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Investigation of electrostatic discharge using indirect electrical and direct optical measurement techniques
Schrama, Claudia Antoinette Maria
Schrama, Claudia Antoinette Maria
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2023
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2024-04-18
Abstract
Electrostatic discharge has been studied for many years, but due to the complexity of the dynamics, sparks are still a rich subject of investigation. In the presence of a strong electric field, random seed electrons lead to avalanche breakdown. As the electrons begin to shield the field, a streamer forms producing a conductive channel. The main arc carries the bulk of the stored charge and energy across the channel. A shock wave propagates outwards as the charge depletes, leaving a conductive ionized core behind.
This dissertation describes a multi-faceted approach to experimentally explore the dynamics of spark discharges during many of these phases. In literature, there are several commonly used models that relate the nonlinear spark resistance to the integrated current, each of which makes different assumptions about energy dissipation in the spark. The validity range of the models is explored by measuring the spark resistance and observing the plasma conditions.
Indirect electrical measurements provide information on the time-dependent spark resistance and on how energy transferred to a series ‘victim’ resistive load scales with gap length, capacitance, and victim load size. These measurements generally show good agreement with the Rompe and Weizel model, put forth in 1944. A novel dual storage capacitor design was implemented to measure the longer time scale resistance. For the first time to our knowledge, these measurements show that the channel remains conducive for over 150uμs, well after most of the direct emission has disappeared. Direct optical emission measurements give detailed information on the species evolution and the spark plasma’s channel size. Finally, performing 2-color interferometry measurements provides information about shock expansion in the gas and also informs on the degree of ionization and the time-dependent size of the conductive channel.
Since knowing physical limits for how much damaging energy can be transferred to a device or a combustible system is crucial for safety analysis, this work provides information valuable to those concerned with quantifying risks. For those who are developing models and simulations of these complicated phenomena, the measurements give important benchmarks to help test their validity.
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