DESIGN AND ELECTRONIC COMPENSATION OF A DIAMAGNETIC LOOP AND ITS APPLICATION IN THE ASDEX TOKAMAK
Owing to the perpendicular motion of electrons and ions the plasma excludes a small amount delta-phi of the toroidal flux. Measuring delta-phi allows determination of the diamagnetic beta poloidal beta-p'-, defined as the ratio of transverse plasma pressure to magnetic pressure at the plasma surface. beta-p'- is measured by a separate loop mounted outside of the stainless steel vacuum vessel. The design and mounting of the loop are described. As in tokamaks one has delta/delta x 10**-4, even very slight magnetic stray fields, coil displacements and eddy currents in the structure during the discharge pulse can influence the diamagnetic signal. We show the separate interference of vertical, ohmic heating, divertor, radial and toroidal fields, and finally the effect of misalignment with respect to the plasma current. We also describe the method and the electric system for compensating these spurious effects. The final section presents experimental results which demonstrate the operation of the diamagnetic loop during the ohmic heating and neutral injection phases.
Bibliographic Reference: WRITE TO MAX-PLANCK-INSTITUT FUER PLAMAPHYSIK, 8046 GARCHING BEI MUENCHEN (GERMANY), MENTIONING REPORT IPP III/84, 1986
Record Number: 1989124101700 / Last updated on: 1987-01-01
Available languages: en