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Title: First measurements of error fields on W7-X using flux surface mapping

Error fields have been detected and quantified using the flux surface mapping diagnostic system on Wendelstein 7-X (W7-X). A low-field '$${\rlap{-}\ \iota} =1/2$$ ' magnetic configuration ($${\rlap{-}\ \iota} =\iota /2\pi $$ ), sensitive to error fields, was developed in order to detect their presence using the flux surface mapping diagnostic. In this configuration, a vacuum flux surface with rotational transform of n/m = 1/2 is created at the mid-radius of the vacuum flux surfaces. If no error fields are present a vanishingly small n/m = 5/10 island chain should be present. Modeling indicates that if an n = 1 perturbing field is applied by the trim coils, a large n/m = 1/2 island chain will be opened. This island chain is used to create a perturbation large enough to be imaged by the diagnostic. Phase and amplitude scans of the applied field allow the measurement of a small $$\sim 0.04$$ m intrinsic island chain with a $${{130}^{\circ}}$$ phase relative to the first module of the W7-X experiment. Lastly, these error fields are determined to be small and easily correctable by the trim coil system.
Authors:
 [1] ;  [2] ;  [2] ;  [2] ;  [2]
  1. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
  2. Max-Planck-Institut fur Plasmaphysik, Greifswald (Germany)
Publication Date:
Report Number(s):
5233
Journal ID: ISSN 0029-5515
Grant/Contract Number:
AC02-09CH11466
Type:
Accepted Manuscript
Journal Name:
Nuclear Fusion
Additional Journal Information:
Journal Volume: 56; Journal Issue: 10; Journal ID: ISSN 0029-5515
Publisher:
IOP Science
Research Org:
Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
Sponsoring Org:
USDOE Office of Science (SC), Fusion Energy Sciences (FES) (SC-24)
Contributing Orgs:
The W7-X Team
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; stellarator; error fields; flux surface mapping; W7-X
OSTI Identifier:
1335163
Alternate Identifier(s):
OSTI ID: 1281330

Lazerson, Samuel A., Otte, Matthias, Bozhenkov, Sergey, Biedermann, Christoph, and Pedersen, Thomas Sunn. First measurements of error fields on W7-X using flux surface mapping. United States: N. p., Web. doi:10.1088/0029-5515/56/10/106005.
Lazerson, Samuel A., Otte, Matthias, Bozhenkov, Sergey, Biedermann, Christoph, & Pedersen, Thomas Sunn. First measurements of error fields on W7-X using flux surface mapping. United States. doi:10.1088/0029-5515/56/10/106005.
Lazerson, Samuel A., Otte, Matthias, Bozhenkov, Sergey, Biedermann, Christoph, and Pedersen, Thomas Sunn. 2016. "First measurements of error fields on W7-X using flux surface mapping". United States. doi:10.1088/0029-5515/56/10/106005. https://www.osti.gov/servlets/purl/1335163.
@article{osti_1335163,
title = {First measurements of error fields on W7-X using flux surface mapping},
author = {Lazerson, Samuel A. and Otte, Matthias and Bozhenkov, Sergey and Biedermann, Christoph and Pedersen, Thomas Sunn},
abstractNote = {Error fields have been detected and quantified using the flux surface mapping diagnostic system on Wendelstein 7-X (W7-X). A low-field '${\rlap{-}\ \iota} =1/2$ ' magnetic configuration (${\rlap{-}\ \iota} =\iota /2\pi $ ), sensitive to error fields, was developed in order to detect their presence using the flux surface mapping diagnostic. In this configuration, a vacuum flux surface with rotational transform of n/m = 1/2 is created at the mid-radius of the vacuum flux surfaces. If no error fields are present a vanishingly small n/m = 5/10 island chain should be present. Modeling indicates that if an n = 1 perturbing field is applied by the trim coils, a large n/m = 1/2 island chain will be opened. This island chain is used to create a perturbation large enough to be imaged by the diagnostic. Phase and amplitude scans of the applied field allow the measurement of a small $\sim 0.04$ m intrinsic island chain with a ${{130}^{\circ}}$ phase relative to the first module of the W7-X experiment. Lastly, these error fields are determined to be small and easily correctable by the trim coil system.},
doi = {10.1088/0029-5515/56/10/106005},
journal = {Nuclear Fusion},
number = 10,
volume = 56,
place = {United States},
year = {2016},
month = {8}
}