Magnetic diagnostics in the large helical device

Measurement systems for magnetic flux and magnetic field are being developed in the large helical device (LHD). Specification of the measurement systems is described. Careful attention should be paid to the set-up, especially thermal insulation to superconducting coils. Physical interpretation of magnetic flux as well as local magnetic field measured in finite-β plasmas has been conducted with three-dimensional magnetic field analysis code. This calculation indicates that non-linear changes in magnetic flux as a function of 〈β〉 should be considered for precise estimates.