The rapid determination of plasma equilibrium parameters at JET from external magnetic measurementsFunded under: EAEC-FUSION 12C
The control of the plasma shape and position in a tokamak requires a fast, reliable and sufficiently accurate method of determining the plasma boundary. At JET, a method using Taylor series expansions of the magnetic flux surrounding the plasma has been developed which meets these requirements; the calculation takes 1 ms per time slice and comparisons with Langmuir probe and CCD camera data suggest the accuracy is approximately 1 cm, comparable with the full Grad-Shafranov equilibrium codes in use at JET (EFIT, IDENT). The expansion method has been adapted for use in the pumped divertor phase at JET where it is now used as part of the control software for the plasma shape and position system. The plasma boundary data (position and poloidal field) is also supplied to the FAST code to calculate some global parameters such as poloidal beta, internal inductance and plasma energy. Good agreement with calculations based on diamagnetic measurements is obtained. This information could now be used to control the plasma beta or energy and extend the duration of H- and VH-modes.
Bibliographic Reference: Report: JET-P(94)70 EN (1994) 19 pp.
Availability: Available from the Publications Officer, JET Joint Undertaking, Abingdon, Oxon. OX14 3EA (GB)
Record Number: 199511183 / Last updated on: 1995-10-10
Original language: en
Available languages: en