Kinetic Equilibrium Reconstructions of Plasmas in the MAST Database and Preparation for Reconstruction of the First Plasmas in MAST Upgrade

Kinetic Equilibrium Reconstructions of Plasmas in the MAST Database and Preparation for Reconstruction of the First Plasmas in MAST Upgrade

Kinetic Equilibrium Reconstructions of Plasmas in the MAST Database and Preparation for Reconstruction of the First Plasmas in MAST Upgrade 150 150 Mathew
UKAEA-CCFE-PR(21)79

Kinetic Equilibrium Reconstructions of Plasmas in the MAST Database and Preparation for Reconstruction of the First Plasmas in MAST Upgrade

Reconstructions of plasma equilibria using magnetic sensors and a Dα constraint were routine during operation of the MAST spherical tokamak, but reconstructions using kinetic profiles was not. These are necessary for stability and disruption analysis of the MAST database, as well as going forward for operation in the upgrade to the device, MAST-U. The three dimensional code VALEN is used to determine eddy currents in the 3D vessel structures for vacuum coil test shots, which are then mapped to effective resistances in the 2D vessel groupings in the EFIT equilibrium reconstruction code to be used in conjunction with nearby loop voltage measurements for estimated currents in the structures during reconstruction. Kinetic equilibrium reconstructions with EFIT, using all available magnetic sensors as well as Thomson scattering measurements of electron temperature and density, charge exchange recombination spectroscopy measurements of ion temperature, and internal magnetic field pitch angle measurements from a motional Stark effect (MSE) diagnostic are performed for a large database of MAST discharges. Excellent convergence errors are obtained for the portions of the discharges where the stored energy was not too low, and it is found that reconstructions performed with temperature and density measurements but without MSE data usually already match the pitch angle measurements well; adding MSE data corroborates, but generally does not substantially change, the reconstructions. A database of 275 kinetic equilibria is used to test the ideal MHD stability calculation capability for MAST. Finally, the necessary changes to conducting structure in VALEN, and diagnostic setup in EFIT have been completed for the upgrade from MAST to MAST-U, enabling kinetic reconstructions to commence from the first plasma discharges of the upgraded device.

Collection:
Journals
Journal:
Plasma Physics and Controlled Fusion
Publisher:
IOP (Institute of Physics)
Published date:
13/04/2021
The published version of this paper is currently under embargo and will be available on 13/04/2022