W7-X Dispersion Interferometer’s Current Signal Processing and Future Bayesian Model Based Data Analysis
The dispersion interferometer (DI) diagnostic, which can be used to measure line integrated electron density, currently performs data acquisition and signal processing with an FPGA embedded on the SIS8300-L board. This W7-X interferometer is being developed to calculate a real time estimation of the line integrated electron density, store raw data and transmit processed signal for control purposes via a real-time network. This diagnostic has a complex non-linear signal model involving arccosine ambiguity that has to be estimated to obtain the parameter of interest. The complexity of the model, required assumptions and final estimation of the uncertainty motivates to address alternatives using other methods. The use of Bayesian probability theory and forward modeling would achieve a purely mathematical model reaching a more informed estimation of a value and a rigorous determination of its uncertainty. This technique has been typically used for post processing. A real-time processing implementation is needed and still missing. Possible approaches are the use of on an FPGA (Field Programmable Gate Array) or a Hardware/Software combination which can make use of efficient backplane communications of the current platform the DI is currently using. If achieved, the approach could be useful for diverse applications generating signals for control systems or determining required parameters. This projects reach includes improvement of data integration and signal processing on smart systems or other platforms that have incoming data from several peripherals, in the way some diagnostics are integrated using Bayesian graphical models.