Overview of first Wendelstein 7-X high-performance operation

Wendelstein 7-X Team, I. Abramovic, J. Proll

Research output: Contribution to journalReview articleAcademicpeer-review

10 Citations (Scopus)
4 Downloads (Pure)

Abstract

The optimized superconducting stellarator device Wendelstein 7-X (with major radius R = 5.5 m, minor radius a = 0.5 m, and 30 m3 plasma volume) restarted operation after the assembly of a graphite heat shield and 10 inertially cooled island divertor modules. This paper reports on the results from the first high-performance plasma operation. Glow discharge conditioning and ECRH conditioning discharges in helium turned out to be important for density and edge radiation control. Plasma densities of 1-4.5 × 1019 m-3 with central electron temperatures 5-10 keV were routinely achieved with hydrogen gas fueling, frequently terminated by a radiative collapse. In a first stage, plasma densities up to 1.4 × 1020 m-3 were reached with hydrogen pellet injection and helium gas fueling. Here, the ions are indirectly heated, and at a central density of 8 · 1019 m-3 a temperature of 3.4 keV with Te/Ti = 1 was transiently accomplished, which corresponds to nTi(0)TE = 6.4 × 1019 keV s m-3 with a peak diamagnetic energy of 1.1 MJ and volume-averaged normalized plasma pressure {B}= 1.2%. The routine access to high plasma densities was opened with boronization of the first wall. After boronization, the oxygen impurity content was reduced by a factor of 10, the carbon impurity content by a factor of 5. The reduced (edge) plasma radiation level gives routinely access to higher densities without radiation collapse, e.g. well above 1 × 1020 m-2 line integrated density and Te = Ti = 2 keV central temperatures at moderate ECRH power. Both X2 and O2 mode ECRH schemes were successfully applied. Core turbulence was measured with a phase contrast imaging diagnostic and suppression of turbulence during pellet injection was observed.

Original languageEnglish
Article number112004
Number of pages11
JournalNuclear Fusion
Volume59
Issue number11
DOIs
Publication statusPublished - 5 Jun 2019

Fingerprint

plasma density
refueling
conditioning
pellets
turbulence
helium
injection
plasma radiation
impurities
radii
plasma pressure
stellarators
phase contrast
hydrogen
radiation
gases
glow discharges
graphite
assembly
modules

Keywords

  • divertor
  • ECR heating
  • impurities
  • NBI heating
  • plasma performance
  • stellarator
  • turbulence

Cite this

@article{c25dedda85434fc1b86fe32fad2bac22,
title = "Overview of first Wendelstein 7-X high-performance operation",
abstract = "The optimized superconducting stellarator device Wendelstein 7-X (with major radius R = 5.5 m, minor radius a = 0.5 m, and 30 m3 plasma volume) restarted operation after the assembly of a graphite heat shield and 10 inertially cooled island divertor modules. This paper reports on the results from the first high-performance plasma operation. Glow discharge conditioning and ECRH conditioning discharges in helium turned out to be important for density and edge radiation control. Plasma densities of 1-4.5 × 1019 m-3 with central electron temperatures 5-10 keV were routinely achieved with hydrogen gas fueling, frequently terminated by a radiative collapse. In a first stage, plasma densities up to 1.4 × 1020 m-3 were reached with hydrogen pellet injection and helium gas fueling. Here, the ions are indirectly heated, and at a central density of 8 · 1019 m-3 a temperature of 3.4 keV with Te/Ti = 1 was transiently accomplished, which corresponds to nTi(0)TE = 6.4 × 1019 keV s m-3 with a peak diamagnetic energy of 1.1 MJ and volume-averaged normalized plasma pressure {B}= 1.2{\%}. The routine access to high plasma densities was opened with boronization of the first wall. After boronization, the oxygen impurity content was reduced by a factor of 10, the carbon impurity content by a factor of 5. The reduced (edge) plasma radiation level gives routinely access to higher densities without radiation collapse, e.g. well above 1 × 1020 m-2 line integrated density and Te = Ti = 2 keV central temperatures at moderate ECRH power. Both X2 and O2 mode ECRH schemes were successfully applied. Core turbulence was measured with a phase contrast imaging diagnostic and suppression of turbulence during pellet injection was observed.",
keywords = "divertor, ECR heating, impurities, NBI heating, plasma performance, stellarator, turbulence",
author = "{Wendelstein 7-X Team} and T. Klinger and T. Andreeva and S. Bozhenkov and C. Brandt and R. Burhenn and B. Buttensch{\"o}n and G. Fuchert and B. Geiger and O. Grulke and Laqua, {H. P.} and N. Pablant and K. Rahbarnia and T. Stange and {Von Stechow}, A. and N. Tamura and H. Thomsen and Y. Turkin and T. Wegner and I. Abramovic and S. Akaslompolo and J. Alcuson and P. Aleynikov and K. Aleynikova and A. Ali and A. Alonso and G. Anda and E. Ascasibar and Bahner, {J. P.} and Baek, {S. G.} and M. Balden and J. Baldzuhn and M. Banduch and T. Barbui and W. Behr and C. Beidler and A. Benndorf and C. Biedermann and W. Biel and B. Blackwell and M. Beurskens and J. Coenen and A. Langenberg and S. Liu and Oosterbeek, {J. W.} and J. Proll and H. Schmitz and M. Schneider and R. Schroeder and H. Schumacher and A. Werner",
year = "2019",
month = "6",
day = "5",
doi = "10.1088/1741-4326/ab03a7",
language = "English",
volume = "59",
journal = "Nuclear Fusion",
issn = "0029-5515",
publisher = "Institute of Physics",
number = "11",

}

Overview of first Wendelstein 7-X high-performance operation. / Wendelstein 7-X Team ; Abramovic, I.; Proll, J.

In: Nuclear Fusion, Vol. 59, No. 11, 112004, 05.06.2019.

Research output: Contribution to journalReview articleAcademicpeer-review

TY - JOUR

T1 - Overview of first Wendelstein 7-X high-performance operation

AU - Wendelstein 7-X Team

AU - Klinger, T.

AU - Andreeva, T.

AU - Bozhenkov, S.

AU - Brandt, C.

AU - Burhenn, R.

AU - Buttenschön, B.

AU - Fuchert, G.

AU - Geiger, B.

AU - Grulke, O.

AU - Laqua, H. P.

AU - Pablant, N.

AU - Rahbarnia, K.

AU - Stange, T.

AU - Von Stechow, A.

AU - Tamura, N.

AU - Thomsen, H.

AU - Turkin, Y.

AU - Wegner, T.

AU - Abramovic, I.

AU - Akaslompolo, S.

AU - Alcuson, J.

AU - Aleynikov, P.

AU - Aleynikova, K.

AU - Ali, A.

AU - Alonso, A.

AU - Anda, G.

AU - Ascasibar, E.

AU - Bahner, J. P.

AU - Baek, S. G.

AU - Balden, M.

AU - Baldzuhn, J.

AU - Banduch, M.

AU - Barbui, T.

AU - Behr, W.

AU - Beidler, C.

AU - Benndorf, A.

AU - Biedermann, C.

AU - Biel, W.

AU - Blackwell, B.

AU - Beurskens, M.

AU - Coenen, J.

AU - Langenberg, A.

AU - Liu, S.

AU - Oosterbeek, J. W.

AU - Proll, J.

AU - Schmitz, H.

AU - Schneider, M.

AU - Schroeder, R.

AU - Schumacher, H.

AU - Werner, A.

PY - 2019/6/5

Y1 - 2019/6/5

N2 - The optimized superconducting stellarator device Wendelstein 7-X (with major radius R = 5.5 m, minor radius a = 0.5 m, and 30 m3 plasma volume) restarted operation after the assembly of a graphite heat shield and 10 inertially cooled island divertor modules. This paper reports on the results from the first high-performance plasma operation. Glow discharge conditioning and ECRH conditioning discharges in helium turned out to be important for density and edge radiation control. Plasma densities of 1-4.5 × 1019 m-3 with central electron temperatures 5-10 keV were routinely achieved with hydrogen gas fueling, frequently terminated by a radiative collapse. In a first stage, plasma densities up to 1.4 × 1020 m-3 were reached with hydrogen pellet injection and helium gas fueling. Here, the ions are indirectly heated, and at a central density of 8 · 1019 m-3 a temperature of 3.4 keV with Te/Ti = 1 was transiently accomplished, which corresponds to nTi(0)TE = 6.4 × 1019 keV s m-3 with a peak diamagnetic energy of 1.1 MJ and volume-averaged normalized plasma pressure {B}= 1.2%. The routine access to high plasma densities was opened with boronization of the first wall. After boronization, the oxygen impurity content was reduced by a factor of 10, the carbon impurity content by a factor of 5. The reduced (edge) plasma radiation level gives routinely access to higher densities without radiation collapse, e.g. well above 1 × 1020 m-2 line integrated density and Te = Ti = 2 keV central temperatures at moderate ECRH power. Both X2 and O2 mode ECRH schemes were successfully applied. Core turbulence was measured with a phase contrast imaging diagnostic and suppression of turbulence during pellet injection was observed.

AB - The optimized superconducting stellarator device Wendelstein 7-X (with major radius R = 5.5 m, minor radius a = 0.5 m, and 30 m3 plasma volume) restarted operation after the assembly of a graphite heat shield and 10 inertially cooled island divertor modules. This paper reports on the results from the first high-performance plasma operation. Glow discharge conditioning and ECRH conditioning discharges in helium turned out to be important for density and edge radiation control. Plasma densities of 1-4.5 × 1019 m-3 with central electron temperatures 5-10 keV were routinely achieved with hydrogen gas fueling, frequently terminated by a radiative collapse. In a first stage, plasma densities up to 1.4 × 1020 m-3 were reached with hydrogen pellet injection and helium gas fueling. Here, the ions are indirectly heated, and at a central density of 8 · 1019 m-3 a temperature of 3.4 keV with Te/Ti = 1 was transiently accomplished, which corresponds to nTi(0)TE = 6.4 × 1019 keV s m-3 with a peak diamagnetic energy of 1.1 MJ and volume-averaged normalized plasma pressure {B}= 1.2%. The routine access to high plasma densities was opened with boronization of the first wall. After boronization, the oxygen impurity content was reduced by a factor of 10, the carbon impurity content by a factor of 5. The reduced (edge) plasma radiation level gives routinely access to higher densities without radiation collapse, e.g. well above 1 × 1020 m-2 line integrated density and Te = Ti = 2 keV central temperatures at moderate ECRH power. Both X2 and O2 mode ECRH schemes were successfully applied. Core turbulence was measured with a phase contrast imaging diagnostic and suppression of turbulence during pellet injection was observed.

KW - divertor

KW - ECR heating

KW - impurities

KW - NBI heating

KW - plasma performance

KW - stellarator

KW - turbulence

UR - http://www.scopus.com/inward/record.url?scp=85070780303&partnerID=8YFLogxK

U2 - 10.1088/1741-4326/ab03a7

DO - 10.1088/1741-4326/ab03a7

M3 - Review article

AN - SCOPUS:85070780303

VL - 59

JO - Nuclear Fusion

JF - Nuclear Fusion

SN - 0029-5515

IS - 11

M1 - 112004

ER -