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Application of Emissive Probes for Plasma Potential Measurements in Fusion Devices
Author(s) -
Schrittwieser R.,
Ionita C.,
Balan P.C.,
Cabral J.A.,
Figueiredo F.H.,
Pohoata V.,
Varandas C.
Publication year - 2001
Publication title -
contributions to plasma physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.531
H-Index - 47
eISSN - 1521-3986
pISSN - 0863-1042
DOI - 10.1002/1521-3986(200109)41:5<494::aid-ctpp494>3.0.co;2-x
Subject(s) - plasma , langmuir probe , tokamak , electron , atomic physics , electron temperature , plasma diagnostics , materials science , fusion , plasma parameters , kinetic energy , physics , nuclear physics , linguistics , philosophy , quantum mechanics
In experimental fusion devices, up to now, only cold probes were used to determine the plasma potential in the s crape‐ o ff l ayer (SOL), and their floating potential was assumed to be proportional to the plasma potential. However, drifting electrons or beams shift the current‐voltage characteristic of a cold probe by a voltage, which corresponds to the mean kinetic energy of the drifting electrons. This problem can be avoided by the use of electron emissive probes, since an electron emission current is independent of electron drifts in the surrounding plasma. In addition emissive probes are insensitive to electron temperature fluctuations in the plasma. We have used an arrangement of three emissive probes in the edge plasma region of ISTTOK (Instituto Superior Técnico tokamak) at Lisbon. The probes have been mounted in such a way that the tips are positioned on the same poloidal meridian but on different minor radii in the SOL. With this arrangement, the plasma potential has been measured in the edge region of the ISTTOK, and first results are presented in this contribution.