Laboratory for fusion research

Jožef Stefan Institute,
Jamova 39,
SI-1000 Ljubljana,

Leader: Doc. Dr Sabina MarkeljCoworkers: Mitja Kelemen, Matic Pečovnik, Prof. Dr Primož Pelicon, Zdravko Rupnik, Dr Primož Vavpetič, Dr Iztok Čadež

INSIBA – In-situ ion beam analysis

INSIBA experimental chamber is attached to PIXE-ERD beam line at the 2 MV tandem accelerator at Jožef Stefan Institute (JSI), Slovenia. The set up allows creation of displacement damage by implanting high energy ions at a given sample temperature for simulation of irradiation damage caused by neutrons in fusion reactor. Samples can be simultaneously or sequentially irradiated by high energy ions and exposed to a well-controlled flux of atomic deuterium or to deuterium ions from an electron cyclotron resonance (ECR) ion gun. The sample is mounted on a holder with temperature controlled heater, capable of heating the sample up to 1200 K. The resulting deuterium depth profile is measured by the nuclear reaction analysis (NRA) method utilizing D(3He, α)p nuclear reaction. For one depth profile typically six analysing beam energies are used ranging from 0.7 MeV to 4.3 MeV. The proton detector used for the NRA measurement is mounted at a 160 degree scattering angle. Another detector is mounted at the 165° angle and is used for Rutherford Backscattering Spectroscopy (RBS) technique which determines the irradiation dose and depth profiles of species that are heavier than the probing beam ions.


The set up can be changed also for experiments with ERDA method, where detection of elastically recoiled particles is performed. There a small glancing angle of the probing ion beam with respect to the sample surface is needed as the recoiled particles exiting the target in the forward direction are detected. In our case typically 4.3 MeV beam of Li ions is used and is directed to the target at 15° glancing angle with respect to the sample surface. Li ions were used since they give better depth resolution as compared to the He ion beam due to the higher stopping power and the surface peaks of H and D are further apart.


The set up enables:

  • classical NRA, RBS, ERDA material analysis for heavy element analysis and hydrogen isotope depth profiling in materials (20 samples can be mounted at once)
  • in situ hydrogen isotope depth profiling in materials during or after sample exposure to hydrogen ions or atoms
  • computer controlled sample heating up to 1000 K
  • high energy (MeV) ion beam irradiation (W ions, He ions, protons)
  • Sample exposure to hydrogen atoms and molecules
  • Sample exposure to ions (H, D, He, Ar, O) with energies from 0.1 keV to 5 keV



Markelj, S., Schwarz-Selinger, T., Pečovnik, M., Založnik, A., Kelemen, M., Čadež, I., Bauer, J., Pelicon, P., Chromiński, W., Ciupinski, L., 2019. Displacement damage stabilization by hydrogen presence under simultaneous W ion damage and D ion exposure. Nucl. Fusion 59, 086050.

Markelj, S., Založnik, A., Schwarz-Selinger, T., Ogorodnikova, O.V., Vavpetič, P., Pelicon, P., Čadež, I., 2016. In situ NRA study of hydrogen isotope exchange in self-ion damaged tungsten exposed to neutral atoms. Journal of Nuclear Materials 469, 133–144.

Založnik, A., Pelicon, P., Rupnik, Z., Čadež, I., Markelj, S., 2016. In situ hydrogen isotope detection by ion beam methods ERDA and NRA. Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms 371, 167–173.

VEVOF - Experiments with vibrationally excited hydrogen molecules

Within our fusion related program we are performing experiments with vibrationally excited H₂ and D₂ molecules. For this purpose, a specialized unique vibrational spectrometer has been built. Its operation is based on the properties of dissociative electron attachment (DEA) of low energy electrons (0-5 eV) in hydrogen. A magnetic field is used in this spectrometer for guiding the electron beam and for extracting and separating H- and D- from heavier ions and electrons. Original ion extraction system based on penetrating electric field was constructed for focusing and detection of low energy ions.


 Studies of vibrational population of hydrogen molecules are performed, which are created by:

  • Atom recombination on metal surfaces exposed to the partially dissociated neutral atmosphere,
  • Recombination at Pd membrane after hydrogen permeation,
  • Effusion from hot tungsten capillary and
  • Thermal desorption.

New data are acquired on DEA in H₂ and D₂.


Čadež I., Hall R. I., Landau M., Pichou, F., Winter M., Schermann C., Electron attachment to molecules and its use for molecular spectroscopy. Acta Chim. Slov., 2004, vol. 51, pp. 11-21.

Čadež, I., Markelj, S., Pelicon, P., Rupnik, Z., 2009. Reemission of neutral hydrogen molecules from tungsten. Journal of Nuclear Materials 390–391, 520–523.

Markelj, S., Rupnik, Z., Čadež, I., 2008. An extraction system for low-energy hydrogen ions formed by electron impact. International Journal of Mass Spectrometry 275, 64–74.

E. Krishnakumar, S. Denifl, I. Cadez, S. Markelj and N. J. Mason, Dissociative Electron Attachment Cross Sections for H₂ and D₂,Phys. Rev. Lett. 106, 243201 (2011)

Markelj, S., Čadež, I., 2011. Production of vibrationally excited hydrogen molecules by atom recombination on Cu and W materials. The Journal of Chemical Physics 134, 124707.

TDS and AES - Thermal Desorption Spectroscopy and Auger Electron Spectroscopy


AmTDS - Thermal desorption spectroscopy of Ammonia


Temperature programmed desorption of sample is performed to study ammonia or hydrogen isotope atom surface adsorption on metals. The experimental set up consists of the Hydrogen Atom Beam Source (HABS) (MBE Komponenten GmbH) and the residual gas analyzer (RGA) (Pfeiffer, Prisma Plus quadrupole mass spectrometer, 1–100 amu/e) mounted to a small ultrahigh vacuum chamber pumped by a 500 l/s turbomolecular vacuum pump (Pfeiffer, TMU 521Y P N).

A sample holder is mounted on the flange facing turbo-molecular pump. Sample can be linearly heated up to 1100 K and exposed to hydrogen atom beam from HABS. Ammonia is introduced through a side leak by small stainless steel tube directed to the center of the sample. NH₃, D₂, or a mixture of both is introduced through HABS, and the gas composition in the chamber is monitored by RGA either by recording the entire mass spectra in the 1–100 amu/e range or by recording the time variation of a set of characteristic mass peaks in the spectrum [multiple ion detection (MID) mode].


Markelj, S., Založnik, A., Čadež, I., 2017. Interaction of ammonia and hydrogen with tungsten at elevated temperature studied by gas flow through a capillary. Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films 35, 061602.


Sources available:

  • Source of vibrationally hot H₂ and D₂ has been constructed in house for spectroscopic studies in hydrogen plasma.
  • A commercial hydrogen atom beam source (HABS) by MBE Komponenten GmbH [K. G. Tschersich, J. P. Fleischhauer, and H. Schuler, J. Appl. Phys. 104, 034908 (2008)] for production of partly dissociated hydrogen gas. Production of H or D atoms depending on the use of gas H₂ or D₂, respectively.
  • A commercial electron cyclotron resonance (ECR) ion gun (energy range 25 eV – 5 keV) by Tectra Gen II The ion gun is a filamentless ion source based on a microwave plasma discharge.


AES Auger Electron Spectroscopy


Auger Electron Spectroscopy (AES),  Instrument: DESA 100, Producer: STAIB Instrumente GmbH. DESA 100 STAIB is compact instrument with cylindrical mirror analyzer (CMA) geometry, that can be build in into existing vacuum systems. While keeping all the advantages of the CMA, such as unbeatable sensitivity, small size and integrated electron source, the additional new features of DESA 100 are large working distance, uncritical sample positioning and electrically variable energy resolution.


Photos:  Auger electron spectrometer before mounting (left) and as mounted in the UHV system (right).


The spectrometer for Auger electron spectroscopy is intended for the analysis of the surface of various materials, and in particular allows: determination of contamination of samples with hydrocarbons, oxides; analysis of the amount of adsorbed molecules on the studied samples and analytical composition of thin layers.

For access to the instrument for measurements contact dr. Sabina Markelj.

External coworkers

Dr Anže Založnik

Fusion research in the department F2 of the Jožef Stefan Institute has started in 2003 with a project at EURATOM. The project subject was to contribute in the field of atomic processes in edge plasma of a tokamak. The main goal is to study processes with neutral hydrogen atoms and molecules interacting with materials relevant for fusion. From the very beginning the use and development of ion beam methods at Tandetron accelerator at Microanalitical center have been progressing hand in hand. 

Particular impetus for the research was the organizational change of the European program to the strategic goal for successful construction and operation of the international ITER tokamak. The European research has been coordinated by the newly established EUROfusion Consortium and our work is strongly integrated within Work package “Preparation of Efficient Plasma-Facing Component (PFC) Operation for ITER and DEMO˝ (WP PFC).

The Laboratory for fusion research was founded in the year of 2019 when the Fusion technologies program group was established at IJS. Our group has been part of Slovenian Fusion Association from the very beginning. We have a very active collaboration with other laboratories working on fusion in particular with Forschungszentrum Jülich GmbH, Max-Planck-Institut fur Plasmphysik, Garching, Aix Marseille Universite, CEA, VTT.

The main research in the laboratory is related to plasma wall interaction. In our research we exploit ion beam methods that have been under development at the 2MV accelerator laboratory <link> where we have constructed a special beam line and chamber. With methods like NRA and ERDA depth distribution of hydrogen isotopes can be followed in-situ and in real time during specific experimental exposures of samples to hydrogen. In our laboratory we have also constructed and developed a unique spectrometer for detection of vibrationally excited hydrogen molecules. The detection method is based on dissociative electron attachment into hydrogen molecules. In the laboratory we have also constructed an ultra-high vacuum chamber where a mass spectrometer is used to study adsorption and desorption of gases to and from materials.


The main area of expertise is the study of hydrogen atom interaction with materials for fusion:

  • Hydrogen depth profiling in materials by ion beam methods, where our main field of expertise is to follow processes on surface and in the bulk in-situ and in real time.
  • Irradiation of samples by high energy ions with the purpose to create defects in crystal lattice.
  • Analysis of samples exposed to plasma from fusion devices by microbeam.
  • Rate equation modelling of hydrogen adsorption, desorption and recombination on the surface and diffusion and trapping in the bulk of material.

Spectroscopy of vibrationally excited hydrogen molecules - study of their production on surfaces and their interaction with materials.