Rise time

About: Rise time is a research topic. Over the lifetime, 4748 publications have been published within this topic receiving 47512 citations.

Formation of Wide Streamers during a Subnanosecond Discharge in Atmospheric-Pressure Air

Abstract: Results are presented from experimental and computational studies of a subnanosecond breakdown of atmospheric-pressure air in a nonuniform electric field. It is shown that the ionization waves (streamers) formed in the prebreakdown stage have a nearly spherical or conical shape. The diameter of the streamer in its widest part is found to increase with increasing voltage and discharge gap length. For a rise time of the voltage pulse of ≈0.5 ns and its amplitude of ≈250 kV, streamers about 8 cm in diameter were observed in a 7-cm-long gap.

Compact submicrosecond, high current generator for wire explosion experiments

Abstract: The PIAF generator was designed for low total energy and high energy density experiments with liners, X-pinch or fiber Z-pinch loads. These studies are of interest for such applications as surface and material science, microscopy of biological specimens, lithography of x-ray sensitive resists, and x-ray backlighting of pulsed-power plasmas. The generator is based on an RLC circuit that includes six NWL 180 nF–50 kV capacitors that store up to 1.3 kJ. The capacitors are connected in parallel to a single multispark switch designed to operate at atmospheric pressure. The switch allows reaching a time delay between the trigger pulse and the current pulse of less than 80 ns and has jitter of 6 ns. The total inductance without a load compartment was optimized to be as low as 16 nH, which leads to extremely low impedance of ∼0.12 Ω. A 40 kV initial voltage provides 250 kA maximum current in a 6 nH inductive load with a 180 ns current rise time. PIAF has dimensions of 660×660×490 mm and weight of less than 100 kg...

Dynamic response modelling and characterization of a vertical electrothermal actuator

Abstract: Mathematical modelling and characterization of the dynamic response of a microelectromechanical system (MEMS) electrothermal actuator are presented in this paper. The mathematical model is based on a second-order partial differential equation (one-dimensional heat transfer) and a second-order ordinary differential equation (mechanical dynamic equation). The simulations are implemented using the piecewise finite difference method and the Runge–Kutta algorithm. The electrothermal modelling includes thermal conduction, convective thermal loss and radiation effects. The temperature dependence of resistivity and thermal conductivity of single crystal silicon have also been taken into consideration in the electrothermal modelling. It is calculated from the simulation results that the 'cold' beam of the electrothermal actuator is not only a mechanical constraint but also a thermal response compensation structure. The 0–90% electrothermal rise times for the individual 'hot' and 'cold' beams are calculated to be 32.9 ms and 42.8 ms, respectively, while the 0–90% electrothermal rise time for the whole actuator is calculated to be 17.3 ms. Nonlinear cubic stiffness has been considered in the thermal-mechanical modelling. Dynamic performances of the device have been characterized using a laser vibrometer, and the 0–90% thermal response time of the whole structure has been measured to be 16.8 ms, which matches well with the modelling results. The displacements of the device under different driving conditions and at resonant frequency have been modelled and measured, and the results from both modelling and experiment agree reasonably well. This work provides a comprehensive understanding of the dynamic behaviour of the electrothermal actuation mechanism. The model will be useful for designing control systems for microelectrothermal actuated devices.

Compact High Voltage IGBT Switch for Pulsed Power Applications

Abstract: This paper describes the development of a semiconductor based switch for use in pulsed power technology. Because of the more stable operating conditions, given by the semiconductor devices, this switch could be used to replace the up to now in pulsed power technology common used spark gaps. We defined a technical concept for a semiconductor based switch with a maximum voltage of 20 kV and a current capability in the order of 1 kA. This concept also should enable to generate pulses widths of a few mus. We found an IGBT with a maximum blocking voltage of 1700 V, a signal rise time of 100 ns, and a short circuit current rate of 650 A to be suited to realize our concept for the switch. Because of the defined maximum voltage of 20 kV it was necessary to use a series connection of the IGBTs. To ensure a synchronous switching of the in series connected devices, a trigger unit was built up which was inductively connected to the driver circuits of the single IGBTs. Single devices where tested and separated for the series connection. With the handicap of a given 155 mm circuit board we designed a complete switch, basing on industrial standards, with 15 IGBTs and a finally maximum blocking voltage of 18 kV, and a current capability of 500 A. The design of this circuit also included the development of a protecting circuit (active clamp) to protect the single devices of an over voltage damage during the switching, and also to avoid an inhomogeneous split up of the voltage to the different devices.

BiCMOS embedded RF-MEMS switch for above 90 GHz applications using backside integration technique

Abstract: We demonstrate a novel back-side processed, back to front self-aligned BiCMOS embedded RF-MEMS switch for the 90 to 140GHz frequency band. The switch integration is very simple, adding only one mask step to the underlying high-performance BiCMOS process. Moreover, it offers low cost, wafer level packaging. The insertion loss of the switch is less than 0.5dB up to 140GHz, and isolation is better than 15dB in the frequency range of 90 to 140GHz. The switch-on time is measured as 10µs. No performance degradation was observed after 5 billion cold switching cycles demonstrating the high reliability of the switch. An on-chip charge-pump (CP) circuit is realized using enhanced PMOS transistor to excite the switch with an output voltage of up to 50V and a rise time of 2µs.