Development of a virtual Z{sub eff} diagnostic for the W7-X stellarator
- Max-Planck-Institut fuer Plasmaphysik, Euratom Association, Wendelsteinstr. 1, 17491 Greifswald (Germany)
For the W7-X stellarator a diagnostic system for measurement of local Z{sub eff} values from the visible bremsstrahlung continuum is foreseen. The method is based on passive, absolute measurement of the bremsstrahlung intensity along several lines of sight. In order to eliminate the spurious impact of other radiation sources of different spectral intensity distribution than the bremsstrahlung, like the line radiation, it is intended to spectrally resolve the detected radiation, e.g., by use of microspectrometers. The visible bremsstrahlung background can be extracted by making use of the 1/{lambda}{sup 2} dependence of its intensity (expressed in unit W/m{sup 3} sr nm) in the high temperature plasmas by using Bayesian data analysis techniques. In a second step, the local values of Z{sub eff} as a function of the effective plasma radius are derived by inversion, using different regularization methods, of the line-integrated bremsstrahlung signals with the knowledge of the magnetic flux surfaces. Inversion of the full model based on statistical methods allows taking into account all conceivable uncertainties accompanying Z{sub eff} measurement and provides uncertainties of the local Z{sub eff} values and valuable information on other uncertain parameters of the model. In this paper we show the first steps in developing a virtual Z{sub eff} diagnostic for W7-X which allows the optimization of the statistical model as well as of the future diagnostic setup.
- OSTI ID:
- 21266666
- Journal Information:
- Review of Scientific Instruments, Vol. 79, Issue 10; Conference: HTPD08: 17. topical conference on high-temperature plasma diagnostics, Albuquerque, NM (United States), 11-15 May 2008; Other Information: DOI: 10.1063/1.2956826; (c) 2008 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0034-6748
- Country of Publication:
- United States
- Language:
- English
Similar Records
Design and commissioning of a new diagnostic for routine determination of Z{sub eff} from visible bremsstrahlung measurements on TEXTOR
Z{sub eff} from spectroscopic bremsstrahlung measurements at ASDEX Upgrade and JET