Diagnosis of Pulsed Spark Discharge Plasma by Triple Langmuir Probes

To optimize the structure and performance of high current pulsed electron beam source, an accurate measurement of pulsed plasma distribution is really necessary. Based on the generation mechanism of pulsed spark discharge plasma and the working principle of triple Langmuir probes, the probe structure and diagnostic circuit parameters were designed, which satisfied the spatial resolution of 7.5 mm³. The original signals were collected and recorded by a digital oscilloscope, and the electron temperature and electron density could be calculated through a processing program written by Matlab software, where the time resolution is 0.04 μs. When measuring at the beam source outlet with the working conditions of vacuum pressure 7.0×10^-3 Pa and discharge voltage 8000 V,the peak value of electron temperature and density reached 3.8 eV and 4.0×10¹⁸m^-3. For the different working conditions, it was found that the electron temperature decreased with the increment of vacuum pressure, while the electron density was the opposite. Using the higher discharge voltage, the electron temperature and electron density increased consistently. The testing results were in accord with theoretical analysis and experimental regularity. The self-developed diagnostic system can be applied for the measurement of pulsed discharge plasma satisfactorily.