Speaker
Dr
Dmitry Moseev
(Max-Planck-Institut für Plasmaphysik)
Description
The collective Thomson scattering (CTS) diagnostic for ion temperature and MHD measurements is being installed at the Wendelstein 7-X (W7-X) stellarator.
W7-X is designed for high β operation, with β approximately around 5%. The target electron density of W7-X plasmas is 1.5$\cdot$10$^{20}$ m$^{-3}$ and the target electron temperature in the center is 8-10 keV. The CTS diagnostic has no fundamental limitations on measuring the ion temperature at the W7-X target plasma parameters.
The diagnostic utilizes a 140 GHz heating gyrotron as a source for the probing radiation and uses the ECRH quasi-optical transmission lines both for the probing and receiving beams. The exploitation of the receiver in the ECE range of frequencies is one of the challenges of the diagnostic. The quasi-optical transmission line allows measuring at two toroidal locations with different topologies of the magnetic field.
The diagnostic is equipped with steerable mirrors in the bean-shaped cross-section, which allows flexible scattering geometries on the low field side, however the plasma center is not accessible at the standard magnetic field of 2.5 T on axis due to absorption of the probing beam. In the triangular cross-section, remote steering antennas are installed both for the receiver and the probe. These antennas are steerable in one dimension, thus making a beam overlap search possible, as well as ion temperature profile measurements including the plasma center. The number of scattering geometries in the triangular cross-sections is limited because of the steering limitations.
The scattering spectra will be analyzed using the electrostatic eCTS code, which is integrated into the Bayesian integrated data analysis framework Minerva.
This contribution concentrates on the design aspects and commissioning of the CTS diagnostic at Wendelstein 7-X.
Primary author
Dr
Dmitry Moseev
(Max-Planck-Institut für Plasmaphysik)
Co-authors
Mr
Andrea Pavone
(IPP Greifswald)
Dr
Carsten Lechte
(Stuttgart University)
Mr
Fabian Wilde
(IPP Greifswald, KIT)
Dr
Frank Leipold
(DTU)
Dr
Harald Braune
(IPP Greifswald)
Dr
Heinrich Peter Laqua
(IPP Greifswald)
Ms
Ivana Abramovic
(IPP Greifswald, TU/e)
Dr
Jesper Rasmussen
(DTU)
Mr
Jonathan van den Berg
(TU/e)
Mr
Michael Weissgerber
(IPP Garching)
Dr
Mirko Salewski
(DTU)
Dr
Morten Stejner
(DTU)
Prof.
Robert C. Wolf
(IPP Greifswald)
Dr
Stefan Kragh Nielsen
(DTU)
Dr
Stephan Marsen
(IPP Greifswald)
Mr
Thomas Jensen
(DTU)
Dr
Torsten Stange
(IPP Greifswald)
Dr
Walter Kasparek
(Stuttgart University)
