Topic
Rise time
About: Rise time is a research topic. Over the lifetime, 4748 publications have been published within this topic receiving 47512 citations.
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TL;DR: In this paper, the Druyvesteyn method was used to determine the electron energy distribution, and the electron density, ne, and effective electron temperature, Teff, were calculated as a function of time from the I-V curves.
Abstract: A Langmuir probe has been used to make measurements of plasma parameters as a function of time at the substrate position in a magnetically-filtered pulsed cathodic arc discharge. Electron density, ne, and effective electron temperature, Teff, were calculated as a function of time from the I–V curves. The Druyvesteyn method was used to determine the electron energy distribution. Ion density was calculated using the assumption of plasma quasi-neutrality and an average ion charge state. Results show that over the plateau region (350–600 µs) of the pulse, the electron energy distribution is Maxwellian with Teff = Te = (10 ± 1) eV. During the rise and fall times of the pulse, the electron energy distribution is non-Maxwellian with an effective temperature of up to 15 to 20 eV during the rise time and ~7 eV during the fall time. The electron density during the plateau is ne = (3.0–6.0 ± 0.5) × 1017 m−3.
16 citations
TL;DR: In this paper, a dip-style multi-parameter sensor is used to measure the viscosity of a fluid in frequencies up to 700 Hz, in contrast to average measurements based on spectral properties.
Abstract: An acousto-optic modulator (AOM) is used to tune the spectral properties and add a dynamic component to a long period fiber grating (LPG). Most of the physical parameters that an LPG is sensitive to, can be obtained through passive analysis of the spectral changes. Here, we show that by adding a temporal response component to the grating sensitivity, dynamic parameters such as fluid viscosity, can be extracted. By measuring the modulation signal rise time and/or the acousto-optic efficiency, we demonstrate a compact, dip-style, multi-parameter sensor, which is able to measure, among various parameters, the viscosity of a fluid in frequencies up to 700 Hz. Further, we show that taking the temporal response into consideration, the sensor has a linear response against viscosity, in contrast to average measurements based on spectral properties. The non-linear component of the average measurements arises from a relaxation of the initial acoustic perturbation on a timescale longer than the initial rise time.
16 citations
TL;DR: In this article, the evolution of the self-modulation instability for bunches with finite rise times was studied using particle-in-cell simulations and it was shown that there are large variations of the wake amplitude and phase velocity with finite-rise time bunches.
Abstract: We study the evolution of the self-modulation instability for bunches with finite rise times. Using particle-in-cell simulations we show that, unlike with long bunches with sharp rise times, there are large variations of the wake amplitude and phase velocity with finite rise time bunches. These results show that bunches with sharp rise times are important to seed the self-modulation instability and to ensure stable acceleration.
16 citations
13 May 2012
TL;DR: In this article, the authors investigated the time and frequency characteristics of the arcing between pantograph and overhead lines in electrical transportation systems, where the power spectrum and the frequency content were calculated in the bands of interest and a time-frequency representation was used to observe the evolution of the power spectra over time and the location of the main contributions.
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.
16 citations
TL;DR: In this paper, high-speed PeLEDs driven by nanosecond electrical pulses with a rise time of 1.2 nns were reported with a maximum radiance of approximately 480 kW sr-1 ǫm-2 at 8.3 kA cm-2, and an external quantum efficiency (EQE) of 1% at approximately 10 kA mm-2.
Abstract: While metal-halide perovskite light-emitting diodes (PeLEDs) hold the potential for a new generation of display and lighting technology, their slow operation speed and response time limit their application scope. Here, high-speed PeLEDs driven by nanosecond electrical pulses with a rise time of 1.2 ns are reported with a maximum radiance of approximately 480 kW sr-1 m-2 at 8.3 kA cm-2 , and an external quantum efficiency (EQE) of 1% at approximately 10 kA cm-2 , through improved device configuration designs and material considerations. Enabled by the fast operation of PeLEDs, the temporal response provides access to transient charge carrier dynamics under electrical excitation, revealing several new electroluminescence quenching pathways. Finally, integrated distributed feedback (DFB) gratings are explored, which facilitate more directional light emission with a maximum radiance of approximately 1200 kW sr-1 m-2 at 8.5 kA cm-2 , a more than two-fold enhancement to forward radiation output.
16 citations