15-19 April 2018
Paradise Point Resort & Spa
America/Los_Angeles timezone

8.43 Real-time Dispersion Interferometry for Density Feedback in Fusion Devices

17 Apr 2018, 16:00
1d 2h
Paradise Point Resort & Spa

Paradise Point Resort & Spa

1404 Vacation Rd, San Diego, CA 92109

Speakers

Kai Jakob Brunner (Max-Planck-Institut for Plasma Physics, Greifswald) Akiyama Akiyama (National Institute for Fusion Science) Matthias Hirsch (Max-Planck-Institut for Plasma Physics, Greifswald) Jens Knauer (Max-Planck-Institut for Plasma Physics, Greifswald) Petra Kornejew (Max-Planck-Institut for Plasma Physics, Greifswald) Beate Kursinski (Max-Planck-Institut for Plasma Physics, Greifswald) Heike Laqua (Max-Planck-Institut for Plasma Physics, Greifswald) Jens Meinicke (Max-Planck-Institut for Plasma Physics, Greifswald) Humberto Trimino-Mora (Max-Planck-Institut for Plasma Physics, Greifswald) Robert C. Wolf (Max-Planck-Institut for Plasma Physics, Greifswald)

Description

Interferometry as one of the most common core fusion diagnostics has traditionally suffered from incomplete vibration compensation. Dispersion interferometry promises a more complete compensation of vibrations. For this reason it is being employed in an increasing number of experiments. However, thus far none of them have shown reliable real-time low-latency processing of dispersion interferometry data. Nonetheless this is a necessity for most machines when trying to do density feedback control, most notably in long discharges like the ones planned at the W7-X stellarator and ITER. In this paper we report the development of a new phase extraction method specifically developed for real-time evaluation using FPGAs. It has been shown to operate reliably during the OP1.2a operation phase at W7-X and is now routinely being used by the W7-X density feedback system up to very high densities above 1.4e20 1/m² without 2π-wraps. During the development of the method new insights into the signal composition of a dispersion interferometer have been gained leading to a new signal calibration relevant to other phase evaluation methods.

Primary author

Kai Jakob Brunner (Max-Planck-Institut for Plasma Physics, Greifswald)

Co-authors

Akiyama Akiyama (National Institute for Fusion Science) Matthias Hirsch (Max-Planck-Institut for Plasma Physics, Greifswald) Jens Knauer (Max-Planck-Institut for Plasma Physics, Greifswald) Petra Kornejew (Max-Planck-Institut for Plasma Physics, Greifswald) Beate Kursinski (Max-Planck-Institut for Plasma Physics, Greifswald) Heike Laqua (Max-Planck-Institut for Plasma Physics, Greifswald) Jens Meinicke (Max-Planck-Institut for Plasma Physics, Greifswald) Humberto Trimino-Mora (Max-Planck-Institut for Plasma Physics, Greifswald) Robert C. Wolf (Max-Planck-Institut for Plasma Physics, Greifswald)

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