Bremen 2017 – wissenschaftliches Programm
P 5.7: Poster
Montag, 13. März 2017, 16:30–18:30, HS Foyer
Development and implementation of an average Zeff measurement for ASDEX Upgrade plasmas — •T. Welzel1,2, A. Kappatou2, R. McDermott2, U. Stroth2,1, R. Dux2, R. Fischer2, T. Pütterich2, and The ASDEX Upgrade Team2 — 1Physik-Department E28, Technische Universität München, D-85748 Garching, Germany — 2Max-Planck-Institut für Plasmaphysik, Boltzmannstraße 2, 85748 Garching, Germany
The effective charge Zeff is an indicator of the plasma purity. Knowledge of Zeff is important to many physics investigations, however, it is not routinely measured on ASDEX Upgrade. This work aims to develop and implement a fast, automatic and reliable routine measurement of average Zeff. There are two different ways to determine this value. At ASDEX Upgrade, Zeff can be inferred from the individual measurements of the dominant impurities in the plasma. Another approach is to determine the average effective charge via background bremsstrahlung emission measurements, which depend upon the wavelength, electron temperature and density as well as on Zeff. Using other diagnostics to measure the electron density and temperature, Zeff can be calculated. However, the bremsstrahlung emission measurements can be disturbed for example by light reflected on the tokamak wall. The main focus of this work lies in determining suitable measurements of the bremsstrahlung, which will then be used to provide a routine measurement of the average Zeff in ASDEX Upgrade. The Zeff values derived with this method are benchmarked against those obtained by directly measuring the impurity densities in the plasma.