Showing papers on "Rise time published in 1994"

A Long Pulse Modulator For Reduced Size And Cost

Abstract: A novel modulator has been designed, built and tested for the TESLA test facility. This e{sup +} e{sup {minus}} accelerator concept uses superconducting RF cavities and requires 2ms of RF power at 10 pps. As the final accelerator will require several hundred modulators, a cost effective, space saving and high efficiency design is desired. This modulator used a modest size switched capacitor bank that droops approximately 20% during the pulse. This large droop is compensated for by the use of a resonant LC circuit. The capacitor bank is connected to the high side of a pulse transformer primary using a series GTO switch. The resonant circuit is connected to the low side of the pulse transformer primary. The output pulse is flat to within 1% for 1.9 ms during a 2.3 ms base pulse width. Measured efficiency, from breaker to klystron and including energy lost in the rise time, is approximately 85%.

Start-up pressure transients in a capillary rheometer

Abstract: The “rise time” required to achieve a steady pressure reading in a capillary rheometer operated at constant piston speed can be very long, up to several hours under certain circumstances. This phenomenon can pose a serious problem in the measurement of melt viscosity, and it would be useful to be able to estimate the rise time in the planning of experiments. Based on experiments involving several types of polyethylene, we found that the rise time increases with L/D and the amount of polymer initially in the reservoir and decreases with diameter and piston speed. When the rise time is short, melt viscoelasticity contributes to the rise time, but when it is long, melt compressibility is the dominant factor. A model was developed for the latter case, and this was found to give an accurate prediction of the rise time, given the viscosity and compressibility. The model can also be used to determine the power-law parameters from the start-up pressure trace, P(t), for a single experiment. Alternatively, if the viscosity is known, the compressibility can be inferred from a single pressure trace.

Hot-carrier-reliability design rules for translating device degradation to CMOS digital circuit degradation

Abstract: Long term ring-oscillator hot-carrier degradation data and simulation results are compared to demonstrate that a circuit reliability simulator BERT can predict CMOS digital circuit speed degradation from transistor DC stress data. Initial fast degradation is noted and attributed to the "zero crossing" effect caused by PMOSFET current enhancement. Saturation drain current, measured at V/sub gs/=V/sub ds/=Vdd/2, is a better monitor for CMOS circuit hot-carrier reliability. We present generalized hot-carrier-reliability design rules, lifetime and speed factors, that translate DC device lifetime to CMOS digital circuit lifetime. The design rules can roughly predict CMOS circuit degradation during the initial design and can aid reliability engineers to quickly estimate the overall product hot-carrier reliability. The NMOSFET and PMOSFET lifetime factors are found to obey 4/ft/sub rise/ and 10/ft/sub fall/, respectively. Typically, the NMOSFET and PMOSFET speed degradation factors are 1/4 and 1/2, respectively, with saturation region drain current as the monitor while, for a 100 MHz operating frequency and for an input rise time of 0.35 ns, the NMOSFET and PMOSFET lifetime factors are 120 and 300, respectively. >

Fuel injector failure detection circuit

Abstract: In a engine and associated fuel injector failure detection circuit, the engine having at least one combustion chamber, a battery, and at least one fuel injector having a high side and a low side terminal for introducing a fuel in the at least one combustion chamber, the fuel injector failure detection circuit comprising a one shot timer for transmitting a constant voltage state signal output when the fuel injector reaches a set current threshold at a start of an injector current peak time duration. A voltage sense comparator is provided for transmitting a low voltage state signal output when the low side terminal of the fuel injector produces a fly-back voltage pulse. A mechanism for monitoring current of the fuel injector during a rise time duration and the peak time duration ia also included. The circuit further provides a mechanism for disconnecting all electrical power supplied to the at least one fuel injector if the injector current fails to reach a peak level during the rise time duration or the fly-back voltage pulse fails to occur at the end of the peak time duration. Moreover, a mechanism for monitoring the fly-back voltage pulse produced by the low side terminal of the fuel injector is also included in the circuit.

Dynamic Pressure Metrology

Abstract: According to the ANSI MC88.1-1972 standard A Guide for the Dynamic Calibration of Pressure Transducers, the properties to be determined when calibrating a dynamic pressure transducer are sensitivity, amplitude as a function of frequency, phase as a function of frequency, resonant frequency, damping ratio, rise time and overshoot. A static calibration yields only the sensitivity. The properties of dynamic pressure transducers and various methods for determining them are reviewed.

A transistorized Marx bank circuit providing sub-nanosecond high-voltage pulses

Abstract: An improved version of a Marx bank circuit has been developed using 2N5551/2N5550 transistors as switching elements in avalanche mode which provides a negative pulse of about 4 kV amplitude and

Magnetic pulse compressor for prepulse discharge in spiker‐sustainer excitation technique for XeCl lasers

Abstract: A high‐voltage pulse output modulator using a step‐up transformer with two stages of magnetic pulse compression circuits has been developed as a spiker for the purpose of obtaining the breakdown of the gas mixture when using the spiker‐sustainer excitation technique for pumping XeCl discharge lasers. When the transformer input is fed by a current pulse with a peak value and a full width of 1.16 kA and 1.6 μs, respectively, formed by a discharge of an initially charged 19‐kV, 57‐nF capacitance in series in the transformer primary loop, the 2.7‐nF output capacitor bank (Cp) of the spiker can be charged up to 67 kV with a (10%–90%) rise time of 59 ns. The modulator has been tested at a repetition rate of up to 600 Hz in burst mode using a resistor in parallel with Cp as the load.

Discharge lamp lighting device

Abstract: PURPOSE:To provide a discharge lamp lighting device by which rise time can be shortened and evenness of light output can be obtained with simple control. CONSTITUTION:A discharge lamp lighting device is provided with a DC converter 11, a PWM regulator 13 to convert output voltage outputted from this DC converter into pulse voltage of prescribed width so as to be outputted and a full bridge driver 14 to impress the pulse voltage on a discharge lamp 15, and is provided with a voltage detecting circuit 16 to detect voltage to be impressed on the discharge lamp 15, an electric current detecting circuit 17 to detect an electric current flowing to the discharge lamp 15, a multiplier 18 to obtain a product of a voltage detecting signal detected by the voltage detecting circuit 16 and an electric current detecting signal detected by the electric current detecting circuit 17 and a comparator 19 to output a comparison signal obtained by comparing an integrated value outputted by this multiplier 18 with a preset reference value. A pulse width modulating means 11 is provided to control the pulse width of the pulse voltage so that this comparison signal becomes zero.

Comparing the indirect field-oriented control with a scalar method

Abstract: Two methods of induction motor control are examined. The indirect field-oriented (IFO) and the slip-control (SC) methods are formally compared. Their block diagrams are derived, analyzed and their similarities shown. It is demonstrated that the difference between the two is just due to a feedforward block that computes the current phase to be supplied to the motor in an IFO controller. This proves that the implementation complexity of either controller is almost identical. To perform comparative tests, both control methods were implemented using a single hardware. The torque rise time and frequency response of the speed control are presented. Based on experimental results, it is shown that the speed sensor resolution and the sampling rate of the controller strongly influence the dynamic response in the IFO method. The SC method is less sensitive to these parameters although it always presented a worse dynamic response. The IFO speed control presented a flat frequency response whereas the SC method presented a peak which could lead to an oscillatory speed response. It is also shown that the variation of the rotor electrical time constant influences strongly and in a similar way both control methods. Finally, it can be concluded that the implementation complexity of both control strategies are almost identical, although the IFO control method has a much better performance than the SC control method. >

Avoiding peripheral nerve stimulation: Gradient waveform criteria for optimum resolution in echo‐planar imaging

Abstract: Adaptation of Mansfield and Harvey's theory of magnetically induced neural stimulation indicates that, for trapezoidal gradient waveforms and at the relatively low modulation frequencies commonly used in echo-planar imaging, an increase in rise time even to the point of creating a triangular waveform can prove advantageous over the use of simple sinusoidal modulation. For example, a higher image resolution is in principle possible before the neural stimulation limit is reached. For higher modulation frequencies and fast ramp trapezoidal waveforms, the peak gradient can be lower than that for a sinusoidal waveform by a factor approaching 2/pi for equal resolution. This means that by using a multimode resonant gradient drive, the amplifier power requirements are greatly relaxed. The signal sampling bandwidth required is also lower, because, due to the trapezoidal nonlinear sample pattern, sample points are spaced linearly during the waveform plateaus.

Thermoelastic response of pulsed photothermal deformation of thin plates

Abstract: A theoretical investigation of the dynamic thermoelastic response of pulsed photothermal deformation (PTD) deflection detections for some Q‐switch laser pulses and finite thickness samples has been presented. The results show that signals can be characterized by a quasistatic process when the laser pulse rise time is on the order of 1 μs and the sample thickness is in submillimeter range (typically for semiconductor wafers). However, as the pulse rise time decreases or the sample thickness increases, the dynamic wave behavior gradually becomes apparent, and the quasistatic approximation gives only a contour curve of the dynamic time evolution. When the rise time decreases on the order of 10 ns or less for the same kind of the samples, the PTD deflection signal reflects a totally dynamic wave behavior.

Modeling and measurement of bistable semiconductor lasers

Abstract: A theoretical model of bistable semiconductor lasers (BSL) under optical triggering is proposed, which takes into account the amplification and absorption processes in the laser structure. It has been found that the main factor limiting the highspeed operation of BSLs is the carrier lifetime in the absorber. A novel solution has been proposed consisting of bombarding the absorber with a proton beam. This paper presents the first experimental and theoretical results on the transition time and the turn-on jitter of such a BSL with optical triggering. Measurements on bulk and multiple quantum well BSLs revealed the dependence law of transition time and turn-on jitter on the injection currents. It has been found that, for a constant current in one active section, the rise time decreases but the fall time increases with injection current in the other section. An optimal current value can then be found to minimize the overall transition time. The measured turn-on jitter and relaxation oscillation period decrease with increasing injection current, in good agreement with theoretical predictions. 2.5 Gb/s optical triggering with a bit-error-rate less than 10/sup -9/ is demonstrated, for the first time, by using such a BSL without electrical reset. >

A high‐voltage pulser circuit with subnanosecond rise time

Abstract: A fast (≤1 ns rise time) high‐voltage pulser circuit was developed using 2N5551/2N5550 transistors in avalanche mode as switching elements. This circuit has transistors in series stack configuration and provides ∼2 kV amplitude and ≤1 ns rise time into 50 Ω with a 13 ns delay and <500 ps jitter. A simple arrangement to generate two symmetrical opposite polarity pulses from single pulse of either polarity is also presented.

A switching type of fuzzy controller

Abstract: Proposes a switching-type fuzzy controller to obtain a satisfactory performance (fast rise time, small overshoot and small steady-state error) in the step response, by constructing some specific scaling factors in five control regions of the system. We provide a method to select suitable scaling factors of the fuzzy controller in each region. It is shown by simulation that the proposed scheme has the ability to improve the transient and steady-state performances of the controlled system simultaneously. The simulation also shows that this scheme can be used to curb the effect of load disturbance in the control process. >

Transmission-line-noise immune input buffer

Abstract: An input buffer for an integrated circuit and providing reduced sensitivity to input noise present in a transmission line environment. This input buffer deskews an input signal where the rise time is much slower than the fall time, such as that from an open-collector output driver, so that the rising edge propagation delay and falling edge propagation delay of the input buffer are approximately equal.

The effect of rise time and field gradient on nonlinear bit shift in thin film heads

Abstract: We present a discussion of nonlinear bit shift in thin film inductive heads. A three dimensional finite element model and two dimensional dynamic and self consistent model were used to calculate the nonlinear bit shift as a function of rise time, write current waveform and pole tip saturation. The analysis shows a strong dependency of nonlinear bit shift on rise time and write pole magnetic image. A comparison of experimental data with the theoretical model is presented. >

Characterisation of voltage shapes acting on the insulation of rotating machines supplied by inverters

Abstract: Use of frequency inverters for supply of electrical rotating machine is becoming more usual, particularly for applications needing a rotating speed variation. New semiconductors, like Gate Turn-off thyristor (GTO) or Insulated Gate Bipolar Transistor (IGBT), can work at very high frequency, up to 10 kHz, with very short rise times down to less than 0.1 /spl mu/s. In order to study the ageing associated with these voltage shapes, we have first tried to characterise them. The inverter is a Pulse Width Modulated one (PWM) feeding a 220 V squirrel cage induction motor modified to observe the propagation of voltage shape in the winding. This adaptation results in 36 shielded coaxial wires distributed on the 6 coils and the 17 turns. Turn-to-turn and turn-to-ground voltages are recorded. A spectral analysis shows that the driving frequency is the main frequency propagating in the winding with no attenuation. On the other hand, the motor input turn-to-turn voltages show very short rise time voltage waves (typically 2000V//spl mu/s) which are very attenuated and a delay growing during propagation in the winding. Moreover, on the input coils, high frequency oscillations and overvoltages are observed, depending on supply cable length. >

Adjustment of scan velocity modulation concurrent with the amount of transition rise time, pre-shoot, and overshoot of a video signal

Abstract: A microprocessor generates an output signal in accordance with user controlled sharpness selection. The output signal is supplied to a video processor and to a scan velocity modulation circuit for concurrently varying in the same sense the amount of picture sharpness produced by the scan velocity modulation circuit and by the video processor.

Output buffer circuit

Abstract: PURPOSE: To obtain an output buffer circuit in which a rise time or a fall time of an output voltage at an output terminal is decreased and transfer delay time of an output voltage is minimized. CONSTITUTION: A capacitive means including a gate electrode capacitance of an output drive MOS transistor(TR) is gradually charged to make a rise time or a fall time short in the output buffer circuit and the output buffer circuit is provided with threshold voltage charge means 1, 2 charging quickly the capacitive means up to a threshold voltage of the output drive MOS TR.

Indirect rotor position sensing for variable reluctance motors

Abstract: Rotor position sensing is essential in providing stable operation for closed-loop control of variable reluctance (VR) motors over a wide speed range. Position sensing can be carried out by two different methods; either by using direct position sensors or by using an indirect sensing method. There are obvious disadvantages in using direct position sensors. In this paper further developments in indirect rotor position detection using the waveform detection (WD) technique for VR motors are described. In principle, rise and fall times of an active or inactive phase can be used for position detection. However, position detection by monitoring the rise or fall times of the active phase current has been found suitable only in a narrow operating range. In order to overcome this problem, the rise or fall times of a small magnitude diagnostic current injected into an inactive phase can be monitored for position detection. Theoretical analysis and simulation results reported elsewhere have revealed that the use of the inactive (diagnostic) phase chop current rise time leads to instability in the drive system and hence is not recommended. In this paper, the inactive (diagnostic) phase chop current fall time is used instead for position detection. A hard-wired digital closed-loop controller is designed and implemented to drive a 3-phase VR stepping motor. Experimental results obtained conclude that rotor position detection using the WD technique with diagnostic phase chop current fall time provides reliable position detection and stable operation for the drive system over a wide operating range. >

Fine line thin dielectric circuit board characterization

Abstract: The rough surface of the copper foil, introduced to enhance its interfacial adhesion to the dielectric medium, will increase the signal propagation time constant and reduce the characteristic impedance of a signal line. The influence increases as the dielectric thickness decreases. Two high resolution resonant measurement techniques will be presented for such studies. The additional delay term due to the internal inductance at the frequency of interest is proportional to the square root of the signal rise time in the transient measurement. The additional delay associated with the signal rise time degradation due to skin effect resistance loss is minimized by measuring the delay at 1% of the voltage swing. We will also compare the results of different measurement techniques in this paper.

Development of a pulsed power supply for a large‐bore copper vapor laser

Abstract: A pulsed power supply has been developed for exciting a copper vapor laser with a bore diameter of 80 mm and a discharge length of 2890 mm. The pulsed power supply has two thyratrons, an LC‐inversion circuit and a two‐staged magnetic pulse compression circuit. An efficiency of 82% has been obtained which is defined as the ratio of energy stored in the storage capacitor to the output energy of the magnetic pulse compression circuit, with a voltage greater than 40 kV, averaged output power of 24 kW, and voltage rise time of 70 ns. The pulsed power supply was successfully operated for more than 2000 h and an optical output power of 272 W was obtained.

High Gain GaAs Switches For Impulse Sources; Measurement Of The Speed Of Current Filaments

Abstract: A high peak power impulse pulser that is controlled with high gain, optically triggered GaAs Photoconductive Semiconductor Switches (PCSS) has been constructed and tested. The system has a short 50 ohm line that is charged to 100 kV and discharged through the switch when the switch is triggered with as little as 90 nJ of laser energy. The authors have demonstrated that the GaAs switches can be used to produce either a monocycle or a monopulse with a period of total duration of about 3 ns. For the monopulse, the voltage switched was above 100 kV, producing a peak power of about 48 MW to the 30 ohm load at a burst repetition rate of 1 kHz. The laser that is used is a small laser diode array whose output is delivered through a fiber to the switch. The current in the system has rise times of 430 ps and a pulse width of 1.4 ns when two laser diode arrays are used to trigger the switch. The small trigger energy and switch jitter are due to a high gain switching mechanism in GaAs. This experiment also shows a relationship between the rise time of the voltage across the switchmore » and the required trigger energy and switch jitter. The time evolution of the current filaments in an optically triggered, high gain GaAs switch was studied by recording the infrared photoluminescence from the filaments. When the system is triggered with two laser diode arrays that are activated within 1 ns of each other, two current filaments are observed. By delaying one laser with respect to the other, the evolution of the filament was recorded in a time resolved fashion. The filament that is triggered first crosses the switch, the voltage drops and the other filament ceases to grow. By varying the delay between the trigger lasers, the tip velocity is measured to be up to 5.9 {+-} 1 {times} 10{sup 9} cm/s.« less

Pulsed electrical breakdown in liquid helium in the /spl mu/s range

Abstract: Information about breakdown time-lags under pulsed voltage stress is prerequisite to the insulation design of superconducting devices. Experiments have been carried out using a pulse generator which provides a step voltage with 200 ns rise time and a long decay time constant of more than 1 ms. The present experiments may bridge the information gap between time lag measurements in the ns range using extremely high field strengths, and existing data found with usual lightning impulse voltage. The test device is described in the paper, and some typical results are discussed in detail. >

Scanning optical system having first and second knife edge detectors and first and second rise time detection circuits

Abstract: In a scanning optical system, a first light detecting body is disposed so as to be coplanar with a surface to be scanned, whereas a second light detecting body is disposed in front of the surface to be scanned. Outputs of the light detecting bodies are applied to a first rise time detecting circuit and a second rise time detecting circuit to detect rise times, respectively. The rise times are applied to a comparing circuit, which compares a difference therebetween to detect a displacement of a beam of light that is scanning the surface to be scanned from the focus. A control circuit outputs a signal for correcting the displacement from the focus. Simultaneously therewith, a spot judging circuit detects the profile of a spot of the beam of light that is scanning the surface to be scanned from the rise time.

Fundamental investigation of vacuum PD tube [photodiode]

Abstract: As a fundamental study of photodiodes (PDs) for electron bombardment, two types of PDs have been experimentally investigated to be applied in electron tubes. A PD bombarded from the front surface (FB-PD), where a pn junction of planar structure existed, was evaluated to measure the fast response characteristics such as a 2.1 ns rise time. However, more than an order of magnitude increase of dark current was also confirmed after a long term stability test of 1000 hours. On the other hand, a PD bombarded by electrons from the rear surface (RB-PD) showed no increase of dark current after the stability test and a fast rise time of 2.7 ns. However, it was clarified that the rise time of RB-PD depended on the applied voltage to the PD, and an applied voltage of 200 V was necessary to achieve such a fast response. Since it was a much higher voltage than expected, some modifications may be necessary to achieve a fast response with a lower applied voltage, considering the yield of the PDs. Comparisons of the two types of PDs for some other characteristics are discussed. Preliminary test results of an electron bombardment APD are also discussed. >

Influence of the high voltage pulse shape on the plasma source ion implantation process

Abstract: Using a two fluid model, we investigate the effects on the ion impact energy, of varying the shape of a large, negative, finite rise time, voltage pulse to a planar target. Two pulse shapes are tested, one with exponential shutoff, and one with a powered linear shutoff. For pulse lengths under 50 μs, we find that pulse shaping can be used to make moderate changes in the energy distribution of the implanted ions. For pulse lengths over 50 μs, there is a negligible difference in the ion impact energy distribution for the pulse shapes tested.

Memory device with built-in address transition detecting circuit

Abstract: PURPOSE: To obtain an address transition detecting circuit which detects a level of power supply voltage, generates an ATD(address transition detection) pulse when the voltage is on an appropriate level and can prevent error from occurring at a rise time, etc. CONSTITUTION: A summator 114 outputs a signal SMO which is an ATD pulse in response to each output, as an input, of a power detecting circuit 110, a short pulse generating circuit 112A which generates a pulse in response to a chip enable signal and short pulse generating circuits 112Bs which generate a pulse by address transition. The power detecting circuit 110 has an inverter where a trip level is set at 3V that is a lower bound of an appropriate level of power supply voltage Vcc, and when the Vcc becomes the 3V, an output signal that rises in voltage together with the Vcc changes to be logic 'low'. Also, a sense amplifier and its peripheral circuits are enabled at the transition time of the signal SMO from logic 'high' to logic 'low'. Therefore, when the sense amplifier etc. operate, a normal operation can be performed because the Vcc already reaches its appropriate level.

Inertial confinement fusion in a Z-θ pinch

Abstract: The implosion of a dense θ-pinch plasma driven by an annular Z-pinch is considered. A cryogenic fiber is coaxially located within an annular Z-pinch. The imploding Z-pinch traps an applied axial magnetic field and conserves flux. The axial magnetic field increases due to compression of the outer pinch and attains values up to 100 megagauss with field rise times of dB z /dt > 50 MG/ns and with orders of magnitude shorter rise time than the Z-pinch current. An azimuthal θ-current is induced on the fiber surface with a similar rise time, which could not otherwise be achieved in a simple fiber Z-pinch due to the large inductance initially presented by the small diameter axial plasma. The implosion transfers Z-pinch kinetic energy to the magnetic field and then to the θ-pinch. The final plasma pressure of the θ-pinch exceeds the magnetic pressure so that the θ-pinch then expands ― the only confinement is inertial

Submillisecond photorefractive response time of KNbO(3):Rb(+).

Abstract: We investigate the photorefractive response time of diffraction gratings in Rb+-doped KNbO3 crystals. Two components of charge carriers, with different response times, are found to contribute to the photoinduced index gratings. One component, which contributes to approximately 70% of the index grating, shows a submillisecond rise time when the total intensity of the writing beams is larger than 5 W/cm2. The dependence of the response time on the light intensity and the grating wave vector is also investigated.