TY - GEN
T1 - Fundamentals of PPT discharge initiation
T2 - 39th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit 2003
AU - Cooley, James E.
AU - Choueiri, Edgar Y.
PY - 2003
Y1 - 2003
N2 - In order to understand the fundamentals behind pulsed plasma thruster discharge initiation, the phenomenon of undervoltage (i.e. at a voltage slightly below the breakdown voltage) breakdown through electron pulse injection is explored. This phenomenon is not only the mechanism employed by sparkplug-based PPT initiation systems, but is also the basis for a new optical initiation system which promises improved performance and lifetime. A theoretical model is derived which predicts the injected electron density required to induce breakdown. These results are compared to experimental measurements in which laser pulses on a tungsten surface are used to cause electrons to be injected into a discharge gap with a parallel-plate geometry. It is found that for argon at 2 Torr, the theory and experiment both give the required current density on the order of 10-7-10-8 A/m2 at voltages ranging from 90% to 99% of the breakdown voltage. The similarity suggests that the theoretical interpretation is reasonable: the pulse of electrons alters the space charge in the gap and augments the electric field, making ionization more likely and causing the gas to breakdown.
AB - In order to understand the fundamentals behind pulsed plasma thruster discharge initiation, the phenomenon of undervoltage (i.e. at a voltage slightly below the breakdown voltage) breakdown through electron pulse injection is explored. This phenomenon is not only the mechanism employed by sparkplug-based PPT initiation systems, but is also the basis for a new optical initiation system which promises improved performance and lifetime. A theoretical model is derived which predicts the injected electron density required to induce breakdown. These results are compared to experimental measurements in which laser pulses on a tungsten surface are used to cause electrons to be injected into a discharge gap with a parallel-plate geometry. It is found that for argon at 2 Torr, the theory and experiment both give the required current density on the order of 10-7-10-8 A/m2 at voltages ranging from 90% to 99% of the breakdown voltage. The similarity suggests that the theoretical interpretation is reasonable: the pulse of electrons alters the space charge in the gap and augments the electric field, making ionization more likely and causing the gas to breakdown.
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M3 - Conference contribution
AN - SCOPUS:84897788654
SN - 9781624100987
T3 - 39th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit
BT - 39th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit
Y2 - 20 July 2003 through 23 July 2003
ER -