Improved Understanding of the Ball-Pen Probe through Particle-In-Cell Simulations

Murphy-Sugrue, S, Harrison, J, Walkden, NR, Bryant, PM and Bradley, JW
(2017) Improved Understanding of the Ball-Pen Probe through Particle-In-Cell Simulations. Plasma Physics and Controlled Fusion, 59 (05).

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Ball-pen probes (BPP)have been deployed in the SOL of numerous tokamak experiments and low-temperature magnetised plasmas to make direct measurements of the plasma potential and electron temperature. Despite strong empirical evidence for the success of the BPP it lacks a theoretical underpinning of its collection mechanism. In this paper we investigate the capability of the probe to measure the plasma potential by means of particle-in-cell simulations. The BPP is found to float at a potential offset from the plasma potential by a factor TₑαBPP. By simulating BPPs and Langmuir probes, excellent agreement has been found between the measured electron temperature and the specified source temperature. The transport mechanism for both ions and electrons has been determined.E×B drifts are observed to drive electrons and ions down the tunnel. This mechanism is sensitive to the diameter of the probe

Item Type: Article
Uncontrolled Keywords: particle-in-cell, ball-pen probe, Langmuir probe, plasma potential, electron temperature
Depositing User: Symplectic Admin
Date Deposited: 21 Feb 2017 16:42
Last Modified: 19 Jan 2023 07:19
DOI: 10.1088/1361-6587/aa60d0
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