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Title: A divertor scraper observation system for the Wendelstein 7-X stellarator

Abstract

Two graphite divertor elements called scrapers have been installed on the Wendelstein 7-X stellarator in the throat of the magnetic island divertor. To diagnose one, we have designed, built, calibrated, and installed a new infrared/visible imaging endoscope system to enable detailed observations of the plasma interactions and heat loads at one of the scrapers and the nearby divertor surfaces. The new system uses a shuttered pinhole-protected pair of 90° off-axis 228 mm focal length aluminum parabolic mirrors, and two flat turning metal mirrors, to send light to a sapphire vacuum window 1.6 meters away, beyond which we have co-located telephoto lens-based infrared and visible cameras. The back-to-back off-axis parabolas serve to cancel out most aberrations, enabling the use of off-the-shelf commercial optics outside of the vessel. For the infrared, we use a 3-5 μm 1-megapixel FLIR SC8303HD camera and for the visible, a 5-megapixel CMOS PCO 5.5 edge camera. A short 1-m quartz pickoff fiber is used to send 200-1100 nm light to a compact spectrometer, also located in the same iron shield box as the cameras. The camera field of view covers the 700 mm length of the scraper, and includes locations monitored by thermocouples and Langmuir probes embeddedmore » in some of the scraper tiles. Predicted and actual optical test performances of the overall system are then compared.« less

Authors:
ORCiD logo [1];  [2];  [2]; ORCiD logo [2]; ORCiD logo [2];  [2];  [2];  [2]; ORCiD logo [2];  [2];  [2];  [2]
  1. Los Alamos National Laboratory, P.O. Box 1663, Los Alamos, New Mexico 87545, USA
  2. Max-Planck-Institute für Plasma Physik, Wendelsteinstrasse 1, 17491 Greifswald, Germany
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Fusion Energy Sciences (FES); European Commission (EC)
Contributing Org.:
W7-X Team
OSTI Identifier:
1467276
Alternate Identifier(s):
OSTI ID: 1463041
Report Number(s):
LA-UR-17-31225
Journal ID: ISSN 0034-6748
Grant/Contract Number:  
AC52-06NA25396; 633053
Resource Type:
Accepted Manuscript
Journal Name:
Review of Scientific Instruments
Additional Journal Information:
Journal Volume: 89; Journal Issue: 10; Conference: High Temperature Plasma Diagnostics ; 2018-04-16 - 2018-04-16 ; San Diego, California, United States; Journal ID: ISSN 0034-6748
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; 47 OTHER INSTRUMENTATION; Magnetic Fusion Energy; Imaging diagnostic, Infrared, Visible, Divertor, wall protection, plasma

Citation Formats

Wurden, G. A., Fellinger, J., Biedermann, C., Drewelow, P., Ford, O., Gamradt, M., Greve, H., Herold, F., Jakubowski, M., Jenzsch, H., Niemann, H., and Puig Sitjes, A. A divertor scraper observation system for the Wendelstein 7-X stellarator. United States: N. p., 2018. Web. https://doi.org/10.1063/1.5035078.
Wurden, G. A., Fellinger, J., Biedermann, C., Drewelow, P., Ford, O., Gamradt, M., Greve, H., Herold, F., Jakubowski, M., Jenzsch, H., Niemann, H., & Puig Sitjes, A. A divertor scraper observation system for the Wendelstein 7-X stellarator. United States. https://doi.org/10.1063/1.5035078
Wurden, G. A., Fellinger, J., Biedermann, C., Drewelow, P., Ford, O., Gamradt, M., Greve, H., Herold, F., Jakubowski, M., Jenzsch, H., Niemann, H., and Puig Sitjes, A. Mon . "A divertor scraper observation system for the Wendelstein 7-X stellarator". United States. https://doi.org/10.1063/1.5035078. https://www.osti.gov/servlets/purl/1467276.
@article{osti_1467276,
title = {A divertor scraper observation system for the Wendelstein 7-X stellarator},
author = {Wurden, G. A. and Fellinger, J. and Biedermann, C. and Drewelow, P. and Ford, O. and Gamradt, M. and Greve, H. and Herold, F. and Jakubowski, M. and Jenzsch, H. and Niemann, H. and Puig Sitjes, A.},
abstractNote = {Two graphite divertor elements called scrapers have been installed on the Wendelstein 7-X stellarator in the throat of the magnetic island divertor. To diagnose one, we have designed, built, calibrated, and installed a new infrared/visible imaging endoscope system to enable detailed observations of the plasma interactions and heat loads at one of the scrapers and the nearby divertor surfaces. The new system uses a shuttered pinhole-protected pair of 90° off-axis 228 mm focal length aluminum parabolic mirrors, and two flat turning metal mirrors, to send light to a sapphire vacuum window 1.6 meters away, beyond which we have co-located telephoto lens-based infrared and visible cameras. The back-to-back off-axis parabolas serve to cancel out most aberrations, enabling the use of off-the-shelf commercial optics outside of the vessel. For the infrared, we use a 3-5 μm 1-megapixel FLIR SC8303HD camera and for the visible, a 5-megapixel CMOS PCO 5.5 edge camera. A short 1-m quartz pickoff fiber is used to send 200-1100 nm light to a compact spectrometer, also located in the same iron shield box as the cameras. The camera field of view covers the 700 mm length of the scraper, and includes locations monitored by thermocouples and Langmuir probes embedded in some of the scraper tiles. Predicted and actual optical test performances of the overall system are then compared.},
doi = {10.1063/1.5035078},
journal = {Review of Scientific Instruments},
number = 10,
volume = 89,
place = {United States},
year = {2018},
month = {8}
}

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Figures / Tables:

FIG. 2 FIG. 2: ZEMAX optical model, showing light rays through a 4 mm diameter pinhole, with two off-axis parabolas, M1 and M2, arranged to cancel aberrations.

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Works referenced in this record:

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    Works referencing / citing this record:

    Measurement and modeling of magnetic configurations to mimic overload scenarios in the W7-X stellarator
    journal, May 2019


    Infrared imaging systems for wall protection in the W7-X stellarator (invited)
    journal, October 2018

    • Jakubowski, Marcin; Drewelow, Peter; Fellinger, Joris
    • Review of Scientific Instruments, Vol. 89, Issue 10
    • DOI: 10.1063/1.5038634