Current-Mode Triple and Quadruple Langmuir Probe Methods With Applications to Flowing Pulsed Plasmas

Evidence of Branching Phenomena in Current-Driven Ionization Waves

“…The downstream plasma state is measured using a quadruple Langmuir probe (QLP) in current-saturation mode [22], which provides the plasma density and temperature at high spatial and temporal resolution. The probe consists of four independent electrodes, biased relative to one another as shown in Fig.…”

“…The plasma currents collected by electrodes 2, 3, and 4 are measured via wideband Pearson current monitors, and the current collected by electrode 1 is calculated via a current balance between the four electrodes. Conversion of the measured currents and bias voltages to the plasma state variables is accomplished by the solution of a nonlinear system of equations derived from kinetic theory [23], and developed for this particular probe configuration to provide plasma temperature T e , plasma density n e , plasma potential φ, and ion thermal Mach number S i [22,25]. Example collected probe currents are shown in Fig.…”

Dynamics of the expansion discharge originated by a dense plasma focus

“…The triple probe, referred operated in current mode, is suitable for flowing, steady, and unsteady plasmas in the collisionless regime. The implementation of current mode originates from the fact that the voltage needed in the voltage mode operation (voltage that comes from the probe which is floating) is a high impedance measurement that can be susceptible to electromagnetic noise in pulsed plasmas [1][2][3][4][5][6]. …”

“…Triple probes offer an advantage over single and double Langmuir probes, allowing simultaneous measurement of plasma parameters without the need for voltage sweeps that can be limiting in pulsed plasma environments, specially if the discharges are not reproducible from shot to shot [1,2,4,6]. Triple probes can be operated in either voltage or current modes.…”

Overview of NASA's Pulsed Plasma Thruster Development Program

“…Also the issue of voltage fluctuations due to pickup of electromagnetic emissions on the ungrounded probe leads was eliminated. The theory for the current collection method was developed in detail 11 . The experimental results of the plasma characterization include the insight that electron temperatures ranged in excess of 10 electron volts during the rise of the discharge current, but typically less than 5 electron volts for the rest of the pulse.…”