Probe measurements of the magnetic field structure of fast wave toroidal eigenmodes



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Texas Tech University


The magnetic field structure of fast Alfvén wave toroidal eigenmodes in the ion cyclotron range of frequencies has been investigated on a small research Tokamak. A study of various materials showed that boron nitride rods inserted deep into the plasma affect (and are affected by) the plasma considerably less than rods made of quartz, alumina, and Macor, for example. Differential magnetic loop probes, protected by boron nitride sheaths, were then constructed and used to make radial scans of bz(r), bθ(r), their phases for the fast Alfvén wave. Analysis of the scans indicate the presence of two or more eigenmodes at the time of measurement.