New model for the ion collection by cylindrical probes over a wide range of collisionality

Technical Report · Thu Feb 27 04:00:00 EST 2025

DOI:https://doi.org/10.2172/2524042· OSTI ID:2524042

Kortshagen, Uwe ^[1]; Held, Julian ^[1]

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1. Univ. of Minnesota, Minneapolis, MN (United States)

Langmuir probes remain one of the most important diagnostic tools for plasma processing applications. Modern probe analysis usually relies on the electron current part of the Langmuir probe characteristic using the Druyvesteyn method. However, for electronegative plasmas or for discharges containing dust the analysis of the ion current attracted by the probe can be desirable to determine the ion density. But, even at low pressures of a few Pa, the ion current is affected by collisions due to the large cross section for charge exchange. Available theories for collisional or collision-enhanced ion currents onto probes are complex and not well validated. Thus, in this contribution, we compare available collisional probe theories for the ion current to results of particle-in-cell (PIC) simulations. To this end, the probe surrounded by a semi-infinite plasma is simulated using a modified version of the open-source code EDIPIC. A dataset of currents for different neutral gas pressures is obtained and compared to the different theories from the literature. Based on these results, we propose a simpler and more intuitive model for the ion current collected by the probe, based on the model of Gatti and Kortshagen (Phys. Rev. E 78, 046402, 2008), developed for the charging of dust particles.

• Research Organization: Univ. of Minnesota, Minneapolis, MN (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Fusion Energy Sciences (FES)
• DOE Contract Number: SC0024479
• OSTI ID: 2524042
• Report Number(s): DOE-UMN--24479
• Country of Publication: United States
• Language: English

Related Subjects

Langmuir probe
collisional ion current
ion current
orbital motion limited current
plasma