ISSN:
1089-7623
Source:
AIP Digital Archive
Topics:
Physics
,
Electrical Engineering, Measurement and Control Technology
Notes:
Biasing a Langmuir probe to collect electrons creates a magnetic perturbation by drawing current along a field line. This perturbation propagates along the magnetic field as a shear-Alfvén mode and marks the affected field lines with a potential perturbation at the probe sweep frequency. This technique has been used in TEXT-U edge plasmas to locate a connection between two sensor probes separated by either 12 or 28 m along a field line, and this connection has been verified using magnetic field line tracing codes. The driver probe creates a shadow which spreads in the poloidal direction with increasing distance parallel to the magnetic field due to both the change of safety factor with minor radius and collisional effects. Determination of the radial and poloidal structure of the perturbation down the magnetic field therefore provides a measurement of the safety factor q as a function of minor radius in the edge. In addition, the technique for locating field lines has been used to establish a purely parallel connection between two floating probes and therefore provides a measurement of parallel wave number k(parallel)≤0.1 m−1 and parallel correlation length l(parallel)≥12 m. © 1997 American Institute of Physics.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.1147838
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