Transport of electrons in the tunnel of an ion sensitive probe

0364036 - ÚFP 2012 RIV GB eng J - Journal Article
Komm, Michael - Adámek, Jiří - Dejarnac, Renaud - Gunn, J. P. - Pekárek, Z.
Transport of electrons in the tunnel of an ion sensitive probe.
Plasma Physics and Controlled Fusion. Roč. 53, č. 1 (2011), 015005-015005. ISSN 0741-3335. E-ISSN 1361-6587
R&D Projects: GA AV ČR KJB100430901; GA MŠMT 7G09042; GA MŠMT LA08048
Institutional research plan: CEZ:AV0Z20430508
Keywords : Tokamak * plasma * katsumata probe * ExB drift * ion temperature * tunnel * electron
Subject RIV: BL - Plasma and Gas Discharge Physics
Impact factor: 2.425, year: 2011
http://iopscience.iop.org/0741-3335/53/1/015005/pdf/0741-3335_53_1_015005.pdf

Ion sensitive probes serve to measure the ion temperature in magnetized plasma. The principle of the probe is based on geometrical shielding of the ion collector from plasma electrons. According to the basic theory, when the collector is retracted in the tube, electrons should not be able to reach it and the collector becomes sensitive to ions. However, experimental results show that the electron shielding only works in the case when the potential of the collector is the same as the potential of the inside surface of the tube. This problem is investigated using a full 3D particle-in-cell Cartesian code. A positive potential structure is formed at the entrance of the tube due to the space charge of ions that gyrate inside. This structure produces E × B drifts, which push electrons into the shielded space. Simulations revealed that electrons can penetrate inside the geometrical shadow in all studied cases.
Permanent Link: http://hdl.handle.net/11104/0199621