Tens Of kV Research Articles

Enhanced Coil Design for Inductive Power-Transfer-Based Power Supply in Medium-Voltage Direct Current Sensors

This paper presents an integrated coil design method for inductive power-transfer (IPT) systems. Because a medium-voltage direct current (MVDC) distribution network transmits power at relatively high voltages (typically in the tens of kV), accurate fault diagnosis using high-performance sensors is crucial to improve the safety of MVDC distribution networks. With the increasing power consumption of high-performance sensors, conventional power supplies using optical converters with 5 W-class output characteristics face limitations in achieving the rated output power. Therefore, this paper proposes a safe and reliable power supply method using the principle of IPT to securely maintain the insulation distance between the distribution network and the current sensor-supply line. A 100 W prototype IPT system is investigated, and its feasibility is validated by comparing its performance with conventional optical converters.

The tunable resonant IC antenna concept and its design for DTT experiment

The intrinsic poor loading of Ion Cyclotron (IC) plasma-facing antennas makes the use of Tuning and Matching Systems (TMSs) a necessity. The antenna plus TMS is a resonant system; in the TMS and access lines high voltages (tens of kV) must be accounted for in the unavoidable unmatched part of the feeding lines. In this work, we propose and test an innovative type of IC launcher; it is based on achieving resonance of the self-standing antenna, i.e. without the TMS. A mechanical full-metal tuning mechanism is described and demonstrated to allow wide-band operation. A systematic analysis of possible antenna topologies has led to identifying a structure that can allow good impedance matching along with compliance with maximum electric field constraints. Most of the design is carried out using a simplified plasma and a commercial analysis tool and then validated with a realistic plasma using TOPICA code.

Design of Power Supply Based on Inductive Power Transfer System for Medium Voltage Direct Current Sensor

This paper proposes a medium voltage direct current (MVDC) sensor power supply method based on inductive power transfer (IPT). Given that MVDC distribution networks transmit power at high voltages (several tens of kV), control through sensors is necessary to prevent exacerbating MVDC distribution network accidents. Moreover, these high voltages in MVDC distribution networks mean that high voltage insulation is required between the sensor and the distribution line and for any power supply device electrically connected to the sensor. Therefore, this paper proposes a safe and reliable power supply method using the principle of IPT to maintain a suitable insulation distance between the distribution network and the current sensor supply line. After proposing and designing a transmitter/receiver pad and IPT system by considering the current sensor specifications, a 50-W experimental prototype is developed. The experiments demonstrated that the proposed IPT system can resolve concerns about the breakdown of insulation between distribution networks and power supply lines.

Spatiotemporal corona discharge characteristics of nanoelectrode: array carbon nanotubes

Corona discharge is a widely-used phenomenon that requires a sharp electrode to generate a strong electric field (106 V m−1) at high voltages (typically in the tens of kV). The advent of nanoelectrodes has overcome the technical limitations of traditional electrodes, dramatically improving the density of discharge points and enabling low voltage (several kV) corona discharges with nanometer-sized tips. Consequently, nanoelectrode discharge technology has the potential to revolutionize the miniaturization of plasma equipment in the future. However, research on the discharge characteristics of nanoelectrodes is still relatively sparse. This paper focuses on an array of carbon nanotubes (ACNTs) and proposes a numerical simulation model based on the hybrid hydrodynamics model and ion migration model. The accuracy and efficiency of this model are demonstrated by a high degree of agreement between the results from numerical simulations and experiments. In addition, the corona discharge characteristics of ACNTs are studied and discussed, particularly the spatiotemporal evolution of charged particles near the tip. This paper may provide a method of analysis for optimizing and broadly applying nanoelectrodes.

An improved high-voltage high-frequency multi-winding transformer structure for anode power supply in ECRH

An improved multi-winding transformer structure is proposed for high-voltage (tens of kV) high-frequency (hundreds of kHz) applications for anode power supply in ECRH. The relationship between the number of secondary winding layers and leakage inductance and parasitic capacitance is studied for the proposed structure. The results show that winding structure parameters has little effect on the leakage inductance and great effect on the parasitic capacitance. The parasitic capacitance of single-layer winding is the minimum and that of double-layer winding is the maximum. For multi-layer winding, the more layers, the smaller the parasitic capacitance is. The high-frequency multi-winding transformer is built and tested in the anode power supply, where the output is 0–30 kV, the switching frequency is 100 kHz, the maximum output power is 3 kW. The test results verify the analysis.

Generation and Control of Electrohydrodynamic Flows in Aqueous Electrolyte Solutions.

To drive electrohydrodynamic (EHD) flows in aqueous solutions, the separation of cation and anion transport pathways is essential because a directed electric body force has to be induced by ionic motions in liquid. On the other hand, positive and negative charges attract each other, and electroneutrality is maintained everywhere in equilibrium conditions. Furthermore, an increase in an applied voltage has to be suppressed to avoid water electrolysis, which causes the solutions to become unstable. Usually, EHD flows can be induced in non-aqueous solutions by applying extremely high voltages, such as tens of kV, to inject electrical charges. In this study, two methods are introduced to generate EHD flows induced by electrical charge separations in aqueous solutions, where two liquid phases are separated by an ion-exchange membrane. Due to a difference in the ionic mobility in the membrane, ion concentration polarization is induced between both sides of the membrane. In this study, we demonstrate two methods. (i) The relaxation of ion concentration gradients occurs via a flow channel that penetrates an ion-exchange membrane, where the transport of the slower species in the membrane selectively becomes dominant in the flow channel. This is a driving force to generate an EHD flow in the liquid. (ii) A long waiting time for the diffusion of ions passing through the ion-exchange membrane enables the generation of an ion-dragged flow by externally applying an electric field. Ions concentrated in a flow channel of a 1 x 1 mm2 cross-section determine the direction of the liquid flow, corresponding to the electrophoretic transport pathways. In both methods, the electric voltage difference required for an EHD flow generation is drastically reduced to near 2 V by rectifying the ion transport pathways.

What we can learn from measurements of air electric conductivity in 222Rn‐rich atmosphere

AbstractElectric conductivity of air is an important characteristic of the electric properties of an atmosphere. Testing instruments to measure electric conductivity ranging from ~10−13 to 10−9 S m−1 in natural conditions found in the Earth atmosphere is not an easy task. One possibility is to use stratospheric balloon flights; another (and a simpler one) is to look for terrestrial environments with significant radioactive decay. In this paper we present measurements carried out with different types of conductivity sensors in two 222Rn‐rich environments, i.e., in the Roselend underground tunnel (French Alps) and in the Institute of Radioprotection and Nuclear Safety BACCARA (BAnC de CAllibrage du RAdon) chamber. The concept of the conductivity sensor is based on the classical time relaxation method. New elements in our design include isolation of the sensor sensitive part (electrode) from the external electric field and sensor miniaturization. This greatly extends the application domain of the sensor and permits to measure air electric conductivity when the external electric field is high and varies from few tens of V m−1 to up to few tens of kV m−1. This is suitable to propose the instrument for a planetary mission. Two‐fold objectives were attained as the outcome of these tests and their analysis. First was directly related to the performances of the conductivity sensors and the efficiency of the conductivity sensor design to shield the external electric field. Second objective aimed at understanding the decay mechanisms of 222Rn and its progeny in atmosphere and the impact of the enclosed space on the efficiency of gas ionization.

A revolutionary concept to improve the efficiency of ion cyclotron antennas

The successful design of an ion cyclotron (IC) antenna mainly relies on the capability of coupling high power to the plasma (MW), feature that is currently reached by allowing rather high voltages (tens of kV) on the unavoidable unmatched part of the feeding lines. This requirement is often responsible of arcs along the transmission lines and other unwanted phenomena, such as rectification discharges or hotspots, that considerably limit the usage of IC launchers. In this work, we suggest and describe a revolutionary approach based on high impedance surfaces, which allows to increase the antenna radiation efficiency and, hence, to highly reduce the imposed voltages to couple the same level of power to the plasma. High-impedance surfaces are periodic metallic structures (patches) displaced usually on top of a dielectric substrate and grounded by means of vertical posts usually embedded inside a dielectric, in a mushroom-like shape. In terms of working properties, high impedance surfaces are electrically thin in-phase reflectors, i.e., they present a high impedance, within a given frequency band, such that the image currents are in-phase with the currents of the antenna itself, thus determining a significant efficiency increase. While the usual design of a high impedance surface requires the presence of a dielectric layer, some alternative solutions can be realised in vacuum, taking advantage of double layers of metallic patches. After an introductory part on the properties of high impedance surfaces, this work documents both their design by means of numerical codes and their implementation on a scaled mock-up.

Open flux in Saturn’s magnetosphere

We characterise the interaction between the solar wind and Saturn’s magnetosphere by evaluating the amount of ‘open’ magnetic flux connected to the solar wind. This is deduced from a large set of Hubble Space Telescope images of the ultraviolet aurora, using the poleward boundary of the main aurora as a proxy for the open-closed field line boundary in the ionosphere. The amount of open flux is found to be 10–50GWb, with a mean of 35GWb. The typical change in open flux between consecutive observations separated by 10–60h is -5 or +7GWb. These changes are a result of imbalance between open flux creation at the dayside magnetopause and its closure in the magnetotail. The 5GWb typical decrease in open flux is consistent with in situ measurements of the flux transported following a reconnection event. Estimates of average, net reconnection rates are found to be typically a few tens of kV, with some extreme examples of unbalanced magnetopause or tail reconnection occurring at ∼300kV. The range of values determined suggest that Saturn’s magnetosphere does not generally achieve a steady state between flux opening at the magnetopause and flux closure in the magnetotail. The percentage of magnetic flux which is open in Saturn’s magnetosphere is similar to that measured at the Earth (2–11%), but the typical percentage that is closed between observations is significantly lower (13% compared to 40–70%). Therefore, open flux is usually closed in smaller (few GWb) events in Saturn’s magnetosphere. The exception to this behaviour is large, rapid flux closure events which are associated with solar wind compressions. While the rates of flux opening and closure should be equal over long timescales, they are evidently different on shorter (up to tens of hours) timescales. The relative independence of the magnetopause and tail reconnection rates can be attributed to the long loading timescales required to transport open field lines into the tail.

Emittance Characterization of Ion Beams Provided by Laser Plasma

Laser ion sources offer the possibility to obtain ion beams useful for particle accelerators. Nanosecond pulsed lasers at intensities of the order of 108 W/cm2, interacting with solid matter in a vacuum, produce plasma of high temperature and high density. To increase the ion energy, an external post-acceleration system can be employed by means of high voltage power supplies of some tens of kV. In this work, we characterize the ion beams provided by an LIS source and post-accelerated. We calculated the produced charge and the emittance. Applying 60 kV of accelerating voltage and laser irradiance of 0.1 GW/cm2 on the Cu target, we obtain 5.5 mA of output current and normalized beam emittance of 0.2 mm mrad. The brightness of the beams was 137 mA (mm mrad)−2.

Optical Transmission of Thermal Measurements From High Voltage Devices in High Vacuum Conditions

The paper describes a system for digitization and optical transmission of thermal measurements on high voltage devices in high vacuum environmental conditions and presents the tests conducted on a prototype. The system has been designed in particular to satisfy such technical requirements as to be mounted on the grounded grid of the SPIDER facility (a 100-keV/60-A particle accelerator) and to withstand frequent fault conditions in which the voltage of the grid transiently rises up to some tens of kV. The system is based on a circuit which samples and transmits the signals to the central acquisition system while preserving the signals and avoiding any electrical links between the high voltage device and the vacuum vessel. Moreover, the system has to be designed so as to minimize the electromagnetic noise affecting the low amplitude signals from the thermocouples (TCs). The circuit design is presented, describing the layout and the electronic components for the acquisition of the TC signals and for the data transmission via optical fiber. When SPIDER is operational, with up to 1-h pulse duration, the circuit is powered by a battery, which is in turn recharged by the energy coming from a photovoltaic cell when SPIDER is not operational and the circuit is not acquiring. Data are digitally transmitted according to RS-232 protocol for easy interfacing to the central data acquisition system. The circuit has been tested to check its proper operation, with particular care devoted to the data transmission and the recharging phase. The results are reported and discussed.

Treatment of PVC using an alternative low energy ion bombardment procedure

In many applications, polymers have progressively substituted traditional materials such as ceramics, glasses, and metals. Nevertheless, the use of polymeric materials is still limited by their surface properties. Frequently, selective modifications are necessary to suit the surface to a given application. Amongst the most common treatments, plasma immersion ion implantation (PIII) has attracted the attention of many researchers owing to its versatility and practicality. This method, however, requires a power supply to provide high voltage (tens of kV) negative pulses, with a controlled duty cycle, width and frequency. Owing to this, the implementation of PIII on the industrial scale can become economically inviable. In this work, an alternative plasma treatment that enables low energy ion bombardment without the need of a high voltage pulse generator is presented. To evaluate the efficiency of the treatment of polymers, polyvinylchloride, PVC, specimens were exposed to 5 Pa argon plasmas for 3600 s, at excitation powers, P, of between 10 and 125 W. Through contact angle and atomic force microscopy data, the influence of P on the wettability, surface free energy and roughness of the samples was studied. Surface chemical composition was measured by X-ray photoelectron spectroscopy, XPS. To evaluate the effect of aging under atmospheric conditions, contact angle and XPS measurements were performed one and 1334 days after the treatment. The plasma potential and ion density around the driven electrode were determined from Langmuir probe measurements while the self-bias potential was derived with the aid of an oscilloscope. From these data it was possible to estimate the mean energy of ions bombarding the PVC surface. Chlorine, carbon and oxygen contamination were detected on the surface of the as-received PVC. Upon exposure to the plasma, the proportion of chlorine was observed to decrease while that of oxygen increased. Consequently, the wettability and surface energy increased after the treatment but such modifications were not stable after aging: the contact angle increased for all the samples, modifying the initially hydrophilic surface into a highly hydrophobic one. Consistently, the surface composition also changed after aging: there was carbon enrichment due to further losses of oxygen and chlorine. Another relevant factor for the elevation of θ was the change in morphology induced by the treatment. At greater powers, the uniform matrix of the PVC was transformed into a columnar structure containing randomly distributed sharp pillars. Interpretation of such results is proposed in terms of the total energy deposited in the solid by ionic collisions.

Enhancement of the Electromechanical Performances of a Single Dielectric Barrier Discharge Actuator

In this paper, a parametric study of a single dielectric barrier discharge (SDBD) plasma actuator has been performed in order to enhance its electromechanical performances. Three input parameters have been investigated: the dielectric thickness, the waveform of the applied high voltage and the voltage slew rate. The goal is to increase the velocity of the discharge-induced electric wind and/or to reduce the electrical power consumption of the discharge. First, electrical measurements with high voltages ranging from 5 to 30 kV have been conducted, with a frequency set here to 1 kHz. This consisted of current recordings and electrical power consumption computations. Secondly, the velocity of the produced electric wind has been measured with a Pitot tube probe. From these velocity profiles, the maximum velocity, the produced mass flow rate and the electromechanical efficiency of the discharge have been determined. It highlights that the way to enhance the electromechanical performances of such a surface discharge consists in using a thick dielectric (at least a few millimeters) and a sine high voltage (several tens of kV) at a moderate frequency value.

Nanosecond High Voltage Pulse Generator Using Water Gap Switch for Compact High Power Pulsed Microwave Generator

Nanosecond and sub-nanosecond high voltage pulses can provide new applications. A cancer treatment by an ultra-short pulse high electric field is one of them. High power pulsed microwave has been proposed to apply the high electric field for that treatment. This work focuses on the design of a compact high power pulsed microwave generator using a nanosecond pulse power generator for the cancer treatment. To obtain fast rise time of voltage and current for nanosecond pulses, a switch has to have low inductance. Water gap switches have this property. Since water has a dielectric strength exceeding 1 MV/cm, gap distances for switching can be reduced to several hundreds of micrometers, and still allow switching of tens of kV. The narrow gaps allow us to reduce the switch inductance. In this study, the water gap switch was built in a Blumlein pulse forming line. The Blumlein line was designed to provide a pulse of 1 ns and to match an impedance to 16 Omega of an antenna. By using the water gap switch in the Blumlein line, the voltage rise time obtained approximately 750 ps at 13 kV of a peak pulse voltage. An electromagnetic wave was radiated underwater by the loop antenna. A measuring antenna at 0.15 m and 0.4 m from the radiating antenna caught electric field intensities of 116 kV/m and 32 kV/m, respectively. A frequency element of 250 MHz had higher intensity.

高エネルギーイオンを用いて形成したダイヤモンドライクカーボン膜のマイクロトライボロジー特性

The effects of high energy ion-implantation treatment on the mechanical properties of diamond-like carbon (DLC) films have been investigated in this study. The micro-tribological properties of DLC films formed by using various methods such as ion-beam enhanced deposition (IBED) and plasma based ion-implantation (PBII) have been examined by means of atomic force microscopy (AFM) and acoustic emission (AE) oscillation scratch tester. With the PBII method DLC films were deposited on silicon wafer under conditions of a pulse bias of −5 to −20kV in an atmosphere of CH4 plasma. DLC films were deposited with the IBED Method by means of ion-plating and the deposition was performed using the methods of dynamic mixing and static mixing at an acceleration voltage of 120kV. These main results of above-mentioned tests are summarized as follows. (1) In case of DLC films deposited by the PBII method, there is an existing peak voltage at which the maximum hardness and durability were provided. (2) DLC films deposited with PBII method shows higher hardness than these deposited with the IBED method does but they also have brittleness is large. Therefore, the quantity of micro wear of DLC films with PBII was larger than that of DLC films with IBED. (3) The critical load of PBII-DLC films increased with an increase on a peak voltage. And, the adhesive strength of ion beam mixing DLC films deposited at 120kV is similar to that of PBII films deposited at a peak voltage of several tens of kV.

Distributions of current and auroral precipitation in Jupiter's middle magnetosphere computed from steady-state Hill–Pontius angular velocity profiles: solutions for current sheet and dipole magnetic field models

We present an analysis of the magnetosphere–ionosphere coupling current system which is associated with the maintenance of plasma corotation in Jupiter's middle magnetosphere. The formulation follows Cowley and Bunce (Planet. Space Sci. 49 (2001) 1067), but here the angular velocity of the equatorial plasma is computed using the steady-state theory of Hill (J. Geophys. Res. 84 (1979) 6554) and Pontius (J. Geophys. Res. 102 (1997) 7137) rather than being determined by a simple empirical model. Results are compared both for a realistic magnetospheric current sheet magnetic field model and for a simple dipole field. The results for the current sheet model confirm previous conclusions concerning current and auroral precipitation distributions based on the empirical angular velocity model. Specifically, we find that upward field-aligned currents flow from the ionosphere to the equatorial current sheet over the whole radial range from ∼20 R J to the outer boundary of the region considered at 100 R J, thus returning from the current sheet to the ionosphere at larger radial distances outside this region. The upward currents are of sufficient intensity to require the existence of field-aligned voltages which accelerate magnetospheric electrons down into the atmosphere, thus creating intense auroras. At ionospheric heights, the upward field-aligned current densities are several tenths of a μA m −2 , flowing in a narrow latitudinal band less than ∼1° wide, located at ∼16° dipole co-latitude. The associated field-aligned voltages are several tens of kV, resulting in precipitated electron energy fluxes capable of exciting UV auroras of hundreds of kR intensity. The model thus forms an appropriate basis on which to understand the origin of Jupiter's ‘main auroral oval’ emissions. For the dipole field, the steady-state equatorial angular velocity profile is found to be very similar to that for the current sheet model. Nevertheless, the different mapping of the field lines to the ionosphere results in a magnetosphere–ionosphere coupling current system which has significantly different properties. In particular, the height-integrated ionospheric Pedersen current intensity is found to be factors of ∼2–3 less than that for the current sheet model, and since the field-aligned current is also found to be spread over a much broader latitudinal band, ∼5° wide centred at ∼10° dipole co-latitude, the field-aligned current density is reduced by more than an order of magnitude. Only small (few kV) field-aligned voltages are thus required to carry the upward current in this case, resulting in much weaker electron precipitation, and much weaker, few kR, UV auroras. Our results thus emphasise that while the magnetic field model may not greatly effect the steady-state angular velocity profile, it nevertheless is of crucial significance in determining the consequent magnetosphere–ionosphere coupling current system, and the resulting auroral precipitation.

Hollow cathode discharge as pulsed X-ray source

Pre-ionization controlled transient hollow cathode discharges operating at pulsed high voltages of some tens of kV and gas pressure around 0.1 mbar are used to generate electron beams of some tens of A during about 10 ns. These latter are used to produce bremsstrahlung X rays which are energy analyzed. X ray spectrum is used as a tool for beam diagnostic. Evidenced beam properties and discharge versatility allow to consider the use of these devices as miniature X ray source. Its feasibility is studied.

Simultaneous observations of temporally and spatially resolved two-dimensional profiles of ion-confining potentials and ion fluxes using novel ion-energy spectrometer arrays

Newly designed spectrometer arrays for ion-energy-spectrum observations are proposed and constructed in both end regions of the GAMMA 10 tandem mirror so as to obtain two dimensionally resolved radial profiles of end-loss-ion fluxes IELA, ion temperatures, and ion-confining potentials φc by the use of a single plasma discharge alone. Each spectrometer unit in the array has a specific structure with obliquely placed multiple grids with respect to the direction of the ambient plasma-confining magnetic fields. This structure is proposed to obtain precise ion-energy spectra without the disturbance of simultaneously incident energetic electrons into the array, since widely distributed “multigridded Faraday cup” signals have significant electron disturbances on ion spectra even if over a few tens of kV are applied to the electron-repeller grid. In tandem-mirror experiments, plasma-confining potentials produced by electron cyclotron heatings play one of the most critical roles in the improvement of simple-mirror confinement. Thus, diagnostics of these confining potentials using clear ion spectra are of essential importance. From these motivations, the spatial distribution details and relations of φc and IELA are investigated by the use of the novel ion spectrometers. Axisymmetric profiles of φc are found to have a good correlation with axisymmetric plugging distributions in IELA. These are consistently interpreted in terms of the Pastukhov theory of the relation of φc with IELA. Information on such specific spectrometer arrays would contribute to researchers in a wide variety of plasma devices, who employ analyzers for flux, temperature, and potential diagnostics under energetic plasma circumstances.

The electrical insulation system of a forced flow cooled superconducting (sc) magnet

The discharge of stored magnetic energy of sc magnets in the GJ range requires discharge powers up to several hundreds of MW. The present state-of-the-art of sc high current cables in the 50 kA range leads to voltages of several tens of kV. Forced flow cooled conductors allow a rigid winding construction with higher discharge voltages. At Forschungszentrum Karlsruhe a sc poloidal field model coil (∅ 3 m) was constructed and tested at about 20 kV. The typical components of the electrical insulation system were developed. Partial discharge measurements and pulse voltage were applied. It was demonstrated that the engineering basis of the insulation system for about 20 kV was developed.

Synoptic maps of polar caps for stable interplanetary magnetic field intervals during January 1992 geospace environment modeling campaign

Observations from January 27–28, 1992, when four polar‐orbiting DMSP satellites were in operation, are used to construct synoptic maps of convective flows and particle regions within the polar ionosphere. We chose periods of relative steady interplanetary magnetic field (IMF) and use data from multiple satellite passes during each period to obtain unprecedented two‐dimensional coverage. For strongly negative IMF By, convection patterns are similar to those that have been previously obtained but also show significant IMF Bz effects. For Bz » |By|, we see strong sunward flow near the pole, but antisunward convection on open field lines at lower latitudes on the nightside. The particle observations reveal the two‐dimensional structure of the cusp/mantle region and the existence of a strong polar arc within the circular convection cell that has a negative electric field divergence on open field lines. The particle observations also readily identify the magnetic separatrix when a satellite crosses the inner edge of the cusp or the boundary between the plasma sheet and polar rain. However, on the morningside and often on the afternoonside, we find a distinct and well‐defined region of soft‐electron and magnetosheath‐like ion precipitation [(the “soft‐electron zone” (SEZ)] lying between the plasma sheet and the region of polar rain. Separatrix identification is uncertain at local times where the SEZ is present; however, it appears that large portions of the SEZ are on open field lines. Dawn‐dusk displacements of the open field line regions in the two polar caps are seen that are consistent with IMF By effects. Additionally, the dayside separatrix is observed to be further poleward for positive than for negative IMF Bz, whereas Bz is not observed to have a significant effect on the location of the nightside separatrix. Also, we consistently find larger cross polar‐cap potential drops in the southern hemisphere than in the northern hemisphere. This suggests that there are significant (tens of kV) magnetic‐field‐aligned potential drops along high‐altitude regions of open field lines where the magnetic field is weak and particle motion strongly violates the guiding center approximation.