Present and perspective roles of soft X-ray tomography in tokamak plasma position measurements
Section snippets
Introduction, ITER relevance
The computerised tomography technique, which allows the reconstruction of the emissivity cross-section from its line integral measurements, has been applied in fusion plasma science since the early 1980s. A review of plasma tomography methods is presented in Ref. [1]. In the past two decades, plasma tomography applications have profited from the computer speed and capacity increase so that quite sophisticated algorithms, with a numerically rigorous introduction of constraints, have been
Rapid tomography and SXR position measurements on TCV
On TCV, minimum Fisher regularisation (MFR) is successfully applied in the tomographic reconstruction [8] of both SXR and bolometric data. The SXR diagnostics consist of ten pinhole cameras, see Fig. 1, each with linear arrays of 20 Centronix photodiodes and 47 μm beryllium filter foil [9]. In the MFR, the reconstructed images of emissivity cross-section are obtained on a grid of rectangular pixels. The default size of a pixel is 37 mm, full coverage of the TCV cross-section corresponds to
Technical feasibility of the real time tomography hardware
Real-time SXR tomography with position feedback on TCV translates to digitising 200 analogue signals fi, multiplying them with a pre-calculated inversion matrix Mji (typically 630×200 real numbers), finding the maximum of the resulting emissivity tomograms gj (630 numbers), extracting the core of emissivity gj, determining its center of gravity [rsxr, zsxr], possibly multiplying it by compensation factors and, if necessary, converting the calculated position to analogue signals. On TCV, the
Acknowledgements
The authors appreciate the professional support of Peter Milne from D-TACQ Solutions Ltd., http://www.d-tacq.com/. This work was partly supported by the Swiss National Science Foundation.
References (9)
Soft X-ray tomography during ELMs and impurity injection in JET
Nucl. Fusion
(1998)- E. van der Goot, Software for the real time X-ray tomography system at JET, JET Report JET-P(91)28, July...
Overview of TCV results
Nucl. Fusion
(2001)- J. Mlynar et al., Investigation of the consistency of magnetic and soft x-ray plasma position measurements on TCV by...
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