MoD-PMI 2015
International workshop on Models and Data for
Plasma-Material Interaction in Fusion Devices

	
  PROGRAM and ABSTRACTBOOKLET

Aix-Marseille University3	
  place	
  Victor	
  Hugo,	  13001	
  Marseille,	
  France
25-27 May 2015

MoD-PMI 2015	
  Invited Speakers	  Tommy	
  Ahlgren	
  University	
  of	
  Helsinki	
  Marie-­‐France	
  Barthe,	  CNRS	
  Orléans	  Charlotte	
  Becquart	
  Université	
  de	
  Lille	  Bas	  Braams	
  IAEA	
  Vienna	
  María	
  José	  Caturla	  Universidad	
  de	
  Alicante	
  Michele	
  Ceriotti	
  
EPFL	
  
Huiqiu	  Deng	  Hunan	
  University	  Gregory	  de	
  Temmerman	
  ITER	
  Organization	
  Christian	  Grisolia	
  CEA	
  Cadarache	
  Kalle	  Heinola	
  
CCFE	
  &	
  University	
  of	
  Helsinki	
  Atsushi	
  M.	
  Itoh	  NIFS	
  Jorge	  J.	
  Kohanoff	
  University	
  of	
  Belfast	  Heun-­‐Tae	
  Lee	
  Osaka	
  University	
  Jörg	
  Neugebauer	
  MPI	
  für	
  Eisenforschung	
  Olga	
  Ogorodnikova	
  NRNU	
  MEPhI	
  	
  Kazuhito	  Ohsawa	
  Kyushu	  University	
  Anthony	  Paxton	  King's	  College	
  London	
  Klaus	
  Schmid	  IPP	
  Garching	
  Toshiyuki	
  Takayanagi	  Saitama	
  University	  Pavel	
  Vladimirov	
  Karlsruhe	
  Institute	
  of	
  Technology	
  Scientific CommitteeYves	
  Ferro	
  (Chair)	
  Bas	
  Braams	  Jean-­‐Paul	  Allain	
  Gregory	  de	
  Temmerman	
  Maria	
  Ganchenkova,	  Daiji	
  Kato	  Predrag	  Krstic	  Christian	
  Linsmeier	
  Duc	
  Nguyen-­‐Manh	  Kai	
  Nordlund	
  Takuji	  Oda	
  Klaus	
  Schmid	
  Aix-­‐Marseille	
  Univsersity	
  	
  IAEA	  Vienne	
  University	
  of	
  Illinois	
  ITER	
  Organization	
  MEPhI	  NIFS	
  Stony	
  Brook	
  University	
  FZ	
  Jülich	  CCFE	
  Culham	
  University	
  of	
  Helsinki	
  Seoul	  National	
  University	
  IPP	
  Garching	
  

	
  

Local Organizers
	
  Ferro	  Yves	  (chair)	
  Addab	  Younes	  Cannuccia	
  Elena	  	
  Ferry	
  Laura	  	
  Khamchanh	
  Régis	
  	
  

	
  

	
  

	
  

MoD-PMI 2015	
  How to come	  The Saint-Charles campus of Aix-Marseille University is next to the train station.
Shuttles are joining the airport Marseille-Provence, Marignane, to the train station “GareSaint-Charles”, Marseille. Shuttles can be booked in advance here: http://mpshuttle.fr/en/
Oral session will be held in the “Sciences Naturelles” amphitheater.
Poster sessions will be held in rooms 51 and 52.

	
  
	
  

Restaurant(	
  Oral(sessions(	
  Sciences'Naturelles'

	
  
	
  

Poster(sessions(Rooms'51'and'52'

	
  
	
  
	
  

Main(entrance(

	
  
	
  

Shu4les(to(the(airport(

	
  
	
  
	
  
	
  
	
  
	
  

MARSEILLE(
Train(sta0on(

	
  
	
  

3	
  
	
  

MoD-PMI 2015	  Strolling around the “Vieux Port”	
  Strolling$around$the$«$Vieux$Port$»$

	
  
	
  
	
  
	
  

MALL%

Terrasses$du$port$

	
  
	
  
	
  

History%%
Museum%

	
  
	
  

	
  
	
  

An:c$Greek$Harbor$

MUCEM%

	  Old$and$new$building$Viewpoint$

Old%districts%
City$Hall$

	
  
	
  
	
  

RESTAURANTS%

	
  
	
  
	
  
	
  

Subway%sta:on$PHARO%

Big$Park$
Viewpoint$

	
  
	
  
	
  
Here are some examples of what you can enjoy around the “Vieux Port”.
How to join the conference site?
The conference site is next to the subway station “Saint-Charles”
Line 1 join “Saint-Charles” to “Vieux Port” within 5 minutes; it is just three stations away.
	
  

	
  

	
  

MoD-PMI 2015	
  ProgramMonday 25 May 2015

13:00 – 14:00

Registration

14:00 – 14:15

Opening
Yves Ferro

Session 1 - Molecular Dynamics
Chair: Charlotte Becquart
14:15 – 14:50

Self-trapping and trap mutation in bulk tungsten: a DFT and
Molecular Dynamics investigation (I1)Charlotte Becquart

14:50 – 15:25

New interatomic potentials for studying the behavior of noble gas
atoms in tungsten (I2)
Huiqiu Deng

Break
15:50 – 16:25

Tungsten Fuzzy Nanostructure Growth by Molecular Dynamics andMonte Carlo Hybrid Simulation (I3)
Atsushi M Itoh

16:25 – 17:00

Modelling of Hydrogen Interactions with Beryllium Surfaces in
Fusion Reactor (I4)
Pavel Vladimirov

Session 2
17:00 – 18:30

Poster session

5	
  
	
  

MoD-PMI 2015	  Tuesday 26 May 2015

Session 3 –Quantum Effects In Molecular Dynamics
Chair: Bas Braams
8:40 – 9:15

Modelling and Data Needs for Plasma-Material Interaction in Fusion
Devices: Perspective from the IAEA Atomic and Molecular Data Unit
(I5)
Bas Braams

9:15 – 9:50

Time-dependent simulation of electronic stopping from firstprinciples (I6)
Jorge J. Kohanoff

9:50 – 10:25

Quantum nuclei in materials: (when) do we need to worry? (I7)
Michele Ceriotti

Coffee break
11:10 – 11:45

Quantum theory of transport and trapping of hydrogen in iron (I8)
Anthony Paxton

11:45 – 12:20

Nuclear quantum effects in tritium diffusion in α-iron (I9)Toshiyukii Takayanagi

Lunch

Session 4 – Experimental Data for Modelling
Chair: Gregory de Temmerman
14:00 – 14:35

The need for a better understanding of plasma-material interactions
in ITER and the role of modelling (I10)
Gregory de Temmerman

14:35 – 15:10

Vacancy defects studied in tungsten by using Positron annihilation
spectroscopy (I11)Marie-France Barthe

15:10 – 15:45

Experimental studies of hydrogen transport parameters in tungsten(I12)
Heun-Tae Lee

Coffee break
16:25 – 16:50

Influence of aluminum oxide coating oxygen presence in plasma on
deuterium retention in tungsten (O1)
Leon Begrambekov

16:50 – 17:15

Deuterium retention in polycrystalline tungsten at low fluences (O2)
Régis Bisson

Summary and discussion
17:15 – 18:00

6	
  
	
  

MoD-PMI 2015	
  Wednesday 27 May 2015
Session 5 – Multi-scale modelling 1: DFT and statistic methods
Chair: Joerg Neugebauer
8:40 – 9:15

Understanding
thefundamental
mechanisms
behindembrittlement: An ab initio guided multiscale approach (I13)
Jörg Neugebauer

H

9:15 – 9:50

Setting up plasma pulse-scale simulations with electronic structure
calculations (I14)
Kalle Heinola

9:50 – 10:25

Hydrogen recycling in tungsten during plasma pulse simulations
with rate equations (I15)
Tommy Ahlgren

Coffee break
Chair: Daiji Kato
11:05 – 11:40

Multiscale modelling of radiation effects
implantation versus neutron irradiation (I16)Maria José Caturla Terolinmaterials:

ion

11:40 – 12:05

Hydrogen trapping at vacanciesand hydrogen impact on vacancy
diffusion and self-diffusion in Ni (O3)
Döme Tanguy

12:05 – 12:30

Vacancy nanoclusters in irradiated W and W alloys: First-principles
assessments and multi-scale modelling (O4)
Duc Nguyen-Manh

Lunch
Session 6 – Multi-scale modelling 2: Rate-equations and Reaction Diffusion models
Chair: Klaus Schmid
14:00 – 14:35

Modeling isotope exchange in W using fill level dependent trapping(I17)
Klaus Schmid

14:35 – 15:10

Macroscopic rate equation modeling of trapping/detrapping ofhydrogen isotopes in tungsten materials (I18)
Christian Grisolia

Coffee break
15:40 – 16:15

Migration, trapping and release of deuterium from tungsten in thepresence of high density of defects: theory and experiment (I19)
Olga Ogorodnikova

16:15-16:35

Materials research in Jülich: hydrogen retention in beryllium (O5)
Dmitry Matveev

Summary and discussion
16:35- 17:15
Closing	
  
7	
  
	
  

MoD-PMI 2015	
  Poster session

P-1

Thin tungsten oxide layers : structural properties and deuterium retention
Younès Addab

P-2

The Xolotl Plasma-Surface Interactions Simulator
Sophie Blondel

P-3

Path integral molecular dynamics for the nuclear quantum effects in the Frenkel
defects in BCC Fe
Bingqing Cheng

P-4

Experiment and modelling of hydrogen isotope exchange in beryllium layers asmean of T inventory control in ITERDavid Douai

P-5

DFT calculations of voids in α-Fe
Dmytro Kandaskalov

P-6

Meta-stable state of 111-crowdion binding with VH6 complex in tungsten
Daiji Kato

P-7

Comparing He ion energy transfer to W and Fe surfaces through molecular
dynamics simulationsPeter Klaver

P-8

Joint experimental and theoretical efforts to bridge the gap between today’s
experiments and future fusion devices
Timo Dittmar

P-9

Modelling and Experiments of Plasma-Material Interactions in Presence of fusion
Neutrons
Maya Padivattathumana

P -10

Magnetic sheath effect on the gross and net erosion rates due to impurities
Nicolas Mellet

P -11

Aluminium studies for laboratory plasma: particle growth and hydrogen retention
Jonathan Mougenot

P - 12

W2, W4, WH, WH2: Ab initio and DFT benchmarks
Michal Novotny

P - 13Modelling of D atom absorption and diffusion dynamics in self-ion damaged
tungsten exposed to deuterium atom beamAnze Zalzonik

P - 14

Kinetic Monte Carlo simulation and rate theoretical approach for influence of
vacancy on hydrogen diffusivity in tungsten
Deqiong Zhu
8	
  

	
  

MoD-PMI 2015	
  P - 15

Some aspects of determination of hydrogen binding energies with defects inmetalsMikhail Zibrov

P - 16

Raman spectroscopy investigation of beryllium based materials
Cédric Pardanaud

P – 17

Aspects of ion-metal and electron-metal interactions in fusion relevant energy
regimes
Svetlana Ratynskaia

P – 18The microphysics of ion-surface recombination and calculations of the heat sheathtransmission factor
Panagiotis Tolias

P – 19 Hydrogen diffusion and vacancies formation in tungsten: DFT and statistical models
Nicolas Fernandez

9	
  
	
  

MoD-PMI 2015	  Booklet
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  

Abstracts

10	
  
	
  

MoD-PMI 2015

I-1

Self trapping and trap mutation in bulk tungsten: a DFT and Molecular
Dynamics investigation

J. Boissea,b, C. Domaina,c, A. De-Backera,dC.S. Becquarta,*a

Unité Matériaux et Transformations, UMET, UMR 8207, Université de Lille 1, F-59655
Villeneuve d’Ascq, Franceb
Laboratoire d'Energétique et de Mécanique Théorique et Appliquée, LEMTA , UMR 7563,
Université de Lorraine, F-54504 Vandoeuvre-lès-Nancy, Francec
EDF-R&D, Département MMC, Les renardières, F-77818 Moret sur Loing, FrancedCCFE, Culham Science Centre, Abingdon, Oxon, OX14 3DB, UK

Being virtually insoluble in metals, but very mobile, He atoms can be trapped, associate withvacancies, forming platelets and bubbles. He atoms have been shown to contribute toswelling, cause intergranular embrittlement and produce roughening and blistering at metal
surfaces. Being repelled by the metal atoms, they form stable clusters, which are also
mobile. This tendency to form clusters is so strong that when too many He atoms areaggregated together it can be less costly to relieve the strain created by the interstitial
elements by the ejection of one or more matrix atoms leading to the formation of one or more
Frenkel Pairs (FP), i.e. vacancies and Self Interstitial Atoms (SIAs). When no vacancy is
initially present, the He cluster will be trapped by the vacancy it created, in a self-trapping(ST) event; whereas when one or more vacancies are already associated with the He cluster,
the same mechanism is referred to as trap mutation (TM) or loop punching, if more than one
SIA is created.
We have investigated the thermodynamics and kinetics of ST and TM in tungsten using
Density Functional Theory (DFT) calculations and Molecular Dynamics with a recently
developed potential for W-He adjusted on DFT calculations.
The stability of helium-vacancy clusters (HenVm) as well as pure interstitial helium clusters intungsten results from a competitive process between thermal emission of vacancies, selfinterstitial atoms and helium atoms, depending on the helium-to-vacancy ratio in mixed
clusters or helium number in pure interstitial helium clusters and will be presented in thiswork. We investigated in particular the ground state configurations as well as the activation
barriers of self trapping and trap mutation, i.e. the emission of one SIA along with thecreation of one vacancy from a vacancy-helium or pure helium object.

*Corresponding author: charlotte.becquart@univ-lille1.fr
11	
  
	
  

MoD-PMI 2015

I-2

New interatomic potentials for studying
the behavior of noble gas atoms in tungsten

Fen Zhou a, Jingzhong Fang a, Huiqiu Denga,*, Jianglong Liu a, Shifang Xiao a, Xiaolin Shu b,
Fei Gao c, Wangyu Hu aca

Department of Applied Physics, School of Physics and Electronics, Hunan University,
Changsha 410082, Chinab
Department of Physics, School of Physics and Nuclear Energy Engineering, Beihang
University, Beijing 100191, Chinac
Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann
Arbor, Michigan 48109, USA

The fiber-formed nanostructures (“fuzz”) have been observed on the surface of tungsten as
exposed to the low-energy and high-flux He plasma irradiation, however they were notformed on the W surface by exposure to Ar or Ne plasmas. To date the fuzz formation
mechanism is still unclear. To study the different behavior of noble gas X (=He, Ne and Ar)
atoms in the bulk and on the surface of tungsten, new ab initio-based potentials for W–He,
W–Ne and W–Ar interactions were developed by fitting the results obtained from firstprinciples density functional theory calculations. The “s-band model” was used to describe
the many-body interactions between each of the noble gas atoms and its neighboring W
atoms. These potentials reproduced the formation energies of point defects and themigration barriers of single noble gas atoms. The simulations using these potentials
successfully predicted that the tetrahedral interstitial site is more stable than the octahedral
interstitial site for X (= He, Ne or Ar) interstitials. Based on the new potentials, the binding
interactions of a single X atom with the Xn and Xn-Vacancy clusters and the diffusion
properties of Xn clusters in bulk W were studied using molecular dynamics simulations. The
simulation results indicate that the binding energies obtained using the new potentials arewell in agreement with the results of the first-principles calculations. The migration energiesof the clusters increase with both the increase in the atomic radius of noble gases and theincrease in the size of the clusters. The diffusion, nucleation and clustering behavior of noble
gas atoms in bulk W have been studied detailedly. The glide of dislocation loops induced by
Xn clusters or bubbles has also been discussed.

*Corresponding author: hqdeng@hnu.edu.cn

12	
  
	
  

MoD-PMI 2015

I-3

Tungsten Fuzzy Nanostructure Growth by Molecular Dynamics andMonte-Carlo Hybrid Simulation

A. M.Itoa,*, T. Murashimab, T. Tamurac, R. Kobayashic, A. Takayamaa, S. Kajitad, S.
Takamurae, N. Ohnod, M. Yajimaa, Y. Yoshimotof, S. Ogatab, and H. Nakamuraa,caNational Institute for Fusion Science, 322-6, Oroshi-cho, Toki 509-5292, Japan.
Tohoku University, 6-3, Aramaki-Aza-Aoba, Aoba-Ward, Sendai 980-8578, Japan.
cNagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555, Japan.
dNagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan.
eAichi Institute of Technology, 1247 Yachigusa, Yakusa-cho, Toyota 470-0392, Japan.
f
The university of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
b

Fuzzy nanostructure is induced by helium plasma irradiation onto a tungsten surfaces [1].
The fuzzy nanostructure which generated on the divertor walls in nuclear fusion reactors
brings about the decrease of the thermal conductivity of the tungsten materials and theincrease of the tritium retention. We have tried to clarify the formation mechanisms of the
fuzzy structure by multi-scale simulation approach. The formation process of the fuzzy
nanostructure can be classified into the irradiation process, the diffusion and agglomeration
process, the bubble structure growth process, and the fuzzy nanostructure growth process,which we call the four-step process [2]. In the four-step process, the former three processes
were clarifyed by using the binary collision approximation (BCA), the density functional
theory (DFT), and the molecular dynamics (MD), respectively.
In the fourth processes, the fuzzy nanostructure growth had been successfully reproduced by
the MD and Monte-Carlo (MD-MC) hybrid simulation [2,3]. In the MD-MC hybrid simulation,
the long time diffusion of helium atoms was simulated by the random walk based on the MC,
and the deformation of the tungsten material due to pressure from the helium bubbles was
simulated by the MD. As a result, it was understood that the fuzzy nanostructure grew only
when helium retention is under the steady state. In addition, the height of the fuzzy
nanostructure increased proportionally to the square root of helium plasma irradiation time,
which agrees with the experimental observations [4,5].
In this paper, we propose the mechanism of the enhancement of the convex-concave
surface structure, and introduce the improvement of the MD-MC hybrid simulation to
reproduce more long fuzzy nanostructure. If we achieve to create sub-micro-meter fiber, we
can compare the surface fractal dimension which had been measured by the experiment [6].

[1]
[2]
[3]
[4]
[5]
[6]

S. Takamura, N. Ohno, D. Nishijima, and S. Kajita, Plasma Fusion Res. 1 (2006) 051.
A. M. Ito, et al, J. Nucl. Mater. (2015) in press, doi:10.1016/j.jnucmat.2015.01.018
A. M. Ito, et al., in: IAEA Fusion Energy Conference, 2014, pp. MPT/1–MPT/3.
M. Baldwin and R. Doerner, Nucl. Fusion 48 (2008) 035001.
Y. Noiri, et al.,J. Nucl. Mater. (2015)in press, doi:10.1016/j.jnucmat.2015.01.036
S. Kajita, et al.,Phys. Lett. A 387 (2014) 2533-2538.

*Corresponding author: ito.atsushi@nifs.ac.jp (A. M. Ito)
13	
  
	
  

MoD-PMI 2015

I-4

Modelling of Hydrogen Interactions with Beryllium Surfaces in Fusion ReactoraP. Vladimirova,*,D.Bachurina, and Ch. Stihla
Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany

Beryllium is a candidate material for the first wall of future fusion reactor. It is also considered
as a neutron multiplier in the tritium breeding blanket. In both cases, hydrogen isotopes are
generated inside beryllium bulk via transmutations induced by fusion neutrons and willinteract with beryllium external and internal (gas bubble) surfaces. Therefore, theoreticalinvestigation of such effects is of high importance for the understanding of beryllium
behaviour in fusion environment.
This contribution reviews the results of the first principles modelling of hydrogen isotope
interaction with beryllium surfaces. Using ab initio molecular dynamics, we simulated thehydrogen molecule dissociative adsorption on Be (0001) surface for various hydrogensurface coverages. Our simulations show that the H2adsorption energy depends onhydrogen coverage, being 0.75 eV for the clean surface and about 1.2 eV for 1ML coverage.
Moreover, if the kinetic energy of impinging molecule is significantly higher than the barrier,but not sufficient for implantation under the surface, the molecule will be reflected with a highprobability. This sheds light on the physical meaning of the sticking coefficient. Preferablehydrogen adsorption sites for different coverage were found. Adsorbed hydrogen atoms repel
each other up to the third nearest neighbour distance, thus preventing
H2associativedesorption at low H-coverage. The repulsion of hydrogen atoms at highcoverage results in a notable surface stress and leads to surface reconstruction, which canbe viewed as formation of chemical bonds characteristic for BeH2polymer chains. Thistendency is further enhanced if subsurface hydrogen is present in addition to hydrogen at thesurface. In this case, amorphous chemical compound containing structural units similar to
those of BeH2is formed at the surface. These chains are elevated above the surface in the
middle, but still attached to it by their ends. We suggest, therefore, that decomposition of
BeH2formed at the external surface could be one of the possible hydrogen desorption
mechanisms, as supported by experiments [1].
In addition, we have shown that adsorbed hydrogen notably changes the surface energy ofthe major crystallographic surfaces. The general tendency consists in the surface energy
decrease with increasing hydrogen coverage, but then, at higher concentrations, hydrogenatoms begin to repel each other, and the surface energy increases again. The variations inthe surface energies are, however, quite different for the diverse surfaces tested, leading to
the change of the most energetically favourable surface from the basal (0001) plane for low
H-coverage to the pyramidal type II (112̅2) for high coverage. Moreover, equilibrium Hcoverage is different for different surfaces within one facetted gas bubble. This leads to thecomplex modification of the gas bubble form according to the H-surface coverage and its
bulk concentration. Drastic changes in the bubble form were also observed in the high-dosehydrogen implantation experiments[2].

[1]R.P. Doerner, et al., J.Nucl.Mater. 390-391(2009) 681-684[2] S.P. Vagin, et al., J.Nucl.Mater. 258–263(1998) 719-723*Corresponding author:pavel.vladimirov@kit.edu (P. Vladimirov)
14	
  
	
  

MoD-PMI 2015

I-5

Modelling and Data Needs for Plasma-Material Interaction in Fusion Devices:
Perspective from the IAEA Atomic and Molecular Data Unit
B. J. Braams* and H.-K. Chung
Nuclear Data Section, Division of Physical and Chemical Sciences (NAPC), International
Atomic Energy Agency (IAEA), Vienna, Austria

The mission of the Atomic and Molecular Data Unit (AMDU) at IAEA is to support
development of fusion as an energy source by the provision of internationally recommended
data for atomic, molecular and plasma-material interaction (PMI) processes and relatedmaterial microstructure properties. In the area of PMI the twin main concerns are erosion andtritium retention. Microstructure properties are important to us as they provide the link
between radiation damage and tritium retention. The Unit has active Coordinated Research
Projects (CRP) on PMI with beryllium [1], irradiated tungsten [2] and steel [3], and we aremindful of the importance of liquid metals as well. PMI is an important topic in our othermeetings as well, for example [4] and [5]. We are keenly interested in uncertainty
assessment and data evaluation, e.g. [6] and [7].
We will use the opportunity of speaking at MoD-PMI to highlight key issues in modelling anddata development for problems of PMI for fusion. One key issue is the effective treatment ofelectronic excitation in the context of molecular dynamics (MD) simulations of radiation
damage or other fast particle collision processes. This involves fundamental questions of thederivation of an effective model (perhaps Langevin dynamics for the nuclei coupled to a heat
equation for the electron temperature) starting from quantum or Ehrenfest dynamics. It also
involves assessment of suitable electronic structure methods and of the fitting of the resulting
internuclear potential or the force. A second key issue is that of development and validationof accurate MD potentials just for the ground electronic state, but for relevant non-crystalline
mixed materials at relevant high energies as after impact by a fast particle. A third key issue
is systematic uncertainty quantification from the electronic structure calculations through thedevelopment of MD potentials (or of rates for other simulations) to the calculation of
microstructure properties after exposure to plasma and/or radiation.

[1] CRP PMI with Beryllium: https://www-amdis.iaea.org/CRP/Beryllium/[2] CRP Irradiated Tungsten: https://www-amdis.iaea.org/CRP/IrradiatedTungsten/[3] CRP Steel Surfaces: https://www-amdis.iaea.org/CRP/SteelSurfaces/[4] ICTP-IAEA Joint Conference on Models and Data for Plasma-Material Interaction in
Fusion Devices: https://www-amdis.iaea.org/Workshops/ICTP2014/[5] Decennial IAEA Technical Meeting on A+M+PMI Data for Fusion Science andTechnology: https://www-amdis.iaea.org/meetings/AMPMI14/[6] Joint IAEA-ITAMP Technical Meeting on Uncertainty Assessment for Theoretical Atomic
and Molecular Scattering Data: https://int-amdis.iaea.org/meetings/ITAMP/[7] 4th Biennial Technical Meeting of the International Atomic and Molecular Code Centre
Network: https://int-amdis.iaea.org/CCN/Meetings4/*Corresponding author: b.j.braams@iaea.org (B. J. Braams)
15	
  
	
  

MoD-PMI 2015

I-6

Time-dependent simulation of electronic stopping from first-principles
J. Kohanoffa,*, E. Artachob, and A. A. Correaca

Atomistic Simulation Centre, Queen’s University Belfast, Belfast BT7 1NN, UKb
CIC Nanogune, Ave. Tolosa 76, Donostia San Sebastian 20018, Spainc
Lawrence Livermore National Laboratory, Livermore, CA 94550, USA

Materials in fusion reactors, especially those in the first wall, are subject to intense irradiation
with 14.1 MeV neutrons. While most neutrons will go through the wall without interacting, afraction of them will hit atoms in the material and transfer part of their kinetic energy to these,
so-called, primary knock-on atoms (PKA). The PKA become them themselves projectiles that
self-irradiate the material, damaging it. According to the velocity of the PKA, there are two
asymptotic regimes: nuclear stopping at low velocities, and electronic stopping at highvelocities. In the intermediate velocity region both mechanisms coexist. Most of the modelling
work done so far has focused on the nuclear stopping regime, which can be addressed via
molecular dynamics simulations based on empirical force fields. Although the fundamentals
of electronic stopping have a long research history, from the first-principles simulation pointof view, the electronic stopping regime has only been studied in the past few years [1].
Here I will present the approach we have been using to describe irradiation, and in particular
self-irradiation, of materials in the electronic stopping regime. The methodology is based ontime-dependent density-functional theory (TDDFT) and the Ehrenfest approximation, and issuitable for ion (or atom) irradiation. The simulation is started by assigning an initial velocity
to the projectile and proceeds by integrating numerically the time-dependent Kohn-Shamequations of motion for electronstogether with Newtonian equations of motion for the nuclei.
The forces on the nuclei arise from the time-dependent electronic density. This results in acontinuous increase of electronic energy due to non-adiabatic energy transfer from the
projectile to the electrons. The rate of energy transfer is directly related to the electronic
stopping. In addition, it is possible to compute non-adiabatic forces on the nuclei and otherquantities. We have used this approach to study proton and α-particle irradiation of a numberof materials such as LiF [1,2], Al [2,3,4], Au [5], Ge [6], and SiO2, and the self-irradiation of
Fe. The latter are directly relevant to fusion reactors.

[1] M. Pruneda, D. Sánchez-Portal, A. Arnau, J. I. Juaristi and E. Artacho, Physical Review
Letters99, 235501 (2007).
[2] M. A. Zeb, J. Kohanoff, D. Sánchez-Portal and E. Artacho, NIMB 303, 59 (2013).
[3] A. A. Correa, J. Kohanoff, E. Artacho, D. Sánchez-Portal and A. Caro, Physical Review
Letters, 108, 213201 (2012).
[4] A. Schleife, Y. Kanai and A. A. Correa, Physical Review B 91, 014306 (2015)[6] M. A. Zeb, J. Kohanoff, D. Sánchez-Portal, A. Arnau, J. I. Juaristi and E. Artacho,
Physical Review Letters, 108, 225504 (2012).
[6] R. Ullah, F. Corsetti, D. Sánchez-Portal and E. Artacho, Physical Review B 91, 12503(2015).

*Corresponding author: j.kohanoff@qub.ac.uk (J. Kohanoff)
16	
  
	
  

MoD-PMI 2015

I-7

Quantum nuclei in materials: (when) do we need to worry?

M. Ceriotti*
Laboratory of Computational Science and Modelling (COSMO), MXG 338 (Bâtiment MXG),
Station 12, CH-1015 Lausanne

I will present an introduction to the modeling of the quantization of ionic degrees of freedom
in materials, that is necessary to describe zero-point energy or tunneling effects. I will discusspath integral molecular dynamics and colored-noise acceleration, the most relevant
experimental observables related to nuclear quantum effects, and the situations in which they
can be expected to be important - including water, hydrogen-containing materials and point
defects in metals.

*Corresponding author: michele.ceriotti@epfl.ch
	
  
17	
  
	
  

MoD-PMI 2015

I-8

Quantum theory of transport and trapping of hydrogen in iron

Anthony T. Paxton* and Ivaylo H. Katzarov
Department of Physics, King's College London, Strand, London WC2R 2LS

I will describe recent progress in the calculation of diffusivity of hydrogen in body centred
cubic iron. Electronic structure is described within the tight binding approximation and the
dynamics of hydrogen is rendered using quantum statistical mechanical methods based
within the Feynman path integral formulation. I focus in particular upon two aspects of the
problem. One is the capture and escape from traps arising at crystal lattice defects, inparticular the vacancy. The other is the isotope effect, which highlights the non classicaldependence upon the mass of the diffusing particle.

*Corresponding author: Tony.Paxton@kcl.ac.uk

18	
  
	
  

MoD-PMI 2015

I-9

Nuclear quantum effects in tritium diffusion in α-ironToshiyuki Takayanagi
Department of Chemistry, Saitama University, Shimo-Okubo 255, Sakura-ku, Saitama City,
Saitama 338-8570, JAPAN

Molecular dynamics simulation is a very useful tool and has been extensively used in various
fields including physics, chemistry, biology and material sciences. The working equations
mostly used in the standard molecular dynamics simulation are Newton equations based onclassical mechanics, where nuclear quantum effects, such as zero-point energy andtunneling, are completely ignored. The validity of classical dynamics has not yet been fully
established in many cases since we do not have an exact quantum method that can beapplied to dynamical processes with many degrees of freedom. Recently, ring-polymer
molecular dynamics (RPMD) simulation have been becoming a practical and usefulcomputational tool that can describe quantum nuclear effects in various dynamical processes
at a relatively accurate level [1]. The RPMD method is an approximate quantum mechanicalsimulation technique based on path-integral formalism that enables inclusion of nuclear
quantization effects. The RPMD model allows for the simulation of real-time dynamical
trajectories and provides a consistent framework for simulating both quantum mechanicaland classical mechanical degrees of freedom. This method has been recently applied toobtain various dynamical quantities including chemical reaction rate coefficients as well as
diffusion coefficients [2-4]. However, it is also known that RPMD fails to describe highfrequency vibrational motions [5].
In this work, we apply the RPMD method as well as CMD (centroid molecular dynamics [6],also including nuclear quantum effects with a slightly different theoretical treatment) method
to hydrogen diffusion in α-iron [7]. We have employed the embedded atom model potential
energy interaction partly constructed with DFT calculations. It was found that the H and T
diffusion has the crossover temperature of 500 and 300 K, respectively, derived from thetemperature dependence of the calculated diffusion coefficients. This indicates that nuclear
quantum effects are not negligible below these temperatures. In addition, we found thatvibrational quantization is also playing an essential role in diffusion mechanisms because of
the existence of second-order saddle point with imaginary frequencies.
[1] S. Habershon, D. E. Manolopoulos, T. E. Markland, T. F. Miller III, Ann. Rev. Phys. Chem.
64 (2013) 387.
[2] Y. V. Suleimanov, Ro. Collepardo-Guevara, D. E. Manolopoulos, J. Chem. Phys. 134(2011) 044131.
[3] Y. V. Suleimanov, J. Phys. Chem. C 116 (2012) 11141.
[4] J. W. Allen, W. H. Green, Y. Li, H. Guo, Y. V. Suleimanov, J. Chem. Phys. 138 (2013)
221103.
[5] S. Habershon, G. S. Fanourgakis, D. E. Manolopoulos, J. Chem. Phys. 129 (2008)
074501.
[6] J. Cao, G. A. Voth, J. Chem. Phys. 99 (1993) 10070.
[7] T. Yoshikawa, T. Takayanagi, H. Kimizuka, M. Shiga, J. Phys. Chem. C 116 (2012),
23113.
	  *Corresponding author: tako@mail.saitama-u.ac.jp (T. Takayanagi)
19	
  
	
  

MoD-PMI 2015

I - 10The need for a better understanding of plasma-material interactions in ITER
and the role of modellingaG. De Temmermana
ITER Organization, Route de Vinon sur Verdon, CS 90 046, 13067 Saint Paul-lez-Durance
Cedex, France
gregory.detemmerman@iter.org

ITER, currently being built in Southern France, aims at producing 500MW of output power for
durations of 400s, thereby demonstrating the scientific and technological feasibility of fusion
power for peaceful purposes. In a fusion device, power from the core plasma has to be
exhausted by the plasma-facing components, mainly in the divertor area, a special area ofthe plasma chamber where the open magnetic field lines intersect the primary plasma facing
components and where the plasma is neutralized and pumped away. The plasma-facing
surfaces in the divertor are thus exposed to extreme heat (>10MW.m-2) and particle fluxes(up to 1024m-2s-1 or 1.6x105A.m-2) for extended durations and accordingly tounprecedented ion fluences. In addition, the very high localized heat fluxes caused byunmitigated edge-localized modes (ELMs) (several GW.m−2 for 0.5–1ms) are high enoughto lead to material erosion, melting, and vaporization for most materials and represent a
serious concern for the lifetime of the plasma-facing components. ELM mitigation is requiredin ITER to keep the energy density below the melting threshold of tungsten. A large number(>107) of mitigated ELMs (with E<0.5MJ.m-2) is however expected over the divertor lifetime.
Bombardment of tungsten surfaces by low-energy ions (D/He) is known to lead to strong
morphology changes which are well-documented and subject to intensive investigations. The
impact of those morphology changes on the long-term evolution of the material thermomechanical properties is however not known. Similarly, while significant surface damage canoccur for surfaces exposed to large number of ELM-like transients even at the moderateenergy densities expected during mitigated ELMs, the impact of the strong materialcracking/roughening on the power handling capability of the material is not yet clear.
It is probably not possible to address all those issues experimentally before ITER starts
operating, but the preparation for ITER operations implies building the strongest possible
physics basis. Modelling has therefore a key role to play in the plasma-material interaction
area. Ultimately, the goal of numerical simulations should be to build a model that is global
enough to capture the behaviour of a material under fusion conditions and can ‘predict’changes of the material thermo-mechanical properties under prolonged operation.
This talk will introduce the various challenges related to power exhaust and plasma-wallinteractions in ITER with an emphasis on the open questions where further research isneeded and modelling can help.
Corresponding author: gregory.detemmerman@iter.org (G. de Temmerman)

20	
  
	
  

MoD-PMI 2015

I - 11

Vacancy defects studied in tungsten by using Positron annihilation
spectroscopy
M-F. Barthea,*, P.E. Lhuilliera, M. Sidibea, C. Genevoisa, P. Desgardina, B. Decampsb,
R.Schaeublinc, A.De Backerd, C. S. Becquartda

CEMHTI, CNRS/Orléans University, 3A Rue de la Férollerie, 45071 Orléans, Franceb
CSNSM, Bâtiment 108, 91405 Orsay, Francec
MPTDM, ETH Zürich, HCI G515, 8093 Zürich SwitzerlanddUMET, UMR 8207, Université de Lille 1, EM2VM, Villeneuve d’Ascq, France	  Tungsten has been chosen to recover parts of the divertor and is a candidate material forfirst wall armor of future thermonuclear fusion reactors (ITER and DEMO) where it will be
subjected to extreme conditions: neutron irradiation, He and H fluxes and high temperatures.
The introduction of He, point defects and H in metals lead to the evolution of the
microstructure and macroscopic properties such as mechanical properties (embrittlement,swelling..) that have to be understood to foresee the lifetime of the component in suchextreme conditions.
Positron annihilation spectroscopy (PAS) is a well-known and established technique,able to characterize vacancy defects and free volumes in materials. It is sensitive to the sizeof the defects from the single vacancy and to their clustering or their decoration with
impurities (such as He…) with a great advantage of probing thin damage region by using
slow positron beams. In this presentation the principles of the technique will be reminded andsome examples of the results obtained in W will be developed. We show how carefully
designed experimental investigations using PAS and other techniques such as TEM, NRA(nuclear reaction analysis), and modeling can complement each other and provide a route to
the understanding of the microstructure evolution of materials in these conditions.
On one hand, in the objective of determining the properties of vacancy defect and theirinteraction with He, the distribution and the nature of 3He implantation-induced defects intungsten samples have been studied by PAS as a function of implantation fluence. The
results show that monovacancies are generated along the ion path and that theirconcentration varies directly with the implantation fluence. The annealing induces
agglomeration to form large vacancy clusters. These results are in good agreement with
object kinetic Monte-Carlo (LAKIMOCA) simulations.
On the other hand, in the aim of studying and understanding the evolution of the
microstructure of tungsten under irradiation in an environment close to the one of future
fusion reactors such as ITER and DEMO, irradiation of W samples with W ions were carriedout as a function of dose and temperature. PAS revealed small vacancy clusters. Their sizeand concentration increase with irradiation dose up to 1 dpa and annealing of irradiatedsamples a change in their size and concentration. TEM observations show that the formationof vacancy defects, namely voids or vacancy loops, depends on the irradiation dose andtemperature.
Acknowledgements: Irradiations done at JANNuS (Joint Accelerators for Nanoscience and Nuclear
Simulation) Orsay at CSNSM (Orsay, France) and Saclay at CEA (France) which are part of the EMIR
French accelerators network. This work has been carried out within the framework of the EUROfusion
Consortium and has received funding from the European Union’s Horizon 2020 research andinnovation programme under grant agreement number 633053. The views and opinions expressedherein do not necessarily reflect those of the European Commission.

*Corresponding author: marie-france.barthe@cnrs-orleans.fr (M.F. Barthe)

21	
  
	
  

MoD-PMI 2015

I - 12

Experimental studies of hydrogen transport parameters in tungsten

H.T. Leea,*, Y. Hamajia, K. Ibanoa, M.Oyaa, and Y. Uedaa
aGraduate school of Engineering, Osaka University, Suita, Japan

Tritium inventory and permeation will certainly grow more in importance with ITER and next
step devices employing metal plasma facing materials or components, as a consequence ofthe expanded use of tritium coupled with longer pulse or steady state operation. Specifically,tungsten is presently planned for use in the ITER divertor and possibly as an armor material
for the first wall in next-step devices.
To improve our modeling and predictive capabilities of tritium inventory and permeation infusion devices employing tungsten, we must solve the hydrogen transport equation, which
requires solution to the diffusion equation with appropriate boundary conditions and trapping
parameters. In general, the boundary conditions and trap parameters are time dependent
due to the physico-chemical changes occurring at the tungsten surface from material mixing /erosion processes or changes in bulk material properties from neutron or heat loads.
Presently, large uncertainties exist in accurately determining the nature of such boundary
conditions and trap parameters, which hinders a robust and accurate estimate of tritium
inventory and permeation in fusion devices.
In this presentation, we present our on-going efforts to establish the foundation necessary toquantitatively predict hydrogen transport (release, trapping, permeation) in tungsten. We
address the following three phenomena that are important for quantifying tritium transport.
First, the changes in boundary condition and its impact on the inward diffusive flux asfunction of temperature due to impurity induced near surface changes (C, N, He, Ar, Ne) orby surface melting are discussed. Second, we present our effort on determining thefundamental parameter of hydrogen diffusion coefficient in the temperature range of interestin fusion (300 < T < 1000 K). Third, we present novel ion/electron beam and tritium tracer
experiments that appear promising in determining some of the fundamental parameters,
which may allow testing and bridging of first principle simulations with laboratory
experiments.

*Corresponding author: heunlee@wakate.frc.eng.osaka-u.ac.jp (H.T. Lee)
22	
  
	
  

MoD-PMI 2015

I - 13

Understanding the fundamental mechanisms behind H embrittlement:
An ab initio guided multiscale approach

Jörg Neugebauer*, Gerard Leyson, Blazej Grabowski, and Tilmann Hickel
Max-Planck-Institut für Eisenforschung, Max-Planck-Str. 1, 40237 Düsseldorf, Germany

The mechanical integrity of many materials is impacted by the presence of hydrogen andeven minute amounts of a few ppm may give rise to fracture and embrittlement. This isparticularly true for metallic alloys designed to withstand high mechanical loads. From amodeling point of view, the description of the impact of H on mechanical properties ischallenging since it is well known to interact with almost all microstructural and point defects.
Thus, a quantitative description of how H impacts and interacts with the various defects
requires to model large length- and timescales while also having to take into accountatomistic effects. In the talk it will be shown how combining ab initio calculation withthermodynamic concepts allows to determine free energies at finite temperatures with ahitherto unprecedented accuracy. These concepts have been successfully used to (i) identify
the relevant mechanisms at atomic scale and (ii) to construct atomistically informed
mesoscale/macroscale concepts that allow to model H embrittlement on the length and timescales relevant for experiment.

*Corresponding author: neugebauer@mpie.de (J. Neugebauer)

23	
  
	
  

MoD-PMI 2015

I - 14

Setting up plasma pulse-scale simulations withelectronic structure calculations
K. Heinolaa,bab

University of Helsinki, P.O.Box 43, 00014 University of Helsinki, Finland
Culham Centre for Fusion Energy, Abingdon, OX14 3DB, United Kingdom

In a fusion device, the interactions between the plasma and the surrounding armour material
take place in time-scales ranging from microseconds to hours, and in length-scales fromnanometres to centimetres. The experimental observations typically cover these time-scales,
whereas the spatial resolution is usually observed as an integral over vessel surface areas.
For understanding the underlying microscopic phenomena leading to observed larger scale
events, dedicated laboratory experiments and computational studies need to be carried out
focusing on the microscopic effects on the surface and in the bulk of the fusion relevantmaterials, such as tungsten (W) and beryllium (Be).
Use of electronic structure calculations is an essential tool in studying the microscopic effects
theoretically. Obtained results are used as building blocks when increasing the knowledge on
effects taking place in larger length and time scales, and studied with applicable
computational tools such as Molecular Dynamics, kinetic Monte Carlo calculations, andfurther with the Rate Theory calculations. Computational studies extended into multiple
length and time-scales allow understanding and extrapolating the experimentally observed
materials effects under plasma conditions. Starting from electronic structure calculations westudy the effects of hydrogen (H) trapping and diffusion in W, point defects, and defectclustering. The theoretical results will be used in multi-scale Rate Theory calculations, andcompared with implantation experiments, and thermally activated desorption results. Recent
W-Be-H results obtained with Molecular Dynamics calculations will be discussed andcompared against the experimental erosion and deposition data obtained from JET’s ITERLike Wall campaign.
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
*Corresponding author: kale.heinola@ccfe.ac.uk (K. Heinola)
24	
  
	
  

MoD-PMI 2015

I - 15

Hydrogen recycling in tungsten during plasma pulse simulations
with rate equations
T. Ahlgren*, K. Heinola and L. Bukonte
University of Helsinki, P.O.Box 43, 00014 University of Helsinki, Finland

Hydrogen recycling between fusion plasma and plasma facing materials is one of the mostimportant issues to achieve stable steady state fusion operation. It affects also the hydrogenisotope retention (i.e. tritium inventory). Most of the particles in the plasma have entered theplasma through recycling from the plasma facing components.
Using rate theory equations we simulate hydrogen recycling and retention in tungsten during
plasma pulses. Results show that there are short periods of times during which H particle flux
back towards the plasma is larger than the flux into the tungsten material. Moreover, thevacancy formation in tungsten is simulated for both high energy deuterium irradiation
experiments and below threshold displacement energies. The vacancy formation is seen to
be flux dependent especially for low energy irradiations.

*Corresponding author: tommy.ahlgren@helsinki.fi (T. Ahlgren)
25	
  
	
  

MoD-PMI 2015

I - 16

Multiscale modelling of radiation effects in materials: ion implantation versus
neutron irradiation
M. J. Caturla*
Dept. De Fisica Aplicada, Universidad de Alicante, Alicante E-03690, Spain

Modelling radiation effects requires bridging a wide range of time and length scales. For
example, defects are produced in a picosecond timescale while diffusion of these defects
can expand seconds or hours. A multiscale approach, using different simulation methods,
have proven to be a very successful way to model damage production and damage
evolution. However, care must be taken in the transfer of information from one simulationlevel to the next, to make sure all the relevant processes are included in the model.
In this presentation we will provide a description of the most commonly used multiscalemodelling approach: combining density functional theory calculations, molecular dynamics
simulations and object kinetic Monte Carlo, to provide information that can be directlycompared to experimental measurements of damage in irradiated materials. We will focus on
one example: damage produced in Fe and FeCr alloys. And we will discuss one particularissue: the differences between ion implantation and neutron irradiation. Currently, ion
implantation is commonly used to obtain information about defect production and defectevolution, in an attempt to build models for neutron damage. We will point out the differences
and commonalities between the two types of irradiation, and those aspects that should betaken into consideration when building models for neutron irradiation from information
obtained from ion implantation.

*Corresponding author: mj.caturla@ua.es (M. J. Caturla)

26	
  
	
  

MoD-PMI 2015

I - 17

Modeling isotope exchange in W using fill level dependent trapping
K. Schmid*, T. Schwarz-Selinger
Max-Plank Institut für Plasmaphysik, Boltzmannstrasse 2 85748 Garching, Germany

Common diffusion trapping models for modeling hydrogen transport in metals are limited totraps with single de-trapping energies and a saturation occupancy of one. While they aresuccessful in predicting typical mono isotopic ion implantation and thermal degassing
experiments, they fail at describing recent experiments on isotope exchange at low
temperatures. Following the predictions of DFT calculations we have developed a new
diffusion trapping model [1] that is based on fill-level-dependent de-trapping, where each trapsite can contain an integer number of hydrogen atoms and the de-trapping energy depends
on the current fill level. This model allowed us to describe the isotope exchange experiments
conducted close to room temperature where common diffusion trapping codes predict noisotope exchange since all traps are filled and inactive.
The main input data into the new fill-level-dependent de-trapping code is the fill level
dependence of hydrogen binding energy in a particular trap site. These numbers are only
available from DFT calculations at the moment and are thus limited to small defects likemono-vacancies. However from previous experiments it seems that in W trapping is probably
dominated by dislocations [2]. Therefore the initial comparison with experiments using thedata for mono-vacancies only qualitatively reproduced the data but a quantitative match
required an ad-hock fit of the activation energies.
In this presentation we will discuss the implication of fill-level-dependent de-trapping both formono-isotopic and for isotope exchange experiments. We will show that for mono-isotopic
experiments the new model is indiscernible within experimental uncertainties from common
diffusion trapping models. For isotope exchange experiments we will show that common
diffusion trapping models not just underestimate the isotope exchange at low temperatures
but that they also fail at correctly describing propagation of the diffusion front during isotope
exchange experiments.

[1] K. Schmid et Al, J. Appl. Phys 116 (2014) 134901[2] A. Manhard et Al, J. Nucl. Mat. 415 (2011) p. 632*Corresponding author: Klaus.schmid@ipp.mpg.de (K. Schmid)

27	
  
	
  

MoD-PMI 2015

I - 18Macroscopic rate equation modeling of trapping/detrapping of hydrogenisotopes in tungsten materials
E. A. Hodillea, Y. Ferrob, C.S. Becquartc, R. Bissonb, N. Fernandezb, J. Mougenotd and C.
Grisoliaa,*a

CEA, IRFM, F-13108 Saint Paul lez Durance, France
Aix-Marseille Université, PIIM, CNRS, UMR 7345, 13397 Marseille, FrancecUniversité Lille I,UMET, UMR 8207, 59655 Villeneuve d’Ascq cédex Franced
LSPM-CNRS, Université Paris 13, Sorbonne Paris Cité, F-93430 Villetaneuse, Franceb

Macroscopic rate equations (MRE) are used to investigate migration and trapping ofhydrogen isotopes (HIs) in metallic materials at scales relevant to realistic experiments suchas thermal desorption spectrometry (TDS) measurements realized after plasma or ions
exposure of a tungsten (W) sample. In usual MRE models as TMAP7, HIIPC or our own
code MHIMS (Migration of Hydrogen Isotope in MaterialS), each trapping site can only trap asingle HI and each type of trapping site has a unique and constant detrapping energy. In thefirst part of this presentation, the free parameters of the MHIMS code are adjusted thanks towell defined TDS experimental data. Then, MHIMS is frozen and used to extrapolate todifferent experiences as retention versus ions fluence or evolution of retention of HIs in
function of the sample temperature: the predicted results are in good agreement with theexperimental data. However, DFT calculations have shown that in a single crystal of W atroom temperature up to 6 HIs can be trapped in a single type of trap such as a monovacancy. In such a vacancy, the detrapping energy increases as the number of HIs
decreases. These results are not the one used in MHIMS. Thus, a new version of the code
called “MHIMS-reservoir” has been developed based on these DFT outcomes. Thisapproach has been recently used by K. Schmid and co-workers to model the isotopic
exchange observations which are difficult to reproduce with a usual MRE model. In thefollowing part of the presentation, the newly implemented MHIMS-reservoir equations are
first described and then, their outcomes confronted to experimental TDS measurements after
ions implantation in a tungsten single crystal (SCW). In the simulation with no time lag
between implantation and TDS, the TDS spectrum is composed of 3 peaks. The first TDS
peak observed at low temperature corresponds to vacancies filled with 6 HIs; the second
peak at medium temperature to vacancies filled with 5-3 HIs; and the third one at hightemperature, which is the dominant one, to vacancies filled with 2-1 HIs. Experimentally, one
or two peaks are observed. Complete simulation with all the step followed in the experimentshows that the number of peaks observed experimentally is highly dependent on the time lag
between implantation and TDS measurements.
Using DFT values for detrapping energies, the MHIMS reservoir model is able to fit theexperimental TDS measurements presented by Poon and co-workers taking into account the
TDS chamber baking at 400 K during 1.5 h which precedes the TDS measurement. In thecase of TDS measurement from Quastel and co-workers, we have to decrease thedetrapping energies by 10 % in order to fit the experimental spectrum. This could be
explained by the high impinging deuterium flux (1020 D/m²/s) used in those experiments
which induces traps creation.

*Corresponding author: christian.grisolia@cea.fr (C. Grisolia)

28	
  
	
  

MoD-PMI 2015

I - 19Migration, trapping and release of deuterium from tungsten in the presence ofhigh density of defects: theory and experiment
O.V. Ogorodnikova*
National Research Nuclear University "MEPHI", Kashirskoe sh.31, Moscow, Russia

Due to practical importance of using of tungsten (W) as a plasma-facing material for
fusion application and wide accumulated database, the deuterium (D) accumulation andrelease in W are analyzed in the present contribution. Those plasma-facing components offusion reactors will be exposed to 14 MeV neutrons. Ion irradiation with energetic heavy ionsis currently recognized as the only non-activating method to simulate the fast neutron
damage produced in fusion reactors. Therefore, in this work, 20 MeV W ions were used tosimulate n-induced damage in W samples. Following to the damage production by theirradiation at different dpa levels, samples were loaded by D2 gas, D thermal atoms or lowenergy D plasma. Each sample was exposed once to the certain experimental condition.
Post-mortem measurements were nuclear reaction method (NRA) and thermal desorption
spectroscopy (TDS). The D retention in damaged W was compared to that in undamaged W.
The formation of blisters observed in the case of undamaged W was suppressed after preirradiation of W with self-ions because of creation of a high density of defects in damaged W
which prevent any local super-saturation and, therefore, quenching blister formation.
Rate equations have been used to model experimental data. The diffusivity, solubility,reflection coefficient, surface barrier, binding energies of D with different types of defects anddensity of defects are input parameters for rate equation model. These parameters can bederived from the first-principle (DFT) calculations, effective-medium theory (EMT), molecular
dynamics (MD) and TRIM calculations. Incorporation of binding energies of D with a vacancy
and a dislocation recently calculated by DFT [1,2] and penetration probability and ion range
calculated by MD and TRIM [3] in the rate equation model allows us to validate different
predictions against experimental data. A comparison of calculations using different
theoretical models with experimental values can clarify the physics underling the hydrogenmetal interaction and can provide an answer on several important questions, namely, (i)which type of trap corresponds to certain D binding energy, (ii) which is a range of validity of
MD and TRIM models as well as limitation of DFT calculations and (iii) which process is ratelimited in respect to the D uptake and release in W. Modelling of experimental data of the D
depth profile in pre-damaged W after exposure to thermal atoms, D2 gas or low-energy
plasma did not show any local super-saturation that is in an agreement with experiments andexplains the mechanism of the blister formation. It was shown analytically and confirmed
experimentally that the D migration and trapping in a presence of high density of defects in W
depends on the penetrated ion flux, incident D energy, defect density and sample
temperature.

[1] D.F. Johnson and E.A. Carter, J. Mater. Res., 25 (2) (2010).
[2] D. Terentyev, private communication.
[3] O.V. Ogorodnikova and S. Markelj, in preparation.
*Corresponding author: igra32@rambler.ru (O. Ogorodnikova)
29	
  
	
  

MoD-PMI 2015

O-1

Influence of aluminum oxide coating oxygen presence in plasma on deuterium
retention in tungsten
L. Begrambekova‫٭‬, A. Ayrapetova, A. Evsina, C Grisoliab, A. Kaplevskya, Ya. Sadovskya, andA. ZakharovaaNational Research Nuclear University (MEPhI), Moscow, Russiab
CEA, IRFM, F-13108 Saint Paul lez Durance, France

The report presents the results of the experiments made in MIKMA device [1] with thesamples of PLANSEE tungsten. The samples were irradiated by the ions of deuterium (ordeuterium with oxygen addition) plasma.The irradiating ion current density was (3.97.9)×1019 at/m2sec, the sample temperature – 500 K. The amount of gases retained in thesamples after each experiment were determined by Thermal Desorption Spectrometry(TDS). The samples were not annealed after each TDS.
Experimental results (fig. 1.) show that fluence dependence of deuterium trapping in tungsten
is determined by ion energy. Aluminum oxide coating increases retention of the implanted
deuterium atoms preventing their diffusion to the surface. Irradiation of the tungsten with ionsof the oxygen added plasma leads to the decrease of deuterium trapping. Oxygen seems toinitiate surface reactions activating deuterium atom recombination and release from thesurface. The same processes courses the release of pre-implanted deuterium atoms fromthe aluminum oxide coated tungsten, when the last one is irradiated by the ions of theoxygen added hydrogen plasma. The irradiation activated processes leading to observed
phenomena are discussed.

Fig.1. Deuterium retention in both tungsten and tungsten with aluminum oxide coating after
irradiation under various conditions.
[1] Airapetov A., Begrambekov L., Brem S. et al. J. of Nucl. Mater. 415(2011)1042.
*Corresponding author: lbb@plasma.mephi.ru (L. Begrambekov)
	
  

30	
  
	
  

MoD-PMI 2015

O-2

Deuterium retention in polycrystalline tungsten at low fluencesaR. Bissona,*, F. Ghiorghiua, and T. Angota
Aix-Marseille Université, CNRS, PIIM UMR 7345, 13397 Marseille, France

Fuel retention is one of the critical issues for plasma facing materials in fusion devices
because of nuclear safety regulation related to the tritium inventory. In this contribution, we
will present our progress in building a consistent database on deuterium retention intungsten, which is being used in an integrated experiment-multi-scale modeling approach
dedicated to reveal fundamental mechanisms behind deuterium and tritium retention intungsten materials (WHISCI A*MIDEX project). This is a mandatory step for any reliable andpredictive ITER wall model to be developed.
In an introducing part, we will present our experimental setup which has been designed to
avoid any spurious effects related to contamination and air exposure. In our apparatus,
tungsten samples are prepared, implanted with deuterium ions and characterized all in-situ inultrahigh vacuum. For precise quantification of deuterium retention, a high-sensitivity
Temperature Programmed Desorption (TPD) is used allowing exploring fluences as low as afew 1017 D/m2. This sensitivity eases the comparison with theoretical methods and allows
detecting any surface effects in retention/release processes. We underline the fact that agreat number of parameters are controlled independently in this apparatus, such as the ion
kinetic energy, the ion flux, the sample temperature during ion implantation, the time between
ion implantation and retention measurement… as well as the quality of the sample since weobtained implanted polycrystalline samples exhibiting a single deuterium desorption peak.
Then, we will present systematic studies on how deuterium retention depends on some ofthese parameters. First, we will confirm a “universal” retention vs. fluence relationship for
polycrystalline tungsten by extending in-situ results of Ogorodnikova et al. [1] to low fluences,from 1021 D+/m2 down to 1017 D+/m2. Second, we will evidence a release of implanted
deuterium from tungsten at room temperature, a behavior that can be rationalized with recent
DFT results [2]. Third, the deuterium retention dependency with the implantation temperature
will be presented for low fluences. These new results will be compared with high fluences
results from Roszell et al. [3] as well as post-implantation annealing experiments performedin our laboratory.

[1] O.V. Ogorodnikova, J. Roth, and M. Mayer, J. Nucl. Mater. 313-316 (2003) 469[2] R. Bisson, et al., J. Nucl. Mater., submitted[3] J.P. Roszell, J.W. Davis, and A.A. Haasz, J. Nulc. Mater. 429 (2012) 458*Corresponding author: regis.bisson@univ-amu.fr (R. Bisson)

31	
  
	
  

MoD-PMI 2015

O-3

Hydrogen trapping at vacancies and hydrogen impact on vacancy diffusionand self-diffusion in Ni

1

Y. Wang1,2, D. Connétable2 and D. Tanguy1
Institut Lumière Matière, UMR 5306, Université Lyon 1-CNRS, Villeurbanne
2
CIRIMAT,UMR 5085, ENSIACET, Toulouse

We study possible implications of vacancy-hydrogen clusters in environmental damage of"structural" metallic alloys (oxidation, hydrogen (H) embrittlement, eventually irradiation). In
Ni (and Pd), Fukai has shown that gigantic concentrations (up to 25 at. %) of vacancies canbe stabilized by H [1,2,3] and that it could increase by several orders of magnitude thediffusion coefficients of the host metal. The conditions, however, are extreme: originally, theproject concerned hydrides at high temperature (600-900C, pH2=3GPa). One can wonder ifthese effects exist in the service conditions of Ni based alloys: room temperature and
CH=2000ppm for H embrittlement and 600K, CH= 2500ppm to 1at.% for stress corrosion
cracking in pressurized water reactors. We have performed EAM and DFT calculations of H
segregation energies at vacancies in Ni. The maximum binding is 0.27eV and 0.4eV in the
single and divacancy respectively, in good agreement with Fukai's Thermal Desorption
Spectroscopy results. By a comprehensive calculation of the formation energy of VHnclusters (n=1 to 14), it was shown that segregation occurs mostly on the octahedral site (offcentered) in the vacancy (O1) with almost no O1-O1 interactions, strong O1-T1 (tetrahedral)
repulsion and weak attractive O1-O2 interaction. Approximately constant effective pairinteractions can be extracted from these formation energies. Together with the segregationenergies in the dilute limit, they constitute a simple energetic model from which we canderive the equilibrium distributions and concentrations of VHn (analytical formulas arevalidated against Monte Carlo simulations). The knowledge of the statistical weight of thevarious clusters enables to select a limited number of configurations to evaluate migration
barriers, and from this, the diffusion coefficient of the clusters. H drastically slows down thevacancies, but this effect is overcompensated by the increase in equilibrium vacancies andfinally Ni self-diffusion is markedly increased.
We have also studied the trapping of H at vacancies. We show that we can use a random
walk model to derive the effective diffusion coefficient, as a function of the vacancy
concentration. The use of First Passage Time Analysis [4] enables to consider the inner sites
connectivity in the model and go beyond Oriani's formulation. Finally, a simple model is
proposed which is valid at high vacancy concentrations (KMC simulations are used as acheck) and for defects larger than vacancies, like small precipitates. We believe suchmodeling can be useful to design microstructures optimized to slow down H penetration.
Journal of Alloys and Compounds 614 (2014) 211-220, acta mater 78 (2014) 135, Phys. Rev.
B 2015 (accepted) [1] Y. Fukai et N. Okuma, Phys. Rev. Lett. 73 (1994) p. 1640
[2] Y. Fukai, J. Alloys Comp. 356-357 (2003) p. 263[3] E. Hayashi, Y. Kurokawa and Y. Fukai, Phys. Rev. Lett. 80 (1998) p. 5588
[4] B. Puchala, M. L. Falk and K. Garikipati, J. Chem. Phys. 132 (2010) 134104*Corresponding author: dome.tanguy@univ-lyon1.fr (D. Tanguy)

32	
  
	
  

MoD-PMI 2015

O-4

	
  

Vacancy nanoclusters in irradiated W and W alloys:
First-principles assessments and multi-scale modelling
	
  
	
  
a

D. Nguyen-Manha,*, D. Masona, J. Wrobela and S. Dudareva
Culham Centre for Fusion Energy, Abingdon, OX14 3DB, United Kingdom

	
  
	
  
	
  
Understanding of irradiation-induced vacancy behaviour in tungsten is one of outstanding
and debate issues since the 1960s although numerous studies have been taken with regard
to the generation and formation of defect structures formed under irradiation. On one hand, anucleation and growth of vacancies into voids and dislocation loops can be observed indamage microstructures in W and W alloys using neutron and ion irradiation. On the other
hand, the vacancy population produced by irradiation was unaccounted for in form ofvacancy defects which could not be reliably sized within nano scale using TEM but small
vacancy clusters can be detected by Positron Annihilation Spectroscopy (PAS).
By employing multi-scale approach based on first-principles assessment for which theinhomogeneous and low electron density in vacancy-cluster regions has been taken into
account, we have performed a systematic study of energetic and kinetic properties of nanovacancy in bcc TMs with a particular focus on tungsten and origin of the observed
anomalous effects of solute segregation in W alloys. The formation and migration energies ofvacancy clusters in nanometer-size scale as well as different dissociation pathway of
vacancy clusters have been investigated in order to assess the stability and transformation ofdifferent defect configurations by using density functional theory (DFT) calculations in
combination with molecular relaxation and kinetic Monte-Carlo simulations at various rangesof temperature and time. Importantly, our ab-initio data base for vacancy cluster calculations
have been used to designing a new EAM-type interatomic potentials for which the surface
corrections to the embedding functional have been implemented. By cross-checking bothformation and migration energies for nanoclusters of vacancies, the agreement between newcorrected EAM potentials with DFT calculations is very satisfactory. The predicted
temperature of vacancy-cluster dissociation is consistent not only with observation of thevoids ibut also with the variation of dislocation length in high-temperature annealing of selfion irradiated tungsten [1]. Finally, we describe briefly the extension of a combined DFT-MC
formalism by considering vacancy as a new element in a multi-component alloys in order tostudy the origin of coherent precipitates in W-2%Re alloys under irradiation [2].

[1] F. Ferroni et.al., Acta Mat. 90 (2015) 380[2] A. Xu at al., Acta Mat., 87 (2015) 121*Corresponding author: duc.nguyen@ccfe.ac.uk (D. Nguyen-Manh)
33	
  
	
  

MoD-PMI 2015

O-5

Materials research in Jülich: hydrogen retention in beryllium
D. Matveeva*, T. Dittmara, M. Köppena, B. Unterberga, M. Reineltb, P. Dollasea,
M. Eichlera, A. Allouchec, Y. Ferroc, and Ch. LinsmeieraaForschungszentrum Jülich GmbH, Institut für Energie- und Klimaforschung – Plasmaphysik,
52425 Jülich, Germanyb
Fraunhofer-Institut für Verfahrenstechnik und Verpackung IVV, D-85354 Freising, Germanyc
Aix-Marseille University-CNRS, PIIM UMR 7345, Marseille 13397, France

Interactions of the beryllium first wall with hydrogenic plasma species and intrinsic andseeded plasma impurities represent a particular interest for ITER. The main issues are thewall lifetime, formation of mixed layers (e.g. Be-W-N) in the divertor, and tritium retention.
Forschungszentrum Jülich focuses its activities on these aspects of plasma-wall interactions,as well as on the development of advanced materials for first wall components. This
contribution will give a short overview of experimental setups in Jülich, namely the linear
plasma device PSI-2 and two multi-purpose experiments combining surface preparation,
treatment and analysis (Artoss and the new XPS facility). Furthermore, the synergy ofmodelling and experiments will be illustrated on the example of hydrogen retention in Be
addressed by means of diffusion-trapping modelling.
The diffusion-trapping model for Be is based on a system of coupled reaction-diffusion
equations incorporated in the CRDS code [1] and supplied with an input from DFT simulation
results [2]. The code is used to interpret experimental results on hydrogen retention in Be [3,4]. The model allows introducing multiple diffusing species including mobile traps, multiple
trapping in mono-vacancies, and surface-limited desorption processes. CRDS was
successfully applied earlier to explain temperature-programmed desorption (TPD)
experiments with monocrystalline and polycrystalline Be irradiated to low D fluences (~3×1019 D/m2) in the Artoss facility [1]. In this contribution, we revise hydrogen retention andtransport mechanisms addressed in earlier works and investigate how different model
assumptions with respect to involved processes and their parameters influence the simulated
TPD spectra. The particular interest represent low-temperature desorption peaks (below 500
K) observed for fluences above 2×1021 D/m2.

[1] R. Piechoczek et al., J. Nucl. Mater. 438 (2013) S1072[2] A. Allouche, J. Phys. Chem. C 114 (2010) 3588
[3] M. Reinelt, et al., New J. Phys. 11 (2009) 043023[4] M. Oberkofler, et al., J. Nucl. Mater 415 (2011) S724

*Corresponding author: d.matveev@fz-juelich.de (D. Matveev)

34	
  
	
  

MoD-PMI 2015

P-1

Thin tungsten oxide layers : structural properties and deuterium retention.

Y. Addaba, C. Martina,*, C. Pardanauda, G. Giacomettia, M. Cabiéb, J.L Gardareinc, C. PerrinPellegrinod and P. Roubina.
a

Aix-Marseille Université, Laboratoire PIIM UMR 7345 - 13397 Marseilleb
Aix-Marseille Université, CP2M, 13397 - Marseillec
Aix-Marseille Université, IUSTI UMR 7343 CNRS, 13453 MarseilledAix-Marseille Université, IM2NP UMR 7334 - 13397 Marseille

Because of its favorable physical properties such as a low erosion yield, a high melting
temperature, a high thermal conductivity and a low hydrogen isotope permeation, tungsten is
the material used for plasma facing components (PFCs) receiving highest fluxes in operating
tokamaks (ASDEX-upgrade, JET-ILW) and will compose the ITER divertor. However,tungsten has a strong chemical affinity with oxygen and native oxide is naturally present on
tungsten surfaces. On PFCs, oxide layers (WO3-x) can be formed due to the presence of O2
as a contamination, PFCs high temperature (few hundred degrees) and in case of accidental
scenarii. Oxidation will induce a modification of tungsten wall properties especially regarding
the erosion yield [1,2], the reflectivity and the deuterium retention [3,4,5] which will dependon the structure, the stoechiometry and the thickness of the oxide layers formed.
In order to study the effect of oxidation on tungsten PFCs properties, the behavior of oxide
layers under deuterium bombardment and thermal cycling in divertor-like conditions, we haveproduced thin WO3-x layers which mimic the possible oxidation of tungsten PFCs. Tungsten
samples were thermally oxidized, controlling temperature and oxygen partial pressure. We
used recrystallized and non recrystallized polycrystalline tungsten samples.
Once characterized, W samples were put into vacuum (∼10-7mbar) and thermally oxidized at
400°C and at different oxygen partial pressures. The tungsten oxide layers formed were
80nm - 250nm thick. Different growth rates of oxide layers depending on P(O2) at 400°C
have been measured. X-rays diffraction shows the existence of monoclinic and orthorhombic
structure. The local structure of the formed oxide layers is investigated at different scales by
Raman spectroscopy, SEM, TEM, and AFM. Annealing of the tungsten oxides is being
performed and shows an evolution of oxide layer. Deuterium bombardment and annealing
under deuterium atmosphere of the samples are under investigation. Retention, chemical
erosion, stoechiometry and structure modification of the tungsten oxides will be studied.

[1] J. Roth et al., Data on low energy light ion sputtering, (1979)[2] M.I Guseva, A.L. suvorov, S.N. Korshunov, et al., J. Nucl. Mater 266-269 (1999)[3] A. Pezzoli, D. Dellasega, V. Russo et al., J. Nucl. Mater (2014),
http://dx.doi.org/10.1016/j.jnucmat.2014.11.035[4] N. Matsunami, N. Ohno, M. Tokitani, J. Nucl. Mater 390-391 (2009)[5] V.Kh. Alimov, B. Tyburska, M. Balden, et al., J. Nucl. Mater 409 (2011)*Corresponding author: celine.martin@univ-amu.fr (C. Martin)
35	
  
	
  

MoD-PMI 2015

P-2

The Xolotl Plasma-Surface Interactions Simulator

Sophie Blondela,*, David E. Bernholdta, Jay Jay Billingsa,b, Crystal L. Jernigana, Alexander J.
McCaseya, Jeremy S. Mereditha, Philip C. Rotha, Barry F. Smithc, Danqing Wuc, and Brian D.
WirthdaComputer Science and Mathematics Division, Oak Ridge National Laboratory, Oak Ridge,
TN 37831, USAb
The Bredesen Center, University of Tennessee, Knoxville, TN 37966, USAc
Mathematics and Computer Science Division, Argonne National Laboratory, Lemont, IL
60439, USAd
Nuclear Engineering Department, University of Tennessee, Knoxville, TN 37966, USA

Plasma surface interactions in fusion tokamak reactors involve an inherently multiscale,
highly non-equilibrium set of phenomena, for which current models are inadequate to predictthe divertor response and feedback on the plasma. In this presentation, we describe thecode development of Xolotl, a new continuum advection-reaction-diffusion cluster dynamics
code which simulates the divertor surface response to fusion relevant plasma exposure. Our
initial effort focused on the simulation of the behavior of tungsten material during theexposure of 100 eV helium plasma.
The rate-equation theory used by Xolotl to predict the time evolution of the divertor surface
will be first described, including the different reactions taking place, the diffusion of mobile
clusters, the drift of small helium clusters toward the surface, how they are modeled after
what is seen in atomistic simulations, and how the physics parameters were obtained.
As well, an uncertainty quantification effort is being conducted as a part of the developmentof Xolotl. It aims at understanding the effect of the input parameters – physical quantities
obtained from atomistic simulations for instance – on the final results of the simulation. The
uncertainty quantification strategy and tools will be presented.

*Corresponding author: blondels@ornl.gov (Sophie Blondel)

36	
  
	
  

MoD-PMI 2015

P-3

Path integral molecular dynamics for the nuclear quantum effects in the
Frenkel defects in BCC Fe
B. Chenga,*, and M. Ceriottiaa

Lab COSMO,
EPFL, 1015 Lausanne, Switzerland

The Frenkel defects created from irradiation damage have significant influence on themechanical properties of metals. Molecular dynamics (MD) simulations have been routinely
used to probe the defect production rate and mechanism of the displacement cascades [1].
In the conventional MD simulations, nuclei are typically treated as classical point mass. On
the other hand, the quantum nature of the nuclei, even for the heavy ones such as Fe, canaffect the relative free energy between different configurations. Therefore, it is of interest toinvestigate how nuclear quantum effects (NQEs) alter the free energy associated with the
Frenkel defects.
In the present study, path integral molecular dynamics simulations were employed toevaluate the quantum correction term in the free energy estimation for the Frenkel defect in
BCC iron. Using the empirical EAM force field for bulk iron with a Frenkel pair embedded, we
predicted that the quantum nuclear effects stablize the Frenkel defects by a small amount.
The nuclear quantum contribution to the free energy associated with a Frenkel pair was
estimated to be -14±1 meV. We also found that the NQEs promote both the interstitial andthe vacancy formations. The quantum effects are quite localized near the defects, spreading
only towards the nearest neighboring atoms.

[1] Bacon, David J., and Tomas Diaz de la Rubia, J. Nucl. Mater216 (1994): 275-290.

*Corresponding author: bingqing.cheng@epfl.ch (B. Cheng)
37	
  
	
  

MoD-PMI 2015

P-4

Experiment and modelling of hydrogen isotope exchange in beryllium layers asmean of T inventory control in ITER
D. Douaia,*, D. Kogutb, M. J. Baldwinc, R. P. Doernerc, D. Sinelnikovd,
N. Mamedovd, V. Kurnaevd, H.-W. Beckere, and T. Schwarz-SelingerfaCEA, IRFM, F-13108 Saint-Paul-lez-Durance, France.
Aix-Marseille Université, CNRS, PIIM, UMR 7345, 13013 Marseille, Francec
UCSD, Center for Energy Research, 9500 Gilman Drive, La Jolla, CA 92093-0417, USAdNational Research Nuclear University «MEPhI», 115409 Moscow, Russia
eRuhr-Universität Bochum, RUBION, D-44801 Bochum, GermanyfMax-Planck-Institut für Plasmaphysik, Boltzmannstr. 2, 85748 Garching, Germanyb

In the nuclear phase of ITER, wall conditioning will certainly contribute to the control of thetritium inventory - a major safety issue since the agreed safety limit inside the vessel must be
kept under 640g during D:T operation [1] - by depleting tritium from the walls and in particularfrom that co-deposited with beryllium. High isotopic exchange efficiency in Glow Discharge
Conditioning (GDC) or Ion Cyclotron Wall Conditioning (ICWC) plasmas have been reported[2]. However, the mechanisms at play in the interaction between hydrogen and beryllium
layers are still poorly understood at a microscopic level, and there is in particular no specifictheory or model in the literature to describe isotopic exchange.
We present here a 1D Diffusion Trapping Model for Isotopic eXchange - DITMIX - developedin order to understand the interaction mechanisms between hydrogenic species andberyllium co-deposited layers. The model is based on existing approaches to simulatehydrogen transport in metals [3,4] and includes processes like hydrogen implantation,
trapping in ion-induced trap sites, detrapping to a solute (mobile) state, diffusion in Be andrecombination to molecular form at the surface. Simulated profiles of hydrogen atoms are ina good agreement with those measured by 15N-NRA on pre-characterized 600 nm thick Be:H
layers, which were irradiated by D+ ions with well-defined fluxes and energies, for different
durations and surface temperatures. However, the model predicts larger amounts of D atoms
in the bulk of Be:Hlayers than those experimentally obtained from 4He-ERD measurements,
casting some doubt on the processes involved.
DITMIX yields important information on the efficiency of the foreseen conditioning techniques
for T inventory control. Hence GDC applied in ITER during one day or more is just efficientenough to remove an amount of tritium comparable to the estimated retention in a nominal
ITER D:T shot [2], even in combination with baking at 513 K. Pulsed ICWC at 343 K - thewall temperature during ITER operation – would be efficient for D+ fluxes to the wall as highas 1020–1021 m-2.s-1.

[1] J. Roth et al., Plasma Phys. Control. Fusion 50 (2008) 103001[2] D. Douai et al.,http://dx.doi.org/10.1016/j.jnucmat.2014.12.034[3] O. V. Ogorodnikova et al., J. Nucl. Mater. 273, 66 (1999).
[4] M. Baldwin, et al. Nucl. Fusion 54,073005 (2014).
*Corresponding author: david.douai@cea.fr
38	
  
	
  

MoD-PMI 2015

P-5

DFT calculations of voids in α-Fe
Dmytro Kandaskalov a,b*, Claude Mijoulea and Damien Connétableaa

CIRIMAT, Ecole Nationale d’Ingénieurs en Arts Chimiques et Technologiques (ENSIACET),
31030, Toulouse, Franceb
Aix-Marseille Université, CNRS, IM2NP UMR 7334, St. Jérôme,
Av. Escadrille Normandie Niemen, F-13397 Marseille, France

The point defects such vacancies are known to play significant role on diffusion in crystals.
Vacancies and cavities can still lead to changes in micro-structure with subsequent changes
in materials properties. They induce damage on the mechanical properties for alloys andmetals displacement, such fragility, tensile strength, crack resistance, ductility, creep
behaviors, and lead to premature aging structures. The formation of vacancy clusters occurs
via various types of reactions of vacancy’s point defects.
We present a first principles study of multi-vacancies (Vn, n=1, until 15) in α-Fe bulk andmonovacancy on (100) and (110) surfaces by means of the density functional theory [1-2].
For the monovacancy, the formation energy (Ef=2.16 eV), diffusion coefficient (D0=0.16
cm2/s) and migration activation energy (Em=0.64 eV) are found in agreement withexperimental and theoretical data of the literature [3-5]. The vacancy formation energy on
Fe(100)surface
is
more
than
twice
smallerthanon
Fe(110)surface.
The second and first nearest neighboring configuration (2NN & 1NN) for divacancies is foundto be the most stable configurations. Other divacancies configurations (3-7NN) have binding
energy close to 0.0 eV. We show that most stable divacancy (2NN) diffuses through the 1NN
configuration with a barrier equivalent to the one of the monovacancy.
To complete the description of divacancies, the mechanisms of formation/dissociation fromisolated monovacancies are discussed in detail. We finally present results on Vn vacancies
with n ={3, 15}. We show that most stable vacancy is more compact vacancy which contains
biggest number of 1NN and 2NN fragments.
Our calculations are performed using the Vienna ab initio simulation package VASP using
projected-augmented wave (PAW) method for the description of the pseudopotential.
Exchange and correlation are described with the functional of Ceperley and Adler
parameterized by Perdew and Zunger with the nonlocal generalized gradient approximation(GGA) of Perdew and Wang 91.

[1] D. Kandaskalov, C. Mijoule, D. Connétable, J. Nucl. Mat. 441 (2013) 168[2] D. Kandaskalov. Thèse de Doctorat. Etude théorique de d´efauts ponctuels et complexes
dans les métaux : application au fer-cc et nickel-cfc,. INP Toulouse (2013).
[3] L. De Schepper, D. Segers, L. Dorikens-Vanpraet G Knuyt, LM Stals and P. Moser, Phys.
Rev. B27 (1983) 5257
[4] T. Ohnuma, N. Soneda, and M. Iwasawa, Acta Materialia57 (2009) 5947
[5] C. Domain, and C.S. Becquart, Phys. Rev. B65 (2002) 024103*Corresponding author: dmytro.kandaskalov@im2np.fr (D. Kandaskalov)

39	
  
	
  

MoD-PMI 2015

P-6

Meta-stable state of 111-crowdion binding with VH6 complex in tungsten
D. Katoa,b*, H. Iwakiric, K. Morishitad,Y. Watanabee, and T. Murogaa,baNational Institute for Fusion Science, Toki 509-5292, Japanb
Dept. Fusion Science, SOKENDAI, Toki 509-5292, Japanc
University of the Ryukyus, Okinawa 903-0213, Japand
Institute of Advanced Energy, Kyoto University, Uji 611-0011, Japane
Japan Atomic Energy Agancy, Rokkasho 039-3212, Japan

Since tungsten will be used for plasma facing component materials in ITER and is acandidate material also for DEMO reactors, tritium retention in neutron damaged tungsten isa key issue. Recently, experimental works with fission neutrons and high-energy heavy
surrogate ions have been performed to evaluate the radiation effects [1, 2]. These works
show significant enhancement of the retention in the damaged tungsten and primary roles ofradiation induced vacancies and/or vacancy clusters (voids).
In divertor plasmas, the tungsten target would be exposed to low-energy and high-flux
plasma particles as well as neutron. Strong enhancement of the hydrogen retention in singleand polycrystalline tungsten specimens has been observed at higher fluxes [3]. A distinct
feature of plasma irradiation from gas permeation obeying the Sieverts’ law is that incident
hydrogen atoms/ions from the plasma can readily overcome permeation barriers of thesurface without high pressures. One can, therefore, assume that under the continuous highflux implantation local concentration of hydrogen atoms can exceed the solubility limit of thetungsten. In such cases, the tungsten matrix may contain super-saturated hydrogen atoms
and sustain extremely high stresses. Therefore, the blistering of tungsten surfaces may be
induced by the exceedingly high local concentration of hydrogen atoms beyond the solubility
limit of the tungsten [3, 4].
For a better characterization of radiation damages in the tungsten under the divertor
condition, we examined impact of hydrogen cluster formations on the radiation damages inthe tungsten. The present density functional theories (DFT) calculations revealed that an
octahedron hydrogen cluster prevents the vacancy from recombining with a self-interstitialatom in a neighbouring 111-crowdion. The formation energy of the meta-stable state issmaller than sum of the individual formation energies for the VH6 complex and the 111crowdion indicating that the VH6 complexes can trap the 111-crowdion. This implies that theradiation damage remaining after collision cascades by energetic primary knock-on atoms
will be increased in the presence of the hydrogen clusters.

[1] Y. Hatano,et al., Nucl. Fusion 53 (2013) 073006[2] M.H.J ‘t Hoen, et al.,Nucl. Fusion 52 (2012) 023008[3] V.Kh. Alimov, et al., J. Nucl. Mater. 375 (2008) 192[4] J.B. Condon, T. Schober, J. Nucl. Mater. 207 (1993) 1*Corresponding author: kato.daiji@nifs.ac.jp (D. Kato)

40	
  
	
  

MoD-PMI 2015

P-7

Comparing He ion energy transfer to W and Fe surfaces
through molecular dynamics simulations
T. P. C. Klavera,*, I. Tanyelia, E. Westerhofa and B. J. Thijssebab

FOM institute DIFFER, Eindhoven, The Netherlands
Department of Materials Science and Engineering, Delft University of Technology, Delft, The
Netherlands

Exposing W and Fe surfaces to similar He plasma leads to different surface evolution. We
investigate, through molecular dynamics (MD) simulations, if a difference in energy
transferred from He to the surfaces contributes to the different surface evolution. W and Fe
surfaces with four different orientations were bombarded with 60 eV He ions, impacting 0-10
degrees from the surface normal. Comparable numbers of He atoms reflect back from the W
and Fe surface monolayers or escape again after first penetrating a little below the surface.
However, due to the less unequal mass ratio between He-Fe compared to He-W, He ionstransfer energy to Fe more efficiently. As a result, He atoms that reflect from Fe surfaces
carry away less kinetic energy than those reflecting from W. This rules out ion energy
transfer as an explanation why similar plasma exposure on W leads to several times thicker
fuzz layers than on Fe. Somewhat counter-intuitively perhaps, He ions that do not reflect orescape back to the vacuum thermalize at a greater depth below the surface in Fe than in W
(25.4 vs. 11.8 Angstrom), despite the more efficient energy exchange between He and Fe.
The thermalisation depth result also shows the limits of binary collision approximation (BCA)
results, such as from the TRIM code. TRIM results for reflected He ion energies were quite
close to MD results. However, the rather simple model of the BCA does not reproduce theunexpected deeper thermalisation depth of He ions in Fe, making it quite doubtful if what
happens to He inside W and Fe is described properly.

*Corresponding author: klaver2@gmail.com (Peter Klaver)	
  

	
  

41	
  
	
  

MoD-PMI 2015

P-8

Joint experimental and theoretical efforts to bridge the gap between today’s
experiments and future fusion devices
T. Dittmara*, M. Köppena*, A. Alloucheb, J. Brödera, L. Buzia, P. Dollasea, M. Eichlera,
Y. Ferrob, D. Matveeva, R. Piechoczeka, M. Reinharta, B. Unterberga, Ch. LinsmeieraaForschungszentrum Jülich GmbH, Institut für Energie- und Klimaforschung – Plasmaphysik,
52425 Jülich, Germanyb
Aix-Marseille University-CNRS, PIIM UMR 7345, Marseille 13397, France
	
  
	
  

Extrapolating from existing fusion experiments to next generation plasma devices like ITER,
DEMO and beyond means bridging several orders of magnitude in almost every plasma anddevice parameter. To allow for reliable predictive scaling of available results to future
devices, a good understanding of the involved processes and validated modelling is crucial.
This presentation will illustrate how this can be achieved in a close interplay between
dedicated experiments and modelling.
Three experimental setups are selected to demonstrate such a successful combination ofexperiments, density functional theory (DFT) calculations and modelling: the XPS setup, theARTOSS experiment and the linear plasma device PSI-2.
The new XPS-setup experiment which is dedicated to investigate chemical reactions and ionsurface interactions was used to measure valence band spectra of Be and Be-N. These werethen used to verify DFT results on phase formations expected at first wall. In addition, we
compare measured core levels of different tungsten compounds to calculated core levels
using the DFT code Fleur [1].
ARTOSS, combining classic surface science tools with accelerator based techniques,
focuses on studies on hydrogen retention and release behaviour, especially in Be and Bebased materials. DFT-calculations [2] predict different kinetics for hydrogen and Be selfinterstitial diffusion parallel and perpendicular to the basal plane of Be single crystals.
Temperature-programmed desorption (TPD) experiments of monocrystalline andpolycrystalline Be irradiated with low D fluences (~ 3×1019 D/m2) in ARTOSS are modeledusing a diffusion-trapping model implemented within the CRDS code. This leads to a refinedmodel of hydrogen retention and transport mechanisms in Be based on DFT calculation
results.
Last but not least, the PSI-2 linear plasma device is dedicated to the understanding ofplasma-material interactions at reactor-relevant wall loading conditions. Besides giving an
overview of experimental capabilities of the device, we present the data and modelling
results on the influence of the particle flux density, plasma impurity content and tungsten
material microstructure on the D retention.

[1] S. Blügel and G. Bihlmayer, NIC Series Vol. 31, p. 85[2] A. Allouche et al., J. Phys. Chem. C. 114(2010) 3588

*Corresponding authors:t.dittmar@fz-juelich.de (Timo Dittmar)
m.koeppen@fz-juelich.de (Martin Köppen)
42	
  

	
  

MoD-PMI 2015

P-9

Modelling and Experiments of Plasma-Material Interactions in Presence of
Fusion Neutrons
P.N. Mayaa*, S.P. Deshpandea, P. Nandia, M. Warrier b, P.M. Raolec, S. KhirwadkarcaITER-India, Institute for Plasma Research, A-29, GIDC Electronic Estate,
Gandhinagar 382016, Indiab
Computational Analysis Division, BARC, Visakhapatnam, Andhra Pradesh,
530012, IndiacInstitute for Plasma Research, Bhat, Gandhinagar, 382428, India

The interaction of the hydrogen isotope plasma along with the energetic neutrons (14MeV)
and alpha particles (3.5 MeV) can cause material erosion, structural damage, fuel retention
and changes of thermo-mechanical properties of the material that lead to the eventual
mechanical failure of the material depending on the choice of the wall material. In this work
we report on neutron induced material damage and the subsequent plasma wall interactions
in tungsten, which is the proposed divertor material for ITER. The modelling of neutron
damage is currently a priority need due to the non-availability of a fusion relevant highfluence neutron source. ITER-like neutron fluxes can cause very high dpa (displacement peratom) which is a measure of the damage in the system. The interaction of the fusion plasma
with the neutron damaged material can trigger hitherto unobserved phenomena which mightlead to the failure of the materials much before the anticipated life-time. Hence it becomes
extremely important to understand the damage created by the neutrons and the subsequentplasma-wall interactions due to the hydrogen isotopes and alpha particles.
One of the standard approaches is to simulate the neutron damage by creating theequivalent damage by the use of energetic heavy ions. The surrogate ion irradiation ismodelled as a series of elastic collisions with the lattice atoms and inelastic scattering by theelectron cloud. The elastic collisions result in the formation of primary knock-on atoms (PKA)
which results in the formation of ion-vacancy pairs (Frenkel pairs) and their dynamics leading
to the formation of vacancy and interstitial clusters. The evolution of these clusters has twoconsequences: (1) trapping of D/T ions from the plasma at the defect sites leading to fuelretention and (2) microstructural changes leading to the thermo-mechanical failure of thematerial. The consistent modelling of such a system involves different time and space scales
which makes it an inherent multi-scale problem. Here we outline our approach to thisproblem starting from ab-initio/density functional calculations of activation energies of specificdefects to rate equation models of predicting the fuel retention and the material damage. The
crucial part is understanding the dynamics on the individual scales and how to link the
different scales. Specifically, we discuss the Frenkel pair generation due to energetic
tungsten and gold ion irradiation using molecular dynamics simulations and binary collisionmodels. The details of the collision dynamics and the short-time (~few ns) evolution of the
Frenkel pairs will be presented which will be eventually used in a higher level Monte Carlocode for calculating the long-term evolution of point defects and their clustering.

*Corresponding author: pnmaya@iter-india.org (P.N. Maya)

43	
  
	
  

MoD-PMI 2015

P - 10Magnetic sheath effect on the gross and net erosion rates due to impurities
N. Melleta,*, B. Pégouriéb, C. Martina, J.P. Gunnb, H. Bufferandc and P. Roubinaa

CNRS, Aix-Marseille Université, PIIM, UMR 7345, 13397 Marseille, France.
b
CEA, IRFM, F-13108 Saint-Paul-lez-Durance, France.
c
Aix-Marseille Université, CNRS, Centrale Marseille, M2P2 UMR 7340, F-13451 Marseille,
France.
In fusion reactors, erosion processes determine the lifetime of plasma-facing components
and the contamination of the confined plasma by impurity production. In the vicinity of thesurface, the magnetized sheath plays a primary role in gross erosion. Acceleration of
impurity ions across the strong electric field layer defines their impact angle and energy,
which both influence the sputtering yield and reflection coefficient. While the increase of
impact energy is taken into account in most edge fluid codes, the angular deflection has
been implemented only recently (for example in [1] for the main species). In [2] we haveshown that the deflection is larger for the impurities than for the deuterium in the Tore Supralimiter conditions. The sheath also affects the net erosion rate through its influence on
prompt or local redeposition. Two mechanisms contribute: (1) the redeposition of the atomsof tungsten ionized in a distance smaller than the gyro-radius of the singly charged ion, which
are promptly redeposited in their first Larmor gyration, and (2) the redeposition of the ions,which do not have sufficient kinetic energy to escape the sheath potential [3].
The average impact angle of various impurities for the case where only the cyclotron motion
is taken into account was compared with a self-consistent particle-in-cell (PIC) model of thesheath [4]. Two limits can be distinguished: (1) A low density limit that corresponds to far
SOL regions, where the sheath decreases the impact angle and (2) a high density limit that isrelevant for WEST or ITER divertors, where the sheath increases the impact angle. In thecase of tungsten self-sputtering in WEST, the gross erosion obtained with the full sheath
treatment can differ by a factor two with respect to the ballistic approximation where only theion cyclotron motion is taken into account.
To calculate the local redeposition we use the data provided by the PIC simulations of themagnetic sheath: the electric field, the electron density, and its energy distribution function.
We also concentrate on the effect of the ionization cross section. In the case of ITER
detached scenario, the electrons are in most cases not energetic enough to ionize theeroded tungsten atoms. The mean free path could be thus be mostly determined by the autoionization of formerly excited tungsten atoms. Comparisons with existing models [3,5] andcalculations of the net erosion velocity for a set of impurities assuming WEST and ITER
conditions are performed.
[1] H. Bufferand, J. Bucalossi, G. Ciarolo et al, doi:10.1016/j.jnucmat.2014.09.061[2] N. Mellet, C. Martin, B. Pégourié et al, Nucl. Fusion 56, 123006 (2014)[3] A.V. Chankin, D.P. Coster, and R. Dux, Nucl. Fusion 56, 025003 (2014)[4] J.P. Gunn, Phys. Plasmas 4, 4435 (1997)[5] D. Tskhakaya, and M. Groth, doi:10.1016/j.jnucmat.2014.10.086*Corresponding author: tel.: +33 491 282 708, e-mail: nicolas.mellet@univ-amu.fr

44	
  
	
  

MoD-PMI 2015

P - 11

Aluminium studies for laboratory plasma:particle growth and hydrogen retention
A. Michau, J. Mougenot*, K. Hassouni, S. Kasri, K. Ouaras, M. Redolfi, C. Quirós
and G. Lombardi
Université Paris 13, Sorbonne Paris Cité, Laboratoire des Sciences des Procédés et desMatériaux, CNRS UPR3407, Villetaneuse 93430, France

Prediction of tritium retention by plasma-wall material and plasma dusts is a major question
according to the well-functioning and safety of tokamaks. That is why erosion, particle growth
and retention processes are studied for different plasma-facing components PFCs (astungsten, beryllium or carbon). However experimental studies in laboratory on beryllium arelimited by its toxicity. Aluminium is an alternative element (Be-like) which can replace him tocharacterize the formation of compounds, especially the oxides and possibly the hydrides [1].
Both experimental and numerical studies on aluminium are currently leading in our lab. We
focused here on the numeric works partially supported by Eurofusion WP-PFC (SP3/4)
project.
Our first objective is to describe dust formation (carbon, aluminium and tungsten) magnetizedplasma. We consider a laboratory discharge system where plasma is ignited by ECR
between 0.1 and 1 Pa. Observed particles may be formed from hydrocarbon precursors
introduced in the feed gas but also through plasma-surface interaction in H2/Al or H2/W
system. We develop a 1D model for hydrogen discharge obtained in this system. We solve
for the transport equations of hydrogen ions (H+, H2+, H3+, H-), electron energy (that yield theelectron temperature) and H-atom in the radial direction discharge on the dipolar magnet
equatorial symmetry plane. We have obtained characteristics of the H2 discharge. In thissystem we are now implementing aluminium particle formation by sputtering and aerosol
growth and transport inside the discharge.
Our second objective is to describe surface finish and hydrogen retention in material using
HIIPC (Hydrogen Isotope Inventory Processes Code) model. Resulting from several
collaborations, this model simulates the hydrogen inventory in the PFCs (tungsten, beryllium
or carbon) [3]. It describes the hydrogen retention in the tungsten during a real tokamak
material thermal cycle [4] and will be extended to reproduce hydrogen desorption spectrum(in collaboration with A*MIDEX WHISCI project). The model is also currently used todescribe hydrogen retained in aluminium.

[1] L. Marot, C. Linsmeier, B. Eren et al. Fusion Eng. Des. 88 (2013) 1718-1721[2] K. Ouaras, L. Colina Delacqua, et al. J. Plas. Phys. 80 (2014) 833-841[3] C. Sang, X. Bonnin, M. Warrier et al.J. Nucl. 52 (2012) 043003[4] X. Bonnin, E. Hodille, N. Ning et al. J. Nucl. Mater. In-press (2015)*Corresponding author: jonathan.mougenot@lspm.cnrs.fr (J. Mougenot)

45	
  
	
  

MoD-PMI 2015

P - 12

W2, W4, WH, WH2: Ab initio and DFT benchmarks
Michal Novotný1 *,Ján Škoviera1, Ivan Černušák1 , Takuji Oda2
1

Comenius University, Faculty of Natural Sciences, Department of Physical and Theoretical
Chemistry, Mlynská dolina CH-1, Bratislava, Slovakia
novotnym@fns.uniba.sk
2
Seoul National University, College of Engineering, Department of Nuclear Engineering, 1Gwanak-ro, Gwanak-gu, Seoul 151-744, Korea

Large-scale simulations investigating properties of tungsten in plasma facing materials andfirst wall plasma interaction in fusion devices are based largerly on DFT data. We reportbenchmark calculations on selected properties of model systems (W2, W4, WH, WH2) tocompare the density functional data with wave-function based data. Some of these systems
were studied previously [1-4] but the systematic comparisons with DFT are scarce. For
geometry optimization we used GAUSSIAN09 program [5] exploiting DFT with various
popular functionals: BLYP, B3LYP, B3PW91, PW91PW91, mPW91PW91, PBEPBE,PBE1PBE, M062X, M06L, LC-BLYP, LC-ωPBE, LC-PW91PW91, B97X, B97XD; and twobasis sets: cc-pVDZ-PP, cc-pVTZ-PP. For the wave-function based calculations we used the
MOLCAS program package [6] in conjunction with ANO-RCC basis set. X1Σ+g state of W2
calculated with just four functionals (ωB97XD, M06L, M062X, B97D) is compared with data in[4]. For quintet W4 and 6Σ+ WH/WD we used scalar relativistic coupled-cluster method - DKCCSD(T). To obtain the spectroscopic constants for WH/WDwe performed the Dunham
analysis. For 5B2 WH2 the geometries and harmonic frequencies were compared with datafrom [2,3]. We have also tested the effects of both semiempirical and ab initio dispersion
corrections. The dispersion corrections were calculated either with standalone functionals
already containing dispersion (B97D, ωB97XD, B97D3) or adding a semi-empiricaldispersion potential to the conventional Kohn-Sham DFT energy. Several schemes wereconstructed for these purposes from which we chose the Grimme D3 method with a BeckeJohnson damping function [7]. Except for W4 the benchmarks show that most of thefunctionals are quite reliable to describe such systems. We have also shown that for thesecases dispersion has only a negligible effect.
The support from EU within the framework of Eurofusion (Task WPHCD-NB).) and from
Slovak Grant Agency (VEGA 1/0092/14) is gratefully acknowledged.

[1] Ma Z., Balasubramanian K., Chem. Phys. Lett. 181 (1991) 467.
[2] Balasubramanian K., Ma Z., J. Phys. Chem. 95 (1991) 9794.
[3] Wang X., Andrews L., J. Phys. Chem. A 106 (2002)6720[4] Borin A. C., Gobbo J. P., Roos B. O., Chem. Phys. Lett.490 (2010) 24.
[5] Gaussian 09, Revision D.01, Frisch M. J., Trucks G. W., Schlegel H. B. et al. Gaussian,Inc., Wallingford CT, 2009[6] Aquilante F., De Vico L., Ferré N. et al. J. Comp. Chem. 31(2010) 224[7] Grimme S., Ehrlich S., Goerigk L. J. Comp. Chem. 32 (2011) 1456
*Corresponding author: novotnym@fns.uniba.sk

46	
  
	
  

MoD-PMI 2015

P - 13Modelling of D atom absorption and diffusion dynamics in self-ion damaged
tungsten exposed to deuterium atom beam
A. Založnika,*, S. Markelja, and K. SchmidbJožef Stefan Institute, Jamova cesta 39, 1000 Ljubljana, Sloveniab
Max-Planck-Institut für Plasmaphysik, Boltzmannstrasse 2, D-85748 Garching, GermanyaThe study of plasma-material interaction is important in order to successfully predict andunderstand the evolution of the first wall and its feedback on plasma operation. The majorityof the experiments on plasma-material interaction are performed with energetic ion or plasma
bombardment of the material. However, the edge plasma in fusion device consist not only ofions, but also of neutrals (molecules and atoms). Therefore, experiments studying interactionof neutral species with material are needed in order to fully understand the edge plasmamaterial interactions and retention mechanisms. Moreover, low energy (< eV) atom beam isalso advantageous over the ion beam experiments whenever creating additional damage inthe material is not desirable, since defects in the material act as strong binding sites forhydrogen.
In situ studies of D retention and diffusion dynamics in self-ion damaged tungsten were
performed. Polycrystalline W samples were pre-irradiated by 20 MeV W ions, simulating theneutron damage that will be created in fusion reactors, and exposed to neutral D atom beamat different sample temperatures [1]. Deuterium concentration depth profiles were measured
by Nuclear Reaction Analysis (NRA). The modelling of these experimental data will be
performed using TESSim code [2,3]. We have implemented surface processes into the code,taking into account interactions of deuterium atoms with the surface and different desorption
mechanisms (Langmuir-Hinshelwood and Eley-Rideal), coupled with the diffusion into thebulk of the material. It also allows using multiple adsorption sites with different binding
energies. The damage profile will be included, taking into account various defects withdifferent binding energies. The code will be used to determine some important parameters of
deuterium-tungsten interaction potential (e.g. binding energies of different adsorption sites
and energy barrier for diffusion into the bulk). Hot-atom desorption mechanism will be
additionally implemented into the code in order to improve the accuracy of the current model.

[1] S. Markelj et al, Phys. Scr., 2014 (2014) 014047[2] K. Schmid, V. Rieger, and A. Manhard, J. Nucl. Mater., 426 (2012) 247[3] K. Schmid, U. von Toussaint, and T. Schwarz-Selinger, J. Appl. Phys., 116 (2014) 134901*Corresponding author: anze.zaloznik@ijs.si (A. Založnik)

47	
  
	
  

MoD-PMI 2015

P - 14

Kinetic Monte Carlo simulation and rate theoretical approach
for influence of vacancy on hydrogen diffusivity in tungstenaD. Zhua, and T. Odaa,*
Department of Nuclear Engineering, Seoul National University,
1 Gwanak-ro, Gwanak-gu, Seoul 151-742, South Korea

Tritium retention in reactor materials needs to be minimized for establishing an efficient andsustainable tritium fuel cycle in fusion reactors. Large tritium retention also causes radiationsafety concerns. Therefore, understanding and controlling tritium behavior such as releaseand accumulation in fusion reactor materials is an important research subject. Since theretention in plasma-facing components (CFCs) may get large, the tritium behaviour intungsten, a promising candidate for CFCs, have received increasing attention.
The diffusion coefficient is one of the fundamental physical quantities that govern the tritium
behavior in tungsten. It is directly relevant with the rate of tritium release and permeation
from/through tungsten. In addition, it is a vital input in analyzing experimental results ofthermal desorption spectroscopy (TDS) and nuclear reaction analysis (NRA), which havebeen widely performed to acquire information on hydrogen-defect interactions.
Among several reported hydrogen diffusivities in tungsten, the one given by Frauenfelder [1]has been most utilized: 𝐷 = 4.1×10!! exp −0.39  𝑒𝑉/𝑘𝑇 . However, DFT calculation results
showed disagreement with the experimental result: specifically, DFT calculation indicatesaround 0.20 eV as the diffusion barrier [2]. Heinola and Ahlgren [3] examined thisdisagreement by using transition-state theory (TST) coupled with DFT calculation. It was
shown that the diffusion coefficients obtained with DFT+TST approach are comparable withthose of Frauenfelder’s experiment, if experimental data at low temperatures (<1500 K) areexcluded. The exclusion was suggested considering that low-temperature data weresignificantly affected by defects that act as hydrogen trap [3].
In the present study, kinetic Mote Carlo (KMC) simulation is performed to quantitatively
evaluate the influence of vacancy on hydrogen diffusivity in tungsten. For simplicity, three
processes are only taken into account: (i) hydrogen migration, (ii) hydrogen trap by vacancy,and (iii) detrap from vacancy. Kinetic parameters of these processes such as migrationenergy and trapping energy are determined based on DFT calculation results. Consequently,
the low-temperature data of Frauenfelder’s experiment [2] are nicely reproduced by KMC
simulation if a reasonable concentration of vacancy is assumed. In addition, an equation toevaluate the lower limit of hydrogen diffusivities in defective tungsten is derived by a ratetheoretical approach. The indicated lower limit fairly agrees with reported experimental data.

[1] R. Frauenfelder, J. Vac. Sci. Technol. 6 (1969) 388.
[2] Y.L. Liu, Y. Zhang, G.N. Luo, G.H. Lu, J. Nucl. Mater. 390-391 (2009) 1032.
[3] K. Heinola, T. Ahlgren, J. Appl. Phys. 107 (2010) 113531.
*Corresponding author: oda@snu.ac.kr (T. Oda)

48	
  
	
  

MoD-PMI 2015

P - 15

Some aspects of determination of hydrogen binding energies with defects inmetalsM. Zibrova,b,c,d,e*, Yu. Gasparyana, A. Shubinaa, and A. PisarevaaNational Research Nuclear University MEPhI (Moscow Engineering Physics Institute),
Kashirskoe shosse 31, 115409 Moscow, Russia;b
FOM Institute DIFFER, NL-3439 MN Nieuwegein, The Netherlands;c
Gent University, Sint-Pietersnieuwstraat 41, B-9000 Gent, Belgium;dMax-Planck-Institut für Plasmaphysik, Boltzmannstraße 2, D-85748 Garching, Germany;eTechnische Universität München, James-Franck-Straße 1, D-85748 Garching, Germany

Hydrogen inventory in metals with a positive heat of solution strongly depends on thepresence of defects; therefore precise determination of hydrogen-to-defect binding energies
is essential. In most cases, these energies are obtained by fitting numerically simulated
thermal desorption (TDS) spectra to experimental ones. However, determination of thebinding energies is ambiguous in this approach, as the parameters describing the defects arefree parameters in the model, and therefore one spectrum can be fitted by using several
combinations of various parameters.
There also exists a method of a direct determination of H binding energies with defects froma series of TDS measurements of identical samples performed with different heating rates.
Although this method is known since 80-s [1, 2], no strict justification of its applicability has
been made so far. Based on diffusion-trapping equations, it was shown in this work that suchapproach is valid in the case of infinitely high recombination rate at the surface,independently of the trap profile and the initial distribution of trapped hydrogen.
In order to demonstrate the feasibility of this method and explore its possible limitations,numerical simulations of TDS spectra from tungsten with different heating rates by using the
TMAP7 code were performed. Various binding energies, trap profiles, and initial trap
populations were used. In order to model different surface conditions, various recombination
rate coefficients were used. It was observed that the binding energies can be correctly
determined only in the case of a high H-H recombination rate at the surface, whereas the
reduced recombination rate leads to overestimated values of binding energies. Based on the
results of the simulations, a new transport parameter characterising the regime of H release
was proposed. This parameter involves the surface recombination rate, the H diffusivity inthe material, and the parameters of the trapping sites. It was shown that H release from thematerial is not affected by surface processes only in the case when the parameter proposed
is much larger than unity.

[1] W.Y. Choo, J. Lee. Metal. Trans. A 13 (1982) 135[2] A.A. Pisarev, V.V. Bandurko, V.N. Tsyplakov, At. Energy 62 (1987) 36*Corresponding author: M.Zibrov@differ.nl (M. Zibrov)
49	
  
	
  

MoD-PMI 2015

P - 16

Raman spectroscopy investigation of beryllium based materials
C. Pardanauda,*, G. Giacomettia, C. Martina, A. Allouchea, Y. Ferroa, P. Roubina,
M. Oberkoflerb, M. Köppenc, T. Dittmarc, Ch. LinsmeiercC. P. Lungud, C. Porosnicud, I. Jepud,
P. Dincad, M. Lungud, O.G. Pompiliand,R. Mateuse, E. AlveseaPIIM, CNRS – Aix-Marseille Université, Centre Saint Jérôme, 13397 Marseille cedex 20,
Franceb
Max-Planck-Institut für Plasmaphysik, Boltzmannstraße 2, D-85748 Garching, Germanyc
FZJ GmbH, Institut für Energie- und Klimaforschung – Plasmaphysik, 52425 Jülich,
GermanydNational Institute for Laser, Plasma and Radiation Physics, 077125, Magurele-Bucharest,
Romaniae
Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa,
Av. Rovisco Pais, 1049-001, Lisboa, Portugal
Hydrogen isotope retention in beryllium is an important issue as this element is thedominant plasma-facing component (PFC) in ITER [1-4]. The aim here is to study the abilityof Raman spectroscopy, a non-contact technique based on inelastic scattering of photons, togive information on the structure and composition of Be samples containing D, N and W. Twotypes of materials are investigated. First a polycrystalline Be sample bombarded by D ions (afew keV/atom, a few 1017 cm-2), provided by IPP in Garching. Atomic quantification was
performed using ion beam analysis. Second, Be and Be50W50 deposits containing few
percents of D or N, provided by IAP in Bucharest. They were synthesized using thethermionic vacuum arc method [5]. Atomic quantifications were performed using ion beam
analysis at IST in Lisboa.
Vibrational changes induced by D irradiation were then identified in Raman spectra. We
report the presence of 6-7 bands that we attribute to Be-D vibrations whereas the pristine
sample contains only one band due to the Be-Be vibrational stretching mode. DFT (density
functional theory) calculations of vibrational frequencies were done to interpret these results.
Atomic force microscopy was used to characterize the surface roughness. We found that in
the bombarded sample dendritic structures are present within the implantation spot. These
structures are typically a few micrometers long and are composed of nanodomes, typically
100 nm high. The Be-D bands are located mainly on these dendritic structures. The Raman
spectra analysis suggests that ion implantation induces stress in the material and that these
dendrites are formed as a consequence of stress saturation. These observations show thatthe bombardment induces growth processes and surface modifications.
On the contrary, no such structures, nor such Raman bands, were found for arc-depositedmaterials and 3 different bands, not observed after ion implantation, were observed. One ofthese bands may be attributed to Be-O bonds. The two other bands, observed for D and N
containing samples, are interpreted as defect induced bands. In addition, for the Be50W50
sample, the Be-Be vibrational stretching mode was not observed, showing that Be and W are
not forming separated clusters in the sample but are forming an alloy.
[1] M. Oberkofler, Ch. Linsmeier, J. Nucl. Mater 415, S724 (2011)[2] A. Allouche, M. Oberkofler, M. Reinelt, et al. J. Phys. Chem. C 114, 3588 (2010)[3] M. Reinelt, A. Allouche, M. Oberkofler, et al., New J. Phys. 11, 043023 (2009)[4] S. Brezinsek, M. F. Stamp, Nishijima, D. et al, Nuc. Fus. 54, 103001 (2014)[5] C.P. Lungu, I. Mustata, V. Zaroschi, et al., Phys. Scr. T128 157–161(2007)*Corresponding author: cedric.pardanaud@univ-amu.fr (C. Pardanaud)

50	
  
	
  

MoD-PMI 2015

P - 17

Aspects of ion-metal and electron-metal interactions in fusion relevant energy
regimes
P. Tolias and S. Ratynskaia*

KTH Royal Institute of Technology, EUROfusion-VR, Stockholm, Sweden

The microphysics of ion-metal and electron-metal interactions in the plasma boundary offusion devices affect not only the wall material but also the surrounding plasma. These
interactions involve processes such as secondary electron emission [1], electronbackscattering [2], low-energy electron-reflection [3], ion-backscattering [4], ion-surface
recombination [5] and surface assisted molecule formation. Such processes have beenstudied experimentally and theoretically in regimes that correspond to impact energies muchhigher than the ones encountered in divertor plasmas. Extrapolations to fusion relevant
regimes are not viable, since the microphysics change drastically in very low energy ranges.
Furthermore, thermionic emission [6] is a very important process for dust and droplet
dynamics. Thermionic electrons control the onset of a thermal instability that occurs due tothe strong coupling of charging and heating [7]. Through this instability, thermionic emission
effectively controls dust melting and impurity generation in fusion plasmas. Consequently,
dust dynamics can be expected to be very sensitive to the treatment of the thermioniccurrent. However, experimental data are very sparse for the tungsten Richardson constantand the work function at very high surface temperatures, whereas they are no experimental
data for liquid metals (where by electronic structure arguments deviations from theRichardson-Dushman expression can be expected).
In this presentation we shall discuss: (i) why low energy extrapolations are not valid forplasma-solid interactions, (ii) which experimental data are needed in order to enhance thepredictive power of codes, (iii) the necessity for updated data compendia for plasma materialinteractions by providing instances of outdated datasets currently used in fusion.

[1] P. Tolias, Plasma Phys. Control. Fusion 56, 045003 (2014).
[2] P. Tolias, Plasma Phys. Control. Fusion 56, 123002 (2014).
[3]L. Vignitchouk, P. Tolias and S. Ratynskaia, Plasma Phys. Control. Fusion 56, 095005(2014).
[4] W.Eckstein, Reflection (Backscattering) Technical Report IPP 17/12, IPP (2009).[5] P.
Tolias, Revisiting the sheath heat transmission factor in the high recycling
regime: ion surface recombination (Plasma Phys. Control. Fusion, 2015).
[6] C. Herring and M. H. Nichols, Rev. Mod. Phys. 21, 185 (1949).
[7] R. D. Smirnov et al., Plasma Phys. Control. Fusion 49, 347 (2007).

* Contact information: srat@kth.se

51	
  
	
  

MoD-PMI 2015

P - 18	  The microphysics of ion-surface recombination and calculations of the heat
sheath transmission factor
P. Tolias*
KTH Royal Institute of Technology, EUROfusion-VR, Stockholm, Sweden

Ion-surface recombination refers to the neutralization of ions in the vicinity of a metal surface
induced by quantum tunneling of bound electrons [1]. It is accompanied with energy
absorption by the metal, making it an important heating mechanism not only for plasmafacing-components but also for dust in case the plasma temperatures are low (eV).
Currently, in fusion plasmas the micro-physics of recombination are not properly taken into
account and it is wrongly assumed that the energy released to the PFC for each event isequal to the ionization energy of the ion [2].
Low energy ions present at the Ångström vicinity of metal surfaces are 100% neutralized dueto the relatively large interaction times and the metal electron availability for tunneling.
Neutralization mainly occurs through resonant and Auger processes [3]. Resonant
neutralization refers to the constant energy transition of an electron from the metal continuumof states to the discrete atomic states; hence it is not accompanied by energy transfer to themetal. Auger neutralization refers to the transition of metal electrons at a higher binding
energy atomic state; hence it is accompanied by potential energy release absorbed by thevalence electrons, which leads to either electron emission or heating of the metal.
Neutralization can also occur by a combination of these processes. The contribution of eachprocess to the neutralization rate strongly depends on the particular ion / metal combination.
A first-principles approach without adjustable parameters has not been developed yet [4].
However, for sub-keV ions theoretical approaches can be developed based on Hagstrum’s
elementary theory [3] by (i) assuming that the level shift stems from the image interaction, (ii)assuming that when both two-electrons and many-electron processes are permissible, theformer dominate, (iii) utilizing the theoretical electronic density of states of the metal.
We developed such an approach for the tokamak relevant case ofandions incident
on W surfaces [5]. In the /W case, resonant neutralization dominates and there is no PFC
heating. In the/W case, resonant channels are forbidden and Auger neutralization
dominates leading to 10.5 eV heating per incident ion. For comparison, neglecting the microphysics leads to 13.6 eV and 24.6 eV per ion. With these revisions, we revisited Pilot-PSI
results for the sheath heat transmission factor ( ) in the high recycling regime [6] andmanaged to explain the observed discrepancies with analytical sheath theory [2]. Finally, we
shall discuss implications stemming from the aforementioned difference between H and He
ions.
[1] R. A. Baragiola, Radiation Effects 61, 47 (1982).
2] P. C. Stangeby, The plasma boundary of magnetic fusion devices, (IOP, 2000).
[3] H. D. Hagstrum, Phys. Rev. 96, 336 (1954); Phys. Rev. 150, 495 (1966).
[4] R. C. Monreal, Prog. Surf. Sci. 89, 80 (2014).
[5] P. Tolias, Revisiting the sheath heat transmission factor in the high recycling
regime: ion surface recombination (Plasma Phys. Control. Fusion, 2015).
[6] M. van den Berg, K. Bystrov, R. Pasquet et al., J. Nucl. Mater. 438, S431 (2013).
Contact information: tolias@kth.se

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MoD-PMI 2015

I - 19Hydrogen diffusion and vacancies formation in tungsten: DFT and statisticalmodelsN. Fernandeza, Y. Ferroa,*, and D. Katoba
Aix-Marseille Université, CNRS, PIIM UMR 7345, 13397 Marseille, Franceb
National Institute for Fusion Science (NIFS), Toki, Gifu 509-5292, Japan

The interaction of hydrogen with tungsten and vacancies is investigated by mean of Density
Functional Theory (DFT). Because DFT is limited to small models of about one hundred
atoms at zero temperature, this work is complemented by a statistical approach with the aim
to yield temperature dependent data that can be directly compared with macro-scale
thermodynamic and kinetic experimental data.
It follows that DFT data are included in a statistical model based on transition state theory
and thermodynamic. Such model allows revising the solubility and diffusivity of hydrogen intungsten. The discrepancy between the experimental diffusion coefficient from Frauenfelder
et al [1] and other DFT results [2] is understood and two diffusion regimes are proposed
depending on the temperature.
The trapping of multiple hydrogen atoms in tungsten vacancies is also investigated. The
hydrogen population in vacancies and the vacancy concentration in tungsten are shown todepend on the temperature. TDS spectra are simulated using simple kinetic laws; despite thesimplicity of the model, the agreement is good agreement with experimental results recordedon single crystalline samples [3,4].
This work is now published as:
N. Fernandez, Y. Ferro, D. Kato, Acta Mater. 94 (2015) 307-318[1] R. Frauenfelder, J. Vac. Sci. Technol., 6 (1969) 388[2] K. Heinola, T. Ahlgren J. Apll. Phys., 107 (2010) 113531[3]O. V. Ogorodnikova, T. Schwarz-Selinger, K. Sugiyama, T. Dürbeck and W. Jacob, Phys.
Scr. T138 (2009) 014053[4] M. Poon, A.A. Haasz, J.W. Davis, Journal of Nuclear Materials 374 (2008) 390.

*Corresponding author: yves.ferro@univ-amu.fr (Y. Ferro)

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MoD-PMI 2015

I - 20DFT calculations and statistic models for the evaluation of accidental beryllium
and tritium releases in ITER facility
L. Ferrya,b, F. Virota,*, M. Barrachina, A. Alliucheb, and Y. Ferrob,*,aInstitut de Radioprotection et de Sûreté Nucléaire (IRSN), St Paul lez Durance, 13115
Cadarache, Franceb

Aix-Marseille Université, CNRS, PIIM UMR 7345, 13397 Marseille, France

The safety analysis of the ITER experimental facility principally aims to evaluate the amountand chemical speciation of radionuclides that can be released to the environment in accident
conditions (the so-called source term). Initially, only tritium, tungsten dusts and corrosion
products present in the coolant system of the vacuum vessel were taken into account.
However, in addition to these products, the beryllium dusts have an extreme chemical toxicity
and must also be considered, which is the focus of the present work. To improve the source
term evaluation, electronic properties, thermodynamic functions of gas and solid beryllium
compounds and interaction between them are key issues.
As the first step, the thermodynamic properties of the gaseous Be-O-H-T system have been
recently investigated on the basis of quantum chemistry calculations [1]. To achieve a
reliable thermo-chemical database of beryllium compounds, the thermodynamic properties ofBe(c), BeH2(c) and BeT2(c) have to be known. Also the kinetic of formation of these mixed
Be/H and Be/T materials are of high interest and both their kinetics and thermodynamics will
be investigated in this study. To this end, a theoretical approach associating solid statephysics and quantum chemistry is developed: it is based on electronic structure calculations
by mean of Density Functional Theory (DFT) methods as implanted in the Quantum
Espresso package.
Beryllium and beryllium hydride models are established and constructed. The procedure
incorporates the supercell size and simulations parameters optimization like the plane wave
cutoff energy, the Brillouin zone k-points and the smearing width. The crystal structure,mechanical properties and electronic structure of Be and BeH2 are calculated and comparedwith the available and experimental data [2-4].
The next step will be about hydrogen trapping in beryllium vacancies, hydrogen interaction
on the beryllium and hydride beryllium surfaces and the phonon properties of these systems.

[1] F. Virot et al., Fusion Eng. Des., 89 (2014) 1544
[2] E. Wachowicz et al., J. Phys. Condens. Matter, 13 (2001) 10767[3] G. S. Smith, et al., Solid State Commun. 67 (1988) 491[4] M. Ahart, et al., J. Chem. Phys., 124 (2006) 014502
Acknowledgements: This work is supported by Region PACA and IRSN.

* Corresponding authors: francois.virot@irsn.fr (F. Virot)
yves.ferro@univ-amu.fr (Y. Ferro)

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MoD-PMI 2015

List of Participants

Addab Younes
Aix-Marseille University - France(P1)

Allouche Alain
Aix-Marseille University - France
Ahlgren Tommy
University of Helsinki

alain.allouche@univ-amu.fr(I15)

Barrachin MarcIRSN – Cadarache
Barthe Marie-France
CNRS – CEMTHI – Orléans– France

younes.addab@univ-amu.fr

tommy.ahlgren@helsinki.fi
marc.barrachin@irsn.fr(I11)

Battes Katharina
Karlsruhe Institute of Technology (KIT)

marie-france.barthe@cnrs-orleans.fr
katharina.battes@kit.edu

Becquart Charlotte
Université de Lille 1 – France(I1)charlotte.becquart@univ-lille1.fr

Begrambekov Leon
MEPhI – Moscow - Russia(O1)

lbb@plasma.mephi.ru

Bisson Régis
Aix-Marseille University - France(O2)

regis.bisson@univ-amu.fr

Blondel Sophie
Oak Ridge National Laboratory – USA(P2)

blondels@ornl.gov

Braams Bas
IAEA, Vienne - Autriche(I5)b.j.braams@iaea.org

Cannuccia Elena
Aix-Marseille University - France

elena.cannuccia@univ-amu.fr

Caturla Terol María José
Universidad de Alicante - Spain(I16)

mj.caturla@ua.es

Ceriotti Michele
EPFL - Suisse(I7)

michele.ceriotti@epfl.chCheng Bingqing
EPFL – Suisse(P3)

tonicbq@gmail.com

Chentouf Sara
Aix-Marseille University

sara.chentouf@univ-amu.fr

Connetable Damien
CIRIMAT - CNRS - France

damien.connetable@ensiacet.fr

Deng Huiqiu
Hunan University - China(I2)

hqdeng@hnu.edu.cn

De Temmerman Gregory
ITER Organization - France(I10)

gregory.detemmerman@iter.org

Dittmar Timo
(P8)
Forschungszentrum Jülich IEK-4 – Germanyt.dittmar@fz-juelich.de

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MoD-PMI 2015
Douai DavidCEA Cadarache(P4)

Eichler Michel
Forschungszentrum Jülich IEK-4 – Germany
Fernandez Nicolas
Aix-Marseille University - France(P20)

Ferro Yves
Aix-Marseille University - France
Ferry Laura
Aix-Marseille University - France

david.douai@cea.fr
m.eichler@fz-juelich.denicolas.fernandez.2@etu.univ-amu.fr
yves.ferro@univ-amu.fr(P21)

Gao Fei
University of Michigan - USAlaura.ferry.1@etu.univ-amu.fr
gaofeium@umich.edu

Ghiorghiu Florin
Aix-Marseille University - France

florin.v.ghiorghiu@gmail.com

Grisolia Christian
CEA Cadarache – France(I18)

christian.grisolia@cea.fr

Heinola Kalle
CCFE, Culham Science Centre, UK(I14)

kalle.heinola@ccfe.ac.uk

Hodille Etienne
CEA Cadarache

etienne.hodille@cea.fr

Itoh Atsushi M.
(I3)
National Institute for Fusion Science - Japan

ito.atsushi@nifs.ac.jp

Kandaskalov Dmytro
Aix-Marseille University - France(P5)

dmytro.kandaskalov@im2np.fr

Kato Daiji(P6)
National Institute for Fusion Science - Japankato.daiji@nifs.ac.jp

Klaver Peter
DIFFER – The Netherlands(P7)

klaver2@gmail.com

Kohanoff Jorge J.
Queen’s University, Belfast - Ireland(I6)

j.kohanoff@qub.ac.uk

Layet Jean-Marc
Aix-Marseille University - France
Lee Heun-Tae
University of Osaka - Japanpiim-direction@univ-amu.fr(I12)

Martin Céline
Aix-Marseille University – France

heunlee@wakate.frc.eng.osaka-u.ac.jp
celine.martin@univ-amu.fr

Matveev Dmitry(O5)
Forschungszentrum Jülich IEK-4 – Germany

d.matveev@fz-juelich.de

Mellet Nicolas
Aix-Marseille University - France(P10)

nicolas.mellet@univ-amu.fr

Mougenot Jonathan
Université, Paris XIII – France(P11)

jonathan.mougenot@lspm.cnrs.fr

Neugebauer Jörg
(I13)
Mas-Planck Institute, Dusseldorf - Germany

neugebauer@mpie.de

56	
  
	
  

MoD-PMI 2015
Nguyen-Manh Duc
CCFE, Culham Science Centre, UK(O4)

duc.nguyen@ccfe.ac.uk

Novotny Michal(P12)
Commenius University Bratislava – Slovakia

novotnym@nic.fns.uniba.sk

Ogorodnikova Olga
MEPhI – Moscow - Russia(I19)

ovo@rzg.mpg.de

Pardanaud Cédric
Aix-Marseille University - France(P16)

cedric.pardanaud@univ-amu.fr

Paxton AnthonyKing’s College London - UK

(I8)

tony.paxton@KCL.ac.uk

Padivattathumana Maya
ITER-India(P9)maya.padivattathumana@iter-india.org

Ratynskaia Svetlana(P17)Royal Institute of Technology (KTH) - Sweden

svetlana.ratynskaia@ee.kth.se

Schmid Klaus(I17)
Max-Planck Institute – Garching – Germany

klaus.schmid@ipp.mpg.de

Takayanagi Toshiyuki
Saitama University - Japan(I9)

tako@mail.saitama-u.ac.jp

Tanguy Döme
Université Claude Bernard Lyon 1(O3)

dome.tanguy@univ-lyon1.fr

Tolias Panagiotis(P18)
Royal Institute of Technology (KTH) - Sweden

tolias@kth.se

Virot François
IRSN - Cadarache

francois.virot@irsn.fr

Vladimirov Pavel(I4)
Karlsruhe Institute of Technology - Germany

pavel.vladimirov@kit.edu

Zaloznik AnzeJozeph Stefan Institute – Slovenia(P13)anze.zaloznik@ijs.si

Zibrov Mikhail
DIFFER – The Netherlands(P15)

m.zibrov@differ.nl

Zhu Deqiong
Seoul National University(P14)

zhudeqiong@snu.ac.kr

57