Measurement of the magnetic field in a spherical torus plasma via electron Bernstein wave emission harmonic overlap

A technique by which magnetic field profile information can be obtained in an spherical focus (ST) was proposed by the observation of harmonic overlaps in the electron Bernstein wave (EBW) emission spectrum. A broadband radiometer was required to implement the technique. Harmonic overlaps occurred at coincidences of the upper-hybrid and electron cyclotron harmonic frequencies and were determined by the magnetic field and electron density profiles in the plasma. The results indicate the spatial origin of EBW emission which are capable of propagating radially outward to the upper-hybrid layer without encountering an absorbing cyclotron resonance.