Profile measurements in the plasma edge of mega amp spherical tokamak using a ball pen probe

0443592 - ÚFP 2016 RIV US eng J - Journal Article
Walkden, N.R. - Adámek, Jiří - Allan, S. - Dudson, B.D. - Elmore, S. - Fishpool, G. - Harrison, J. - Kirk, A. - Komm, Michael
Profile measurements in the plasma edge of mega amp spherical tokamak using a ball pen probe.
Review of Scientific Instruments. Roč. 86, č. 2 (2015), č. článku 023510. ISSN 0034-6748. E-ISSN 1089-7623
R&D Projects: GA ČR(CZ) GAP205/12/2327; GA MŠMT(CZ) LM2011021
Institutional support: RVO:61389021
Keywords : plasma * tokamak * ball pen probe
OECD category: 2.11 Other engineering and technologies
Impact factor: 1.336, year: 2015
http://dx.doi.org/10.1063/1.4908572

The ball pen probe (BPP) technique is used successfully to make profile measurements of plasma potential, electron temperature, and radial electric field on the Mega Amp Spherical Tokamak. The potential profile measured by the BPP is shown to significantly differ from the floating potential both in polarity and profile shape. By combining the BPP potential and the floating potential, the electron temperature can be measured, which is compared with the Thomson scattering (TS) diagnostic. Excellent agreement between the two diagnostics is obtained when secondary electron emission is accounted for in the floating potential. From the BPP profile, an estimate of the radial electric field is extracted which is shown to be of the order ~1 kV/mand increases with plasma current. Corrections to the BPP measurement, constrained by the TS comparison, introduce uncertainty into the ER measurements. The uncertainty is most significant in the electric field well inside the separatrix.
Permanent Link: http://hdl.handle.net/11104/0246278