Event opening by Deputy Director General Mr Juho KORTENIEMI (Ministry of Economic Affairs and Employment of Finland).
Recent years have seen a significant, quickly accelerating dynamic on the path towards making fusion a real option to meet net zero carbon emissions targets. International and national Government-funded programs are assisting the development of fusion technologies with a longer-term deployment window, with private fusion technology developers are focused on the commercialization of fusion over...
The ITER Organization (IO) has recently proposed a new baseline to meet the challenges of timely construction of the machine and achievements of the project’s objectives. One of the main changes the new baseline brings is the switchover of the first wall armour material from Beryllium to Tungsten. This of course increases the importance of diagnostic measurements and control systems aimed at...
Tungsten is an impurity material in fusion plasmas since it is a plasma-facing material for divertor in fusion devices and is sputtered and transported into plasmas. Because of its large atomic number, tungsten is partially ionized even in core plasmas and could lose energy due to high radiation power. To understand tungsten behaviors, a spectroscopic method is useful, and a reliable...
Collisional-radiative (CR) models for atomic and molecular hydrogen are essential for quantitative interpretation of atomic and molecular emission in low temperature plasmas such as the divertor plasma of fusion devices or negative hydrogen ion sources for the neutral beam injection systems for ITER. Moreover, CR models provide effective rate coefficients for neutral models, like the EIRENE...
After a discussion concerning differences between “high-density” plasmas (e.g. laser-produced plasmas) and “low-density” plasmas (e.g. tokamak core plasmas) in term of collisional-radiative modeling (CRM) for high-Z elements, we present specific configuration-average CRM calculations of tungsten plasmas at low electron density Ne = 5 10$^{13}$ cm$^{-3}$ for electron temperatures in the range...
Tungsten remains the element of choice for plasma facing components (PFCs) in the divertor region of ITER [1] and other past and present tokamak experiments [2, 3]. The impurity influx of tungsten from PFCs into the plasma while undesirable, as highlighted by Pütterich et al. [4], needs to be accurately quantified if we are to model tungsten erosion and redeposition. Previous work of Isler [5]...
In this contribution, we will provide an overview of the approach we have been developing over the last few years to model the interaction of hydrogen isotopes (HIs) with fusion-relevant materials. This approach now allows us to model the material from the plasma-exposed surface to the coolant boundary. Following a multiscale (MS) approach, our modeling relies upon electronic structure...
The production of vibrationally excited hydrogen molecules by recombination processes on a tungsten surface exposed to hydrogen is relevant to the understanding and development of hydrogen negative ion sources (e.g. [1, 2]) and to a lesser extent to the modelling the edge plasma in tokamaks (e.g. [3, 4]).
Here we present an overview of our studies of the vibrational distributions in H2 and...
Divertor detachment is the leading candidate for solving the heat exhaust problem in future fusion reactors. Key to understanding detachment is the interaction of the plasma with a background of neutral particles in the divertor region. Collisions of the plasma with these neutral background particles result in a rich range of physical and chemical processes, causing the plasma to dissipate its...
The SOLPS-ITER code uses atomic, molecular and surface data to model the edge plasmas of tokamaks and linear devices. This data is needed over a relatively wide range of plasma temperatures (0.1 eV or lower to approximately 5 keV for the pedestal of ITER) and plasma densities ($10^{17}\;m^{-3}$ to $10^{22} \;m^{-3}$) for the atomic data, and a somewhat smaller temperature range for the...
Impurity seeding in the scrape off layer plasma as well as controlling the contamination of the core plasma by high Z impurities are essential for ITER baseline scenarios. Predictions for the ITER baseline scenarios are often based on fluid descriptions of the impurity transport. However, especially lower ionization stages of high Z impurities (e.g. Ar, W) do not have the time to equilibrate...
Development of critically evaluated data sets for atomic parameters has long been a major part of the research program at the National Institute of Standards and Technology (NIST). Over the last decade NIST researchers and their collaborators created recommended sets of data for a number of fusion-related elements including, e.g., Be, Ar, Fe, Mo, and W. As a result, for example, the number of...
Wall conditioning is essential for controlling hydrogen recycling and the amount of intrinsic impurities to achieve high-performance plasmas in magnetically confined fusion devices. A technique for wall conditioning, boronization, is coating the chamber walls with boron. To examine the effectiveness of boronization, it is essential to investigate where and how much boron is deposited onto the...
Impurity seeding will be required for future reactors such as ITER and DEMO for radiative cooling, plasma control and diagnostics. Fusion plasmas are expected to contain impurities such as carbon, nitrogen, oxygen, argon, and tungsten ions. Some of these impurities are formed through ion seeding, others by erosion of plasma-facing components of the reactor. In the case of DEMO, due to the...
In my talk, I will present a theoretical investigation on electron-D2 resonant collisions, via the low-lying and the Rydberg states of D2−. I will focus, in particular, on low-energy cross section calculations, vibrationally resolved, for the dissociative attachment process in the ground state, and two electronic excited states of D2. Isotopologue effect for H2 and D2 will be shown and...
Accurate electron and positron-impact excitation cross sections for collisions with atoms and molecules are important for modelling various plasmas with applications ranging from medical sciences and plasma processing to astrophysics and fusion. This talk will review recent progress at the Curtin University research group in developing collision codes and their use in modelling collision...
Fusion science and technology present interesting answers as Cambodia looks to diversify its energy sources and move toward sustainable ones. This abstract examines how important it is to advance fusion research in Cambodia by using data on atomic, molecular, and plasma-material interactions. The process of fusion, which uses the energy of atomic nuclei, has enormous potential for producing...
It appears that a partially ionized plasma is formed around any protruded interface of different material phases in a fusion plasma. Such interface potentially and intrinsically releases neutral gas from outgassing, sputtering and evaporation, and ablated vapor from solid, for examples dust, sublimated plasma facing components (PFC), and liquid, for examples molten droplets, liquid PFCs,...
The present study has determined excitation energy of the 127 states of the transmutation of tungsten atoms He-like-(Hf, Ta, Re and Os). In this work, we use the ab initio MCDHF and MBPT methods implemented in GRASP2018 and FAC codes, respectively. We extend the calculation for n = 8 to improve the precision of the atomic data used in line identification, plasma modeling and diagnostics of...
The impact of varying periodic electric fields on the emission line shapes in fusion plasmas, is a subject of significant interest. Tokamak devices, universally employing radio frequency (rf) waves, aim to heat, control, or diagnose plasma through effective coupling. This research focuses on developing a spectroscopic diagnostic tool to analyze the periodic electric field's propagation within...
Molecular dynamics (MD) simulations of successive collision cascades within the same simulation domain and further defect evolution were performed using two different inter-atomic potentials (IAP) in tungsten, one EAM based and the other a `quantum accurate' machine learning potential, SNAP. The micro-structural changes are analyzed as a function of displacements per atom (dpa) up-to...
Component-scale predictive models for how hydrogen isotopes interact with, and are retained by, irradiation-induced defects are required to inform design decisions in materials for fusion power. This is a multiscale materials modelling challenge, with a conceptual gap between electronic structure calculations on one hand, which provide high accuracy estimations of idealised elemental defect...
The choice of elements in structural materials such as stainless-steel can reduce radiation levels due to particle activation. The dose rate to workers and electrical components is managed by the material used for radiation shielding. This work analyses candidate materials used in the ITER neutral beam duct. Quantitative analysis of radiation effects in the Neutral Beam Injection (NBI) section...
In this study, we present an approach for the precise determination of edge plasma density profiles in the KSTAR tokamak, leveraging Bayesian inference and Gaussian process regression techniques in conjunction with atomic data. The methodology relies on a collisional radiative model that captures the interactions between neutral deuterium beam atoms and plasma constituents. This model, built...
In magnetic fusion devices equipped with Tungsten (W) plasma-facing components (PFCs), dilution and radiation studies have become an essential feature of the experimental developments. Among several methods used to diagnose W transport and radiation in fusion plasmas, spectroscopy is one of the most powerful because it allows us to distinguish between the numerous ionisation stages of W. For...
The optical actinometric technique is used to investigate the addition of impurities in the argon and helium microwave discharges during the wall conditioning process of the MT-I spherical tokamak. This technique normalizes the change occurring in the electron energy distribution function with changing plasma conditions through the emission intensity of the selected Ar/He lines. Any change in...
The cross-sections and Maxwellian rate coefficients of electron impact single ionization is theoretically investigated for tungsten ions (W68+ to W71+) for fine structure levels of configurations containing n = 2 orbitals. Maxwellian rate coefficients for ground state are evaluated at the temperature range 20keV to 300keV. Detailed comparison between results from different approximations,...
During D-T nuclear fusion reaction, plasma-facing materials, e.g. Tungsten (W) in ITER, are exposed to a hydrogen-rich environment. Hydrogen is easily absorbed into W and alter the material behavior. Conventionally, hydrogen is well known to cause hardening behavior of materials. Solute hardening is a typical phenomenon associated with hydrogen-induced hardening and it is traditionally...
Hydrogen glow discharge cleaning (H-GDC) is a routine conditioning procedure for the present tokamaks and the future fusion machines, including the ITER. Due to the low energy of hydrogen ions in glow discharge plasmas, the probability of any considerable damage to the plasma facing components was mainly ignored among researchers in the field. In this work, Tungsten and Molybdenum, as the...
This work presents a combined theoretical and experimental approach to understand the complex surface phenomena occurring in fusion and nuclear materials.
Fusion Materials: We investigate the interaction of low-Z (lithium and boron) coatings with carbon under extreme fusion plasma conditions. A multi-scale approach using computational modeling, real-time plasma diagnostics, and ex-vessel...
Since December 2022 WEST has tested actively cooled solid W monoblock plasma facing units mounted on a flat crown forming the lower divertor. These tests aim at long plasma discharges, with thermal loads of the same order of magnitude as those expected for the ITER vertical part of the lower divertor (10 MW/m$^2$). Deuterium plasma durations of more than 360 seconds have been obtained in a...
Tritium (T) transport through the first wall into the coolant is a major concern in fusion reactor studies. When irradiated by plasmas, hydrogen permeation flux through in-vessel components would be significantly higher than that of gas-exposure cases. To support reactor design studies, low energy plasma-driven hydrogen isotope permeation through the first wall has been extensively...
In future thermonuclear devices such as DEMO displacement damage by 14 MeV fusion neutrons will be created in the plasma-facing materials while they are exposed to high fluxes of ions and neutrals of hydrogen isotopes (HIs) at elevated temperatures. It was shown in several studies in the past twenty years that HI retention and transport will be dominated by trapping at the defects created by...
To model hydrogen isotope migration and inventory in a metal under ion irradiation, rate equations are used. The diffusivity, solubility, surface barrier, reflection and sputtering coefficients, mean ion range, and binding energies of deuterium (D) with different types of defects are input parameters in the rate equations. Such parameters can be defined by ab initio calculations by DFT or MD...
Tungsten (W) is considered as a promising plasma-facing material for future fusion reactors. W components will be subjected to an intense flux of 14 MeV neutrons. This will result in creation of radiation defects, production of H and He, and transmutation of W to Rhenium (Re). Radiation defects can trap tritium fuel, posing a stringent limitation to tritium self-sufficiency.
MeV self-ion...
The first Tokamak Facility (TT-1) is commissioned in Thailand since July 2023. Various research and development activities in connection TT-1 are taking shape, domestically, regionally and internationally. There is an ongoing collaboration work between Thai researchers, NIFS (Japan), and ASIPP (China) on fusion neutron detection and measurement. A facility of linear device for fusion-related...
Key input quantities for the modelling of plasma-wall interactions are the energy and angular distributions of the particles impinging onto the wall as well as the corresponding distributions for the particles (re-)entering the plasma.
Traditionally the focus has been on the modifications of the wall induced by the incoming particle influx (i.e. sputtering) and extensive simulation efforts...
Plasma-wall interactions (PWI) in fusion devices pose significant challenges, including erosion of plasma-facing components (PFC), fuel retention, and plasma contamination by impurities. Accurate modelling of these interactions is crucial for the design and operation of future fusion devices. This talk presents recent advancements in 3D modeling of PWI, highlighting the capabilities and...
The erosion of redeposited layers is typically larger than the erosion of the corresponding bulk material. However, the modelling of impurity tracer injection experiments in various fusion devices indicates an additionally enhanced re-erosion of particles during the process of layer formation. This can be interpreted as an “in-situ erosion” of transient layers involving particles, which are...
Predicting the erosion and deposition of tungsten (W) from plasma-facing components, and the resulting impact of W on the fusion performance, requires an appropriate description of plasma interaction with W ions, atoms, and surfaces. Accurate and validated data on these interactions, and the application of such data to simulations of experiments in existing devices, enables the benchmarking...
Sputtering of the wall materials of fusion reactors will both affect the plasma as well as the longevity of the wall itself. Even though sputtering as a phenomenon has been known for a long time, the intricate details are still not fully understood. Especially if the wall material is not a pure metal, but either an alloy or decorated by some other elements, the sputtering becomes more complex....
Understanding plasma-wall interactions is crucial in the development of fusion reactors. These interactions could cause performance loss and contribute to tritium retention by eroding plasma-facing components (PFCs) through physical or chemically assisted physical sputtering (CAPS) [1]. This makes the investigation of sputtering pivotal in fusion reactors. Specifically, CAPS, and more...
Neutron irradiation is an engine in a fusion reactor that generates power, but not all that controllable. The uncontrollable nature of neutron in a magnetic field still needs to be controlled to some extent in order to safely operate the fusion power plant, and one of the potential solutions is to use a tough plasma-facing material. W as a plasma-facing material unavoidably has grains, and the...
Tungsten is considered one of the most promising plasma materials for future fusion reactors. In the fusion reactor environment, the irradiation of high-energy neutrons leads to material collisions, generating vacancies and interstitial atoms, such as Frankel defects. These microscopic defects gradually evolve into larger-scale complex defects, such as dislocations and dislocation loops,...
Integrated modeling of plasma-surface interactions (PSI) provides a comprehensive and self-consistent description, moving the field closer to developing predictive and design capabilities for plasma facing components. This technique, using descriptions for the scrape-off-layer plasma provided by SOLPS, the sheath by hPIC, ion-surface interactions by F-TRIDYN and the sub-surface by Xolotl, has...
Hydrogen transport modelling is crucial for the development of fusion energy, where understanding tritium behaviour in materials is essential for both safety and component design, such as the breeding blanket and plasma-facing materials. Traditionally, this modelling has been dominated by closed-source tools like TMAP7 or in-house codes, leading to fragmented efforts and limited accessibility...
Artificial intelligence is spreading across all science fields, including plasma science and plasma spectroscopy [1]. Various applications have shown promising results in combining diagnostic measures with machine learning techniques, particularly in tomographic reconstruction from sparse bolometric measures and early disruption detection [2,3]. In this communication, we present ongoing work...
To investigate the effects of particle flux on deuterium (D) retention, a series of D plasma exposures were systematically investigated in recrystallized tungsten (W) at ~500 K using two linear plasma devices STEP and Magnum-PSI. A low flux plasma with the highest fluence of 1.0×10^28 m^-2 was achieved in STEP and a high flux plasma with the highest fluence of 1.0×10^29 m^-2 was achieved in...
