A two-dimensional regularization algorithm for density profile evaluation from broadband reflectometry
- Associacao EURATOM/IST, Centro de Fusao Nuclear/Instituto Superior Tecnico, 1096 Lisboa Codex (Portugal)
- MPI fuer Plasmaphysik, EURATOM/IPP Association, D-85748, Garching (Germany)
Broadband reflectometry is a current technique that uses the round-trip group delays of reflected frequency-swept waves to measure density profiles of fusion plasmas. The main factor that may limit the accuracy of the reconstructed profiles is the interference of the probing waves with the plasma density fluctuations: plasma turbulence leads to random phase variations and magneto hydrodynamic activity produces mainly strong amplitude and phase modulations. Both effects cause the decrease, and eventually loss, of signal at some frequencies. Several data processing techniques can be applied to filter and/or interpolate noisy group delay data obtained from turbulent plasmas with a single frequency sweep. Here, we propose a more powerful algorithm performing two-dimensional regularization (in space and time) of data provided by multiple consecutive frequency sweeps, which leads to density profiles with improved accuracy. The new method is described and its application to simulated data corrupted by noise and missing data is considered. It is shown that the algorithm improves the identification of slowly varying plasma density perturbations by attenuating the effect of fast fluctuations and noise contained in experimental data. First results obtained with this method in ASDEX Upgrade tokamak are presented. {copyright} {ital 1997 American Institute of Physics.}
- OSTI ID:
- 451912
- Report Number(s):
- CONF-960543--
- Journal Information:
- Review of Scientific Instruments, Journal Name: Review of Scientific Instruments Journal Issue: 1 Vol. 68; ISSN 0034-6748; ISSN RSINAK
- Country of Publication:
- United States
- Language:
- English
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