Degree Projects at FREIA
BACHELOR AND MASTER PROJECTS IN ACCELERATOR PHYSICS AND LIGHT GENERATION AT THE FREIA LABORATORY
FREIA is a newly built laboratory for advancing accelerator physics. We work on development of various hardware for accelerators, physics of charged particle beams and generation of light by accelerated charges. In particular, at present we are working on characterization of superconducting accelerating cavities; studying of breakdowns in accelerating structures for the Compact Linear Collider; development of efficient microwave sources for driving accelerators; dynamics of vortices in superconductors; generation of single-cycle THz radiation with a field strength in the V/Å range. We offer projects of various complexities from hard-core theoretical studies of the dynamics of vortices in superconductors and generation of single-cycle pulses of THz light to very applied developments in microwave engineering.
The cryo-cooled discharge system
A particle accelerator is a work horse of modern material science and particle physics but also helps to fight cancer or to study art and archeological artefacts. The use of the accelerators is limited to bigger research centers and larger hospitals not due to poor performance or inefficiency but rather due to their often large size and cost. One of the main reasons for the large size is phenomena of vacuum breakdowns. In simple terms a significant increase of the accelerating voltage inside the accelerator will cause an electric discharge which can destroy the machine, thus we keep the accelerator longer and stay at lower voltages.
Uppsala University together with the European Organization for Nuclear Research, CERN, is building a system with large planar electrodes for studies of the fundamental physics of high-fields in vacuum, important for material and surface science, and for development of accelerating technologies. The system will be cooled to cryogenic temperatures and operated in a wide range of temperatures.
In the project the student will work with the system commissioning at the FREIA laboratory.
The tasks include practical work with:
– control system integration
– data collection and analysis
The student will learn about how a cryo-system works. Such system comes with specific challenges for the control and the measurements we want to perform. The student will have to collect measurement data and analyze them. The results from the project will be published in a scientific journal.
Expulsion of magnetic fluxes in type-II superconductors upon the transition from a normal- to superconducting state
If a type-II superconductor is exposed to an external magnetic field upon the transition from a normal- to superconducting state, then the magnetic field gets trapped in the material and the performance of the superconductor degrades. Specifically, the residual resistance of the superconductor, which is a measure of resistance to alternating currents, decreases. In the applications of type-II superconductors such as superconducting accelerating cavities, it is vital to have the residual resistance as low as possible to minimize the heat load produced by accelerating fields in the cavity. In this project, you will study experimentally and theoretically the novel phenomenon of expulsion of magnetic fluxes by the moving superconducting phase front during fast cool down of superconducting cavities.
Coupling of slow waveguide modes to surface plasmons of a subwavelength wire
We are developing a new technique of testing accelerating cavities, in which a subwavelength wire is used to mimic a beam of charged particles. The accelerating field of the cavity couples to surface plasmons of the wire and the electromagnetic energy is transferred from the cavity to the outside world via the wire resembling the process of particle acceleration. In the project you will perform analytical calculations of plasmonic modes of the subwavelength wire, run computer simulations with the professional software ‘CST Microwave Studio’ to study the coupling of cavity modes to the plasmonic modes and participate in experimental verification of the result in our microwave laboratory.
Diffraction of single-cycle THz pulses
THz radiation is becoming increasingly important in several areas of physics, chemistry and biology because its spectral range corresponds to numerous collective excitations in multiatomic systems such as molecular rotations, DNA dynamics, spin waves, Cooper pairs and so forth. Strong single-cycle THz pulses allow engineering new dynamic states of matter and one of the spectacular examples of using THz radiation for controlling the properties of materials is the THz light-induced superconductivity. If you like mathematical challenges, then this project is for you. We will tackle the problem of diffraction of single-cycle THz pulses in free-space. Specifically, the simulations show that the spatial diffraction "results in the differentiation of the temporal profile" of a single-cycle pulse so that the pulses becomes a quasi-half-cycle. In the project we will look into the math and physics behind this phenomenon.
RF power measurement at FREIA
At the FREIA Laboratory, the general focus is on developing particle accelerator technology that later could be used in large research facilities, such as CERN, European Spallation Source (ESS)... We are presently developing a 10 kW RF power amplifier based on solid state transistors. Each transistor needs a dedicated monitoring. The work consists in developing the RF power measurement, using a SWR meter or VSWR (voltage standing wave ratio) and the Arduino microcontroller.
Electro-acoustic stability of superconducting accelerators
The purpose of an accelerating cavity is to accelerate charged particles when they traverse the cavity. Acceleration is realized through a longitudinal electric field. One can imagine the acceleration of particles as surfers riding on an ocean wave. However, there is number of physical effects that make the cavity operation difficult. One of the negative effects reducing the stability of the excited field is the deformation of cavity walls caused by an electromagnetic pressure, a so-called Lorentz force detuning. Collisions of photons with cavity walls create such pressure determined by the Poynting vector. The project is devoted to studying mechanical oscillations of a superconducting cavity caused by the Lorentz force detuning and methods of its prevention.
RF Breakdown studies for CLIC
After the successful start of the LHC accelerator at CERN, we expect many years of discoveries that could lead to better understanding of the universe. Accelerator physicists however continue to plan for future facilities where more detailed studies of particle physics secrets can be done at higher energies. CLIC, the Compact Linear Collider, is the proposed successor to the LHC. In the CLIC particles are accelerated by a very strong electric field. Unfortunately, large electric fields can lead to vacuum discharges which in turn can affect the particle beam and lead to reduced performance of the CLIC accelerator. Studies of the physics behind vacuum discharges and its effect on the beam is therefore an important issue we are investigating in Uppsala.
In this project, students will learn how to manage experimental signals in large data sets stored by the logging system. The signals must be synchronized, analysed and correlated in a data analysis program to determine what physical processes occur during the discharge. The results of these measurements will contribute to the development of theory and verification of accelerating structures by providing information about the kinematics of charged particles inside the accelerating structure
OTHER ONGOING FUTURE PROJECTS
If you are interested in discussing other ongoing or future projects, here is a list of contacts.
Solid state amplifier development
The CLIC accelerator project
RF amplification and transmission