Verification of Various Probe Diagnostics for Pulse and Static Scenario of the PHASMA Device.

Langmuir probes single, double, and triple, are commonly used plasma diagnostics. Triple Langmuir probes (TLP) are used to measure electron temperature, density, and floating potential in the PHASMA (PHAse Space MApping) device during pulsed and steady-state operation. The TLP provides a straightforward approach for measuring temporal and spatially resolved plasma parameters. Here we describe a high-time resolution TLP developed for PHASMA. It consists of three closely spaced Langmuir probes. Two tips are connected in a double probe configuration and the third one samples the change in floating potential during the plasma pulse. The time-resolved measurement of electron temperature depends on the choice of the fixed bias used for the double probe pair. To obtain accurate electron temperature measurements, the fixed bias value is selected based on a comparison of TLP measurements with single and double Langmuir probe electron temperature measurements of the pulsed (plasma gun discharges) and steady-state (helicon source) PHASMA plasmas. We also present comparisons of electron temperature fluctuations measured with the TLP and a double probe.