Study of q-profile determination by pellet ablation at ASDEX Upgrade
The q-profile is correlated to the tokamak's current density profile. It is possible to determine the current profile from measurements of the magnetic field. Pellet injection can be applied to visualize the magnetic field lines. The ablated material is ionized. The ionized particles stick to the magnetic field lines, as will be shown in this report. In the early stages the pellet is surrounded by a cold, dense plasma cloud. This cloud contains a small fraction of neutral particles, undergoing collisional excitation and emitting photons. Therefore it is possible to observe this plasma cloud. For the observation of the pellet ablation with high temporal resolution a fast-framing camera was used. Special software for the analysis of the data has been developed. The results of the pellet ablation method will be compared to the results of other measurement techniques. This investigation shows that it is not possible to determine the q-profile based on the data of the pellet ablation only, because the measured inclination angle is a local quantity while the q-factor is a quantity of a flux surface. However, it is possible to use the inclination angle measurement to improve the accuracy of other q-profile measurements by up to 50%.
Bibliographic Reference: Report: IPP 1/303 DE (1996) 111pp.
Availability: Available from the Max-Planck-Institut für Plasmaphysik, 85748 Garching bei München (DE)
Record Number: 199611382 / Last updated on: 1996-12-04
Original language: de
Available languages: de