High-speed Charge Research Articles

The Discharge Development and Arc Modes in Vacuum at A Long Gap Distance in Vacuum Interrupters

The influence of an arc current on the discharge development and thearc modes of a single coil type axial magnetic field (AMF) electrodewere investigated by a high-speed charge couple device (CCD) videocamera in a long gap distance of 40 mm. The distribution of theaxial magnetic field of the single coil type AMF electrode wascomputed. By computational results, the single coil type AMFelectrode could generate higher axial magnetic flux density than theslot type AMF electrode. It was found that the single coil type AMFelectrode could perform better than the slot type AMF electrode withthe same designing parameters. And the development of the arc modesexperienced diffuse mode, constricted but unstable mode, andconstricted and stable mode with the amplitude of the arc currentincreasing. The correlation between the vacuum arc and the noisecomponents of arc voltage was investigated too. The interruptioncapability could be known in a practical commercial vacuuminterrupter by the test results in a demountable vacuum interrupter(DVC) with a electrode diameter of 50 mm and a gap distance of40 mm.The test results could provide reference to design the highvoltage vacuum interrupter adopting the single coil type AMFelectrode.

High throughput spectrometer for fast localized Doppler measurements

A new custom-built duo spectrometer has been commissioned for fast localized Doppler measurements of plasma ions in the Madison Symmetric Torus. The instrument combines very high optical throughput (transmission efficiency of 6% and etendue of 0.80 mm(2) sr divided into two simultaneous measurements) with good resolution (lambda/Deltalambda=5600). The design is a double grating variant of the Czerny-Turner layout and has been carefully optimized for fast (100 kHz) measurements of the C VI line at 343.4 nm. The instrument is currently being applied for high speed charge exchange recombination spectroscopy measurements.

Experimental Investigation on the Vacuum Arc Behaviors of the Axial Magnetic Field (AMF) Electrode with Single Coil Structure

In this paper, the influence of arc current on vacuum arc behaviors of a new AMF electrode with single coil structure was investigated at long gap distance of 40 mm. A high-speed charge couple device (CCD) video camera was used to observe the arc behaviors. Two groups of arc modes were featured: 1) diffuse arc modes including multi-cathode spots arc, high current diffuse arc and high current diffuse column arc. 2) constricted arc modes including anode plasma jet with local concentration of many cathode spots and group of cathode spots (APJS), anode plasma jet with local concentration of many cathode spots, anode and cathode plasma jets (APJ), and intense arc mode. The vacuum arc behaviors under different amplitude of arc current were researched.

Research on Vacuum Arc Characteristics of a New Electrode Structure Applied in High Voltage Vacuum Interrupter

In this paper the vacuum arc behaviors of the axial magnetic field (AMF) electrode with single coil structure were investigated at gap distance 10 mm and 40 mm respectively. And the axial magnetic field distribution was computed at 10 mm and 40 mm. A high-speed charge couple device (CCD) video camera was used as a major diagnostics to investigate the arc behaviors. At gap distance 10 mm, the vacuum arc maintained diffuse. With the gap distance increasing from 10 mm to 40 mm, the vacuum arc experienced constricted arc modes only in short time at beginning. In most of time, the vacuum arc kept diffuse. The test results proved that the AMF electrode with single coil structure was feasible to be applied in high voltage vacuum interrupter.

Influence of Gap Distance on the Arc Behaviors of Slot Type Axial Magnetic Field (AMF) Electrode

In this paper the influence of gap distance on arc behaviors of slot type AMF electrode was investigated by a high-speed charge couple device (CCD) video camera at different gap distance of 10 mm and 20 mm respectively. The arc kept in diffuse arc modes while the amplitude of arc current reached 22.0 kA at gap distance of 10 mm. With the gap distance of 20 mm, the concentration of arc column near anode occurred while the amplitude of arc current was 14.0 kA. With the amplitude of arc current increasing, the duration time of the concentration of arc column near anode also increased at the same gap distance.

Influence of Gap Distance on Vacuum Arc Characteristics of Cup Type AMF Electrode in Vacuum Interrupters

The greenhouse effect of SF6 is a great concern today. The development of high voltage vacuum circuit breakers becomes more important. The vacuum circuit breaker has minimum pollution to the environment. The vacuum interrupter is the key part of a vacuum circuit breaker. The interrupting characteristics in vacuum and arc-controlling technique are the main problems to be solved for a longer gap distance in developing high voltage vacuum interrupters. To understand the vacuum arc characteristics and provide effective technique to control vacuum arc in a long gap distance, the arc mode transition of a cup-type axial magnetic field electrode is observed by a high-speed charge coupled device (CCD) video camera under different gap distances while the arc voltage and arc current are recorded. The controlling ability of the axial magnetic field on vacuum arc obviously decreases when the gap distance is longer than 40 mm. The noise components and mean value of the arc voltage significantly increase. The effective method for controlling the vacuum arc characteristics is provided by long gap distances based on the test results. The test results can be used as a reference to develop high voltage and large capacity vacuum interrupters.

TEM and electron tomography studies of carbon nanospheres for lithium secondary batteries

The structure of carbon nanospheres of 100–200 nm diameter, which showed superior high-speed charge–discharge behavior as the negative electrode in a lithium ion battery, was investigated with XRD, SEM and TEM with an electron tomography attachment. Observation of carbon 0 0 2 lattice images, as well as electron diffraction patterns, illustrated that heterogeneous microtexture was formed as the polyhedronization of the particle proceeded with heat-treatment. The outside region of the particle heat-treated at 2800 °C has stacking structure of aromatic layers with some distribution of d 002, while the center region consisted of non-graphitic. Structure defects seemed to be concentrated along the ridgelines of the polyhedronized particles after heat-treatment. The electron tomography technique clarified the morphology of the graphitized particles, although the images should be understood with other crystallographic measurements. A slice image computed in the 3D-reconstruction process showed the inner texture of the graphitized particles more clearly than the conventional TEM bright-field image.

Random nature of droplet size and its origins in short circuit CO2 arc welding

The nature of the droplet size variation and its effect on the process behaviour were investigated for short circuit CO2 arc welding using a power supply with constant voltage output. To obtain the droplet images and record the welding current and voltage transient waveforms in phase, an integrated experimental system was established by combining a high speed charge coupled device camera based on laser shadowing and a related optical system with a dual channel analog/digital converter. The droplet size in short circuit transfer mode is defined as the maximum diameter of the molten droplet just before short circuiting. The experimental results reveal that the distribution of droplet size typically has a random nature with a range of between 1 and 2 times the electrode diameter. Excessively large or small droplet size is markedly unfavourable to the process stability. The droplet shape just before short circuiting and the short circuiting experience are also critical factors affecting the process behaviour. The main factors influencing the droplet size and shape are analysed in detail and approaches to control their evolution are then proposed.

Bidirectional electrostatic actuator operated with charge control

A method for driving an electrically floating, bidirectional electrostatic actuator using high-speed switching and charge control has been proposed and verified experimentally. A macroscopic experiment is used to model the operation of a surface-micromachined microelectromechanical systems (MEMS) device having the form of two parallel electrodes, one rigid, and the other flexible. The movable, or electrode, is connected to ground via a switching device, and the stationary electrode is connected to a single voltage source. The free electrode is alternately charged by induction, then left floating and subjected to a field produced by the stationary electrode. This charge-control mode of operation overcomes the travel range limits associated with the well-known snap-through instability. Our proof-of-concept experiment shows that a periodic charging/driving cycle increases the possible travel range of the free electrode by a factor of two over that possible without charge control. The configuration has the potential for use in a variety of optical MEMS applications involving mirror surfaces that must be exposed to the outside world.

Atmospheric pressure glow discharge in air using a water electrode

An atmospheric pressure glow discharge in air is generated between the surface of a water electrode and a metal electrode with a high alternating current (60 Hz) voltage (<20 kV). The gap distance between the two electrodes can be adjusted from 3 mm to a few centimeters. The diameter of the plasma column is in the 3-10 mm range. Photographs taken with a high-speed charge coupled device camera clearly show a cathode fall region, negative glow, positive column, and anode dark space; a structure consistent with that of a normal glow discharge. The initial breakdown process shows that the plasma ignites at the water surface and terminates at the metal electrode. The N/sub 2/ rotational and vibrational temperatures were spectroscopically measured to be about 1800 and 2600 K, respectively.

Application of monochromatic image method in arc plasma diagnostics

An unsaturated image of a TIG arc was acquired using a high-speed charge coupled device (CCD) camera with a narrow-band filter. The spatial distribution of the plasma emission coefficient was reconstructed. The emission coefficient was calculated, allowing distributions of temperature and electron densities to be determined. The results are compared with those obtained from spectroscopic analysis. Good agreement was obtained, except for the shape of outer contours, demonstrating the reliability of the monochromatic image.

Experimental Investigation of Vacuum Arcs in Nonuniform Axial Magnetic Fields

Experiments were conducted in a detachable vacuum chamber with conventional cup-shaped axial magnetic field (AMF) electrodes and three types of AMF electrodes with different nonuniform AMFs. The radial distributions of the AMF were varied by introducing ferromagnetic material into the cup-shaped AMF electrodes. The vacuum arc column and the distribution of cathode spots were photographed with a high-speed charge coupled device (CCD) camera. Experimental results indicate that a nonuniform AMF with higher axial magnetic flux density at the contact periphery than that at the center (saddle-shaped AMF) can resist arc constriction and increase the cathode and anode utilization ratios more effectively than the ordinary bell-shaped AMF profile.

Real-time lock-in imaging by a newly developed high-speed image-processing charge coupled device video camera

Real-time lock-in imaging with high-frequency modulation (up to 16 kHz) was successfully performed at high spatial resolution (640×480 pixels) using a newly developed high-speed image-processing charge coupled device (CCD) video camera. To achieve high-resolution lock-in imaging, the high-speed image-processing CCD video camera incorporates a high-definition TV image sensor that uses a high-definition frame-interline-transfer (FIT) CCD architecture. A novel FIT-CCD driving method, in which vertical CCD shift registers are utilized as a temporary frame memory, enables lock-in imaging at a modulation frequency in excess of the video frame rate (30 Hz). Furthermore, since the high-speed image-processing CCD video camera has a function for subtracting images taken with high-frequency modulation, a lock-in image with no background contrast can be observed in real time. The phase detection function for lock-in imaging, when coupled with real-time image processing using the high-speed image-processing CCD video camera, makes it possible to dynamically observe the phase distribution in a two-dimensional area. As a demonstration of the real-time lock-in imaging, the wave pattern that appears on the surface of water was successfully visualized by a real-time lock-in imaging system that uses the high-speed image-processing CCD video camera.

Diffusing wave spectroscopy method based on high-speed charge coupled device for nonergodic systems of electrorheological fluids

Diffusing wave spectroscopy (DWS) measurement has been developed to work with a high-speed charge coupled device (CCD). A real-time measurement of autocorrelation function for a nonergodic system was performed to study statistical interaction between particles of electrorheological fluids. As a test, DWS measurements on an ergodic system were achieved using both a high-speed CCD and single-mode fiber, and the deviation of the characteristic decay times using these two methods is less than 2% for glass bead/silicone oil suspension. In the method of DWS based on a high-speed CCD, the multispeckle measurement enables one to do the ensemble average directly. The CCD with the highest rate of 8000 frames/s makes it possible to investigate the short-time behavior of nonergodic systems. The structure response time is obtained by measuring the light transmittance through samples under different electric fields. By analyzing diffusion coefficient of a sample, the force response time is also obtained.

Imaging postsynaptic activities of teleost thalamic neurons at single cell resolution using a voltage-sensitive dye

Optical recording of neuronal activities using voltage-sensitive dyes (VSDs) is a useful method for simultaneous multi-site recording. However, it has been rather difficult to distinguish optical signals from individual, identified cells. We applied the optical recording technique using a high-speed charge coupled device (CCD) imaging system to a teleost thalamic nucleus, corpus glomerulosum (CG) which has a well-defined histological organization and large postsynaptic dendrites. Patch-like dye (di-4-ANEPPS) signals were observed in the dendritic layer of the CG in response to afferent nerve stimulations. These responses were completely blocked by an α-amino-3-hydroxy-5-methyl-4-isoxazole-proprionate (AMPA) receptor antagonist, did not propagate, and the size of the patches were close to that of a single dendritic tip of the ‘large cell’. Thus, we found that these patch-like VSD signals most likely represent postsynaptic potentials at individual dendritic tips of the large cells.

Real-time and in situ monitoring of ferroelectric domains during periodic electric field poling of KTiOPO4

We demonstrate a photographic method to view the inversion of ferroelectric domains during the periodic electric field poling of KTiOPO4 by taking advantage of the electro-optic effect and a high speed charge coupled device (CCD) camera. The method is noninvasive and allows monitoring in situ and in real time. The high speed CCD camera opens up the possibility to observe the dynamics of the domains during poling and to probe the samples afterwards to evaluate the grating formed in the material. This monitoring method should be applicable to other ferroelectric crystals, as well.

Pixel electronics for the ATLAS experiment

The ATLAS experiment at LHC will use 3 barrel layers and 2×5 disks of silicon pixel detectors as the innermost elements of the semiconductor tracker. The basic building blocks are pixel modules with an active area of 16.4 mm×60.8 mm which include an n + on n-type silicon sensor and 16 VLSI front-end (FE) chips. Every FE chip contains a low power, high speed charge sensitive preamplifier, a fast discriminator, and a readout system which operates at the 40 MHz rate of LHC. The addresses of hit pixels (as well as a low resolution pulse height information) are stored on the FE chips until arrival of a level 1 trigger signal. Hits are then transferred to a module controller chip (MCC) which collects the data of all 16 FE chips, builds complete events and sends the data through two optical links to the data acquisition system. The MCC receives clock and data through an additional optical link and provides timing and configuration information for the FE chips. Two additional chips are used to amplify and decode the pin diode signal and to drive the VCSEL laser diodes of the optical links.

Backward switching phenomenon from field forced ferroelectric to antiferroelectric phases in antiferroelectric PbZrO3 thin films

Antiferroelectric materials (example: lead zirconate and modified lead zirconate stannate), in which a field-induced ferroelectric phase transition is feasible due to a small free energy difference between the ferroelectric and the antiferroelectric phases, are proven to be very good candidates for applications involving actuation and high charge storage devices. The property of reverse switching from the field-induced ferroelectric to antiferroelectric phases is studied as a function of temperature, applied electric field, and sample thickness in antiferroelectric lead zirconate thin films deposited by pulsed excimer laser ablation. The maximum released charge density was 22 μC/cm2 from a stored charge density of 36 μC/cm2 in a 0.55 μ thick lead zirconate thin film. This indicated that more than 60% of the stored charge could be released in less than 7 ns at room temperature for a field of 200 kV/cm. The content of net released charge was found to increase with increasing field strength, whereas with increasing temperature the released charge was found to decrease. Thickness-dependent studies on lead zirconate thin films showed that size effects relating to extrinsic and intrinsic pinning mechanisms controlled the released and induced charges through the intrinsic switching time. These results proved that antiferroelectric PZ thin films could be utilized in high-speed charge decoupling capacitors in microelectronics applications.

Simultaneous measurements of water impact on a two-dimensional body

This study utilizes a high-speed charge coupled device (CCD) camera as the data acquisition system to simultaneously measure the pressure and flow field. The measurement system can be triggered by an external optical sensor, to obtain the free surface and pressure variations in each time step of the initial stage of water impact. The whole field image was observed by a high-speed area scan sensor camera. Almost no interval between photographing moving objects was allowed owing to the extremely short transfer time and high exposure sensitivity of the camera. Following image transfer, this characteristic and the hardware computational function of a video card not only allowed for binarization, accumulative addition but we could also quickly identify the track of a moving object and obtain the image and numerical data which we needed. Moreover, the flow characteristics are observed via a flow following “seeding” particles, and the digital particle tracking velocimeter (DPTV) so that the flow field velocity distribution can be measured.

Low-noise and high-speed charge detection in high-resolution CCD image sensors

This paper analyzes problems associated with low-noise and high-speed charge detection encountered in high-resolution image sensors. It is found that the conventional Floating Diffusion (FD) charge detection concept is inferior to the previously studied, but not frequently utilized, Floating Gate (FG) approach. A new output charge detection well reset technique and an improved biasing method allowed the design of the FG charge detection amplifier with a comparable conversion gain to FD structures but with much better noise performance at the data rates up to 40 MHz. The theoretical analysis of the FG amplifier performance, including the Correlated Pixel Clamp signal processing method, is confirmed by measurements performed on a high-resolution 1000/spl times/1000 pixel Frame Transfer CCD image sensor built using an Advanced Virtual Phase Technology. The described details of the sensor design include: (1) the over all device architecture, (2) the pixel cross section with the cross section of the lateral overflow drain antiblooming structure, (3) the dual serial register with a single output amplifier, and (4) the resistive gate reset structure for the output charge detection well. The developed image sensor does not need the conventional Correlated Double Sampling (CDS) circuit for the signal processing, since the FG detection node is sensing charge nondestructively without generation of kTC noise. The described progress in the FG charge detection approach thus opens up a possibility for future designs of distributed FG amplifiers that can theoretically reach the ultimate low-noise performance at virtually any clocking frequency.