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Title: Tuning of the rotational transform in Wendelstein 7-X

Abstract

The control of rotational transform in Wendelstein 7-X (W7-X) is key to the island divertor operation and safety of plasma facing components. The island divertor concept in W7-X relies on an edge flux surface with rotational transform of $t$ = 1 resonating with an intrinsic n/m= 5/5 resonance to form a five lobed island chain. This island chain intersects with divertor plates to give rise to the island divertor. Changes in the relative position of the rational surface and the divertor plates can result in changes in divertor performance, thus the control of the rotational transform is essential to operation of the W7-X device. During the first divertor campaign electromagnetic loads resulted in elastic deformations of the shaped modular stellarator coils. Such deformations made these coils more planar, reducing the vacuum rotational transform, subsequently shifting the $t$ = 1 resonance outward. Unintended plasma wall interactions provided the first clear evidence of this effect during plasma operation. Flux surface measurements were utilized to estimate the correct level of current in the planar coils for correction of $t$, and found to be around ~-100 A. Scans of the planar coil current for iota correction were performed during plasma operation. These measurements suggestmore » planar coil currents between -250 and ~ 0 A would place the strike lines at the designed distance from the pumping gaps. Divertor Langmuir and upstream probe measurements confirm these estimates along with measurements of divertor neutral gas pressure.« less

Authors:
ORCiD logo [1]; ORCiD logo [2]; ORCiD logo [3]; ORCiD logo [3]; ORCiD logo [3];  [3];  [3];  [4]; ORCiD logo [3];  [3];  [3];  [2];  [2];  [3];  [3];  [3];  [3];  [3];  [5]; ORCiD logo [5] more »;  [3]; ORCiD logo [6];  [7];  [7]; ORCiD logo [3];  [3];  [3];  [3];  [3];  [3];  [3];  [3];  [3];  [8];  [3];  [3];  [3] « less
  1. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
  2. Forschungszentrum Jülich, Jülich (Germany)
  3. Max-Planck-Inst. für Plasmaphysik, Greifswald (Germany)
  4. Consorzio RFX, Padua (Italy)
  5. Univ. of Cagliari, Cagliari (Italy)
  6. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  7. Wigner Research Center for Physics, Budapest (Hungary)
  8. The Australian National Univ., Canberra (Australia). Plasma Research Lab., Research School of Physical Sciences and Engineering
Publication Date:
Research Org.:
Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Fusion Energy Sciences (FES) (SC-24)
Contributing Org.:
Max-Planck-Inst. für Plasmaphysik, Greifswald (Germany). The W7-X Team
OSTI Identifier:
1562295
Alternate Identifier(s):
OSTI ID: 1565871
Report Number(s):
LA-UR-19-23949
Journal ID: ISSN 0029-5515
Grant/Contract Number:  
AC02-09CH11466; 89233218CNA000001
Resource Type:
Accepted Manuscript
Journal Name:
Nuclear Fusion
Additional Journal Information:
Journal Volume: 59; Journal Issue: 12; Journal ID: ISSN 0029-5515
Publisher:
IOP Science
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; Magnetic Fusion Energy

Citation Formats

Lazerson, Samuel A., Gao, Yu, Hammond, Kenneth, Killer, Carsten, Schlisio, Georg, Otte, Matthias, Biedermann, Christoph, Spolaore, Monica, Bozhenkov, Sergey, Geiger, Joachim, Grulke, Olaf, Nicolai, Dirk, Satheeswaran, Guruparan, Niemann, Holger, Jakubowski, Marcin, Drewelow, Peter, Sitjes, Aleix Puig, Ali, Adnan, Cannas, Barbara, Pisano, Fabio, König, Ralph, Wurden, Glen, Kocsis, Gabor, Szepesi, Tamás, Wenzel, Uwe, Mulsow, Matthias, Rahbarnia, Kian, Schilling, Jonathan, Neuner, Ulrich, Andreeva, Tamara, Thomsen, Henning, Knauer, Jens, Brunner, Kai Jakob, Blackwell, Boyd, Endler, Michael, Klose, Soren, and Rudischhauser, Lukas. Tuning of the rotational transform in Wendelstein 7-X. United States: N. p., 2019. Web. doi:10.1088/1741-4326/ab3df0.
Lazerson, Samuel A., Gao, Yu, Hammond, Kenneth, Killer, Carsten, Schlisio, Georg, Otte, Matthias, Biedermann, Christoph, Spolaore, Monica, Bozhenkov, Sergey, Geiger, Joachim, Grulke, Olaf, Nicolai, Dirk, Satheeswaran, Guruparan, Niemann, Holger, Jakubowski, Marcin, Drewelow, Peter, Sitjes, Aleix Puig, Ali, Adnan, Cannas, Barbara, Pisano, Fabio, König, Ralph, Wurden, Glen, Kocsis, Gabor, Szepesi, Tamás, Wenzel, Uwe, Mulsow, Matthias, Rahbarnia, Kian, Schilling, Jonathan, Neuner, Ulrich, Andreeva, Tamara, Thomsen, Henning, Knauer, Jens, Brunner, Kai Jakob, Blackwell, Boyd, Endler, Michael, Klose, Soren, & Rudischhauser, Lukas. Tuning of the rotational transform in Wendelstein 7-X. United States. doi:10.1088/1741-4326/ab3df0.
Lazerson, Samuel A., Gao, Yu, Hammond, Kenneth, Killer, Carsten, Schlisio, Georg, Otte, Matthias, Biedermann, Christoph, Spolaore, Monica, Bozhenkov, Sergey, Geiger, Joachim, Grulke, Olaf, Nicolai, Dirk, Satheeswaran, Guruparan, Niemann, Holger, Jakubowski, Marcin, Drewelow, Peter, Sitjes, Aleix Puig, Ali, Adnan, Cannas, Barbara, Pisano, Fabio, König, Ralph, Wurden, Glen, Kocsis, Gabor, Szepesi, Tamás, Wenzel, Uwe, Mulsow, Matthias, Rahbarnia, Kian, Schilling, Jonathan, Neuner, Ulrich, Andreeva, Tamara, Thomsen, Henning, Knauer, Jens, Brunner, Kai Jakob, Blackwell, Boyd, Endler, Michael, Klose, Soren, and Rudischhauser, Lukas. Tue . "Tuning of the rotational transform in Wendelstein 7-X". United States. doi:10.1088/1741-4326/ab3df0.
@article{osti_1562295,
title = {Tuning of the rotational transform in Wendelstein 7-X},
author = {Lazerson, Samuel A. and Gao, Yu and Hammond, Kenneth and Killer, Carsten and Schlisio, Georg and Otte, Matthias and Biedermann, Christoph and Spolaore, Monica and Bozhenkov, Sergey and Geiger, Joachim and Grulke, Olaf and Nicolai, Dirk and Satheeswaran, Guruparan and Niemann, Holger and Jakubowski, Marcin and Drewelow, Peter and Sitjes, Aleix Puig and Ali, Adnan and Cannas, Barbara and Pisano, Fabio and König, Ralph and Wurden, Glen and Kocsis, Gabor and Szepesi, Tamás and Wenzel, Uwe and Mulsow, Matthias and Rahbarnia, Kian and Schilling, Jonathan and Neuner, Ulrich and Andreeva, Tamara and Thomsen, Henning and Knauer, Jens and Brunner, Kai Jakob and Blackwell, Boyd and Endler, Michael and Klose, Soren and Rudischhauser, Lukas},
abstractNote = {The control of rotational transform in Wendelstein 7-X (W7-X) is key to the island divertor operation and safety of plasma facing components. The island divertor concept in W7-X relies on an edge flux surface with rotational transform of $t$ = 1 resonating with an intrinsic n/m= 5/5 resonance to form a five lobed island chain. This island chain intersects with divertor plates to give rise to the island divertor. Changes in the relative position of the rational surface and the divertor plates can result in changes in divertor performance, thus the control of the rotational transform is essential to operation of the W7-X device. During the first divertor campaign electromagnetic loads resulted in elastic deformations of the shaped modular stellarator coils. Such deformations made these coils more planar, reducing the vacuum rotational transform, subsequently shifting the $t$ = 1 resonance outward. Unintended plasma wall interactions provided the first clear evidence of this effect during plasma operation. Flux surface measurements were utilized to estimate the correct level of current in the planar coils for correction of $t$, and found to be around ~-100 A. Scans of the planar coil current for iota correction were performed during plasma operation. These measurements suggest planar coil currents between -250 and ~ 0 A would place the strike lines at the designed distance from the pumping gaps. Divertor Langmuir and upstream probe measurements confirm these estimates along with measurements of divertor neutral gas pressure.},
doi = {10.1088/1741-4326/ab3df0},
journal = {Nuclear Fusion},
number = 12,
volume = 59,
place = {United States},
year = {2019},
month = {9}
}

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