Explanipedia

Surface loss probabilities of boron-hydride radicals in W7-X and ASDEX Upgrade Open

M. Mayer, Sehoon An, T. Bräuer, D. Cipciar, C. P. Dhard , et al. · 2025

Numerical analysis of gas exhaust in Wendelstein 7-X using the direct simulation Monte Carlo method Open

S. Varoutis, Christos Tantos, H. Strobel, D. Boeyaert, Y. Igitkhanov , et al. · 2025

The present work is focused on a 3D numerical assessment of the Wendelstein 7-X (W7-X) particle exhaust. For all the numerical simulations the direct simulation Monte Carlo solver of the DIVGAS workflow, has been employed. The complex 3D g…

In-vessel colorimetry of Wendelstein 7-X first wall components after OP2.1 Open

G. Motojima, S. Masuzaki, C. P. Dhard, D. Naujoks, Matthias Hänel , et al. · 2025

Colorimetry has been continuously utilized for the estimation of deposition layer distribution on the first wall panels and divertor target elements in each Operation Phases (OP) of Wendelstein 7-X (W7-X). In OP2.1, significant achievement…

In-vessel inspection of arc traces on the W7-X plasma facing components after the operation phase OP2.1 Open

Dogyun Hwangbo, C. P. Dhard, Shin Kajita, D. Naujoks, Yu Gao · 2024

Updated distribution of arc traces across the interior walls after the operation phase 2.1 of Wendelstein 7-X (W7-X) is reported. A total of 105 new arc places were found, with 95% of them located around the stainless steel panels, diagnos…

Properties of boron layers deposited during boronisations in W7-X Open

M. Mayer, M. Balden, T. Bräuer, D. Cipciar, C. P. Dhard , et al. · 2024

Boronisation was first used for wall conditioning in W7-X during the OP 1.2b operational period, which was characterized by the use of the fine-grain graphite Test Divertor Unit (TDU) and inertial cooling only. After this period, deposited…

First operation and validation of simulations for the divertor cryo-vacuum pump in Wendelstein 7-X Open

Victoria Haak, C. P. Dhard, D. Boeyaert, T. Bräuer, V. Bykov , et al. · 2024

Overview of the first Wendelstein 7-X long pulse campaign with fully water-cooled plasma facing components Open

O. Grulke, Christopher G. Albert, J. A. Alcusón, P. Aleynikov, K. Aleynikova , et al. · 2024

After a long device enhancement phase, scientific operation resumed in 2022. The main new device components are the water cooling of all plasma facing components and the new water-cooled high heat flux divertor units. Water cooling allowed…

Migration and balance of 13C in the stellarator Wendelstein 7-X after 13CH local injection into the island divertor Open

C. Kawan, S. Brezinsek, T. Dittmar, C. P. Dhard, A. Knieps , et al. · 2024

A 13C tracer experiment was carried out to investigate impurity transport and migration in the stellarator Wendelstein 7-X (W7-X). About 4.0 × 1022 molecules of 13C marked methane were injected through the divertor gas injection system dur…

Numerical simulation of neutral gas dynamics in the W7-X sub-divertor Open

S. Varoutis, C. Tantos, H. Strobel, C. Day, C. P. Dhard , et al. · 2024

The present work presents a 2D and 3D modeling of the neutral gas flow in the sub-divertor region of the W7-X. The investigations have been done using the DIVGAS code. The complex 2D and 3D geometries of the divertor components in the sub-…

Exposure of tungsten heavy alloys at high thermal loads in LHD Open

C. P. Dhard, S. Masuzaki, D. Naujoks, R. Neu, Daisuke Nagata , et al. · 2024

Tungsten has been considered a plasma-facing material in a future fusion reactor because of its low sputtering yield and low fuel retention. It has been examined in several tokamaks. In stellarators, it has recently been used for some plas…

Improvement in the simulation tools for heat distribution predictions and control of baffle and middle divertor loads in Wendelstein 7-X Open

Yu Gao, Y. Feng, M. Endler, M. Jakubowski, J. Geiger , et al. · 2022

In the first divertor campaign in Wendelstein 7-X (W7-X), unexpected significant heat loads were observed at particular plasma-facing components (e.g. baffle tiles and middle divertor part) which were not designed to receive high heat flux…

Assessment of carbon net erosion/deposition at the divertor of W7-X Open

M. Mayer, M. Kandler, C. P. Dhard, S. Elgeti, Yu Gao , et al. · 2022

Observation of non-thermal electrons outside the SOL in the Wendelstein 7-X stellarator Open

C. Killer, P. Aleynikov, C. Biedermann, C. P. Dhard, P. Drews , et al. · 2022

Hot spots and bright patterns on plasma-facing components (PFC) in visible light are observed in electron cyclotron resonance heated (ECRH) plasmas at low densities in the stellarator Wendelstein 7-X. The events are often located far outsi…

Carbon erosion/deposition on the divertor of W7-X during the operational period OP 1.2b Open

M. Mayer, M. Balden, S. Brezinsek, Vassily Vadimovitch Burwitz, C. Cupak , et al. · 2022

Carbon net erosion and deposition at the test divertor unit (TDU) of Wendelstein 7-X (W7-X) were measured for the discharge period OP 1.2b in the year 2018 using 18 specially prepared target elements in all 10 TDUs. These had lengths betwe…

Distributions of deposits and hydrogen on the upper and lower TDUs3 target elements of Wendelstein 7-X Open

Mingzhong Zhao, S. Masuzaki, G. Motojima, M. Tokitani, Miyuki Yajima , et al. · 2022

Distributions of deposits and hydrogen (H) on the graphite divertor target elements TM4h4 and TM3v5 in the test divertor units 3 (TDUs3) of Wendelstein 7-X (W7-X) are studied. The TM4h4 and TM3v5 are located at the magnetically symmetric p…

Erosion of tungsten marker layers in W7-X Open

M. Mayer, M. Balden, S. Brezinsek, C. P. Dhard, S. Elgeti , et al. · 2021

In order to get first insight into net tungsten erosion in W7-X, tungsten (W) marker layers were exposed during the operational phase OP 1.2b at one position of the Test Divertor Unit (TDU), at 21 different positions of the inner heat shie…

Plasma-wall interaction studies in W7-X: main results from the recent divertor operations Open

C. P. Dhard, S. Brezinsek, M. Mayer, D. Naujoks, S. Masuzaki , et al. · 2021

Wendelstein 7-X (W7-X) is an optimized stellarator with a 3-dimensional five-fold modular geometry. The plasma-wall-interaction (PWI) investigations in the complex 3D geometry of W7-X were carried out by in situ spectroscopic observations,…

Plasma–surface interaction in the stellarator W7-X: conclusions drawn from operation with graphite plasma-facing components Open

S. Brezinsek, C. P. Dhard, M. Jakubowski, R. König, S. Masuzaki , et al. · 2021

W7-X completed its plasma operation in hydrogen with island divertor and inertially cooled test divertor unit (TDU) made of graphite. A substantial set of plasma-facing components (PFCs), including in particular marker target elements, wer…

Experimental confirmation of efficient island divertor operation and successful neoclassical transport optimization in Wendelstein 7-X Open

T. S. Pedersen, I. Abramovic, P. Agostinetti, M. Agredano Torres, S. Äkäslompolo , et al. · 2021

We present recent highlights from the most recent operation phases of Wendelstein 7-X, the most advanced stellarator in the world. Stable detachment with good particle exhaust, low impurity content, and energy confinement times exceeding 1…

Overview of the results from divertor experiments with attached and detached plasmas at Wendelstein 7-X and their implications for steady-state operation Open

M. Jakubowski, M. Endler, Y. Feng, Yu Gao, C. Killer , et al. · 2021

Wendelstein 7-X (W7-X), the largest advanced stellarator, is built to demonstrate high power, high performance quasi-continuous operation. Therefore, in the recent campaign, experiments were performed to prepare for long pulse operation, a…

Hydrogen content in divertor baffle tiles in Wendelstein 7-X Open

J. Oelmann, E. Wüst, S. Brezinsek, Cong Li, Dongye Zhao , et al. · 2021

Plasma–wall interactions play a crucial role for the performance of fusion devices and the lifetime of plasma-facing components. In this work the results of some plasma–wall interaction processes, namely the erosion/deposition pattern and …

Understanding baffle overloads observed in high-mirror configuration on Wendelstein 7-X Open

Yu Gao, Y. Feng, M. Jakubowski, J. Geiger, M. Endler , et al. · 2020

The operational regimes in the first divertor campaign of W7-X were limited by unexpectedly high heat loads on certain baffle tiles. In the high-mirror configuration, a permanent hotspot on the baffle plate was detected by the thermographi…

Inspection of Arc Trails Formed in Stellarator/Heliotron Devices W7-X and LHD Open

Dogyun Hwangbo, Shin Kajita, C. P. Dhard, M. Tokitani, M. Krause , et al. · 2020

Arc trails found in heliotron/stellarator devices Large Helical Device (LHD) and Wendelstein 7-X (W7-X) were inspected; arcing occurred on different locations at various situations. In LHD, a helium-plasma-induced tungsten nanostructure sa…

<i>Ex situ</i> analysis of W7-X divertor plasma-facing components by picosecond laser diagnostics Open

Dongye Zhao, Rongxing Yi, J. Oelmann, S. Brezinsek, M. Rasiński , et al. · 2020

A key question of long-pulse operation in the stellarator Wendelstein 7-X (W7-X) is the net erosion of plasma-facing components (PFCs), which determines W7-X PFC lifetimes as well as the impact on the impurity influx to the plasma. In orde…

Validating the ASCOT modelling of NBI fast ions in Wendelstein 7-X stellarator Open

S. Äkäslompolo, P. Drewelow, Yu Gao, Adnan Ali, C. Biedermann , et al. · 2019

The first fast ion experiments inWendelstein 7-X were performed in 2018. They are one of the first steps in demonstrating the optimised fast ion confinement of the stellarator. The fast ions were produced with a neutral beam injection (NBI…

Concept for the cryo distribution for the Wendelstein 7-X cryo vacuum pumps Open

M. Nagel, M. Ihrke, M. Pietsch, H.-S. Bosch, C. P. Dhard , et al. · 2019

After the completion of the third experimental campaign in 2018, actively cooled high heat flux divertors (10 pcs.) will be implemented within the stellarator fusion experiment Wendelstein 7-X (W7-X). A cryo vacuum pump will be installed i…

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

T. Klinger, T. Andreeva, S. Bozhenkov, C. Brandt, R. Burhenn , et al. · 2019

The optimized superconducting stellarator device Wendelstein 7-X (with major radius , minor radius , and plasma volume) restarted operation after the assembly of a graphite heat shield and 10 inertially cooled island divertor modules. This…

Depth resolved analysis of hydrogen in W7-X graphite components using laser-induced ablation-quadrupole mass spectrometry (LIA-QMS) Open

J. Oelmann, Cong Li, S. Brezinsek, M. Rasiński, C. P. Dhard , et al. · 2018

A deep understanding of the plasma-wall interaction processes in fusion devices like Wendelstein 7-X is necessary for an efficient plasma operation and a long lifetime of the plasma-facing components.In this work we present an approach emp…

Upgrades of edge, divertor and scrape-off layer diagnostics of W7‐X for OP1.2 Open

D. Hathiramani, Adnan Ali, G. Anda, T. Barbui, C. Biedermann , et al. · 2018

Overview of the plasma-surface interaction on limiter surfaces in the startup campaign of Wendelstein 7-X Open

V. Winters, S. Brezinsek, F. Effenberg, M. Rasiński, O. Schmitz , et al. · 2017

The first operational campaign of Wendelstein 7-X (W7-X) provided an excellent environment for the study of plasma-surface interaction (PSI) in a stellarator. In situ spectroscopic analysis via a combined visible/infrared camera system and…

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