Search

In order to generate high-voltage high-pulsed power, klystron modulators necessarily contain at least one capacitor bank charging structure supplying the energy to be released during the pulse. Conventional charging structures are based on ac/dc front-end units typically based on diode rectifiers combined with power charging structures operated in on/off mode as a second stage, producing prohibitive levels of grid flicker and harmonic contents on the ac grid side while operating at suboptimal power factor. These problems are usually corrected by both costly and spacious external grid compensators. Today, the increased demand on both accelerator peak power and pulselength (translating into higher average power), in conjunction with stricter regulations and standards represent additional challenges also in modulator design. An alternative method for capacitor bank charging, in a steady state allowing for the complete reduction of grid flicker as well as ac line current harmonics and reactive power, was presented by the authors in a preceding publication. This paper presents in further detail the benefits of the proposed power electronic structure and associated control scheme in the context of a review of other solutions suggested for constant power charging and flicker mitigation. This paper also contains a complete description of the proposed control scheme as well as further experimental results, including a thorough assessment of its performance under transient conditions. All experimental results were obtained on a klystron modulator prototype rated for long pulses (3.5 ms), high voltage (115 kV), and high pulsed power (peak power > 2 MW). [ABSTRACT FROM AUTHOR]

We investigate and revisit the deployment of a directional time-varying (rotating) driving magnetic field to suppress the magneto-Rayleigh–Taylor (MRT) instability in dynamic Z-pinches. A rotational driving magnetic field is equivalent to two magnetic-field components, $\Theta $ and Z, that alternate in time, referred to as an alternate Theta-Z-pinch configuration. We consider a finitely thick cylindrical liner configuration in this paper. We numerically integrate the perturbation equation to stagnation time based on the optimal background unperturbed trajectories. We assess the cumulative growth of the dominant mode selected by some mechanism at the beginning of an implosion. The maximum e-folding number at the stagnation of the dominant mode of an optimized alternate Theta-Z-pinch is significantly lower than that of the standard Theta- or Z-pinch. The directional rotation of the magnetic field acts to suppress instabilities, independent of the finite thickness of the liner. The finite thickness effect plays a role only when the orientation of the magnetic field varies in time, whereas it does not play a role in the standard Theta- or Z-pinch. The rotating frequency of the magnetic field and the thickness of the liner both have a monotonic effect on suppression. Their synergistic effect can enhance the suppression of the MRT instability. Because the MRT instability can be well suppressed in this way, the alternate Theta-Z-pinch configuration has potential applications in liner inertial fusion that uses a magnetically driven liner to directly compress the fuel target to initiate fusion. [ABSTRACT FROM AUTHOR]

This paper investigated the dependence of electrostatic field strength for spacecraft materials on voltage ramp rate, by applying an increasing incremental electrostatic field until electrostatic breakdown occurred. Tests on Kapton E found that at ramp rates two or three orders of magnitude lower than the maximum recommended rate, the electrostatic breakdown field, F\mathrm {ESD} was lower by a factor of two or more. This suggests that the tabulated values of F\mathrm {ESD} , which have been used by the spacecraft charging community, could substantially overestimate F\mathrm {ESD} in common slowly evolving spacecraft situations. This paper expanded these ramp rate tests to include a wider range of ramp rates and additional materials. By contrast, Kapton HN and biaxially oriented polypropylene (BOPP) data were found to be consistent with a single mean value F\mathrm {ESD} , rather than the proposed mean field and incremental voltage step ramp rate models. [ABSTRACT FROM PUBLISHER]

This paper deals with the challenges of railgun electromagnetic compatibility. After some general remarks on integration issues, the current regulations, norms, and standards of a high-power railgun are discussed. Different standards for ordnance or staff are considered. Also, preliminary results from the French-German Research Institute of Saint-Louis are presented. Since these laboratory data are not yet representative for future weapon systems, scaling calculations were carried out concerning energy levels, electrical sources, and cabling architecture. The obtained signal profiles are compared to the values defined by U.S., EU, or NATO standards. [ABSTRACT FROM AUTHOR]

In this paper, we demonstrate a plasma misting system capable of inactivating Escherichia coli O157:H7 (E.coli) in a 4 ft3 (approximately 100 L) volume with potential for future use in decontaminating fresh produce. Water droplets, with an average diameter of $5~\mu \text{m}$ , are generated via ultrasonic nebulizers and carried by compressed air. These micrometer-sized droplets flowthrough a set of three cylindrical, microsecond-pulsed dielectric barrier discharges (DBDs). We observe the Coulombic fission of droplets up to a critical radius into submicrometer droplets (Sauter mean of approximately 0.3 $\mu \text{m}$), measured by a laser diffraction analyzer. E.coli, on agar plates, is inactivated by this mist in a time and flowrate-dependent manner. We hypothesize that the observed antimicrobial effect correlates with the concentration of submicrometer droplets. The observed formation of submicrometer droplets from this volumetric DBD is similar to the bursting of droplets observed with electrospray devices using corona discharges. [ABSTRACT FROM AUTHOR]

In this paper, a 3-D stochastic finite-difference time-domain algorithm is developed for simulating wave propagation in isotropic cold plasma medium by using the bilinear transform (BT) technique. The proposed algorithm has a simple formulation and is very easy to apply to isotropic dispersive material. It efficiently calculates the mean value and standard deviation of electromagnetic field components caused by the variability or uncertainty of the plasma’s electron density and collision frequency. The stretched coordinate perfectly matched layer (SC-PML) with a complex-frequency-shifted factor is implemented as the absorbing boundary condition, and the BT technique is also incorporated into the SC-PML. Numerical examples are shown to demonstrate the accuracy and effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

In this paper, two kinds of abnormal rail-armature contact states are assumed and simulated, and the simulated B-dot probe waveforms are compared with the results from the experiments. Through theoretical analysis, simulations, and experiments, relations between the abnormal contact states and the output waveforms of the B-dot probe are investigated. Results show that with the help of the B-dot probe output waveforms, the transition position can be obtained and the intervals between the parallel circuit branches, which are created by the arcs arising from the abnormal contact states, can be primarily measured. [ABSTRACT FROM PUBLISHER]

Wireless intraspacecraft communication technology is being developed for signal transfer on space missions to save weight and simplify the design. One consideration for this new technology is its interaction with space environment-induced electrostatic discharges (ESDs). The short time scales of spacecraft ESD events result in broad frequency band signals that can interact with high-frequency wireless antennas. These interactions present a source of signal noise. However, they also present a possibility of in-flight wireless ESD monitoring. We present laboratory measurements of arcing on common spacecraft insulators using commercially available single-band 2.4-GHz and dual-band 2.4-/5.8-GHz Wi-Fi antennas. These wireless detections are shown to coincide with direct simultaneous measurements of discharge event currents. The amplitudes of the wireless signals are shown to provide a measure of the relative magnitude of the arcs, although the narrow frequency ranges of Wi-Fi antennas make absolute measures of the discharge intensity impractical. The wireless signals are shown to provide very accurate nanosecond timing of ESD events, which presents the potential of identifying arc location on a spacecraft with the use of time-of-flight detection from multiple antennas. [ABSTRACT FROM AUTHOR]

In this paper, collimated plasma jets form from Joule heating and ablation of a radial foil (Al 15- \mu \textm -thin disk) using a pulsed power generator (Cornell Beam Research Accelerator) with 1-MA peak current and 100-ns rise time. Plasma dynamics of the jet are diagnosed with and without an applied uniform external magnetic field ( $\sim 1$ -T axial B_{z} produced from a pulsed Helmholtz coil) and under a change of current polarity, which corresponds to current moving either radially inward or outward from the foil’s central axis. Experimental results are compared with predictions made by numerical simulations (Plasma as an Extended-MHD Relaxation System using an Efficient Upwind Scheme). The influence of the Hall effect on the jet development is observed under opposite current polarities. [ABSTRACT FROM PUBLISHER]

Fusion demonstration (DEMO) concepts are facing challenges in safety and licensing in part due to uncertainties with in-vessel components validation, which relate directly to the materials and design criteria used for assessments. These challenges come from the designed operation under unprecedented operational conditions and reliance on the performance of complex in-vessel components over time spans of years. There are key differences in the structural integrity requirements and associated design criteria for DEMOs and future fusion reactors compared to existing nuclear systems. In this paper, we highlight the justification behind developing DEMO and fusion-specific design criteria by overviewing key shortfalls in existing design codes. Importantly, the key current approaches being undertaken within the EU are described including the development of elastoplastic design rules, evaluation of probabilistic assessments, and multiscale modeling of fusion irradiation effects on materials. Finally, thoughts on potential internationalization of new fusion-specific design codes are postulated. [ABSTRACT FROM AUTHOR]

The dual representation of MARX (XRAM) pulse current generator with magnetic flux compression effect is a novel circuit for current multiplication, which has the advantages of both meat grinder and XRAM that are basic circuit topologies. It contributes to the multiplication of current in two aspects: first, increasing current by magnetic flux compression and second, the current can be increased by paralleled inductors. Compared with the standard XRAM topology, the proposed circuit topology can realize a larger factor of current multiplication more easily, and is better than the standard slow transfer of energy through capacitive hybrid meat grinder circuit topology in aspects of scalability and modularity. Meanwhile, its energy density is increased significantly, which is advantageous to the needs of actual electromagnetic launch. In this paper, theoretical analysis is done to illustrate the excellent performance of the proposed topology and preliminary experiment was conducted to demonstrate its feasibility. [ABSTRACT FROM PUBLISHER]

As the uniform dielectric barrier discharges (DBDs) consisted by a large number of microdischarges in a long timescale may meet the needs of industrial application, the evaluation of the uniformity of DBDs used in the industry is different from that in the laboratory. In this paper, a digital image processing method presented in our previous paper is used to describe the uniformity of DBDs caused by the rotary plate electrode in a long timescale. Whether or not the electrode is rotated, with an increase in time, the gray-level standard deviation Std of the discharge image gradually decreases and reaches its stable value at last. The electrode rotation results in reducing the time constant required to reach a steady state for the gray-level distribution. With an increase in rotary speed, Std gradually decreases and reaches its stable values at last. This means that the electrode rotation improves the uniformity of the discharge. The reason produced the aforementioned phenomena should come from the relative motion of the accumulated charge on the dielectric surface and microdischarge remnants in the volume. [ABSTRACT FROM PUBLISHER]

Normally, a three-electrode spark–gap switch is controlled by the application of an external trigger impulse. In this paper, a novel self-breakdown sharpening switch based on the three-electrode spark–gap switch is proposed. However, in this paper, the trigger electrode is connected to ground through a resistor, with the prespark between the trigger and the main electrodes providing the electrons and ions that initiate conduction of the main gap. A prototype sharpening switch with a breakdown voltage of 116.0 kV \pm 1.0 kV and a breakdown time of 3.396\ \mu\s\pm 0.036 \ \mu\s is described. When compared with a conventional two-electrode spark–gap sharpening switch, the novel sharpening switch has both a more stable breakdown voltage and lower jitter, and the dc breakdown and impulse breakdown characteristics of the two types of switches are presented and compared. When the impedance of the resistor connected to the trigger electrode is high, it is demonstrated that both the value of this resistor and also the type of load have little effect on the characteristics of the novel switch. However, the breakdown voltage of the novel sharpening switch was found to be sensitive to the rise time of the input pulse from the trigger generator. The prototype sharpening switch has a lifetime at least 20 000 shots and is now in use in a major pulsed power conditioning system. [ABSTRACT FROM PUBLISHER]

High-power terahertz gyrotrons always operate at high-order modes to avoid damage from Ohmic heating. However, the spectral densities of these modes are very high, especially when gyrotrons operate at high-order harmonics. Therefore, the self-excitation condition can be satisfied for several modes simultaneously. Correspondingly, in order to determine which mode will be excited first in the designed terahertz gyrotron, the starting currents of competing modes should be calculated more accurately to predict the operating status. In this paper, an existing linear theory is generalized to take into account the influences of the field profile, finite beam thickness, and velocity spread. Starting currents are calculated for the operating and the most dangerous competing mode in a 0.42-THz second harmonic gyrotron with a complex cavity, which is recently under development at the Terahertz Science and Technology Research Center. The calculations show that the radial and velocity spreads play a critical role in the starting current and prove that the measured output terahertz radiation in the designed device is generated from the interaction between the desired mode and the electron beam. [ABSTRACT FROM PUBLISHER]

A high-current test fixture (HiCTF) was developed to examine material response to repulsive forces generated between electrically conducting material pairs during short pulses of high current, similar to conditions experienced in Electromagnetic Launch applications. Based upon Holm’s contact theory with additional preload and pressure distribution parameters, this test fixture was designed to use a loading press to apply preload to the test specimens while conducting current through the specimen contact interface. The fixture uses an aligned mechanical loading device to provide a preload across the contact interface of the specimen. The HiCTF will allow for investigation of contact response sensitivity as a function of its degradation, impact of geometry variation, surface conditions, material pairing, preload, and contact integrity. Statistically based experimental designs have been constructed and analysis methodologies developed that incorporate likelihood ratio analysis and the Neyer method. The Neyer $D$ -optimal design method, used in sensitivity testing of explosives, shows promise as an appropriate test method for HiCTF results and will be used to provide sufficient information for comparisons and developmental thresholds. Results from HiCTF testing provide insight into the electrical contact phenomenon and high-current material response. This paper provides an overview of the HiCTF, its motivation, analysis methodology, results, observations, and lessons learned. [ABSTRACT FROM PUBLISHER]

Consistent physics and engineering models are required for many use cases at Wendelstein 7-X. Web service technology is used to provide convenient access to common software components and experiment data. The usage of standard web protocols allows the integration in client software written in any programming language. This leads to a better reusability of expert codes and experiment data by a large international team. At W7-X, web services provide common functions such as Biot–Savart calculations and magnetic field line tracing. Further services provide access to databases for diagnostic data or machine models. A new web service was implemented for the creation of 3D magnetohydrodynamic (MHD) equilibrium calculations and a user-friendly access to the results. Consistent interface definitions allow an orchestration of the W7-X web services by user code, as well as a seamless integration into a data analysis framework. In this paper, we present the current state of the MHD equilibrium web services at Wendelstein 7-X. [ABSTRACT FROM AUTHOR]

During reentry, plasma sheath is affected by many flight factors, such as trajectory, velocity, angle of attack, and fluid turbulence. As a result, the plasma parameters are time-varied and nonstationary. The nonstationary effects of reentry plasma sheath on electromagnetic (EM) wave propagation are investigated in this paper. First, the factors that affect the plasma sheath are analyzed, and the plasma sheath variation is divided into three scales. A multiscale reentry plasma sheath electron density model is established. A compatible modeling method is proposed, and this method is proven effective. Finally, we analyze the effects of plasma sheath on EM wave at 1.57542, 2.2, and 5 GHz, which are generally used in GPS and telemetry, tracking, and command systems. Results show that the statistical parameters of complex transmission coefficients are time-varied and nonstationary. [ABSTRACT FROM PUBLISHER]

This paper aimed to investigate the destructive effect of an atmospheric-pressure low-temperature plasma (LTP) on hepatitis B surface antigen (HBsAg) in human blood as well as its impact on the functions of erythrocytes. Dielectric barrier corona discharge was used to generate the atmospheric-pressure LTP to treat the blood samples collected from hepatitis B patients with positive HBsAg, HBeAg, and anti-HBc, but negative HBsAb and HBeAb. The experimental results showed that the antigenicity of HBsAg in blood samples changed from positive to negative after being treated with the LTP for more than 40 s. Furthermore, the investigations demonstrated that after more than 30 s treatment of the LTP, osmotic fragility and malondialdehyde level of erythrocytes increased significantly, and Na+–K+-ATPase activity of erythrocytes decreased remarkably. Our results revealed that the LTP could effectively destruct HBsAg in blood and inhibit erythrocyte functions during the process. [ABSTRACT FROM AUTHOR]

An introduction to the fourth installment of Special Issues of "IEEE Transactions on Plasma Science" about spacecraft charging technology is presented.

Finding a solution for air species contamination of atmospheric pressure plasmas in plasma medical treatment is a major task for the new field of plasma medicine. Several approaches use complex climate chambers to control the surrounding atmosphere. In this paper, ambient species are excluded in plasma–human-skin-cell treatment by ensheathing the plasma jet effluent with a shielding gas. Not only does this gas curtain protect the plasma jet effluent from inflow of air species but it also, more importantly, allows controlling the effluent reactive species composition by adjusting the mixture of the shielding gas. In the present investigations, the mixture of nitrogen to oxygen within the gas curtain around an argon atmospheric pressure plasma jet (kinpen) is varied. The resulting reactive plasma components produced in the jet effluent are thus either oxygen or nitrogen dominated. With this gas curtain, the effect of reactive oxygen species (ROS) and reactive nitrogen species (RNS) on the cell viability of indirectly plasma-treated HaCaT skin cells is studied. This human keratinocyte cell line is an established standard for a skin model system. The cell viability is determined by a fluorometric assay, where metabolically active cells transform nonfluorescent resazurin to the highly fluorescent resorufin. Plasma jet and gas curtain are characterized by numerical flow simulation as well as by optical emission spectroscopy. The generation of nitrite within the used standard cell culture medium serves as a measure for generated RNS. Measurements with the leukodye dichlorodihydrofluorescein diacetate show that, despite a variation of the shielding gas mixture, the total amount of generated reactive oxygen plus nitrogen species is constant. It is shown that a plasma dominated by RNS disrupts cellular growth less than a ROS-dominated plasma. [ABSTRACT FROM PUBLISHER]

In many relevant cases requiring a net energy comparable with that of a household appliance, the power supplies (PSs) and the electrical systems must be oversized to sustain short peak demands. The same equivalent energy could be achieved by storing and distributing the power over the time. These considerations lead to a new PS concept based on the exploitation of the energy stored between the actual operations. The new compact ($60\,\,\text {cm} \times 120\,\,\text {cm} \times 190$ cm) PS is able to generate arbitrary currents up to 2 kA by an integrated energy storage system based on supercapacitors. The delivered output power (approximately 200 kW) is obtained from a very low and tunable input power (<1 kW). Furthermore, a portion of the injected power can be recovered in the storage system. Even though the system was designed for a specific project (the PROTO-SPHERA spherical tokamak), the presented approach can be applied to general-purpose PSs, and there are encouraging prospects to extend it to large facilities with higher currents and voltages. [ABSTRACT FROM AUTHOR]

These instructions give guidelines for preparing papers for this publication. Presents information for authors publishing in this journal. [ABSTRACT FROM PUBLISHER]

A design for a high-power relativistic inverted magnetron oscillator (IMO) is presented and modeled numerically using the massively parallel electromagnetic particle-in-cell code, improved concurrent electromagnetic particle in cell (ICEPIC). The inverted magnetron presented here is designed to operate in the $L$ -band for magnetic fields ranging from 0.07 to 0.1 T with voltages ranging from ~250 to 480 kV. Simulations in that voltage/magnetic field range demonstrate that the inverted magnetron is capable of fast startup, $\pi $ -mode dominance with little-to-no mode competition, as well as high output power, exceeding 2.5 GW at the high end of voltages examined. End-loss current, a common source of energy loss in relativistic magnetrons, is not present for this IMO design. The IMO radiates RF energy axially through the use of a novel dual-ring radiator that excites the TM01 mode in the downstream waveguide. This approach yields nominal RF output power efficiencies near 20%. ICEPIC simulations predict that the above features combined with the IMO’s stable, robust, and reliable performance in the desired mode over a large voltage range yield a class of high-power microwave source notable for its inverted geometry and T-vane slow-wave structure. [ABSTRACT FROM AUTHOR]

Electrostatic discharge (ESD) continues to pose significant risks to space missions despite decades of intense study. Tabulated values of material breakdown strength used in spacecraft charging models are often based on cursory measurements that may not be fully relevant to a given mission. Materials physics offers insight into the pertinent variables that affect breakdown and how to address them experimentally for spacecraft applications. We present measured distributions of ESD data across several test configurations for three polymeric materials that, taken together, begin to provide an understanding of how to estimate the likelihood of ESD events over a spacecraft’s mission lifetime. We discuss how consequences of these results apply to spacecraft charging modeling and design considerations. [ABSTRACT FROM PUBLISHER]

Based on the step function and the probability distribution function, the risetime (10%–90%) increase of induction voltage adder-output voltage pulses, resulting from cell-driving jitters, was analyzed in detail. Using Taylor series expansion, an analytic solution of the risetime increase was obtained for jitters with normal distributions (assuming that the mean is $\mu $ , the standard deviation is $\sigma $ ). It is found that the risetime increase of output voltages is a function of the $\sigma $ , which can be simply expressed as $2.563\sigma $ . This analytic solution was directly verified by the numerical calculation results. Analytic solutions of the risetime increase for jitters with three-parameter Weibull distribution are also given. It can be used to approximate several distributions (such as normal distribution, exponential distribution, and Rayleigh distribution). The application limitations of these solutions are discussed and presented, especially the reliable probability. Also, the total risetime of the output voltage is presented by considering the risetime increase resulting from cell-driving jitters. [ABSTRACT FROM AUTHOR]

A new two-contact system with double-transversal magnetic field (TMF) structure is investigated regarding its potential for high current interruption. It consists of two concentric TMF contacts, in which the inner contact has a disk-shaped structure (spiral contact) and the outer contact a cup-shaped structure. This contact assembly gives several advantages over the use of single-TMF contacts, as the constricted high-current arc might either split between both inner and outer contacts or commute from the inner to the outer contact and continue its rotation. In both scenarios, we expect a better distribution of the arc energy over a larger contact surface. B-field simulation and Lorentz force calculation are carried out to investigate whether two constricted arcs, with one burning on the inner contact and the other on the outer contact, can coexist given their mutual attraction. Single-phase high current interruption tests were carried out to compare the performance of this new double-TMF contact system with that of a standard spiral-type single-TMF one. These tests have revealed superior performance of the new double-TMF contact system, which could interrupt current amplitude at least 20% higher than the one interrupted by the single-TMF contact system. [ABSTRACT FROM PUBLISHER]

Finite-difference time-domain (FDTD) method is an efficient full-wave numerical method for simulating graphene-based optoelectronic devices. The previous investigation on modeling graphene in leapfrog FDTD methods shows that dispersive errors increase with tuning up the chemical potential of graphene. In this article, a new implementation of graphene’s surface boundary condition (SBC) is proposed to reduce the dispersive errors in the leapfrog FDTD update scheme. To achieve lower dispersive errors, the graphene layer is positioned exactly on the grid lattice of transverse magnetic fields, and each of the transverse magnetic fields is split into two fields on the two sides of graphene. The split magnetic fields are updated using forward and backward differences in the electric fields on the normal direction of graphene plane. Numerical analysis shows that the maximum dispersive error of the proposed graphene model is reduced to only 37.5% of the other publicly reported graphene models in the leapfrog FDTD update scheme. However, the CPU time cost keeps almost the same as the other graphene models. The proposed implementation of the graphene SBC model also shows less CPU time consumption compared with the graphene SBC model which requires to solve a linear system and breaks the leapfrog FDTD update scheme, while the maximum numerical error is the same. The proposed graphene model is applied to simulate graphene terahertz (THz) surface plasmon resonances and modulators to demonstrate the applications in accurately modeling and analyzing graphene-based THz devices. [ABSTRACT FROM AUTHOR]

A 100-kV/60-A high-voltage power supply (HVPS) is developed to supply the auxiliary heating system for a J-TEXT tokamak. This power supply is based on pulse step modulation (PSM) technology and consists of 144 switch modules. To fulfill the isolation, control, and protection requirements, a control system based on the PCI extensions for instrumentation is designed with the PSM technology for the HVPS. Experimental results show that the system has a good control performance and fast response. Thus, the proposed system meets the control requirement of the 100-kV/60-A HVPS. [ABSTRACT FROM AUTHOR]

A new algorithm was developed, which reduces the self-force in particle-in-cell codes on unstructured meshes in a predictable and controllable way. This is accomplished by computing a charge density weighting function for a particle, which reproduces the Green's function solution to Poisson's equation at nodes when using a standard finite element method methodology. This provides a superior local potential and allows for particle–particle particle-mesh techniques to be used to subtract off local force contributions, including fictitious self-forces resulting in accurate long-range forces on a particle and improved local Coulomb collisions. Local physical forces are then computed using the Green's function on local particle pairs and added to the long-range forces. Results were shown with up to five orders reduction in self-force and superior intraparticle forces for two test cases. [ABSTRACT FROM PUBLISHER]

Chinese Fusion Engineering Test Reactor (CFETR) based on the tokamak approach with superconducting magnet technology is envisioned to provide 200-MW fusion power and operate with a goal of an annual duty factor of 0.3–0.5. This report based on a zero-dimensional system study using extrapolations of current physics by considering engineering constraints, is focused on qualitative determination of the engineering parameters of the device. Conservative assumptions of plasma performance based on present day existing experiments were made to assure achievable goals, since CFETR could be a near-term project to bridge the gaps between ITER and DEMO. The baseline of 200-MW fusion power in standard H-mode for a duration longer than 1000 s and in a modest improved H-mode (or hybrid mode) with H98\leq 1.3 for steady-state operation derive a device of R=5.7~m, a=1.6~m in size with Bt=5~T, and total heating and current drive source power of 80 MW. More ambitious operating modes with higher fusion power reaching the alpha-particle dominated self-heating regime for burning plasma study is possible with the same device hardware, if the more advanced physics is incorporated. Since large vacuum chamber design, possible upgrades both on physics and technologies enable operation of the device with larger plasma configuration and provide potentials to demonstrate key physics issues relevant to DEMO. [ABSTRACT FROM PUBLISHER]

D-dot sensors were designed and tested for the measurement of nanosecond high-voltage pulses. Computer simulation results showed that the I-type sensor has an acceptable response in a wide range of frequency among three types of sensors such as I, \nabla, and T. The I-type sensor has coaxial cylinder shape, which consists of a brass inner conductor, a Teflon middle dielectric, and an aluminum outer conductor. Since I-type showed good linearity up to 1.2 GHz, we calibrated the sensor using relatively low frequencies. The attenuation ratio of the integrated signal of the D-dot sensor was calibrated against a standard high-voltage probe (Tektronix P6015, 75-MHz bandwidth). The measured attenuation ratio and standard deviation were 7.70\times 10^12 and 0.0608\times 10^12, respectively. The measured attenuation ratio was in good agreement with the calculated ratio within 7.5%. The operational characteristics of the sensor were tested by measuring nanosecond voltage pulses generated from a Blumlein pulse forming line. We measured high-voltage pulses having 300 kV, 5-ns pulsewidth, and 300-ps rise time using the designed D-dot sensor. The accuracy of the sensor enabled detection of several tens of picosecond differences in the rise time of the high-voltage pulses resulting from different gap distances in the peaking switch. [ABSTRACT FROM AUTHOR]

C5-fluoroketone (CF3C(O)CF(CF3)2, abbreviated C5-FK) and C4-fluoronitrile [(CF3)2CFCN, abbreviated C4-FN] mixed with background gases such as carbon dioxide, oxygen, or air are used as alternatives to SF6 as the insulating and switching medium in high voltage gas insulated switchgear (GIS) due to their good switching and dielectric insulation performance and comparably low global warming potential (GWP). Like SF6, C5-FK and C4-FN are chemically stable inside electrical equipment and non-flammable. Like most complex molecules, they decompose exothermically when exposed to sufficiently high temperatures and do not recombine after decomposing. In this work, we use a custom-built test device to experimentally investigate the conditions and gas compositions under which a decomposition reaction can proceed to completion in C5-FK- and C4-FN-based gas mixtures after being initiated by an electric arc. We also present the related theory. The results show that, for properly selected mixtures, even under extreme failure conditions—internal arc faults—complete decomposition of the C5-FK or C4-FN does not occur. [ABSTRACT FROM AUTHOR]

Cold plasma (CP) has been acknowledged as a potential tool in enhancing the availability of bioactive compounds and antioxidant (AO) potential of plant products. Lotus is an ethno pharmacologically important herb with commercial applications in the food, beverage, and cosmetic industry. The bioactive constituents of the lotus flower are responsible for its medicinal and AO properties. This scrutiny identifies the influence of CP treatment on the bioactive compounds and AO potential of lotus petal powder (LPP). The petals were dried using a microwave drier, milled, and were treated in a low-pressure plasma system at 2.5 kV for 5 min. Physicochemical properties like color, total phenolics, flavonoids, and AO activity of the plasma-treated LPP were investigated and microstructure was evaluated with a scanning electron microscope. A notable increase in the flavonoid content was observed from 35.87 to 89.87 mg quercetin equivalent (QE)/100 g in the treated petal powder, while the phenolics content showed only a slight increment. The AO capacity also increased from 42.92 to 76.63 mg ascorbic acid equivalent (AAE)/100 g. The bioactive compounds were analyzed using gas chromatography–mass spectrometry/mass spectrometry (GC–MS/MS) and found that plasma treatment increased the relative percentage of phytosterols, amyrin, and nuciferine. This increment in the level of phytochemicals can be attributed to the leaching out of components from the stressed surface of LPP, relieving the potential of CP processing on improving the nutritional and health benefits. [ABSTRACT FROM AUTHOR]

To enable the use of additively manufactured polymer materials as structural and insulating components within high-voltage pulsed power systems, a better understanding of material compatibility with common pulser material environments is required. This work examines the effect of long-duration contact of printed polymeric components with three high-voltage insulating oils (Shell Diala S2 ZX-A, Luminol TRi, and Royco 602) at room temperature (~25 °C). Test pieces printed using stereolithography (SLA) were evaluated for changes in dielectric strength, mechanical properties, and composition after submersion in insulating oil for a nine-month duration. Gas chromatography–mass spectrometry (GC–MS) was used for compositional analysis on neat and polymer-exposed oils to identify compositional changes that occurred in the oil over the course of the exposure period. [ABSTRACT FROM AUTHOR]

Arc current in a dc thermal plasma torch was modulated by superimposed ac current with frequency 15 kHz. The plasma jet optical radiation was recorded by a matrix of fast photodiodes. The analysis of records using standard deviations and 3-D phase portraits has shown that the fluctuations in the plasma jet in the frequency range under 5 kHz were suppressed. [ABSTRACT FROM PUBLISHER]

Small amplitude linear and nonlinear dust–electron-acoustic (DEA) waves in an unmagnetized, collisionless, complex, or dusty plasma system have been carried out. The plasma system is assumed to contain inertial and viscous cold electron fluids, nonextensive distributed hot electrons, Maxwellian ions, and negatively charged stationary dust grains. The normal mode analysis is used to study the linear behavior. On the other hand, the standard reductive perturbation technique is used to derive the nonlinear dynamical equations, namely, Burgers equation and further Burgers equation. They are also numerically analyzed in order to investigate the basic features of shock waves and double layers (DLs). It has been observed that the roles of the viscous cold electron fluids, nonextensivity of hot electrons, and other plasma parameters that arose in this investigation have significantly modified the basic features (viz., polarity, amplitude, width, and so on) of the DEA shock waves and DLs. The findings of our results obtained from this theoretical investigation may be useful in understanding the linear as well as the nonlinear phenomena associated with the DEA waves both in space and laboratory plasmas. [ABSTRACT FROM PUBLISHER]

Disinfection and sterilization in hospitals and other public places have always been the focus of attention. In our studies, dielectric barrier corona discharge (DBCD) was used to generate low-temperature plasma (LTP) to treat Pseudomonas aeruginosa (P. aeruginosa, one kind of bacteria responsible for nosocomial infections). The survival colonies of P. aeruginosa were counted with the standard plate-counting method after 30-, 60-, 90-, and 120-s exposures to DBCD. We discovered that LTP could lead to more than 5-log reduction of P. aeruginosa after 120-s treatment. Further experiments indicated that OH and excited N2 in LTP and lower pH value in bacterial suspension might synergistically inactivate P. aeruginosa by destroying its outer structure. [ABSTRACT FROM PUBLISHER]

The Railgun Data Format Standard (RDFS) provides a flexible format for the archival of electromagnetic railgun (EMRG) laboratory test data. This effort utilizes the hierarchical data format version 5 for the data model and file format, as well as extensible markup language for data structure and data type encapsulation. The RDFS was developed through a collaborative effort within the Office of Naval Research (ONR) EMRG program, including members from the Naval Surface Warfare Center Dahlgren, the Naval Research Laboratory, and the Institute for Advanced Technology. The intent behind the RDFS is to facilitate collaborative data sharing among EMRG researchers through the standardization of EMRG test data archives. The structure of the RDFS is discussed, along with details on its implementation and use within the ONR EMRG community. [ABSTRACT FROM PUBLISHER]

The execution of quality management (QM) and quality assurance activities in the construction of a fusion device is a very complex task. Nevertheless, QM is a useful management tool, if we comprehend QM as the request for continuous reflection on present tasks and on the best way to improve the processes with respect to the scientific and technical aims. Therefore, a quality management system has been introduced for the Wendelstein 7-X construction project. A lot of experience exists in industry but for such one-of-a-kind construction projects of an experimental device, we have to adapt the system to our own requirements which differ and are more complex. [ABSTRACT FROM PUBLISHER]

A hybrid X -pinch (HXP) configuration consisting of solid conical electrodes connected by a wire as the load of a pulsed power generator has been tested on four different generators with currents varying from 200 kA to 1.2 MA and with rise times ranging from 50 to 170 ns. Wires of different materials, diameters ranging from 25 to 200 \mum, and lengths from 0.5 to 3 mm were loaded through holes in the cone. It was possible to optimize the wire length and diameter for most materials tested so that the HXP would generate an intense single burst of soft X-rays with energy yield comparable with that obtained using standard X pinches. Furthermore, this soft X-ray source permits a greater variety of materials to be used, including combinations of different materials (e.g., parallel, twisted, or braided wires) or thin tubes with powders inside. Here, we report results obtained with one, two, or three parallel, twisted, or braided wires as well as with fine metal or plastic tubes with a wire inside or filled with melted metal with the goal of extending the spectral bands of HXP radiation and optimizing the energy yield in the soft X-ray burst. [ABSTRACT FROM AUTHOR]

A spherical tokamak (ST) configuration is attractive as the basis for a fusion nuclear science facility (FNSF), due to its small size and relatively low cost. However, the compactness of the ST also exacerbates the power and particle handling problems anticipated in next-step devices, since local fluxes are higher and less space is available for optimizing plasma-facing components. On the other hand, novel divertor geometries that have recently been developed such as the snowflake and super-X divertors can be especially effective at reducing heat fluxes in an ST, helping to meet the exhaust challenge. Here, we present an analysis of the power and particle handling requirements of a candidate ST-FNSF, based on 0-D exhaust projections as well as 2-D edge plasma modeling using the SOLPS code. Both conventional and novel divertor geometries are considered. These show that, for reasonable assumptions on cross-field transport, operating points can be identified that are consistent with both core plasma operation and power and particle exhaust requirements, and these operating points are more easily accessible with novel divertors. [ABSTRACT FROM PUBLISHER]

Multidirectional optical diagnostics combined with fast Fourier transform analysis yielding frequency spectra were used for investigations of oscillation phenomena in a thermal plasma jet on various frequencies. The results show that oscillation amplitude distributions in the plane perpendicular to the jet axis depend on the frequency value and, for some frequencies, are strongly asymmetrical. This phenomenon affects the mean distribution of instabilities in a different way, depending on the frequency range. Instantaneous instability distributions are influenced by the phase of arc-current low-frequency modulation. [ABSTRACT FROM PUBLISHER]