Disentangling the electronic structure of tungsten metal

Projected Density of States (PDOS) spectra of bcc tungsten structure with 3456 atoms calculated using Linear-Scaling BigDFT, compared to hard x-ray photoelectron spectroscopy (HAXPES) valence band spectra. Image adapted from arXiv:2109.04761v1

Tungsten is one of the reference plasma-facing materials in fusion power devices due to its excellent temperature resistance and low tritium retention. The investigation of the electronic structure is key for implementing tungsten-based technologies as it is strongly related to the stability and properties of the material. However, despite the large efforts in studying the electronic properties of tungsten metal, some complex features are still not properly characterised.

The combination of state-of-the-art experimental and theoretical approaches is key to describing the electronic structure of tungsten, as presented in a recent publication in Physical Review B, entitled Lifetime effects and satellites in the photoelectron spectrum of tungsten metal“.

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Our newest contribution to the journal of Fusion Engineering and Design

The final goal of fusion power plants is to produce electricity in the grid. This is planned to be done by heating up water as with fission power plants or thermal power stations. In the case of magnetically confined fusion, neutrons released from the hot fusion plasma escape the magnetic confinement and finish in the wall heating up water. In the case of DEMO (DEMOnstration power plant), the neutron production will be large and the reactor materials have to be neutron-resistant. Thereby, neutronics becomes an increasingly important field of study.

Our recent paper published in the journal of Fusion and Engineering Design entitled Validations of the radiation transport module NEUTRO: a deterministic solver for the neutron transport equation reports on our on-going efforts in this field, carried out in collaboration with the CNEA-CONICET in Buenos Aires (Argentina). It can be accessed for free via this link during the first 50 days after the publication.

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Our recent collaboration selected as featured paper in Physics of Plasmas

Since the theoretical description of the three-ion scheme back in 2015 [1], the scheme has been tested and proven in several fusion devices such as Alcator C-Mod, JET and AUG. The main idea underlying this radiofrequency (RF) scheme comes from the polarization of the wave. In essence, what is sought, is the maximization of the electric field component that rotates as the ions do around the magnetic field. This condition is typically reached when the resonance location of the minority ion species coincides with the so-called L-cutoff of the wave. The result? A highly dominant ion absorption of the wave and a very energetic ion distribution.

We are very happy to announce that the recently published paper Physics and applications of three-ion ICRF scenarios for fusion research has been selected as a featured paper in the prestigious Physics of Plasmas journal, where two members of our group, Mervi Mantsinen and Dani Gallart, have collaborated. The paper presents many of the advances on this scheme during these last years, especially from the experimental point of view and the developed theoretical framework.

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Our recent papers published in open-access RF Topical Conference Proceedings

The RF Topical Conference is held every two years by a different host. Last year it took place at Hefei, China. From our Fusion Group Dr Dani Gallart had the chance to participate to the event; you can read more about his experience in this earlier post.

The RF Topical Conference tackles several radio-frequency topics in plasmas such as: experiments, modelling, interactions of wave and plasma edge and other related subjects. Recently, the conference contributions from the 2019 edition have been  published in the AIP Conference Proceedings and are in open-access. The Fusion Group has contributed to a total of 6 papers which are briefly described in the following:

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Our latest papers in Nuclear Fusion journal

The latest number  of the prestigious Nuclear Fusion journal co-published by IAEA and IOP Publishing is a Special Issue of selected papers originating from the 16th IAEA technical meeting on energetic particles in magnetic confinement systems—theory of plasma instabilities. Held in Shizuoka, Japan, on 3–6 September 2019, this meeting brought together about 100 experts from nuclear fusion research sites worldwide to discuss the physics of energetic particles and plasma instabilities, at the first joint meeting from the two scientific disciplines.

The Special Issue contains the following three papers with contributions from our group related to heating fusion plasmas  with electromagnetic waves in the ion cyclotron range of frequencies (ICRF) in ITER and JET.

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Our recent Nuclear Fusion journal paper on the modelling of ASDEX Upgrade tokamak plasmas

View from the ASDEX Upgrade Control Room.

Our journal article entitled “Shear Alfvén wave continuum spectrum with bifurcated helical core equilibria” has been published in the peer-reviewed Nuclear Fusion journal. Jointly published by IAEA and IOP Publishing, Nuclear Fusion is one of the renowned journals specializing in fusion plasmas.

The paper reports on the first modelling results aimed at understanding low-frequency Alfvén eigenmodes called beta induced Alfvén eigenmodes (BAEs) observed during monster sawtooth crashes in ASDEX Upgrade tokamak plasmas and their comparison with the experimental observations.

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