Showing papers on "Rise time published in 2012"

Effects of Impulse Voltage Polarity, Peak Amplitude, and Rise Time on Streamers Initiated From a Needle Electrode in Transformer Oil

Abstract: An electrothermal hydrodynamic model is presented to evaluate effects of the applied lightning impulse voltage parameters such as polarity, magnitude, and rise time on the initiation and propagation of the streamers formed in an IEC defined needle-sphere electrode geometry filled with transformer oil. Instantaneous velocity, column diameter, head curvature, maximum electric field, and the volume charge density have been investigated as the main characteristics of the streamer. Modeling results indicate that greater applied voltage peak amplitudes form streamers with higher velocity, greater head curvatures, and thicker columns. The bushy negative streamers usually initiate at almost twice the applied voltage magnitude and propagate slower than filamentary positive streamers. Results also show that in transformer oil at the same impulse voltage peak amplitude, shorter rise times create thicker positive and negative streamers.

Experimental determination of dielectric barrier discharge capacitance.

Abstract: The determination of electrical parameters (such as instantaneous power, transferred charge, and gas gap voltage) in dielectric barrier discharge (DBD) reactors relies on estimates of key capacitance values. In the classic large-scale sinusoidal-voltage driven DBD, also known as silent or ozonizer discharge, capacitance values can be determined from charge-voltage (Q-V) plot, also called Lissajous figure. For miniature laboratory reactors driven by fast pulsed voltage waveforms with sub-microsecond rise time, the capacitance of the dielectric barriers cannot be evaluated from a single Q-V plot because of the limited applicability of the classical theory. Theoretical determination can be problematic due to electrode edge effects, especially in the case of asymmetrical electrodes. The lack of reliable capacitance estimates leads to a "capacitance bottleneck" that obstructs the determination of other DBD electrical parameters in fast-pulsed reactors. It is suggested to obtain capacitance of dielectric barriers from a plot of the maximal charge versus maximal voltage amplitude (Q(max) - V(max) plot) in a manner analogous to the classical approach. The method is examined using measurements of current and voltage waveforms of a coaxial DBD reactor in argon at 100 mbar driven by square voltage pulses with a rise time of 20 ns and with different voltage amplitudes up to 10 kV. Additionally, the applicability of the method has been shown for the data reported in literature measured at 1 bar of nitrogen-oxygen gas mixtures and xenon.

Repetitive sub-gigawatt rf source based on gyromagnetic nonlinear transmission line

Abstract: We demonstrate a high power repetitive rf source using gyromagnetic nonlinear transmission line to produce rf oscillations. Saturated NiZn ferrites act as active nonlinear medium first sharpening the pumping high voltage nanosecond pulse and then radiating at central frequency of about 1 GHz: shock rise time excites gyromagnetic precession in ferrites forming damping rf oscillations. The optimal length of nonlinear transmission line was found to be of about 1 m. SINUS-200 high voltage driver with Tesla transformer incorporated into pulse forming line has been designed and fabricated to produce bursts of 1000 pulses with 200 Hz repetition rate. A band-pass filter and mode-converter have been designed to extract rf pulse from low-frequency component and to form TE11 mode of circular waveguide with linear polarization. A wide-band horn antenna has been fabricated to form Gaussian distribution of radiation pattern. The peak value of electric field strength of a radiated pulse at the distance of 3.5 m away from antenna is measured to be 160 kV/m. The corresponding rf peak power of 260 MW was achieved.

A fast preamplifier concept for SiPM-based time-of-flight PET detectors

Abstract: Silicon photomultipliers (SiPMs) offer high gain and fast response to light, making them interesting for fast timing applications such as time-of-flight (TOF) PET. To fully exploit the potential of these photosensors, dedicated preamplifiers that do not deteriorate the rise time and signal-to-noise ratio are crucial. Challenges include the high sensor capacitance, typically 4 300 pF for a 3 mm � 3 mm SiPM sensor, as well as oscillation issues. Here we present a preamplifier concept based on low noise, high speed transistors, designed for optimum timing performance. The input stage consists of a transimpe- dance common-base amplifier with a very low input impedance even at high frequencies, which assures a good linearity and avoids that the high detector capacitance affects the amplifier bandwidth. The amplifier has a fast timing output as well as a 'slow' energy output optimized for determining the total charge content of the pulse. The rise time of the amplifier is about 300 ps. The measured coincidence resolving time (CRT) for 511 keV photon pairs using the amplifiers in combination with 3m m� 3 mm SiPMs (Hamamatsu MPPC-S10362-33-050C) coupled to 3 mm � 3m m� 5 mm LaBr 3 :Ce and LYSO:Ce crystals equals 95 ps FWHM and 138 ps FWHM, respectively.

Accurate measurement of the rise and decay times of fast scintillators with solid state photon counters

Abstract: In this work we present a measurement setup for the determination of scintillation pulse shapes of fast scintillators It is based on a time-correlated single photon counting approach that utilizes the correlation between 511 keV annihilation photons to produce start and stop signals in two separate crystals The measurement is potentially cost-effective and simple to set up while maintaining an excellent system timing resolution of 125 ps As a proof-of-concept the scintillation photon arrival time histograms were recorded for two well-known, fast scintillators: LYSO:Ce and LaBr3:5%Ce The scintillation pulse shapes were modeled as a linear combination of exponentially distributed charge transfer and photon emission processes Correcting for the system timing resolution, the exponential time constants were extracted from the recorded histograms A decay time of 43 ns and a rise time of 72 ps were determined for LYSO:Ce thus demonstrating the capability of the system to accurately measure very fast rise times In the case of LaBr3:5%Ce two processes were observed to contribute to the rising edge of the scintillation pulse The faster component (270 ps) contributes with 72% to the rising edge of the scintillation pulse while the second, slower component (20 ns) contributes with 27% The decay of the LaBr3:5%Ce scintillation pulse was measured to be 154 ns with a small contribution (2%) of a component with a larger time constant (130 ns)

Design Rules for IGZO Logic Gates on Plastic Foil Enabling Operation at Bending Radii of 3.5 mm

Abstract: Findings obtained from bending experiments with mechanically flexible InGaZnO-based thin-film transistors are used to derive design rules for flexible InGaZnO-based n-channel metal-oxide-semiconductor logic circuits. Based on the developed design rules, flexible NAND gates, inverters, and five-stage ring oscillators are fabricated directly on free-standing plastic foils at temperatures ≤ 150 °C. Geometrically well-designed circuits operated at a supply voltage of 5 V are exposed to tensile mechanical strains, induced by bending, up to 0.72% without performance degradation. This corresponds to a bending radius of 3.5 mm. At the same time, increases in the rise time by a factor of ca 2 and reductions in the high and low output voltage levels by ca 10% and 50% have been observed for circuits with disadvantageous geometrical design. Ring oscillators designed to be operated under strain show an increase in oscillation frequency from 22.9 kHz (flat substrate) to 23.32 kHz (bending radius: 3.5 mm). This demonstrates the held-effect mobility increase in a-IGZO-based circuits under tensile mechanical strain. Long-term reliability is evaluated with 20000 cycles of repeated bending and reflattering without circuit failure.

Fast transient capacitor-less LDO regulator using low-power output voltage detector

Abstract: An output-capacitor-less low-dropout regulator (LDO) with a low-power output voltage detector (OVD) is proposed. The OVD is based on an R/C highpass filter which is able to detect the fast-changing voltage at the LDO output and activate an additional path to control the power transistor. The OVD consumes only additional quiescent current to monitor the variation in output voltage in the steady state. In the simulated load-transient response, a maximum undershoot of 1.2 V and a settling time (Δt 2 ) of 67 ns are observed with the proposed OVD for a load current variation from 1 to 50 mA at a rise time of 1 ns. These results are 0.2 V and 473 ns better than the results obtained without the proposed OVD.

Investigation of partial discharge activity by a conducting particle in transformer oil under harmonic AC voltages adopting UHF technique

Abstract: A methodical experimental study was carried out to understand the partial discharges initiated due to particle movement in transformer oil under high frequency ac voltage and under harmonic ac voltages (with different THDs), by adopting UHF technique. It is also observed that irrespective of order of harmonics, increase in THD of the supply voltage shows reduction in levitation voltage. The rise time of the partial discharge current pulse formed due to particle movement is few ns. It is observed that the frequency content of the signal radiated due to partial discharges generated due to particle movement in the electrode gap lies in the UHF signal range, with its dominant frequency near 1 GHz. The supply voltage frequency and the time required for 100 UHF signals to form shows inverse relationship. When the applied voltage is increased above levitation voltage, the UHF signal magnitude formed due to particle movement increases, irrespective of supply voltage frequency. Ternary diagram clearly indicates that irrespective of frequency of the supply voltage, the UHF signal location in the ternary diagram is the same.

A 2.45-GHz $+$ 20-dBm Fast Switching Class-E Power Amplifier With 43% PAE and a 18-dB-Wide Power Range in 0.18- $\mu \hbox{m}$ CMOS

Abstract: In this brief, the losses in Class-E power amplifiers (PAs) with finite dc-feed inductance are analyzed This analysis results in practical analytical expressions, which significantly simplify the design and optimization of Class-E PAs To demonstrate their applicability, the design of a state-of-the-art 245-GHz differential cascode Class-E PA in 018- CMOS with on-chip dc-feed inductor is presented By the proposed combination of a dynamic supply voltage and a dynamic cascode bias voltage, high drain efficiency is achieved over a wide power control range, covering from 22 up to 20 dBm At 20 dBm, a power-added efficiency as high as 436% was measured Additionally, fast envelope switching is obtained by adding a single switch to the common-gate nodes of both the Class-E stage and the second driver stage Measurements show a rise time of merely 25 ns and a 73-dB isolation between the on- and off-states These figures enable ranging applications with submeter accuracy

A fast and low noise charge sensitive preamplifier in 90 nm CMOS technology

Abstract: A fast charge sensitive preamplifier was designed and built in a 90 nm CMOS technology. The work is part of the R&D effort towards the read out of pixel or small strip sensors in next generation HEP experiments. The preamplifier features outstanding noise performance given its wide bandwidth, with a ENC (equivalent noise charge) of about 350 electrons RMS with a detector of 1 pF capacitance. With proper filtering, the ENC drops to less than 200 electrons RMS. Power consumption is 5 mW for one channel, and the closed loop bandwith is about 180 MHz, for a risetime down to 2 ns in the fastest operation mode. Thanks to some freedom left to the user in setting the open loop gain, detectors with larger source capacitance can be read out without significant loss in bandwidth, being the rise time still 5.5 ns for a 5.6 pF detector. The output can drive a 50 ? terminated transmission line.

Development and validation of a tokamak skin effect transformer model

Abstract: A lumped parameter, state space model for a tokamak transformer including the slow flux penetration in the plasma (skin effect transformer model) is presented. The model does not require detailed or explicit information about plasma profiles or geometry. Instead, this information is lumped in system variables, parameters and inputs. The model has an exact mathematical structure built from energy and flux conservation theorems, predicting the evolution and non-linear interaction of plasma current and internal inductance as functions of the primary coil currents, plasma resistance, non-inductive current drive and the loop voltage at a specific location inside the plasma (equilibrium loop voltage). Loop voltage profile in the plasma is substituted by a three-point discretization, and ordinary differential equations are used to predict the equilibrium loop voltage as a function of the boundary and resistive loop voltages. This provides a model for equilibrium loop voltage evolution, which is reminiscent of the skin effect. The order and parameters of this differential equation are determined empirically using system identification techniques. Fast plasma current modulation experiments with random binary signals have been conducted in the TCV tokamak to generate the required data for the analysis. Plasma current was modulated under ohmic conditions between 200 and 300 kA with 30 ms rise time, several times faster than its time constant L/R approximate to 200 ms. A second-order linear differential equation for equilibrium loop voltage is sufficient to describe the plasma current and internal inductance modulation with 70% and 38% fit parameters, respectively. The model explains the most salient features of the plasma current transients, such as the inverse correlation between plasma current ramp rates and internal inductance changes, without requiring detailed or explicit information about resistivity profiles. This proves that a lumped parameter modelling approach can be used to predict the time evolution of bulk plasma properties such as plasma inductance or current with reasonable accuracy; at least under ohmic conditions without external heating and current drive sources.

A High-Speed Multi-Channel Readout for SSPM Arrays

Abstract: Solid-state photomultiplier (SSPM) arrays are a new technology that shows great promise to be used in PET detector modules. To reduce the number of channels in a PET scanner, it is attractive to use resistor dividers, which multiplex the number of channels in each module down to four analog output channels. It is also attractive to have SSPMs with large pixels (3×3 or 4×4 mm2). However, large area SSPMs have correspondingly large capacitances (up to 1 nF) and directly coupling them to a resistive network will create a low-pass filter with a high RC time constant. In order to overcome this, we have developed an application specific integrated circuit (ASIC) that “hides” the intrinsic capacitance of the SSPM array from a resistive network with current buffers, significantly improving the rise time of the SSPM signals when connected to the resistive network. The ASIC is designed for a wide range of SSPM sizes, up to 1 nF (equivalent to 4×4 mm2), and for input currents of 1 to 20 mA per channel. To accommodate various sizes of SSPM pixels, the ASIC uses adjustable current sources (to keep the feedback loop stable). A test ASIC has been fabricated that has 16 input channels, an internal resistor divider array that produces four analog outputs, 16 buffers that isolate the SSPM capacitance from the resistor array, and four output buffers that can drive 100 ohm loads. Thus, detector modules based on SSPMs and this ASIC should be compatible with the block detector readout electronics found in many PET cameras. Tests of this ASIC show that its rise time is <; 2 ns (and it will thus not significantly degrade the ~7 ns rise time of the SSPM pixels) and that the analog decoding circuitry functions properly.

Nonparametric control algorithms for a pneumatic artificial muscle

Abstract: Highlights? Implementation of a self-organizing fuzzy controller for position and force control. ? Controller is experimentally evaluated alongside a PD and fixed rule fuzzy controller. ? Two different pneumatic valves are compared to determine its influence. ? SOFC outperforms the PD and FCC in standard control tests. Accurate control of the PAM is a challenging task due to the nonlinear elasticity and the hysteresis losses in the actuator, the compressibility of air, and the nonlinearities in the pneumatic system. A novel implementation of a self-organizing fuzzy controller (SOFC) for the position and force control of a single PAM is proposed in this work. The performance of the controller is experimentally evaluated alongside two other nonparametric control algorithms; PD and fixed rule fuzzy controller (FFC). In addition a comparison of the performance of two different pneumatic valves (high speed on-off valve (HSV) and proportional pressure regulator (PPR)) is also undertaken to determine the influence of the valve type on the system response. In all the experiments for both position and force control strategies, the SOFC surpasses the PD and FCC in terms of percentage overshoot for step input and percentage RMS error (%RMSE) for ramp input whilst maintaining comparably rise time (Tr) and percentage steady state error (%SSE). It is able to track the reference signal with no oscillation and overshoot of less than 7% for both position and force control. Results show that the HSV performs better in response to abrupt changes (step input) while the PPR performs better in response to an incremental change (ramp input).

Broadband switching functionality based on defect mode coupling in W2 photonic crystal waveguide

Abstract: Broadband switching functionality realized by an ultra-compact W2 photonic crystal waveguide (PCW) is demonstrated with an integrated titanium/aluminum microheater on its surface. Due to the enhanced coupling between the defect modes in W2 PCW, switching functionality with bandwidth up to 24 nm is achieved by the PCW with footprint of only 8 μm × 17.6 μm, while the extinction ratio is in excess of 15 dB over the entire bandwidth. Moreover, the switching speed is measured by alternating current modulation. Response time for this thermo-optic switch is 11.0 ± 3.0 μs for rise time and 40.3 ± 5.3 μs for fall time, respectively.

Ultra-wide bandwidth measurement of partial discharge current pulses in SF6

Abstract: This paper presents ultra-wide bandwidth measurements of partial discharge (PD) current pulses. Using a 33 GHz bandwidth oscilloscope together with a direct, matched coaxial connection to the PD source, pulses have been characterized with a greater degree of accuracy than has previously been achieved, with a minimum observed rise time of 24 ps. The PD source consists of a sharp protrusion in pressurized sulfur hexaflouride (SF6) with a tip radius of 25 µm. Both positive and negative corona pulses were recorded, revealing previously indistinguishable frequency content and features such as the appearance of groups of multiple component pulses occurring within a nanosecond time scale. The upper bandwidth limitation of the complete measurement set-up was established. This was calculated by cross-correlating current pulses with corresponding pulses filtered at lower frequencies to determine their similarity. The tendency for multiple consecutive pulses to occur within a short time period was evident. The results provide valuable data for researchers investigating fundamental physical phenomena of SF6 ionization and PD activity.

The influence of square voltage rise time on partial discharge spectra

Abstract: Literature data regarding the behavior of partial discharge inception voltage (PDIV) under repetitive impulsive voltage waveforms is contradictory. Some authors have found that rise time can lower PDIV, others just the opposite. The picture complicates further when repetitive PDIV (RPDIV) is discussed. In many papers, antenna sensor working in the UHF range were used, but no standardized sensors (and setup geometry) is defined yet. Therefore, if some parameters of the supply waveform could affect partial discharge spectra, that could be one of the possible reasons for the differences reported in literature. In this paper, experiments carried out on crossed pairs subjected to square voltages, aimed at inferring the dependence of rise time on partial discharge pulse spectra, are discussed. The results show that shorter rise times favor the inception of pulses having large magnitude and frequency content. As a consequence, depending on the bandwidth of the sensor-detector chain, PD detection sensitivity can vary with rise time, thus affecting PDIV measurement.

Carbon-Nanotube-Triggered Pseudospark Switch

Abstract: Pseudospark switches are fast-closing low-pressure gas discharge switches with a hollow-cathode geometry. They can be triggered optically or by electron injection, where electrons emitted from a cold cathode emitter are accelerated in the electric field and initiate breakdown. The efficiency of charge carrier accumulation in the hollow-cathode structure determines the performance of the switch operation. The advantages of such switches include high hold-off voltage, high conduction current, fast current rise time, low delay and jitter time, and long lifetime. In this paper, the operating characteristics of a pseudospark switch, triggered by a carbon-nanotube (CNT)-coated electron emitter, are presented. The electron emitter is fabricated by coating randomly oriented CNTs on silicon substrate using chemical vapor deposition method. Field emission characteristics of CNTs are determined and then used as part of the trigger electrode which is integrated into an in-house constructed pseudospark switch. The operating characteristics of the switch are tested under different background pressures and different trigger voltages. Delay and jitter time under different working conditions are analyzed. Hold-off voltage and current rise time are also presented.

Load Frequency Control Using Classical Controller in An Isolated Single Area and Two Area Reheat Thermal Power System

Abstract: In this paper, Load Frequency Control (LFC) of isolated single area and two-area re-heat inter-connected thermal power system has been carried out by the classical controllers i.e. I, PI and PID; and implemented on the system at 1% step load perturbation under nominal loading conditions. The system responses have been simulated in MATLAB R2010a. Responses of deviation in frequencies, deviation in tie-line power and choosing the optimum controller (i.e. better among I, PI & PID controllers) gain values (i.e. ) to have better dynamic responses of the system have been plotted, keeping in view the characteristics such as rise time, settling time, oscillations & peak overshoot. Thus, on the basis of these responses, the dynamic performance of the system has been studied. Effect of variation in regulation parameter (R) and also step load perturbations is simulated for different values. The simulation results indicate that better control performance in terms of overshoot and settling time can be achieved by choosing PID among the other considered classical controllers.

Time and frequency characterization of radiated disturbances in telecommunication bands due to pantograph arcing

Abstract: Radiated emissions from arcing between pantograph and overhead lines in electrical transportation systems extend up to the frequency bands currently used for telecommunications and may therefore affect the quality features of telecommunication systems. The paper investigates on the time and frequency characteristics of the disturbances. Transient amplitude, rise time and pulse duration were measured in the time domain to obtain the associated empirical distributions; the power spectrum and the frequency content were calculated in the bands of interest; finally a time-frequency representation has been used to observe the evolution of the power spectra over time and the location of the main contributions.

SCPEM-Q-switching of a fiber-rod-laser.

Abstract: We demonstrate high-frequency Q-switching of a fiber rod laser with a Single-Crystal Photo-Elastic Modulator (SCPEM) made of a LiTaO3-crystal. This type of photo-elastic modulator can be driven simultaneously with two different eigenmodes to achieve a shorter rise time, which is essential for high-power operation. When operated in the laser cavity, a pulse repetition frequency of 183.6 kHz with an average power of 47 W, a pulse duration of 26 ns, and a peak power of 10.5 kW was achieved.

A nano-watt power CMOS amplifier with adaptive biasing for power-aware analog LSIs

Abstract: This paper presents an ultra-low power CMOS amplifier (AMP) using a simple and novel adaptive biasing current circuit (ABCC). The circuit uses a nano-ampere current source to achieve nano-watt power dissipation and the adaptive biasing technique to achieve high speed operation. The ABCC monitors the input voltages and supplies adaptive biasing current to the AMP. Because the adaptive biasing current is generated only when the AMP does not maintain its “virtual short” characteristic in the feedback configuration, the circuit operates with nano-watt power dissipation. Measurement results demonstrated that the circuit can operate with ultra-low power of 325 nA and high speed of 0.0506 V/μs at the rise time and 0.0579 V/μs at the fall time, when the input pulse frequency and the amplitude were 1 kHz and 0.8 V pp .

Nonlinear effects in transient electrothermal characterization of anatase TiO2 nanowires.

Abstract: As an effective transient thermal characterization technique, the transient electrothermal (TET) technique features a capability of measuring micro/nanoscale samples of diverse electrical conducting natures. In this work, single anatase titanium dioxide (TiO2) nanowires fabricated using the electrospinning method are characterized using the TET technique. Time-dependent nonlinear effect is observed for both rise and fall stages in the voltage-time (U-t) response profile. The coated iridium film and soldered platinum pads possibly compromise the linear Ohmic effect and introduce undesired effects into the whole system. Two quantitative methods: generalized function analysis and direct capacitance derivation, are developed to suppress the nonlinear effect based on U-t profiles. Data processing is performed to determine the thermal diffusivity using global fitting under non-constant electrical heating. The effective thermal diffusivities from modified analysis processes stay in the range from 2 to 6 × 10−6 m2/s. The results from both methods agree well with each other. The general function analysis method is also applicable for samples of short time thermal transport or for an experimental instrument that has relatively long rise time.

X-ray emission from a nanosecond-pulse discharge in an inhomogeneous electric field at atmospheric pressure

Abstract: This paper describes experimental studies of the dependence of the X-ray intensity on the anode material in nanosecond high-voltage discharges. The discharges were generated by two nanosecond-pulse generators in atmospheric air with a highly inhomogeneous electric field by a tube-plate gap. The output pulse of the first generator (repetitive pulse generator) has a rise time of about 15 ns and a full width at half maximum of 30–40 ns. The output of the second generator (single pulse generator) has a rise time of about 0.3 ns and a full width at half maximum of 1 ns. The electrical characteristics and the X-ray emission of nanosecond-pulse discharge in atmospheric air are studied by the measurement of voltage-current waveforms, discharge images, X-ray count and dose. Our experimental results showed that the anode material rarely affects electrical characteristics, but it can significantly affect the X-ray density. Comparing the density of X-rays, it was shown that the highest x-rays density occurred in the ...

Low-power and high-speed thermo-optic switch using hybrid silica/polymer waveguide structure: design, fabrication and measurement

Abstract: Response speed and power consumption are improved for a Mach–Zehnder interferometer (MZI) thermo-optic (TO) switch, by using a hybrid silica/polymer waveguide structure and optimizing both the thickness of the silica under cladding and that of the PMMA-GMA upper cladding. Fabrication techniques, including chemical vapor deposition (CVD), spin-coating and wet-etching, are adopted to develop the switch sample. Under 1550 nm wavelength, the driving powers under ON and OFF states are measured to be 0 and 13 mW, respectively, indicating a switching power of 13 mW. The fiber-to-fiber insertion loss under the ON state is 15 dB, the extinction ratio between the ON state and the OFF state is 18.3 dB, and the rise time and fall time are 73.5 and 96.5 µs, respectively. Compared with the TO switches based on Si/SiO2 or all-polymer waveguide structure, the proposed device possesses both low power consumption and fast response speed, by virtue of the large TO coefficient of the polymer core, thin upper/under claddings ...

Two-component structure of the current pulse of a ranaway electron beam generated during electric breakdown of elevated-pressure nitrogen

Abstract: Conditions are investigated at which two current pulses of ranaway electron beams are generated in elevated-pressure nitrogen during one voltage pulse. It is shown that the regime with two runaway electron beam current pulses takes place at decreased values of the electric field strength E in the gap (or decreased values of the parameter E/p, where p is the gas pressure). The regime with two runaway electron beam current pulses is observed both at high (1500–3000 Torr) and low (below 100 Torr) pressures. It is shown that, for the second runaway electron beam current pulse to form, the voltage across the gap should be partially reduced during the first pulse. At low nitrogen pressures (~10 Torr), the regime in which two runaway electron beams are generated can be implemented by increasing the breakdown strength of the gap and/or increasing the value of E/p. In experiments carried out in atmospheric-pressure air with a picosecond time resolution, a rather complicated structure of the beam current pulse is observed at a voltage rise time of ~300 ps.

300-kA Fast Linear Transformer Driver Stage

Abstract: A modular linear transformer driver (LTD) is a novel fast-discharge high-pulsed power source for primarily stored energy In LTDs, a large number of stages (or cavities) can be connected in series or in parallel conveniently to directly generate high power pulses of 50-200 ns with the required voltage or current This paper introduces an LTD stage developed by us recently This LTD stage consists of 14 bricks in parallel Each brick contains two 40-nF capacitors and a compact multigap gas spark switch in series The switch is a modification of our original version, and the diameter and the height of which have been reduced to 98 and 127 mm, respectively The circuit model of this stage is established in PSPICE, and its output parameters are obtained through simulation Driving a rough-matched resistive load of 027 Ω, its output current peak is 300 kA with an overall rise time of about 110 ns at a charged voltage of the capacitors of about ±90 kV, agreeing well with its simulation result

A 1.2V 2-bit phase interpolator for 65nm CMOS

Abstract: We present a digital phase interpolator (PI) design for 65nm CMOS that avoids conventional analog structures, accurately achieves 2-bits phase resolution across a range of rise time and input delays from t rise : 48ps → 200ps using a ratio t rise /t delay of at least 1 or greater. Increased accuracy is available for certain rise times using ratios increasing between 1 and 10 as verified by simulations across process corners using extracted parasitic capacitances but ignoring MOSFET mismatch effects. Power consumption was estimated at 30nW/MHz → 38nW/MHz across a range of process variation corners in these operating conditions. Monte Carlo simulations across process and MOSFET mismatch conditions show large variations in estimated accuracy. Monte Carlo trials show the PI achieves a worst case DNL error (mean±3σ) of 1.06 LSB using t rise /t delay ratio of 5.3 and 48ps rise time, and a worst case DNL error (mean ±2σ) of 0.49 LSB for t rise /t delay ratio of 4 and 84ps rise time.

Influences of Switching Jitter on the Operational Performances of Linear Transformer Drivers-Based Drivers

Abstract: A whole circuit model of a linear transformer drivers (LTD) module composed of 60 cavities in series was developed in the software PSPICE to study the influence of switching jitter on the operational performances of LTDs. In the model, each brick in each cavity is capable of operating with jitter in its switch. Additionally, the manner of triggering cables entering into cavities was considered. The performances of the LTD module operating with three typical cavity-triggering sequences were simulated and the simulation results indicate that switching jitter affects slightly the peak and starting time of the output current pulse. However, the enhancement in switching jitter would significantly lengthen the rise time of the output current pulse. Without considering other factors, a jitter lower than 10 ns may be necessary for the switches in the LTD module to provide output current parameters with an acceptable deviation.