity resonators, charge coupled devices, excimers, glow discharges, imaging, microwave resonators, ultraviolet generation, XeCl.

Analysis of the factors determining the lifetime of the color direct current plasma display panels (DC PDP) by finding empirical lifetime formulas for Ne-Xe, He-Xe gas mixtures reveal that both high pressure and small discharge current realized by incorporating a current limiting resistor in every cell are essential for long practical use of over 10,000 hours.