T. Dittmar
A5000285332- Fusion materials and technologies
- Magnetic confinement fusion research
- Nuclear Materials and Properties
- Laser-Plasma Interactions and Diagnostics
- Nuclear reactor physics and engineering
- Superconducting Materials and Applications
- Laser-induced spectroscopy and plasma
- Diamond and Carbon-based Materials Research
- Plasma Diagnostics and Applications
- Nuclear Physics and Applications
- Metal and Thin Film Mechanics
- Particle accelerators and beam dynamics
- Ion-surface interactions and analysis
- Hydrogen Storage and Materials
- Ionosphere and magnetosphere dynamics
- Atomic and Molecular Physics
- High-pressure geophysics and materials
- Graphite, nuclear technology, radiation studies
- Advanced Materials Characterization Techniques
- Muon and positron interactions and applications
- High-Energy Particle Collisions Research
- Solar and Space Plasma Dynamics
- Astro and Planetary Science
- Intermetallics and Advanced Alloy Properties
- Nuclear materials and radiation effects
CEA Cadarache
2010-2024
Forschungszentrum Jülich
2015-2024
Institut de Recherche sur la Fusion par Confinement Magnétique
2018-2024
Culham Science Centre
2016-2024
Culham Centre for Fusion Energy
2024
Royal Military Academy
2020
Commissariat à l'Énergie Atomique et aux Énergies Alternatives
2010-2018
Japan External Trade Organization
2015
University of California, San Diego
2011-2014
KTH Royal Institute of Technology
2011
Abstract The optimized superconducting stellarator device Wendelstein 7-X (with major radius , minor and plasma volume) restarted operation after the assembly of a graphite heat shield 10 inertially cooled island divertor modules. This paper reports on results from first high-performance operation. Glow discharge conditioning ECRH discharges in helium turned out to be important for density edge radiation control. Plasma densities with central electron temperatures were routinely achieved...
The provision of a particle and power exhaust solution which is compatible with first-wall components edge-plasma conditions key area present-day fusion research mandatory for successful operation ITER DEMO. work package plasma-facing (WP PFC) within the European programme complements laboratory experiments, i.e. in linear plasma devices, electron ion beam loading facilities, studies performed toroidally confined magnetic such as JET, ASDEX Upgrade, WEST etc. connection both groups done via...
Abstract WEST is an MA class superconducting, actively cooled, full tungsten (W) tokamak, designed to operate in long pulses up 1000 s. In support of ITER operation and DEMO conceptual activities, key missions are: (i) qualification high heat flux plasma-facing components integrating both technological physics aspects relevant particle exhaust conditions, particularly for the monoblocks foreseen divertor; (ii) integrated steady-state at confinement, with a focus on power issues. During phase...
Abstract After the second Deuterium–Tritium Campaign (DTE2) in JET tokamak with ITER-Like Wall (ILW) and full tritium campaigns that preceded followed after DTE2, a sequence of fuel recovery methods was applied to promote removal from wall components. The started several days baking main chamber walls at 240 °C 320 °C. Subsequently, superimposed Ion-Cyclotron Conditioning (ICWC) Glow Discharge (GDC) cleaning cycles deuterium. Diverted plasma operation deuterium different strike point...
Abstract The paper reports the first demonstration of in situ laser-induced desorption — quadrupole mass spectrometry (LID-QMS) application on a large scale fusion device performed summer 2023. LID-QMS allows direct measurements fuel inventory plasma facing components without retrieving them from device. diagnostic desorbs retained gases by heating 3 mm diameter spot wall using 1 ms long laser pulse and detects QMS. Thus, it can measure gas content at any position accessible to laser....
The Wendelstein 7-X (W7-X) optimized stellarator fusion experiment, which went into operation in 2015, has been operating since 2017 with an un-cooled modular graphite divertor. This allowed first divertor physics studies to be performed at pulse energies up 80 MJ, as opposed 4 MJ the phase, where five inboard limiters were installed instead of a This, and number other upgrades device capabilities, extension regimes higher plasma density, heating power, performance overall, e.g. setting new...
Abstract ITER will operate with a tungsten divertor, material featuring surface morphology changes when exposed to helium plasmas, in particular the formation of so called fuzz under specific conditions. Investigating interactions between plasma facing components and plasmas tokamak environment is therefore key point consolidate predictions for divertor performance lifetime. To this end, dedicated campaign was performed full WEST tokamak, cumulating ∼2000 s repetitive L mode discharges. It...
Abstract JET returned to deuterium-tritium operations in 2023 (DTE3 campaign), approximately two years after DTE2. DTE3 was designed as an extension of JET's 2022-2023 deuterium campaigns, which focused on developing scenarios for ITER and DEMO, integrating in-depth physics understanding control schemes. These were evaluated with mixed D-T fuel, using the only remaining tritium-capable tokamak until its closure 2023. A core-edge-SOL integrated H-mode scenario developed tested D-T, showing...
Fuel retention, a crucial issue for next step devices, is assessed in present-day tokamaks using two methods: particle balance performed during shots and post-mortem analysis carried out shutdowns between experimental campaigns. Post-mortem generally gives lower estimates of fuel retention than integrated balance. In order to understand the discrepancy these methods, dedicated campaign has been Tore Supra load vessel walls with deuterium (D) monitor trapped D inventory through The was...
We present here the results of spectroscopic analysis high-resolution visible spectra beryllium hydride and its isotopologues (BeH, BeD, BeT), produced during plasma–surface interactions limiter divertor JET-ILW (ITER-like Wall) pulses. The production, being an important part wall erosion via chemical-assisted physical sputtering, shows dependence on plasma conditions, also isotope content plasma. This work that this is true for molecular energy distributions, parameterized by rotational...
Abstract After a long device enhancement phase, scientific operation resumed in 2022. The main new components are the water cooling of all plasma facing and water-cooled high heat flux divertor units. Water allowed for first long-pulse campaign. A maximum discharge length 8 min was achieved with total heating energy 1.3 GJ. Safe demonstrated attached detached mode. Stable detachment is readily some magnetic configurations but requires impurity seeding small pitch angle within edge islands....
Global gas balance experiments at ASDEX Upgrade (AUG) and JET have shown that a considerable fraction of nitrogen injected for radiative cooling is not recovered as N2 upon regeneration the liquid helium cryo pump. The most probable loss channels are ion implantation into plasma-facing materials, co-deposition ammonia formation. These three mechanisms investigated in laboratory tokamak by numerical simulations. Laboratory ions beryllium tungsten leads to formation surface nitrides, which may...
Tungsten transport is investigated in WEST long pulse L-mode plasmas operated with the strike point on actively cooled upper tungsten divertor. The pulses are mostly heated by lower hybrid waves. It experimentally found that does not centrally accumulate throughout these ∼ 30 s reproducible discharges despite large normalised electron density gradients . To explain observations, turbulent and neoclassical of electrons ions computed GKW Peeters A.G. et al (2009 Computer Phys. Commnun. 180...
Abstract W7-X completed its plasma operation in hydrogen with island divertor and inertially cooled test unit (TDU) made of graphite. A substantial set plasma-facing components (PFCs), including particular marker target elements, were extracted from the vessel analysed post-mortem. The analysis provided key information about underlying plasma–surface interactions (PSI) processes, namely erosion, transport, deposition as well fuel retention graphite components. net carbon (C) erosion...
Abstract A sequence of fuel recovery methods was tested in JET, equipped with the ITER-like beryllium main chamber wall and tungsten divertor, to reduce plasma deuterium concentration less than 1% preparation for operation tritium. This also a key activity regard refining clean-up strategy be implemented at end 2nd DT campaign JET (DTE2) assess tools that are envisaged mitigate tritium inventory build-up ITER. The began 4 days baking 320 °C, followed by further which Ion Cyclotron Wall...
A micro-structuring of the tungsten plasma-facing surface can strongly reduce near thermal stresses induced by ELM heat fluxes. This approach has been confirmed numerical simulations with help ANSYS software. For experimental tests, two 10 × mm2 samples micro-structured were manufactured. These consisted 2000 and 5000 vertically packed fibres dimensions Ø240 µm 2.4 mm Ø150 mm, respectively. The 1.2 bottom parts are embedded in a copper matrix. top have gaps about so they not touching each...
The pre-fusion power operation (PFPO) phase of ITER, as described in the ITER research plan with Staged Approach2, includes both hydrogen (H) and helium (He) plasma operations. In preparation for PFPO, WEST JET ran He campaigns to study plasma-wall interactions a tungsten environment. included back-and-forth transition between H or deuterium (D) allowing assessment achievable content well accessible wall reservoirs respective species. changeovers tokamak pulses fixed divertor configuration....
Abstract For its initial operational phase, ITER has until recently considered using non-nuclear hydrogen (H) or helium (He) plasmas to keep nuclear activation at low levels. To this end, the Tokamak Exploitation Task Force of EUROfusion Consortium carried out dedicated experimental campaigns in He on ASDEX Upgrade (AUG) and JET tokamaks 2022, with particular emphasis put ELMy H-mode operation plasma-wall interaction processes as well comparison H deuterium (D) plasmas. Both pure mixed +...
Tungsten (W) is presently the most attractive plasma facing material for future fusion reactors. Off-normal transient events such as edge localized modes and disruptions are simulated with a pulsed laser system in PISCES-B facility, providing pulses 1–10 ms duration absorbed heat flux factors up to ∼90 MJ m−2 s−1/2. This paper characterizes surface morphology changes damage thresholds under heating on W exposed He or D without Be coatings. damaged form of grain growth, roughening, melting...
Beryllium oxide (BeO) and deuteroxide (BeOxDy) have been found on the melted zone of a beryllium tile extracted from upper dump plate JET-ILW (2011–2012 campaign). Results obtained using Raman microscopy, which is sensitive to both chemical bond crystal structure, with micrometric lateral resolution. BeO wurtzite structure. BeOxDy as three different types are not β-phase but behaves molecular species like Be(OD)2, O(Be-D)2 DBeOD. The presence small amount trapped D2O also suspected. Our...