Fusion Science and Technology / Volume 58 / Number 1 / July 2010 / Pages 471-481
Chapter 8. Diagnostics / Special Issue on Large Helical Device (LHD)
This paper describes present status of magnetic measurements in the Large Helical Device (LHD). The magnetic measurements have been mainly applied for estimation of global parameters and for magnetohydrodynamic (MHD) study rather than the equilibrium control because of net current-free plasmas. The techniques of diamagnetic flux measurement and MHD mode analysis are introduced. The estimation of the diamagnetic flux strongly depends on the plasma currents inducing an eddy current on continuous helical coils. The obtained diamagnetic energy is almost consistent with kinetic energy within the measurement error. The MHD modes have been identified through comparison of magnetic probe signals with virtual perturbation generated by multifilament currents on Boozer coordinates based on three-dimensional MHD equilibria. The validity of this technique was considered through the pressure gradient control experiments.