Degree and Student Projects

Simulation and fitting of polarised neutron reflectivity data

The task within this project will be to simulate and fit polarised neutron reflectivity data from EuS/TM multilayers. Recently, strong room temperature magnetisation was observed in EuS/Co multilayers. In a series of neutron scattering experiments we have collected data that can be used to estimate experimentally the extension of the magnetic polarisation in EuS. You will use a specifically developed fitting tool for reflectivity data, called GenX. Resulting data will be combined with input from x-ray circular magnetic dichroism experiments in order to provide more reliable information. This project requires some basic knowledge about computer use and optionally programming.

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Magnetotransport in amorphous nanoscale films and multilayers

Developing materials and devices where the magnetic and electrical properties are linked is the subject of the relatively new field of spintronics. This project involves studying the electrical transport properties of amorphous magnetic films. Amorphous magnetic films are attractive for spintronic devices due to their high degree of uniformity and potential for tuning of magnetic and electronic properties. Yet, the mechanisms defining their electrical properties are not well understood. The project will involve measurements of resistivity, Hall effect and magnetoresistance in nanoscale films from 10 K up to room temperature. Multilayers of alternating magnetic and non-magnetic layers will also be studied.

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Magneto-optic spectroscopy of advanced materials

This project is focused on the exploration of energy dependent rotation of light from surfaces. The aim is twofold: Establish spectroscopic magneto optical of few elements and secondly to explore how thick a layer has to be to give the signature corresponding to the bulk like response.

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Metal hydrides

Some transition metals are known to easily take up large quantities of hydrogen on interstitial lattice sites. For bulk materials, the thermodynamics and kinetics of such systems are quite well understood. In the case of thin films, this situation changes since the hydrogen-hydrogen interaction is mediated by elasticity, which is a long range force. As a result, thin film metal hydrides show profound finite-size and proximity effects. The changes of thermodynamics and/or kinetics can be well explored by different scattering methods.

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Photochromics

The possibility to alter optical properties of materials by electrical, thermic or optical stimuli offers exciting new applications. Examples range from a usage in motorcycle helmets with visors of variable transmittance providing bikers the comfort of a dark visor in sunlight and the safety of a clear visor in the dark to applications which can have a global impact on energy consumption via passive regulation of heat flux in and out of buildings reducing heating & cooling costs.

The necessary changes in optical transmission can, for many materials, be related to the concentration of hydrogen in transition metal hydrides. However, for these materials a change in hydrogen concentration is needed in order to tune the transmission of photons. For O-containing YHx a different switching mechanism is reported. The darkening of the Yttrium-oxy-hydride YOyHx is stimulated by the illumination with sunlight. This photochromic behaviour has the distinct advantage that the material can automatically regulate a close to constant transmitted intensity. In this project, we will address this class of materials systematically. Our focus will be on revealing the mechanism of the photochromic reaction and control as well as improve the properties of the films.

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Magnetic liquids

Self assembly is one of the most fascinating phenomena in nature, since it can form well ordered structures on almost all length scales. The self assembly process is determined by the interaction between the constituents. Accordingly, a system offering tuneable interaction is an ideal playground for the understanding of the basic concepts of self assembly. We realize such a system by dispersing magnetic and non-magnetic particles in a ferro fluid matrix. Analysing the microscope images from such samples statistically gives quantitative information about phase formation.

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Surface ordering under shear

In fluid mechanics, flow is described by the Navier–Stokes equation in the bulk and a no-slip boundary condition at the solid interface. However, recently, both experiments and theory have shown that on a microscopic scale liquids may undergo significant slip at a solid wall. The magnitude of the slip length and its relation to the relevant surface parameters on that it depends, are, presently, under intense discussion in the literature and not well understood on the nm length scale. We contribute to this issue by investigation of surface ordering in samples that show correlations on mesoscopic length scales as well as Newtonian liquids mainly by scattering techniques. In particular, the use of neutron scattering methods allows to access liquids in contact to solid substrates.

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Topological interactions in polymers under shear

Complex liquids have unique flow properties, displaying behaviours between classical solids and liquids due to their broad distribution of relaxation times. The viscoelastic properties can generally be connected to the microscopic picture of the structure and dynamics of the constituents. On the microscopic scale, this information can be addressed by scattering methods and changes in the structure under shear have been investigated intensively in the past. However, experiments addressing the dynamics of complex liquids under shear are very scarce and even the structure of very high molecular mass polymer melts is not well understood since the Weissenberg effect prevents rheological experiments in a simple Couette geometry. Recently, we have designed a closed shear device specifically to fill both these gaps and performed first successful test experiments. This allows to investigate the topological interactions in highly entangled polymers under shear load systematically and in detail. The experimental results, mainly obtained from neutron small angle scattering and spin echo experiments, will be compared to theoretical expansions of the reptation model, like convective constraint release, as well as computer simulations recently performed in the group.

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Magneto-plasmonics – Understanding the correlation between plasmons and magneto-optics

Plasmons are collective electronic resonances that have a huge impact on the optical properties of metallic materials and nanostructures. With optical diffractometry and ellipsometry in combination with measurements of the magneto-optical effects one has access to all optical properties of a material. With the advent of plasmonics and metamaterials one has the possibility to tune those properties by using nanostructures to control the reflectivity of the material or even the properties of the emitted light itself. This project will involve magnetic nanostructures and optical and magneto-optical measurements for characterization of magneto-plasmons.

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Development of a muon-rejection system for the nuclear-reaction analysis station at the Tandem Laboratory

Background

Ion beam analysis techniques allow for non-destructive studies on near surface hydrogen. Resonant nuclear reaction analysis (NRA), based on the 1H(15N,αγ)12C nuclear reaction, with its cross section exhibiting a narrow resonance (Γ=1.8 keV) at 6.385 MeV, is commonly employed for precise, in-depth, quantification of hydrogen concentrations. The Tandem Laboratory at Uppsala University, employs a resonant-NRA setup that is in regular use. As resonant-NRA relies on the detection of γ-rays emitted from the sample, measurements are subject to the natural background present in any laboratory environment. Fortunately, the high energy of the γ-ray line of interest, separates it well from the majority of lines originating from common radioisotopes. Interference from cosmic-ray muons, however, is still a problem.

Project goal and work plan

The NRA setup at the Tandem Laboratory is currently being upgraded and, as part of this upgrade, the addition of a muon-rejection system is desired to reduce the signal background and improve detection limits. The goal of the project will be to build this system. The project can be divided into the following key tasks:

build a muon-detection system based on coincident-signal detected in two scintillation detectors;
combine the system with the NRA station in anti-coincidence to reject muon events registered during measurement;
quantitively assess the background rejection properties of the system, and the improvement in hydrogen detection-limit it brings;
further optimise the system based on the results obtained;
write a report summarizing the results and conclusion of the work.

The position will be based at the Ångström laboratory in Uppsala, within the Ion-physics Group. This project provides an excellent opportunity to become acquainted with the broad range of research being conducted within the Ion-physics group, and to make a long-standing contribution to its operation.

The project can be adjusted to correspond to 15, 30 or 45 ECTS credits and can start during either the autumn 2023, or spring 2024 semesters.

Desired qualifications/experience

The applicant should be enrolled on a physics program at Uppsala University and possess:

good practical abilities
a strong interest in experimental work;
excellent skills in both written and spoken English;
knowledge/training in Nuclear Physics will be advantageous.

Students seeking diploma-work projects at both Master and Bachelor level are encouraged to apply, as are students seeking project work for courses (but such projects must correspond to at least 15 credits). The possibility of paired or group work can be discussed.

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Energy materials and particle accelerators

Investigate a new class of photochromic materials, potentially used in next generation of smart-windows
Help us to synthetize and characterize – using nuclear physics methods – the materials, building thus the knowledge needed for their potential technological application
Access and use of a National Research Facility for particle accelerators: The Tandem Laboratory

In this thesis project you will:

Learn techniques for ultra-thin film growth
Work with vacuum technology
Use advanced accelerator based analytical techniques
Be involved in an academic research environment

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Eduardo Pitthan Filho

Environmental uptake of radio-nuclei relevant to the European Spallation Source (ESS)

Background

Detailed studies are currently being undertaken to assess the risk posed by a potential radioactive release from the European Spallation Source (ESS), a large neutron research facility under construction in Lund, Sweden. The ESS will produce neutrons using a powerful particle accelerator shooting protons on a tungsten target. The nuclear reactions in its target, will also produce many radioactive by-products that, in the event of a severe accident, could be released into the environment.

A new and highly multi-disciplinary project has been created through funding from the Swedish Radiation Safety Authority, which will investigate the potential risk of radionuclides, specific to the ESS, entering the food chain through crops commonly cultivated in the farmlands surrounding the ESS site. The project will be jointly conducted by the Ion-physics group at Uppsala University (Sweden), Medical Radiation Physics Malmö at Lund University (Sweden), the Biotechnical Faculty at the University of Ljubljana (Slovenia), and the Department of Low and Medium Energy Physics at the Jožef Stefan Institute (Slovenia). To support this work, undergraduate and post-graduate projects are to be created.

Project goal and work plan

The goal of the student’s work, will be to participate in the start-up of the broader project, performing baseline measurements, analysis and modelling to support the work that will be performed over the next four years. Projects can be catered to suite those with an interest in either simulation and modelling, or experimental and analytical work.

The project can be adjusted to correspond to 15, 30 or 45 ECTS credits and can start during either the autumn 2023, or spring 2024 semesters.

Desired qualifications/experience

The applicant should be enrolled on a program at Uppsala University, with a background in either physics, chemistry or environmental science. It is essential that the applicant has excellent skills in both written and spoken English.

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Hydrogen incorporation in silicon crystals studied by ion beams

Background

Medium energy ion scattering (MEIS) provides high-depth resolution and sensitivity by employing projectiles with keV energies. MEIS can also be used for the detection of light recoils with extreme depth resolution and sensitivity. Implementing time-of-flight elastic recoil detection in transmission experiments using a pulsed beam of heavy ions (namely Ar and/or Ne) with keV energies allows simultaneous detection of all light constituents. The loading of hydrogen into materials is technologically highly relevant for sensor and energy storage applications as well as for materials ageing when using hydrogen as process gas in decarbonized industrial applications. At the same time, the thermodynamics of hydride formation, in particularly near surfaces of materials needs to be much better understood.

Project goal and work plan

Investigate the implantation of H in Si crystals
Help us to create and characterize – using keV ions and recoil detection analytical technique – the implanted crystals
Access and use of a National Research Facility for particle accelerators: The Tandem Laboratory

In this thesis project you will:

Learn techniques for in-situ implantation and characterization using keV ions
Work with vacuum technology
Use advanced accelerator based analytical techniques
Be involved in an academic research environment

Desired qualifications/experience

The applicant should be enrolled on a program at Uppsala University and possess:

Good practical abilities
Strong interest in experimental work;
Excellent skills in both written and spoken English.

Contact

Eleni Ntemou

Nanoporous membranes for high efficiency filtering applications

Project and Thesis Topic

Nanoporous membranes, possessing high filtering efficiency, are a promising approach for addressing critical environmental issues, such as the lack of fresh water supply in many parts of the world and the excessive emission of green-house gases. The membranes also play an important role in chemical processing for cosmetics and pharmaceutical industries. The ideal membranes need to have: (i) a minimal thickness for maximal permeance, (ii) a nanoscale and uniform pore size for high filtering selectivity, (iii) a sufficient mechanical strength under relatively high pressure, and a large enough area for practical applications.
Recently, we have developed a novel nanoporous membrane by combining sputtering, microfabrication and ion implantation. As shown in Fig. 1, the membrane features high density of the nanoscale pores. Importantly, our approach enables large-scale production of the materials. In the near term, we will continue to investigate the materials in both fundamental and applied aspects. Hence, this project provides a wide variety of subjects for enthusiastic students, from experimental physics to applications and equipment development.

Join this project, you will learn:

Fabricating the membranes using sputtering, microfabrication and ion implantation.
Characterizing the membrane using electron microscopy, X-ray diffraction, atomic force microscopy and nanoindentation.
Fundamental aspects of interactions between energetic ions and materials, and the mechanism of the pore formation.
Developing equipment for the filtering experiments.

Contact

Tuan Tran

Nanoscale patterning and atomic manipulation of 2-dimensional materials

Project and Thesis Topic

2-dimensional (2D) materials have been a research area that leads to many discoveries in recent years. The materials are only one or few atomic layer thick, but have fascinating physical, chemical and mechanical properties [1]. At the same time, there is an immense interest in structuring 2D materials at the nanoscale and at the atomic level for added advanced functionalities. Recently, we have developed a versatile approach capable of structuring the 2D lattices at the nanoscale as well as engineering the materials at the atomic level. The approach relies on a broad and uniform beam of energetic ions passing through a suspended nanopatterned membrane [2].
The nanopattern membrane, acting as a shadow mask, is fabricated using a multi-step nanofabrication process. Characterization of the structured 2D lattices are done using atomic-resolution transmission electron microscopy (TEM) for studying the atomic defects and the impurities.

Join this project, you will learn:

Fabricating the nanopattern membranes using nano-microfabrication and ion implantation.
Characterizing the membrane using electron microscopy (SEM and TEM).
Fundamental aspects of interactions between energetic ions and 2D materials.

References

[1] Geim, A. K. and K. S. Novoselov (2007). "The rise of graphene." Nature Materials 6(3): 183-191
[2 ] Tran, T. T., et al. (2023). "A contactless single-step process for simultaneous nanoscale patterning and cleaning of large-area graphene." 2D Materials 10(2): 025017.

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Tuan Tran

Simulating hydrogen concentration profiles of energy materials from resonant nuclear reactions

Project

The verification of hydrogen content is decisive for emerging hydrogen-rich materials in sustainable energy applications, such as hydrogen storage in the hydrogen economy. As hydrogen is the lightest element in the universe, experimental investigation of its distribution at the atomic level encounters difficulties. Ion beams offer nondestructive and distinctive analysis of material composition through elastic and inelastic interactions with the different chemical elements. Resonant nuclear reactions with hydrogen atoms can be induced by high-energy 15N-ion beams employed at the Tandem Laboratory (Ångström), and are utilized for depth-resolved measurement of hydrogen in solid thin films, nanostructures, and on surfaces. To obtain hydrogen depth profiles the incident energy of ions is varied positioning the resonance of the nuclear reaction at varying depths within a target while detecting reaction products (e.g. γ-rays). The experimental excitation curve thus displays the depth distribution of the hydrogen density offering superior depth resolution of only several nanometers. However, the hydrogen signal is convoluted with an effective instrumental function and the nuclear reaction cross-section. The project aims to develop a numerical method to determine real hydrogen concentration profiles from experimental excitation curves by numerical deconvolution.

By joining this project, you will:

learn fundamental aspects of interactions between energetic ions and hydrogen-containing materials;
learn advanced accelerator-based analytical techniques;
acquire work experience at a large-scale scientific facility;
develop a numerical analytical methodology;
bridge real experimental data with simulations;
perform benchmark ion beam experiments on ultrathin hydrogen-storing metal films; and simulate hydrogen depth profiles;
be involved in an academic research environment.

Desired qualifications/experience

enrolled in a physics program at Uppsala University;
a strong interest in simulations;
excellent skills in both written and spoken English;
some interest in experimental work.

We encourage applications by students seeking diploma-work projects at Master's level.

Contact

Kristina Komander

Simulation of target and moderator combinations for a compact accelerator-driven neutron source

Background

The production of neutrons by accelerators began in the 1970s with construction of powerful proton accelerators to access neutrons via spallation. At the same time, low-energy driven neutron processes emerged for neutron production using electron accelerators, ion beam accelerators, cyclotrons, and low energy linear accelerators. This wide variety of neutron sources have come to be referred to as Compact Accelerator-driven Neutron Sources (CANS). Due to research reactors within Europe undergoing shutdown, the European Spallation Source user program delayed until 2026 and other large-scale European facilities (ISIS, ILL and PSI) being heavily overbooked, there is currently a serious need for establishing additional neutron sources, especially in Scandinavia. It is believed that a CANS could fulfil this demand.

Project goal and work plan

The goal of the proposed project is to perform preliminary simulation-work that will support the development of a CANS within Sweden. This work will take the form of developing target simulations to constrain possible design parameters, such as target material, beam energy and beam current. The project can be divided into the following key tasks:

develop a simple CANS-target/moderator design in a Monte Carlo simulation package;
run simulations for different target materials, primary-ions and beam energies;
evaluate neutron production in terms of energy and flux;
evaluate target heating and target damage;
evaluate gamma-ray production and shielding requirements;
evaluate possible moderator designs and geometries;
write a report summarising the results and conclusion of the work.

The project can be adjusted to correspond to 15, 30 or 45 ECTS credits and can start during either the autumn 2023, or spring 2024 semesters.

Desired qualifications/experience

The applicant should be enrolled on a physics program at Uppsala University and possess:

a strong interest in simulation;
excellent skills in both written and spoken English.
knowledge/training in Nuclear Physics will be advantageous.

Contact

Ultralow-energy ion implantation for the modification of 2D materials

Background

Low-energy ions are becoming more frequently employed for near-surface modification of materials, in simulating the effect of the fusion plasma on structural components fusion devices, and in tailoring the electronic properties of 2D materials. The 10 keV ion implanter (LEION) is a new setup at the Tandem Laboratory to initiate studies on the above-mentioned topics. The ion source of LEION is capable of producing a range of ion species, extracted from or gaseous solid media, both light and heavy, and with variable charge state. Implantation can be made in, in principle, any material. The precise limitations of the setup are currently unknown and it is therefore vital that these are tested in a systematic manner.

Project goal and work plan

The project will consist of systematically testing the capabilities of LEION, by implanting a broad range of ions into both thick targets such as silicon, and thin targets such as graphene. The implantations will then be assessed by a range of analysis techniques. The project can be divided into the following key tasks:

implantation of ions generated from both gases and solids;
implantation of both light and heavy ions;
implantation into thick targets and 2D materials;
implantation under both hot and cold conditions;
analysis of the implanted materials using, for example, TEM, LEIS and μPIXE;
propose and implement optimisations to LEION based on the results obtained;
to write a report summarising the results and conclusions of the work.

The project can be adjusted to correspond to 15, 30 or 45 ECTS credits and can start during either the autumn 2023, or spring 2024 semesters.

Desired qualifications/experience

The applicant should be enrolled on a program at Uppsala University and possess:

good practical abilities
strong interest in experimental work;
excellent skills in both written and spoken English;
knowledge/training in Nuclear Physics will be advantageous.

Contact

Volatile fission-product diffusion in reactor-fuel matrices

Background

The diffusion of gaseous fission products such as Xe and Kr in nuclear fuel constitute significant performance and safety parameters for reactor operation. The study of diffusion behaviour in nuclear fuels is an experimental challenge however, both due to difficulties in adding gas species to the fuel matrix and in accessing techniques which can and monitor gas concentrations at low-length scales. The majority of diffusion parameters used for UO2 fuel performance analysis, have been derived either: from irradiated material measured in the plenum; or by gas release from the annealing of fuel samples. These methods suffer from the fact that bulk- and grain-boundary thermal and athermal diffusion, as well as radial and axial temperature-variation in the fuel, are highly approximated.

Project goal and work plan

The goal of this project, is to study the thermal-induced diffusion of volatile elements in heavy sample matrices, by medium-energy ion implantation followed by ToF-ERDA (time-of-flight elastic recoil detection analysis). Elemental depth-profiles of the samples are obtained, both as-implanted and post-annealed. The project can be divided into the following key tasks:

implantation of volatile elements in a range of heavy sample matrices, using the ion-implanter at the Tandem laboratory;
assessment of the implantations with ToF-ERDA, using the 5 MeV accelerator at the Tandem Laboratory;
perform sample annealing at a range of temperatures and temperature gradients;
repeat ToF-ERDA measurements to evaluate the thermally-induced diffusion of the implanted ions;
write a report summarizing the results and conclusion of the work.

The project can be adjusted to correspond to 15, 30 or 45 ECTS credits and can start during either the autumn 2023, or spring 2024 semesters.

Desired qualifications/experience

The applicant should be enrolled on a physics program at Uppsala University and possess:

good practical abilities
a strong interest in experimental work;
excellent skills in both written and spoken English;
knowledge/training in Nuclear Physics will be advantageous.

Contact

Materials Physics

We mainly have experimental activities i.e. offer a variety of measurements addressing materials properties (see our research pages for an overview). There are also a number of possible tasks involving numerical simulations (e.g. light scattering or micromagnetic), or improving control programs for experimental setups.

The effect of geometric imperfections on magnetic properties

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Simulation and fitting of polarised neutron reflectivity data

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Magnetotransport in amorphous nanoscale films and multilayers

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Magneto-optic spectroscopy of advanced materials

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Metal hydrides

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Photochromics

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Magnetic liquids

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Surface ordering under shear

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Topological interactions in polymers under shear

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Magneto-plasmonics – Understanding the correlation between plasmons and magneto-optics

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