MIC - Microanalytical Centre

Activities

The Tandetron ion accelerator conducts research with accelerated ion beams, including both analytical methods (Ion Beam Analysis, IBA) and methods for the transformation of materials with high-energy ion beams.

Analytical methods (Ion Beam Analysis, IBA) :

  • PIXE (Proton Induced X-ray Emission)
  • PIGE (Proton Induced Gama-ray Emission)
  • RBS (Rutherford Back Scattering)
  • ERDA (Elastic Recoil Detection Analisys)
  • STIM (Scanning Transmission Ion Microscopy)
  • NRA (Nuclear Reaction Analisys)
  • MeV SIMS (MeV Secondary Ion Mass Spectroscopy)
  • HR-XRS (High Resolution X-ray Spectrometry

Applications:

On beam lines, ion implantation of high-energy ions into selected materials is performed. Since a set of three ion sources allows the formation of any ion from a periodic table of elements, materials can be implanted with a wide range of ions and energies between 100 keV and 12 MeV.

Ion sources

The performance of a tandem accelerator is largely determined by ionic sources, in which we form a low-energy beam of negative ions and direct it into the accelerator tube. Compared to similar installations in Europe, the Ljubljana Tandetron is particularly powerful, as in addition to two standard ion sources (sputter and duoplasmatron), it also uses an extremely bright source of negative hydrogen ions with the internationally established name multicusp. Thus, in the opening source we form ion rays from the entire periodic table of elements, in the duoplasmatron we form ³He and ⁴He ions, and in the multicusp source we form very bright and strong rays of negative hydrogen ions. In a tandem accelerator, negative ions are accelerated and electrons are "peeled" from them by producing rays of positively charged ions with energies in the MeV range at the output.

Pictured below: multicusp source (left), sputter and duoplasmatron (in a common housing in the middle)

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Pictured below: duplazmatron, for ³He / ⁴He beams

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The multicusp ion source allows the formation of an ion beam of negative hydrogen ions with very high brightness. The high brightness of the beam is crucial in the design of a high-energy focused proton beam, with which we perform micro-PIXE spectroscopy. With the installation of the ion source “multicusp”, a high-energy focused proton beam with the highest brightness in the world started operating on the Ljubljana tandem accelerator.

Below are some photos of multicusp origin during servicing and in operation (click to enlarge)

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Beamlines

On the beam line with an external beam, the measurements are performed with the PIXE method in the air on objects that cannot be inserted into a vacuum, e.g. art canvases from the National Gallery, in which the types of original pigments before restoration procedures are determined

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PIXE, RBS, NRA, STIM and MeV-SIMS methods are performed on the ion microbeam with a focused beam, which is moved in the form of a raster along the selected part of the sample. The beam with quadrupole lenses is collected to a diameter of 700 nanometers, and the elemental or molecular distributions in the sample are measured with such lateral resolution. In terms of the scope of measurements, measurements on biological and medical samples stand out.

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On the ERDA / RBS beam line, which is also called INSIBA (IN Situ Ion Beam Analysis), we measure the static and dynamic properties of materials, e.g. the content or dynamics of deuterium diffusion in metals by the NRA method, in which the sample is bombarded with ³He ion beams. Research is very important in the field of fusion, which is why EUROFUSION co-finances the purchase of the very expensive gas ³He.

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At the PIXE measuring station, nuclear astrophysicists are studying nuclear reactions that were crucial in the process of nucleosynthesis after the Big Bang, and nuclear reactions that take place inside stars. They use a combination of light primary ions (¹H, ³He , ⁴He, ⁶Li, ⁷Li ...) from the ion accelerator, and light target nuclei.

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On a beam line with high-resolution X-ray spectrometry, the chemical states of the elements can be determined by measuring high-resolution X-ray emission. Among other things, this method studies chemical processes during battery operation in situ in collaboration with the Institute of Chemistry, and refines the ionization cross-section databases for the APXS spectrometer on the Curiosity rover on Mars in collaboration with the University of Guelph, Canada.

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Accelerator schedule

The tandem ion accelerator "Tandetron" is the heart of the Infrastructure Research Center "Microanalytical Center" (MIC), which operates within the Infrastructure Program of the Jožef Stefan Institute.

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Tandetron is the only research accelerator in the country. Acceleration of ions takes place electrostatically in a direct electric field, which is provided by a rectifier with a voltage of up to 2 MV (two million volts). The accelerator is one of the most technologically advanced electrostatic accelerators, the high voltage is generated in a rectifier with semiconductor diodes, without mechanically moving parts. The rectifier is very stable - at an output voltage of 2 million volts, the voltage instability is only about 100 V.

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Graphics above: Ground plan of the Jožef Stefan Institute's ion accelerator with three ion sources (duoplasmatron, dsputtering source and state-of-the-art ion source multicusp) and four beamlines.

 

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