High-speed Charge-coupled Device Research Articles

The influence of unipolar axial magnetic field on the behavior of vacuum arcs

The behavior of vacuum arcs under the influence of unipolar axial magnetic field (AMF) has been investigated. In experimental investigations, the vacuum arc mode is studied at different arc currents by using high-speed charge-coupled device (CCD) video images. In spite of the AMF, first sign of arc constriction appears at relatively small currents of about 15 kA (RMS). Three different arc modes were found. Based on generalized Ohm's law, the current density distribution in the vacuum arc with unipolar axial magnetic field is computed using three-dimensional finite-element method (FEM) software. The calculated current distribution is confirmed by the vacuum arc appearance taken from CCD video film. The distribution of AMF can be optimized by such experiments and theoretical analysis.

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.

Mechanism of Shock Wave Oscillation in Transonic Diffusers

Self-excited shock wave oscillation in a two-dimensional transonic diffuser is investigated experimentally and analytically. In theexperiments, the temporal position of a shock wave is recorded by a high-speed charge-coupled device camera combined with a schlieren system, simultaneously measuring the e uctuation of the static pressure on the diffuser wall. The temporal variation of the static pressure is also measured to obtain the propagation of pressure disturbances. The results show that a pressure disturbance is generated near the stem of the shock wave and is convected in the downstream direction. In thedownstream region wheretheboundary layer becomes highly turbulent, another disturbance is generated that propagates upstream and causes the shock wave to oscillate. One-dimensional Euler equations are solved numerically, and the power spectral density distribution of the shock wave oscillation is calculated. The numerical results agree very well with the experiments. It is also shown that the present calculation can explain the shock wave oscillation in the diffusers reported so far.

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.

Burning Aluminum Particles Inside a Laboratory-Scale Solid Rocket Motor

Single and agglomerated aluminum droplets were studied in a solid rocket motor test chamber with optical access to the internal flow at 6-22 atm and 2300 K. The chamber was pressurized by burning a main grain ammonium perchlorate/hydroxyl-terminated poly-butadiene propellant, and the burning aluminum droplets were generated by a smaller aluminized solid propellant sample, center mounted in the flow. A 35-mm camera was used with a chopper wheel to give droplet flame diameter vs time measurements of the burning droplets in flight, from which burning rate laws were developed. A high-speed video charge-coupled device with high-magnification optics imaged the flame/smoke cloud surrounding the burning liquid droplets. The intensity profiles of the droplet images were deconvoluted using an Abel inversion to give true intensity profiles. Both single and agglomerated droplets were studied, where agglomerates comprise hundreds of parent particles or more. The Abel inversions show that the relative smoke cloud size is not constant with diameter, but instead grows as the droplet shrinks, by ∼D - 0 . 5 , for both the single and agglomerated droplets. Measured diameter trajectories show that, for single droplets, the mean diameter law is D 0 . 7 5 = D 0 . 7 5 0 - 8.t, and, for agglomerated droplets, D 1 . 0 = D 1 . 0 0 - 20.t. For both single and agglomerated droplets, the burning rate slope k did not change significantly for the chamber pressure range studied.

Flow measurement with an electromagnetic flowmeter in two-phase bubbly and slug flow regimes

In order to investigate the characteristics of an electromagnetic flowmeter in two-phase flow, an alternating-current electromagnetic flowmeter was designed and manufactured. The signals and noise from the flowmeter under various flow conditions were obtained, and analyzed in comparison with the flow patterns observed with a high-speed charge-coupled device camera. An experiment with void simulators, in which a rod-shaped non-conducting material was used, was carried out to investigate the effect of bubble position and void fraction on the flowmeter. Two-phase flow experiments, encompassing bubbly to slug flow regimes, were conducted with a water–air mixture. The simple relation Δ U TP=Δ U SP/(1− α), relating the flowmeter signal between single-phase flow and two-phase flow, was verified with measurements of the potential difference and the void fraction for a bubbly flow regime. Due to the lack of homogeneity in a real two-phase flow, the discrepancy between the relation and the present measurement increased slightly with increasing void fraction and superficial liquid velocity j f. Whereas there is no difference in the shape of the raw signal between single-phase flow and bubbly flow, the signal amplitude for bubbly flow is higher than that for single-phase flow at the same water flow rate, since the passage area of the water flow is reduced. In the case of slug flow, the phase and the amplitude of the flowmeter output show dramatically the flow characteristics around each slug bubble and the position of the slug bubble itself. Therefore, the electromagnetic flowmeter shows a good possibility of being useful for identifying the flow regimes.

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.

Effect of the Sinus of Valsalva on the Closing Motion of Bileaflet Prosthetic Heart Valves

Conventional bileaflet prosthetic mechanical heart valves close passively with backflow. Naturally, the valve has problems associated with closure, such as backflow, water hammer effect, and fracture of the leaflet. On the other hand, in the case of the natural aortic valve, the vortex flow in the sinus of Valsalva pushes the leaflet to close, and the valve starts the closing motion earlier than the prosthetic valve as the forward flow decelerates. This closing mechanism is thought to decrease backflow at valve closure. In this study, we propose a new bileaflet mechanical valve resembling a drawbridge in shape, and the prototype valve was designed so that the leaflet closes with the help of the vortex flow in the sinus. The test valve was made of aluminum alloy, and its closing motion was compared to that of the CarboMedics (CM) valve. Both valves were driven by a computer controlled hydraulic mock circulator and were photographed at 648 frames/s by a high speed charge-coupled device (CCD) camera. Each frame of the valve motion image was analyzed with a personal computer, and the opening angles were measured. The flow rate was set as 5.0 L/min. The system was pulsed with 70 bpm, and the systolic/diastolic ratio was 0.3. Glycerin water was used as the circulation fluid at room temperature, and polystyrene particles were used to visualize the streamline. The model of the sinus of Valsalva was made of transparent silicone rubber. As a result, high speed video analysis showed that the test valve started the closing motion 41 ms earlier than the CM valve, and streamline analysis showed that the test valve had a closing mechanism similar to the natural one with the effect of vortex flow. The structure of the test valve was thought to be effective for soft closure and could solve problems associated with closure.

High-speed fluorescence detection of explosives-like vapors

In this paper, we report on the preparation of novel cross-reactive optical microsensors for high-speed detection of low-level explosives and explosives-like vapors. Porous silica microspheres with an incorporated environmentally sensitive fluorescent dye are employed in high-density sensor arrays to monitor fluorescence changes during nitroaromatic compound (NAC) vapor exposure. The porous silica-based sensor materials have good adsorption characteristics, high surface areas, and surface functionality to help maximize analyte-dye interactions. These interactions occur immediately upon vapor exposure, i.e., in less than 200 ms and are monitored with a high-speed charge-coupled device camera to produce characteristic and reproducible vapor response profiles for individual sensors within an array. Employing thousands of identical microsensors permits sensor responses to be combined, which significantly reduces sensor noise and enhances detection limits. Normalized response profiles for 1,3-dinitrobenzene (1,3-DNB) are independent of analyte concentration, analyte exposure time, or sensor age for an array of one sensor type. Explosives-like NACs such as 2,4-dinitrotoluene and DNB are detected at low part-per-billion levels in seconds. Sensor-analyte profiles of some sensor types are more sensitive to low-level NAC vapor even when in a higher organic vapor background. We show that single-element arrays permit the detection of low-level nitroaromatic compound vapors because of sensor-to-sensor reproducibility and signal averaging.

RDS and IRDS filters for high-speed CCD video sensors

In this brief, we present two filters called "reflection delayed noise suppression" (RDS) and "integration reflection delayed noise suppression" (IRDS) which are useful to increase dynamics of video charge-coupled device (CCD) cameras. The RDS is a band-pass filter built with a parallel short-circuited line. It significantly lowers the most important noise, called reset noise. Unfortunately, this signal processing unit increases the contribution of thermal fluctuations by at least 3 dB. To overcome this disadvantage, a reset low-pass filter can be added to the RDS cell, which leads to the IRDS method. For both methods, we will describe the principle and compare their effects in a theoretical way, and by experimentation on sensing-node amplifier and reset noise in the CCD sensor.

Physical and theoretical aspects of a new vacuum arc control technology-self arc diffusion by electrode: SADE

Our new vacuum arc control technology SADE doubles the high current interruption capability of our conventional axial magnetic field technology. First, we describe the vacuum arc motion behavior recorded by a high speed charge-coupled device video camera. This arc behavior is closely related to axial magnetic field intensity. In particular, it depends on the profile of the externally generated axial magnetic field. The anode spot is likely to move to the highest magnetic field intensity. Second, we describe analytical results for concentration of vacuum arc at the anode side contact surface. This analysis implies the possibility of an ideal magnetic field profile and intensity for vacuum arc control. Finally, we describe experimental results for vacuum arc control compared with the physical and theoretical results mentioned above, and we show a practical electrode configuration for vacuum interrupters and its application in a high current interruption experiment.

Exploration of X-ray and charged-particle spectroscopy with CCDs and PSDs

Two alternative detector types have been studied for use in the Eindhoven Scanning Ion Microprobe set-up. First, the applicability of a Charge Coupled Device (CCD) system for X-ray spectroscopy has been explored. Second, some properties of the SiTek type 1L30 Position Sensitive Detector (PSD) for charged-particle spectroscopy have been studied. A literature survey shows that excellent X-ray spectroscopy with a CCD system is feasible, particularly with a deep-depletion backside-illuminated CCD and low speed read-out. If, however, high-speed CCD read-out is required, such as for scanning microprobe experiments, a CCD system cannot be used for spectroscopy due to excess read-out noise. For the PSD, noise theory calculations are presented, which result in a noise shaping time for optimal energy and position resolution. In practice, however, a much longer time is needed to obtain sufficient energy and position linearity. Characterization measurements of the PSD using our 4 MeV He + microprobe are also described. A position resolution of 0.47 mm and a position linearity of better than 0.15% detector length are found. In addition, an energy linearity better than 0.3% and an energy resolution of 36 keV are measured. The latter will have to be improved, to make the PSD suitable for charged-particle spectroscopy applications.

Design and performance of the SLD vertex detector: a 307 Mpixel tracking system

This paper describes the design, construction, and initial operation of SLD's upgraded vertex detector which comprises 96 two-dimensional charge-coupled devices (CCDs) with a total of 307 Mpixel. Each pixel functions as an independent particle detecting element, providing space point measurements of charged particle tracks with a typical precision of 4 μm in each co-ordinate. The CCDs are arranged in three concentric cylinders just outside the beam-pipe which surrounds the e +e − collision point of the SLAC Linear Collider (SLC). The detector is a powerful tool for distinguishing displaced vertex tracks, produced by decay in flight of heavy flavour hadrons or tau leptons, from tracks produced at the primary event vertex. The requirements for this detector include a very low mass structure (to minimize multiple scattering) both for mechanical support and to provide signal paths for the CCDs; operation at low temperature with a high degree of mechanical stability; and high speed CCD readout, signal processing, and data sparsification. The lessons learned in achieving these goals should be useful for the construction of large arrays of CCDs or active pixel devices in the future in a number of areas of science and technology.

The Fox Movietone News Preservation Project: The Progressive Scan CCD Camera

This paper describes a high-speed charge-coupled device (CCD) camera that has been developed for commercial, industrial, and scientific applications. It uses a 1024-line progressive scan imager with two video output channels. The dual-channel outputs provide a total data rate of 40 million pixels/sec, using “square pixel” sampling. The camera incorporates electronic shuttering triggered by an external source, so that the exposure period and frame rate can be precisely controlled. The camera features high linearity, low noise, wide dynamic range, and low shading. An early prototype of this camera was used by Fox News, Inc., to digitize film news-reels for the Fox Movietone project.

Transient clock voltage and heating e ects in high-speed resistive-gate charge-coupled devices (RGCCDs)

This work investigates the transient clock voltage and heating effects in high-speed GaAs resistive-gate charge-coupled devices (RGCCDs). The resistivity of the resistive-gate (cermet) was chosen as a variable parameter. The transient voltage delays were computed using a circuit model (similar to the transmission line model reported by Lenoble et al. 1990 a). These were combined with the charge transport times computed using a one-dimensional analytical model (Pennathur and Kwok 1992) and estimations were made on the peak operating frequencies. The low frequency limits of the device were computed by analysing the heating effect of the cermet layer on the leakage currents and the resulting thermally-generated carriers. It was observed that there were conflicting requirements on the cermet resistivity when both the speed and the transfer inefficiency of the RGCCDs had to be simultaneously optimized. The decision on the choice of the cermet resistivity largely depends on a trade-off in the device performance.

Effects of the clock voltage waveforms on the charge transfer inefficiency of high-speed charge-coupled devices

Effects of the clock voltage waveforms on the charge transfer inefficiency of high-speed charge-coupled devices

Power dissipation in frame-transfer charge-coupled devices

The power dissipation for large-area high-speed charge-coupled device (CCD) arrays is analyzed. The four mechanisms responsible for power dissipation in a CCD are carrier lift and friction within the CCD channel, load currents through the on-chip output amplifiers, capacitive charge and discharge currents through the epitaxial layer or substrate, and currents flowing through the polysilicon clock register electrodes. These processes are easily calculated for small or slow devices. For large high-speed devices, on the other hand, the conventional analytical techniques are inadequate. The large device area leads to high resistive-capacitive constants in the parallel clock registers, causing clock pulses to degrade in shape as they travel along a clock electrode. A distributed system analysis based on lumped circuit parameters for each pixel is necessary to calculate the current and thus the power dissipated at each point on the surface of the COD. A computer simulation of a standard frame-transfer CCD was performed using SPICE software. The results of the simulation indicate a much lower power dissipation than previously assumed and also point out various problems with conventional device architectures for large-area high-speed CCDs.

High-speed video imaging and digital analysis of microscopic features in contracting striated muscle cells

The rapid motion of microscopic features such as the cross striations of single contracting muscle cells are difficult to capture with conventional optical microscopes, video systems, and image processing approaches. An integrated digital video imaging microscope system specifically designed to capture images from single contracting muscle cells at speeds of up to 240 Hz and to analyze images to extract features critical for the understanding of muscle contraction is described. This system consists of a brightfield microscope with immersion optics coupled to a high-speed charge-coupled device (CCD) video camera, super-VHS (S-VHS) and optical media disk video recording (OMDR) systems, and a semiautomated digital image analysis system. Components are modified to optimize spatial and temporal resolution to permit the evaluation of submicrometer features in real physiological time. This approach permits the critical evaluation of the magnitude, time course, and uniformity of contractile function throughout the volume of a single living cell with higher temporal and spatial resolutions than previously possible.

An enhancement mode Schottky barrier gate charge-coupled device on a high electron mobility transistor structure

An enhancement mode charge-coupled device (CCD) was fabricated for the first time on a selectively doped n-GaAlAs/p−-GaAs heterojunction structure. A dramatic improvement in charge-transfer efficiency (CTE) was observed as the CCD is cooled from 300 to 77 °K. This improvement is attributed to the increase in low field electron mobility of the two-dimensional electron gas at low temperature. Charge capacity was also found to increase upon cooling. The cause is not well understood. An optimized structure for high-speed CCD is proposed.