Speaker
Ireneusz Ksiazek
(Institute of Physics)
Description
The C/O monitor for W7-X will be a spectrometer of special construction with high throughput and high time resolution, suitable for controling concentration of main impurities in plasma. The spectrometer will be fixed at horizontal position and at wavelengths corresponding to Lyman a lines of H-like ions of oxygen (at 1.9 nm), nitrogen (at 2.5 nm), carbon (at 3.4 nm) and boron (at 4.9 nm). Its purpose is fast monitoring of the spectral lines intensities which are reflecting level of impurities associated with general wall condition (oxygen), plasma-wall interaction (carbon, boron) or vacuum system leakage (nitrogen). The system will inform about the accumulation of the impurities and/or transient events associated with plasma wall interaction.
The spectrometer will be composed of four independent channels, with individual dispersive elements and separate detectors. It will be constructed according to Johann geometry with Rowland circles radii adjusted to wavelength ranges registered by the respective channels.
As a dispersive element for oxygen channel the TlAP crystal was chosen. Because in the range of spectra corresponding to the remaining spectral lines, the reflectivities of crystals as well as of gratings are very low it was decided to apply multilayer mirrors as dispersive elements. Multilayer for registering nitrogen spectral line will consist 150 layers of W/Si, for carbon line 90 Cr/Sc layers and for boron 100 Cr/C layers.
Because of the irregular shape of the plasma and simple function of the spectrometer it was decided that the curvature of the mirrors ought to be cylindrical (instead of spherical, enabling imaging of the plasma). As detectors a commercially available CCD designed for high energy detection will be applied. As an alternative detector, a proportional counter of special construction – a multistrip gaseous chamber (MSGC) is considered.
The proposed system will be mechanically divided into two subspectrometers.
Co-authors
Ireneusz Ksiazek
(Institute of Physics, Opole University, Opole, Poland)
Jacek Kaczmarczyk
(Institute of Plasma Physics and Laser Microfusion, Hery 23, 01-497 Warsaw, Poland)
Monika Kubkowska
(Institute of Plasma Physics and Laser Microfusion, Hery 23, 01-497 Warsaw, Poland)
Rainer Burhenn
(Max-Planck-Institut für Plasmaphysik, Wendelsteinstrasse 1, 17491 Greifswald, Germany)
Sebastien Renard
(CEA, IRFM, 13108 Saint-Paul-Lez-Durance, France)
Tomasz Fornal
(Institute of Plasma Physics and Laser Microfusion, Hery 23, 01-497 Warsaw, Poland)
Waldemar Figacz
(Institute of Plasma Physics and Laser Microfusion, Hery 23, 01-497 Warsaw, Poland)
team W7-X
(Max-Planck-Institut für Plasmaphysik, Wendelsteinstrasse 1, 17491 Greifswald, Germany)
