Antimatter and Nuclear Engineering

The Antimatter and Nuclear Engineering group specializes in the development and applications of positron-based spectroscopic tools in condensed matter research. It also works on reactor and radiation physics research. The group has extensive facilities for positron annihilation spectroscopy and access to a wide range of experimental tools at the Department of Applied Physics.
Antimatter and nuclear engineering
Group leader professor Filip Tuomisto

Group leader

Filip Tuomisto

Research

Positron physics and defect spectroscopy

Positron annihilation spectroscopy enables the unambiguous identification and quantification of vacancy defects and their surrounding atoms in crystalline solids. For instance, in the case of semiconductor materials, this type of basic research aims at the understanding of e.g. mechanisms of electrical compensation, the origin of optical absorption and the nature of electronic transitions of photoluminescence. In the past, the group has contributed substantially to the understanding of defect and doping impurity structures both in silicon and compound semiconductors, as well as the physics of positrons in solids.

Our work in this field involves the study of defects in semiconductors, development of positron methods for the study of matter, and nuclear materials research. All the instrumentation has been designed and constructed in-house.

See review:  “Defect identification in semiconductors with positron annihilation: Experiment and theory”, Rev. Mod. Phys. 85, pp. 1583 – 1631 (2013).

Reactor and radiation physics

In reactor physics, the current research interests include Monte Carlo burnup calculation methodology, diffusion coefficient generation by the Monte Carlo method and uncertainty analysis in reactor physics. Essentially all research is computational using and/or developing codes such as SerpentMCNP and NJOY in close collaboration with VTT Technical Research Centre of Finland Ltd.

In radiation physics our interests are in the computational methods of gamma-ray spectrometry and identification. The group is the birthplace of SAMPO codes for spectrum analysis and the expert system SHAMAN for subsequent radionuclide identification and quantification. We also belong to the developers of LINSSI database for gamma-ray spectrometry and are active members of the LINSSI Users' Group.

We are active members of European Nuclear Education Network and Finnish Generation IV -project.

Facilities

We have two continuous variable-energy positron beams equipped with state-of-the-art detector systems and sample manipulation facilities and four measurement stations for fast positron spectroscopy, and a pulsed positron beam for positron lifetime measurements with low-energy positrons. All the instrumentation has been designed and constructed in-house.

Sample manipulation possibilities during positron experiments include:

  • Temperature control from 10 K up to 1000 K that allows for defect charge state determination in semiconductors, in-situ annealing experiments in semiconductors and metals, and, e.g., structural analysis of phase transitions in molecular matter.
  • Monochromatic sample illumination with light wavelength 400 – 2500 nm, allowing for studies of photoionization of defects in semiconductors and, e.g., structural photoresponse in polymers.
  • Sample biasing, allowing for studies of near-surface Fermi level modification effects in semiconductors and positron diffusion.

Courses

The Antimatter and Nuclear Engineering group promotes a few courses and offers positions and subjects for theses.

Courses on nuclear engineering

The courses related with nuclear engineering are lectured in Finnish. For an English alternative, please contact Professor Filip Tuomisto.

Introduction to nuclear energy technology

The course is intended for students minoring in energy sciences. It is lectured every spring. The course has three main parts: current, generation II and generation III nuclear reactors, future generation IV fission reactors and fusion reactors. The contents are basics of nuclear physics and technology, nuclear fuel cycle, nuclear waste management, safety and nuclear specific issues. Fusion reactor concepts, basics of fusion physics and material issues are also covered. The course is lectured in Finnish.

Introduction to reactor physics

The course is lectured every autumn. It gives an overall view of nuclear energy, reactors and power plants and an introduction to neutron physics, nuclear reactor theory, reactor kinetics, heat removal, thermal hydraulics, fuel cycles, nuclear waste management and safety viewpoints. The mathematics and physics courses of the first two years are adequate prerequisites. The course is lectured in Finnish.

Advanced course in nuclear engineering

The course is lectured every spring and concentrates on neutron physics. The course introduces a computational chain that can be used to model nuclear reactors. The course covers transport theory, Monte Carlo method, burnup calculation (Bateman equations) and diffusion theory as well as elementary heat transfer and thermal hydraulics. Applications of the computational chain are demonstrated.

Radiation physics and safety

The subject of the course is radiation, its interactions with matter and its health effects. The emphasis is on the ionizing radiation, its risks and their mitigation. The concept of risk is studied in connection with radiation and nuclear safety. The course includes laboratory exercises on sealed sources and X-ray equipment and gives a possibility to obtain a licence to use them in research and industry. For the licence adequate knowledge of the Finnish regulations on radiation and nuclear safety is required.

Solid-state and materials physics

Members of the group also contribute in teaching courses on solid-state and materials physics.

Laboratory courses

The group actively participates in organizing and developing the laboratory courses on Engineering Physics. These courses give hands-on experience of research work that is welcome among the theoretical physics courses.

Laboratory course on engineering physics

One of the exercises on this BSc-level course is titled "Positron measurements in semiconductors". The goal of this assignment is to familiarize oneself with the equipment used in a positron
lifetime measurement, studying vacancies with positrons and the physics of vacancy defects in GaN samples.

Advanced physics laboratory

One of the exercises on this MSc-level course is titled "Semiconductor studies with positrons". The goal of this assignment is to dig deeper into semiconductor characterization utilizing positron spectroscopy.

Theses

The Antimatter and Nuclear Engineering group offers a wide range of subjects for bachelor’s theses, special assignments and master’s theses. Many of our theses are written at the organizations in this field (VTT, Fortum, STUK, TVO) or instructed by their expert personnel.

For further information, please contact Professor Filip Tuomisto.

Latest publications

Antimatter and Nuclear Engineering, Department of Applied Physics

Unusual properties of the RY3 center in GaN

Publishing year: 2019 Physical Review B
Department of Applied Physics, Antimatter and Nuclear Engineering

Heavily phosphorus doped germanium

Publishing year: 2019 Journal of Applied Physics
Department of Applied Physics, Antimatter and Nuclear Engineering

Direct observation of mono-vacancy and self-interstitial recovery in tungsten

Publishing year: 2019 APL Materials
Department of Applied Physics, Antimatter and Nuclear Engineering

Evolution of phosphorus-vacancy clusters in epitaxial germanium

Publishing year: 2019 Journal of Applied Physics
Department of Applied Physics, Antimatter and Nuclear Engineering

Ga vacancies and electrical compensation in β-Ga 2 O 3 thin films studied with positron annihilation spectroscopy

Publishing year: 2019
Department of Applied Physics, Antimatter and Nuclear Engineering

A large deformation model for chemoelastic porous media - Bentonite clay in spent nuclear fuel disposal

Publishing year: 2019
Antimatter and Nuclear Engineering, Department of Applied Physics

Influence of Fermi level position on vacancy-assisted diffusion of aluminum in zinc oxide

Publishing year: 2018 Physical Review B
Department of Applied Physics, Antimatter and Nuclear Engineering

Preface

Publishing year: 2018 Journal of Crystal Growth
Antimatter and Nuclear Engineering, Department of Applied Physics

Ydinenergia-alan kesäkoululaiset Suomen Turussa

Publishing year: 2018 ATS Ydintekniikka
Antimatter and Nuclear Engineering, Department of Applied Physics

New insight in the uranium valence state determination in UyNd1−yO2±x

Publishing year: 2018 Journal of Nuclear Materials
More information on our research in the Research database.
Research database

Research group members

Jonatan Slotte

Jonatan Slotte

Department of Applied Physics
Senior University Lecturer
Filip Tuomisto

Filip Tuomisto

Department of Applied Physics
Professor
Jarmo Ala-Heikkilä

Jarmo Ala-Heikkilä

Department of Applied Physics
Specialist

Antti Karjalainen

Department of Applied Physics
Doctoral Candidate

Kristoffer Simula

Department of Applied Physics
Doctoral Candidate

Afrina Khanam

Department of Applied Physics
Doctoral Candidate
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