Measurements of plasma parameters in the divertor island of Wendelstein 7-X through line-ratio spectroscopy on helium

Barbui, Tullio; Krychowiak, Maciej; Schmitz, Oliver; Bozhenkov, Sergey A.; Flom, Erik; Fuchert, Golo; Killer, Carsten; Koenig, Ralf; Jakubowski, Marcin; Munoz-Burgos, Jorge; Pasch, Ekkehard; Scott, Evan R.

doi:10.1088/1741-4326/aba9eb

Title: Measurements of plasma parameters in the divertor island of Wendelstein 7-X through line-ratio spectroscopy on helium

Abstract

We report electron temperature T_e and density n_e have been measured in the divertor island of Wendelstein 7-X by means of a new thermal He-beam system utilizing line-ratio spectroscopy. This system is equipped with a poloidal arrangement of five gas valves that allows to infer 2D plasma profiles T_e(R,Z) and n_e(R,Z) across the magnetic island forming the island divertor. A local maximum in T_e(R,Z) was measured along the flux surfaces located between the island center and the outer separatrix. In the island center, characterized by closed field lines, a clear local minimum in T_e was measured, indicating that no direct heat deposition occurs in this region and that the perpendicular heat flux from the core plasma into this domain is small. Increasing the island size leads to a reduction of the connection length in the scrape-off layer (SOL) and to a shift of the island center towards the divertor target. In this scenario, the T_e(R,Z) are reduced in the entire island domain. Density profiles are found flat across the divertor island for both island size scenarios. These findings are supported by similar observations made with a reciprocating probe plunging through the same SOL island at the mid-plane of W7-X representingmore »« less

Authors:

^[1]; Krychowiak, Maciej ^[2];

^[1];

^[2]; Flom, Erik ^[1]; Fuchert, Golo ^[2];

^[2]; Koenig, Ralf ^[2]; Jakubowski, Marcin ^[2]; Munoz-Burgos, Jorge ^[3]; Pasch, Ekkehard ^[2]; Scott, Evan R. ^[2]

Univ. of Wisconsin, Madison, WI (United States)
Max-Planck-Institut für Plasmaphysik, Greifswald (Germany)
Astro Fusion Spectre LLC, San Diego, CA (United States)

Publication Date:: Fri Sep 04 00:00:00 EDT 2020

Research Org.:: Univ. of Wisconsin, Madison, WI (United States)

Sponsoring Org.:: USDOE Office of Science (SC), Fusion Energy Sciences (FES); European Commission (EC)

Contributing Org.:: EUROfusion Consortium; W7-X Team

OSTI Identifier:: 1658804

Grant/Contract Number:: SC0014210; 633053

Resource Type:: Accepted Manuscript

Journal Name:: Nuclear Fusion

Additional Journal Information:: Journal Volume: 60; Journal Issue: 10; Journal ID: ISSN 0029-5515

Publisher:: IOP Science

Country of Publication:: United States

Language:: English

Subject:: 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; stellarator; island divertor; emission spectroscopy

Citation Formats


                    Barbui, Tullio, Krychowiak, Maciej, Schmitz, Oliver, Bozhenkov, Sergey A., Flom, Erik, Fuchert, Golo, Killer, Carsten, Koenig, Ralf, Jakubowski, Marcin, Munoz-Burgos, Jorge, Pasch, Ekkehard, and Scott, Evan R. Measurements of plasma parameters in the divertor island of Wendelstein 7-X through line-ratio spectroscopy on helium.  United States: N. p., 2020. 
Web.  doi:10.1088/1741-4326/aba9eb.

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                    Barbui, Tullio, Krychowiak, Maciej, Schmitz, Oliver, Bozhenkov, Sergey A., Flom, Erik, Fuchert, Golo, Killer, Carsten, Koenig, Ralf, Jakubowski, Marcin, Munoz-Burgos, Jorge, Pasch, Ekkehard, & Scott, Evan R. Measurements of plasma parameters in the divertor island of Wendelstein 7-X through line-ratio spectroscopy on helium.  United States.  https://doi.org/10.1088/1741-4326/aba9eb

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                    Barbui, Tullio, Krychowiak, Maciej, Schmitz, Oliver, Bozhenkov, Sergey A., Flom, Erik, Fuchert, Golo, Killer, Carsten, Koenig, Ralf, Jakubowski, Marcin, Munoz-Burgos, Jorge, Pasch, Ekkehard, and Scott, Evan R. Fri .  
"Measurements of plasma parameters in the divertor island of Wendelstein 7-X through line-ratio spectroscopy on helium".  United States.  https://doi.org/10.1088/1741-4326/aba9eb.  https://www.osti.gov/servlets/purl/1658804.

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@article{osti_1658804,

  title        = {Measurements of plasma parameters in the divertor island of Wendelstein 7-X through line-ratio spectroscopy on helium},

  author       = {Barbui, Tullio and Krychowiak, Maciej and Schmitz, Oliver and Bozhenkov, Sergey A. and Flom, Erik and Fuchert, Golo and Killer, Carsten and Koenig, Ralf and Jakubowski, Marcin and Munoz-Burgos, Jorge and Pasch, Ekkehard and Scott, Evan R.},

  abstractNote = {We report electron temperature Te and density ne have been measured in the divertor island of Wendelstein 7-X by means of a new thermal He-beam system utilizing line-ratio spectroscopy. This system is equipped with a poloidal arrangement of five gas valves that allows to infer 2D plasma profiles Te(R,Z) and ne(R,Z) across the magnetic island forming the island divertor. A local maximum in Te(R,Z) was measured along the flux surfaces located between the island center and the outer separatrix. In the island center, characterized by closed field lines, a clear local minimum in Te was measured, indicating that no direct heat deposition occurs in this region and that the perpendicular heat flux from the core plasma into this domain is small. Increasing the island size leads to a reduction of the connection length in the scrape-off layer (SOL) and to a shift of the island center towards the divertor target. In this scenario, the Te(R,Z) are reduced in the entire island domain. Density profiles are found flat across the divertor island for both island size scenarios. These findings are supported by similar observations made with a reciprocating probe plunging through the same SOL island at the mid-plane of W7-X representing the upstream position in this 3D divertor geometry.},

  doi          = {10.1088/1741-4326/aba9eb},

  journal      = {Nuclear Fusion},

  number       = 10,

  volume       = 60,

  place        = {United States},

  year         = {Fri Sep 04 00:00:00 EDT 2020},

  month        = {Fri Sep 04 00:00:00 EDT 2020}

}

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Title: Measurements of plasma parameters in the divertor island of Wendelstein 7-X through line-ratio spectroscopy on helium

Abstract

Citation Formats

Physics of island divertors as highlighted by the example of W7-AS journal, July 2006

Hybrid time dependent/independent solution for the He I line ratio temperature and density diagnostic for a thermal helium beam with applications in the scrape-off layer-edge regions in tokamaks journal, January 2012

Instantaneous Direct‐Display System of Plasma Parameters by Means of Triple Probe journal, August 1965

Design criteria of the bolometer diagnostic for steady-state operation of the W7-X stellarator journal, October 2010

The divertor program in stellarators journal, October 2002

Temperature profile perturbations due to magnetic islands in TEXTOR journal, March 1997

Edge plasma measurements on the OP 1.2a divertor plasmas at W7-X using the combined probe journal, May 2019

The capabilities of steady state operation at the stellarator W7-X with emphasis on divertor design journal, June 2000

Technical challenges in the construction of the steady-state stellarator Wendelstein 7-X journal, November 2013

Island divertor studies on W7-AS journal, February 1997

Drift effects on W7-X divertor heat and particle fluxes journal, October 2019

Aspects of steady-state operation of the Wendelstein 7-X stellarator journal, December 2012

Qualification and implementation of line ratio spectroscopy on helium as plasma edge diagnostic at ASDEX Upgrade journal, December 2017

Identification and analysis of transport domains in the stochastic boundary of TEXTOR-DED for different mode spectra journal, January 2008

Comparison between stellarator and tokamak divertor transport journal, January 2011

Three-dimensional scrape off layer transport in the helically symmetric experiment HSX journal, June 2016

A multi-purpose manipulator system for W7-X as user facility for plasma edge investigation journal, November 2017

Snakes [JET resonant localised structures] journal, November 1995

Feasibility of line-ratio spectroscopy on helium and neon as edge diagnostic tool for Wendelstein 7-X journal, September 2016

Effect of toroidal plasma currents on the Wendelstein 7-X Scrape-Off Layer journal, November 2019

Characterization of the W7-X scrape-off layer using reciprocating probes journal, June 2019

Bayesian modelling of a thermal helium beam for measurement of electron density and temperature in the W7-X divertor plasma journal, February 2011

Radial electric field and transport near the rational surface and the magnetic island in LHD journal, January 2004

Impact of boronizations on impurity sources and performance in Wendelstein 7-X journal, July 2020

The Thomson scattering system at Wendelstein 7-X journal, September 2016

Physics of island divertors as highlighted by the example of W7-AS
journal, July 2006

Hybrid time dependent/independent solution for the He I line ratio temperature and density diagnostic for a thermal helium beam with applications in the scrape-off layer-edge regions in tokamaks
journal, January 2012

Instantaneous Direct‐Display System of Plasma Parameters by Means of Triple Probe
journal, August 1965

Design criteria of the bolometer diagnostic for steady-state operation of the W7-X stellarator
journal, October 2010

The divertor program in stellarators
journal, October 2002

Temperature profile perturbations due to magnetic islands in TEXTOR
journal, March 1997

Edge plasma measurements on the OP 1.2a divertor plasmas at W7-X using the combined probe
journal, May 2019

The capabilities of steady state operation at the stellarator W7-X with emphasis on divertor design
journal, June 2000

Technical challenges in the construction of the steady-state stellarator Wendelstein 7-X
journal, November 2013

Island divertor studies on W7-AS
journal, February 1997

Drift effects on W7-X divertor heat and particle fluxes
journal, October 2019

Aspects of steady-state operation of the Wendelstein 7-X stellarator
journal, December 2012

Qualification and implementation of line ratio spectroscopy on helium as plasma edge diagnostic at ASDEX Upgrade
journal, December 2017

Identification and analysis of transport domains in the stochastic boundary of TEXTOR-DED for different mode spectra
journal, January 2008

Comparison between stellarator and tokamak divertor transport
journal, January 2011

Three-dimensional scrape off layer transport in the helically symmetric experiment HSX
journal, June 2016

A multi-purpose manipulator system for W7-X as user facility for plasma edge investigation
journal, November 2017

Snakes [JET resonant localised structures]
journal, November 1995

Feasibility of line-ratio spectroscopy on helium and neon as edge diagnostic tool for Wendelstein 7-X
journal, September 2016

Effect of toroidal plasma currents on the Wendelstein 7-X Scrape-Off Layer
journal, November 2019

Characterization of the W7-X scrape-off layer using reciprocating probes
journal, June 2019

Bayesian modelling of a thermal helium beam for measurement of electron density and temperature in the W7-X divertor plasma
journal, February 2011

Radial electric field and transport near the rational surface and the magnetic island in LHD
journal, January 2004

Impact of boronizations on impurity sources and performance in Wendelstein 7-X
journal, July 2020

The Thomson scattering system at Wendelstein 7-X
journal, September 2016