Turbulence-reduced high-performance scenarios in Wendelstein 7-X

Ford, O. P.; Beurskens, M.; Bozhenkov, S. A.; Lazerson, S.; Vanó, L.; Alonso, A.; Baldzuhn, J.; Beidler, C. D.; Biedermann, C.; Burhenn, R.; Fuchert, G.; Hartmann, D.; Hirsch, M.; Langenberg, A.; Laqua, H.; McNeely, P.; Pablant, N.; Pasch, E.; Reimold, F.; Romba, T.; Rust, N.; Schroeder, R.; Scott, E. R.; Stange, T.; Smith, H. M.; Gradic, D.; Wolf, R. C.; Zhang, D.

doi:10.1088/1741-4326/ad5e99

Turbulence-reduced high-performance scenarios in Wendelstein 7-X

Journal Article · Mon Jul 15 00:00:00 EDT 2024 · Nuclear Fusion

DOI:https://doi.org/10.1088/1741-4326/ad5e99· OSTI ID:2426360

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Max Planck Institute for Plasma Physics, Greifswald (Germany)
Research Centre for Energy, Environment and Technology (CIEMAT), Madrid (Spain)
Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)

In the Wendelstein 7-X (W7-X) stellarator, turbulence is the dominant transport mechanism in most discharges. This leads to a 'clamping' of ion temperature over a wide range of heating power, predominantly flat density profiles where hollow profiles driven by neoclassical thermo-diffusion would be expected and by rapid impurity transport in injection experiments. Significantly reduced turbulent transport is observed in the presence of strong core density gradients found transiently after core pellet injection and irregularly after boronisation or boron pellet injection. Density peaking is also achieved in a controlled manner in purely neutral beam heated discharges where particle transport analysis reveals an abrupt reduction in the main-ion particle flux leading to significant density profile peaking not explained by the NBI particle source alone. The plasmas exhibit a heat diffusivity of around $$\chi = 0.25 \pm 0.1\,\mathrm{m}^2\ \mathrm{s}^{-1}$$ at mid radius, a factor of around 4 lower than ECRH dominated discharges. Despite the improved confinement, the achieved ion temperature is limited by broader heat deposition and the lower power-per-particle given the higher density. This is overcome with limited reintroduction of ECRH power, where the low heat diffusivity diffusivity is maintained, the density rise supressed and ion temperatures above the clamping limit are achieved. The applicability of these plasmas for a high performance scenario on transport relevant time scales is assessed, including initial predictions for planned heating upgrades of W7-X, based on a range of assumptions about particle transport.

View Accepted Manuscript (DOE)

Research Organization:: Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)

Sponsoring Organization:: USDOE

Contributing Organization:: W7-X Team

Grant/Contract Number:: AC02-09CH11466

OSTI ID:: 2426360

Journal Information:: Nuclear Fusion, Journal Name: Nuclear Fusion Journal Issue: 8 Vol. 64; ISSN 0029-5515

Publisher:: IOP ScienceCopyright Statement

Country of Publication:: United States

Language:: English

References (65)

Ray-tracing code TRAVIS for ECR heating, EC current drive and ECE diagnostic Marushchenko, N. B.; Turkin, Y.; Maassberg, H. Computer Physics Communications, Vol. 185, Issue 1 https://doi.org/10.1016/j.cpc.2013.09.002	journal	January 2014
Commissioning and initial operation of the W7-X neutral beam injection heating system McNeely, P.; Äkäslompolo, S.; Auerweck, W. Fusion Engineering and Design, Vol. 161 https://doi.org/10.1016/j.fusengdes.2020.111997	journal	December 2020
Performance of the first neutral beam injector at the Wendelstein 7-X stellarator Spanier, Annabelle; Hartmann, Dirk; Äkäslompolo, Simppa Fusion Engineering and Design, Vol. 163 https://doi.org/10.1016/j.fusengdes.2020.112115	journal	February 2021
Wendelstein 7-X on the path to long-pulse high-performance operation Endler, M.; Baldzuhn, J.; Beidler, C. D. Fusion Engineering and Design, Vol. 167 https://doi.org/10.1016/j.fusengdes.2021.112381	journal	June 2021
Phase contrast imaging measurements and numerical simulations of turbulent density fluctuations in gas-fuelled ECRH discharges in Wendelstein 7-X Bähner, J. -P.; Alcusón, J. A.; Hansen, S. K. Journal of Plasma Physics, Vol. 87, Issue 3 https://doi.org/10.1017/S0022377821000635	journal	June 2021
Demonstration of reduced neoclassical energy transport in Wendelstein 7-X Beidler, C. D.; Smith, H. M.; Alonso, A. Nature, Vol. 596, Issue 7871 https://doi.org/10.1038/s41586-021-03687-w	journal	August 2021
ECE Diagnostic for the initial Operation of Wendelstein 7-X Hirsch, Matthias; Höfel, Udo; Oosterbeek, Johan Willem EPJ Web of Conferences, Vol. 203 https://doi.org/10.1051/epjconf/201920303007	journal	January 2019
Neoclassical transport simulations for stellarators Turkin, Y.; Beidler, C. D.; Maaßberg, H. Physics of Plasmas, Vol. 18, Issue 2 https://doi.org/10.1063/1.3553025	journal	February 2011
Tomographic inversion techniques incorporating physical constraints for line integrated spectroscopy in stellarators and tokamaks Pablant, N. A.; Bell, R. E.; Bitter, M. Review of Scientific Instruments, Vol. 85, Issue 11 https://doi.org/10.1063/1.4891977	journal	November 2014
Key results from the first plasma operation phase and outlook for future performance in Wendelstein 7-X Sunn Pedersen, Thomas; Dinklage, Andreas; Turkin, Yuriy Physics of Plasmas, Vol. 24, Issue 5 https://doi.org/10.1063/1.4983629	journal	May 2017
Prospects of X-ray imaging spectrometers for impurity transport: Recent results from the stellarator Wendelstein 7-X (invited) Langenberg, A.; Pablant, N. A.; Wegner, Th. Review of Scientific Instruments, Vol. 89, Issue 10 https://doi.org/10.1063/1.5036536	journal	October 2018
Charge exchange recombination spectroscopy at Wendelstein 7-X Ford, O. P.; Vanó, L.; Alonso, J. A. Review of Scientific Instruments, Vol. 91, Issue 2 https://doi.org/10.1063/1.5132936	journal	February 2020
Variational bounds for transport coefficients in three‐dimensional toroidal plasmas van Rij, W. I.; Hirshman, S. P. Physics of Fluids B: Plasma Physics, Vol. 1, Issue 3 https://doi.org/10.1063/1.859116	journal	March 1989
Nondimensional transport scaling in DIII‐D: Bohm versus gyro‐Bohm resolved Petty, C. C.; Luce, T. C.; Burrell, K. H. Physics of Plasmas, Vol. 2, Issue 6 https://doi.org/10.1063/1.871259	journal	June 1995
Charge-state independent anomalous transport for a wide range of different impurity species observed at Wendelstein 7-X Langenberg, A.; Wegner, Th.; Pablant, N. A. Physics of Plasmas, Vol. 27, Issue 5 https://doi.org/10.1063/5.0004462	journal	May 2020
Correction and verification of x-ray imaging crystal spectrometer analysis on Wendelstein 7-X through x-ray ray tracing Pablant, N. A.; Langenberg, A.; Alonso, J. A. Review of Scientific Instruments, Vol. 92, Issue 4 https://doi.org/10.1063/5.0043513	journal	April 2021
Bayesian inference of spatially resolved Zeff profiles from line integrated bremsstrahlung spectra Kwak, Sehyun; Hergenhahn, U.; Höfel, U. Review of Scientific Instruments, Vol. 92, Issue 4 https://doi.org/10.1063/5.0043777	journal	April 2021
Characterization of injection and confinement improvement through impurity induced profile modifications on the Wendelstein 7-X stellarator Lunsford, R.; Killer, C.; Nagy, A. Physics of Plasmas, Vol. 28, Issue 8 https://doi.org/10.1063/5.0047274	journal	August 2021
Characterization of energy confinement in net-current free plasmas using the extended International Stellarator Database Yamada, H.; Harris, J. H.; Dinklage, A. Nuclear Fusion, Vol. 45, Issue 12 https://doi.org/10.1088/0029-5515/45/12/024	journal	November 2005
On impurity handling in high performance stellarator/heliotron plasmas Burhenn, R.; Feng, Y.; Ida, K. Nuclear Fusion, Vol. 49, Issue 6 https://doi.org/10.1088/0029-5515/49/6/065005	journal	April 2009
Assessment of the plasma start-up in Wendelstein 7-X with neutral beam injection Gradic, D.; Dinklage, A.; Brakel, R. Nuclear Fusion, Vol. 55, Issue 3 https://doi.org/10.1088/0029-5515/55/3/033002	journal	February 2015
Study of neutral hydrogen transport in LHD core plasmas based on high dynamic-range Balmer- α spectroscopy Fujii, K.; Goto, M.; Morita, S. Nuclear Fusion, Vol. 55, Issue 6 https://doi.org/10.1088/0029-5515/55/6/063029	journal	May 2015
Invariance principles and plasma confinement Connor, J. W. Plasma Physics and Controlled Fusion, Vol. 30, Issue 6 https://doi.org/10.1088/0741-3335/30/6/001	journal	June 1988
Density control problems in large stellarators with neoclassical transport Maaßberg, H.; Beidler, C. D.; Simmet, E. E. Plasma Physics and Controlled Fusion, Vol. 41, Issue 9 https://doi.org/10.1088/0741-3335/41/9/306	journal	August 1999
Major results from the stellarator Wendelstein 7-AS Hirsch, M.; Baldzuhn, J.; Beidler, C. Plasma Physics and Controlled Fusion, Vol. 50, Issue 5 https://doi.org/10.1088/0741-3335/50/5/053001	journal	March 2008
BEAMS3D Neutral Beam Injection Model McMillan, Matthew; Lazerson, Samuel A. Plasma Physics and Controlled Fusion, Vol. 56, Issue 9 https://doi.org/10.1088/0741-3335/56/9/095019	journal	July 2014
From W7-X to a HELIAS fusion power plant: motivation and options for an intermediate-step burning-plasma stellarator Warmer, F.; Beidler, C. D.; Dinklage, A. Plasma Physics and Controlled Fusion, Vol. 58, Issue 7 https://doi.org/10.1088/0741-3335/58/7/074006	journal	June 2016
(Expected difficulties with) density-profile control in W7-X high-performance plasmas Beidler, C. D.; Feng, Y.; Geiger, J. Plasma Physics and Controlled Fusion, Vol. 60, Issue 10 https://doi.org/10.1088/1361-6587/aad970	journal	August 2018
Electron-cyclotron-resonance heating in Wendelstein 7-X: A versatile heating and current-drive method and a tool for in-depth physics studies Wolf, R. C.; Bozhenkov, S.; Dinklage, A. Plasma Physics and Controlled Fusion, Vol. 61, Issue 1 https://doi.org/10.1088/1361-6587/aaeab2	journal	November 2018
Suppression of electrostatic micro-instabilities in maximum- J stellarators Alcusón, J. A.; Xanthopoulos, P.; Plunk, G. G. Plasma Physics and Controlled Fusion, Vol. 62, Issue 3 https://doi.org/10.1088/1361-6587/ab630e	journal	January 2020
Enhanced energy confinement after series of pellets in Wendelstein 7-X Baldzuhn, J.; Damm, H.; Beidler, C. D. Plasma Physics and Controlled Fusion, Vol. 62, Issue 5 https://doi.org/10.1088/1361-6587/ab8112	journal	April 2020
EMC3-EIRENE simulation of first wall recycling fluxes in W7-X with relation to H-alpha measurements Winters, V. R.; Reimold, F.; König, R. Plasma Physics and Controlled Fusion, Vol. 63, Issue 4 https://doi.org/10.1088/1361-6587/abe39c	journal	March 2021
Impurity transport studies at the HSX stellarator using active and passive CVI spectroscopy Swee, C.; Geiger, B.; Dux, R. Plasma Physics and Controlled Fusion, Vol. 64, Issue 1 https://doi.org/10.1088/1361-6587/ac3965	journal	November 2021
Impurity temperatures measured via line shape analysis in the island scrape-off-layer of Wendelstein 7-X Gradic, D.; Krychowiak, M.; König, R. Plasma Physics and Controlled Fusion, Vol. 64, Issue 7 https://doi.org/10.1088/1361-6587/ac70fa	journal	June 2022
Observation of impurity accumulation and its compatibility with high plasma performance in W7-X Zhang, D.; Buttenschön, B.; Jablonski, S. Plasma Physics and Controlled Fusion, Vol. 65, Issue 10 https://doi.org/10.1088/1361-6587/acf0e7	journal	August 2023
Major results from the first plasma campaign of the Wendelstein 7-X stellarator Wolf, R. C.; Ali, A.; Alonso, A. Nuclear Fusion, Vol. 57, Issue 10 https://doi.org/10.1088/1741-4326/aa770d	journal	July 2017
Observation of anomalous impurity transport during low-density experiments in W7-X with laser blow-off injections of iron Geiger, B.; Wegner, Th.; Beidler, C. D. Nuclear Fusion, Vol. 59, Issue 4 https://doi.org/10.1088/1741-4326/aaff71	journal	February 2019
Overview of first Wendelstein 7-X high-performance operation Klinger, T.; Andreeva, T.; Bozhenkov, S. Nuclear Fusion, Vol. 59, Issue 11 https://doi.org/10.1088/1741-4326/ab03a7	journal	June 2019
High-performance plasmas after pellet injections in Wendelstein 7-X Bozhenkov, S. A.; Kazakov, Y.; Ford, O. P. Nuclear Fusion, Vol. 60, Issue 6 https://doi.org/10.1088/1741-4326/ab7867	journal	May 2020
Validation of the BEAMS3D neutral beam deposition model on Wendelstein 7-X Lazerson, Samuel A.; Ford, Oliver P.; Nuehrenberg, Carolin Nuclear Fusion, Vol. 60, Issue 7 https://doi.org/10.1088/1741-4326/ab8e61	journal	June 2020
Impact of boronizations on impurity sources and performance in Wendelstein 7-X Sereda, S.; Brezinsek, S.; Wang, E. Nuclear Fusion, Vol. 60, Issue 8 https://doi.org/10.1088/1741-4326/ab937b	journal	July 2020
Radial electric field and density fluctuations measured by Doppler reflectometry during the post-pellet enhanced confinement phase in W7-X Estrada, T.; Carralero, D.; Windisch, T. Nuclear Fusion, Vol. 61, Issue 4 https://doi.org/10.1088/1741-4326/abddee	journal	March 2021
Modeling and measurement of energetic particle slowing down in Wendelstein 7-X Lazerson, Samuel A.; Pfefferlé, David; Drevlak, Michael Nuclear Fusion, Vol. 61, Issue 9 https://doi.org/10.1088/1741-4326/ac0771	journal	July 2021
An experimental characterization of core turbulence regimes in Wendelstein 7-X Carralero, D.; Estrada, T.; Maragkoudakis, E. Nuclear Fusion, Vol. 61, Issue 9 https://doi.org/10.1088/1741-4326/ac112f	journal	August 2021
First neutral beam experiments on Wendelstein 7-X Lazerson, Samuel A.; Ford, Oliver; Äkaslompolö, Simppa Nuclear Fusion, Vol. 61, Issue 9 https://doi.org/10.1088/1741-4326/ac121c	journal	July 2021
Ion temperature clamping in Wendelstein 7-X electron cyclotron heated plasmas Beurskens, M. N. A.; Bozhenkov, S. A.; Ford, O. Nuclear Fusion, Vol. 61, Issue 11 https://doi.org/10.1088/1741-4326/ac1653	journal	October 2021
High-performance ECRH at W7-X: experience and perspectives Laqua, H. P.; Baldzuhn, J.; Braune, H. Nuclear Fusion, Vol. 61, Issue 10 https://doi.org/10.1088/1741-4326/ac1a1b	journal	August 2021
Impurity transport in ion- and electron-root confinement scenarios at Wendelstein 7-X Langenberg, A.; Wegner, Th.; Marchuk, O. Nuclear Fusion, Vol. 61, Issue 11 https://doi.org/10.1088/1741-4326/ac24d4	journal	September 2021
Bolometer tomography on Wendelstein 7-X for study of radiation asymmetry Zhang, D.; Burhenn, R.; Beidler, C. D. Nuclear Fusion, Vol. 61, Issue 11 https://doi.org/10.1088/1741-4326/ac2778	journal	October 2021
Confinement in electron heated plasmas in Wendelstein 7-X and ASDEX Upgrade; the necessity to control turbulent transport Beurskens, M. N. A.; Angioni, C.; Bozhenkov, S. A. Nuclear Fusion, Vol. 62, Issue 1 https://doi.org/10.1088/1741-4326/ac36f1	journal	December 2021
Analysis of hydrogen fueling, recycling, and confinement at Wendelstein 7-X via a single-reservoir particle balance Kremeyer, Thierry; König, R.; Brezinsek, S. Nuclear Fusion, Vol. 62, Issue 3 https://doi.org/10.1088/1741-4326/ac4acb	journal	March 2022
Plasma flow measurements based on charge exchange recombination spectroscopy in the Wendelstein 7-X stellarator Alonso, J. A.; Ford, O. P.; Vanó, L. Nuclear Fusion, Vol. 62, Issue 10 https://doi.org/10.1088/1741-4326/ac7e5b	journal	August 2022
Suppression of anomalous impurity transport in NBI-heated W7-X plasmas Romba, T.; Reimold, F.; Jaspers, R. J. E. Nuclear Fusion, Vol. 63, Issue 7 https://doi.org/10.1088/1741-4326/acd5e1	journal	June 2023
Experimental characterization of the active and passive fast-ion H-alpha emission in W7-X using FIDASIM Poloskei, Peter Zs.; Geiger, B.; Jansen van Vuuren, A. Nuclear Fusion, Vol. 64, Issue 2 https://doi.org/10.1088/1741-4326/ad0dd4	journal	December 2023
Impurity transport study based on measurement of visible wavelength high-n charge exchange transitions at W7-X Swee, Colin; Geiger, Benedikt; Ford, Oliver Nuclear Fusion, Vol. 64, Issue 8 https://doi.org/10.1088/1741-4326/ad5aad	journal	July 2024
The Thomson scattering diagnostic at Wendelstein 7-X and its performance in the first operation phase Bozhenkov, S. A.; Beurskens, M.; Molin, A. Dal Journal of Instrumentation, Vol. 12, Issue 10 https://doi.org/10.1088/1748-0221/12/10/P10004	journal	October 2017
Real-time dispersion interferometry for density feedback in fusion devices Brunner, K. J.; Akiyama, T.; Hirsch, M. Journal of Instrumentation, Vol. 13, Issue 09 https://doi.org/10.1088/1748-0221/13/09/P09002	journal	September 2018
Measurements of visible bremsstrahlung and automatic Bayesian inference of the effective plasma charge Z _eff at W7-X Pavone, A.; Hergenhahn, U.; Krychowiak, M. Journal of Instrumentation, Vol. 14, Issue 10 https://doi.org/10.1088/1748-0221/14/10/C10003	journal	October 2019
The Wendelstein 7-X phase contrast imaging diagnostic Huang, Z.; Edlund, E.; Porkolab, M. Journal of Instrumentation, Vol. 16, Issue 01 https://doi.org/10.1088/1748-0221/16/01/P01014	journal	January 2021
A novel technique for an alignment-insensitive density calibration of Thomson scattering diagnostics developed at W7-X Fuchert, G.; Nelde, P.; Pasch, E. Journal of Instrumentation, Vol. 17, Issue 03 https://doi.org/10.1088/1748-0221/17/03/C03012	journal	March 2022
Resilience of Quasi-Isodynamic Stellarators against Trapped-Particle Instabilities Proll, J. H. E.; Helander, P.; Connor, J. W. Physical Review Letters, Vol. 108, Issue 24 https://doi.org/10.1103/PhysRevLett.108.245002	journal	June 2012
Turbulence Mechanisms of Enhanced Performance Stellarator Plasmas Xanthopoulos, P.; Bozhenkov, S. A.; Beurskens, M. N. Physical Review Letters, Vol. 125, Issue 7 https://doi.org/10.1103/PhysRevLett.125.075001	journal	August 2020
Impact of Magnetic Field Configuration on Heat Transport in Stellarators and Heliotrons Warmer, Felix; Tanaka, K.; Xanthopoulos, P. Physical Review Letters, Vol. 127, Issue 22 https://doi.org/10.1103/PhysRevLett.127.225001	journal	November 2021
Evidence for Convective Inward Particle Transport in a Stellarator Stroth, U.; Geist, T.; Koponen, J. P. T. Physical Review Letters, Vol. 82, Issue 5 https://doi.org/10.1103/PhysRevLett.82.928	journal	February 1999
Design of a Continuous Pellet Fueling System for Wendelstein 7-X Meitner, Steven J.; Baylor, L. R.; Gebhart, T. E. IEEE Transactions on Plasma Science, Vol. 48, Issue 6 https://doi.org/10.1109/TPS.2019.2949692	journal	June 2020