Available positions

If you need more information on any proposal, send an e-mail to the corresponding contact person.

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Experimental physics on the TCV tokamak

Experimental physics on the TORPEX device

Experimental physics on the JET tokamak

Plasma Physics Theory

Superconductivity for fusion

Surface science for fusion

Collaboration with CERN

Open positions in experimental physics on the TCV tokamak

  • Visible light 2D camera diagnostics of the TCV divertor

Contact person: Dr. MER B.P. Duval or Dr. MER H. Reimerdes

One of the outstanding problems that requires resolution for a functional Fusion reactor is that of Fusion power exhaust. In the most promising magnetic “bottle” fusion plasma configuration (the Tokamak such as the TCV device at the Swiss Plasma Center), plasma is directed to a special region called the divertor. Due to the high power exhaust of a fusion reactor, if unmitigated, the power density reaching the divertor would quickly damage the reactor vessel. For this reason, considerable research effort is dedicated to controlling this heat flux and changing the magnetic configuration (the “bottle” shape) and adding highly radiating impurities to the plasma edge that can reduce the heat flux to tolerable levels. To understand the plasma performance in these endeavours, we use plasma diagnostics. Plasmas in this divertor region, where the plasma is relatively cold (compared to the fusion core), emit a lot of power as visible light. Diagnostics using multiple visible cameras are used to monitor this light that, by using filters to isolate specific spectral lines, can be associated with the radiation from chosen impurity species. This PhD project aims at two such diagnostics. The first, called MANTIS, is a multi camera system that has been developed over the last 5 years to provide 2D plasma images with repetition rates up to 1kHz, of up to 10 separate spectral lines whose intensity distributions can be used to diagnose the plasma conditions as they vary through TCV’s plasma discharge. In the second, which shall be a new diagnostic for TCV, the doppler shift of the light from the plasma is cast as a set of fringes on the camera image. From this fringe pattern, the plasma flow across the whole divertor region can be tracked. This technique, known as Coherence Imaging Spectroscopy, or CIS, will be designed, built and operated on TCV with the collaboration of international experts. These are complex optical systems that will require an enthusiastic and practical minded candidate who enjoys working, and evolving, within a lively research group.

  • Study and optimization of electron density profiles, turbulence characteristics and instabilities in the edge and pedestal of TCV plasma

Contact person: Dr. MER S. Coda or Dr. L. Porte or Dr. B. Labit

Observations [1] point to the fact that over all tokamak plasma particle and energy confinement is dominated by transport properties in the plasma edge. At the same time in the so called H-mode regime of plasma confinement, the edge confinement pedestal is very often unstable and there are frequent, large expulsions of plasma particles and energy into the surrounding volume depositing a significant fraction of the plasma particles and energy onto the plasma facing components with the potential to damage these components. The expulsions are referred to as Edge Localised Modes (ELMs). It is planned to operate ITER in the H-mode confinement regime and it is likely that ITER will suffer ELMs. One avenue of current tokamak physics research is to understand the physics of ELMs and explore avenues to quench the ELMs and/or to mitigate their effects. High spatial and temporal resolution measurements of electron density profiles and electron density turbulence in the plasma edge will help elucidate the central role of the plasma edge in tokamak confinement and lead to a better understanding of ELM physics and inter-ELM confinement. A particular goal would be to develop a viable type-II ELM regime, in which target heat loads are significantly reduced while the confinement remains good. As in other tokamaks, this regime is achieved at TCV with high plasma triangularity and high density. We are seeking one or two motivated PhD students to pursue these topics. Part of the work would include further development of a prototype, extremely high resolution, millimeter-wave pulsed reflectometer [2] and Doppler backscattering (DBS) [3] system for the characterisation of edge density profiles, turbulence characteristics and poloidal flow velocity in the plasma edge in both standard confinement, or L-mode, and H-mode regimes. An additional system to feature prominently, particularly in the study of H-mode and ELMs, is the Phase Contrast Imaging diagnostic which measures density fluctuations. It is expected that a significant effort be placed in enhancing the existing hardware and optimising its use. Interaction with the groups from the experimental department as a whole will be necessary and collaboration with the SPC theory group is expected.

[1] O. Sauter et al, Phys. Plasmas 21, 055906 (2014) [2] P. Molina-Cabrera et al, to be submitted to Rev. Sci. Instrum. [3] P. Molina-Cabrera et al, Rev. Sci. Instrum. 89, 083503 (2018)

  • Fast-ion deuterium alpha (FIDA) Spectroscopy

Contact person:Dr. MER B.P. Duval

Neutral heating beams are often used in thermonuclear devices to heat the plasma above that achievable by passing large currents through the plasma resistance (Ohmic Heating). The fast neutral atoms injected are well above thermal (called fast-ions) and must slow down in the plasma to efficiently heat the thermal plasma. FIDA spectroscopy takes the light emitted from the interaction of the fast ions/atoms within the plasma to analyse the spatial and velocity profiles of these ions from injection to thermalisation. These fast ions can be taken as a proxy for the fast Helium atoms created by particle fusion (the basic process of energy production concerned) and as they slow, they are subject to many interactions with the target plasma that can prematurely eject these fast ions, which could be catastrophic as their energy is used to keep the plasma hot and thus reactive. TCV has recently installed such a fast ion heating beam and preliminary FIDA spectroscopy shows a rich range of physical processes. This thesis will commence with the installation of two multi-chord spectroscopic systems to observe FIDA light. Many experimental probes on the effect of plasma shape and other parameters (density, temperature etc.) will follow. The student will use the FIDASIM program developed by a worldwide group to interpret the spectra together with detailed plasma transport modelling to diagnose the fast ion behaviour. This work will be part of a new and developing group at the SPC looking into fast ion behaviour on the TCV Tokamak.

  • Isotope effects for H-mode confinement regime in TCV
    Contact person: Dr. B. Labit

During the Pre-Fusion Power Operation Phase (PFPO), ITER will operate in the so-called H-mode regime of good confinement with Hydrogen and/or Helium as the main ion species. Nevertheless, most of the existing scaling used to quantify H-mode efficiency are based on Deuterium plasmas and therefore the extrapolation to Hydrogen or Helium plasma is largely uncertain. From H or He plasmas, compared to D plasmas, the goal of this thesis is to advance the understanding of crucial issues associated with the H-mode physics among which the L-H transition, the confinement with dominant electron heating, the fueling efficiency, the pedestal transport, the first wall and divertor heat loads, etc. The candidate will design and conduct experiments on the TCV device, the tokamak at the EPFL. New analysis tools together with theoretical models will be implemented.

TCV is now equipped with a high power (1MW) / high-energy (25keV) Neutral Beam Injection (NBI) system, with a second system being planned to deliver fast neutrals at even higher energy (50keV). The injected fast neutrals then ionize in the plasma, producing supra-thermal ions which, in turns, may undergo charge-exchange neutralization and be expelled from the plasma. These ejected fast neutrals can be measured using a neutral particle analyzers and can then be used as a proxy to determine the fast ion distribution function in some relevant phase-space region.
TCV is currently equipped with a compact NPA, and major improvements will be needed to measure the fast ions produced by the second NBI system, hence the development of a new I-NPA, currently at the stage of conceptual design. This thesis will commence with the completion of the design, procurement, installation and commissioning of the I-NPA system, and will then move onto the analysis of the measurements obtained with this system, and other fast ion diagnostics, towards the development of a multi-diagnostic tomographic reconstruction of the fast ion distribution function. This work will be part of a new and developing group at the SPC looking into fast ion behavior on TCV.

  • Thomson scattering data analysis for real-time applications

Contact person: Dr. P. Blanchard

On the TCV tokamak, reliable electron temperature and density profiles are routinely obtained from Thomson Scattering (TS) measurements. In 2013-2014, the TS diagnostic has undergone a substantial upgrade which is opening the road to real-time (RT) applications of such parameters.
In the frame of a PhD, algorithms for RT analysis of TS signals should be first developed and tested along with the implementation of a new DAQ system. The availability of electron temperature and density profiles in RT could then be used for TCV scenario development and actuator control like microwave heating system as well as inputs for RT transport code like RAPTOR.

  • Real Time Control of Tokamaks

Contact person: Dr Federico Felici

The SPC tokamak TCV is equipped with an advanced real-time control system, based on matlab-simulink and which allows rapid and flexible developments. In addition, we have developed a rapid tokamak transport simulator, RAPTOR, capable of simulating in real-time current density and kinetic profiles. This is a perfect environment for PhD thesis project related to real-time control of tokamaks, including magnetic control, plasma profile control, as well as advanced topics such as scenario control, monitoring and supervision.

  • Measurement of turbulence and modes driven by and interacting with the high-energy NBI ions in TCV

Contact person: Dr. Duccio Testa

Analysis of NBI-driven magnetic turbulence and modes in TCV, and interaction of MHD instabilities with the slowing-down NBI ions; develop and test mathematical tools for the magnetic turbulence analysis as needed; develop high-frequency magnetic sensors based on LTCC technology.

Open positions in experimental physics on the TORPEX device

  • Suprathermal ion dynamics in turbulent plasmas

Contact person: Prof. Ivo Furno

Understanding the interaction of plasma turbulence with suprathermal ions, i.e. ions with energies greater than the quasi-Maxwellian background plasma, is a major challenge for the next generation of magnetic fusion reactors. While experimentally challenging in fusion devices, suprathermal ion measurements are accessible in basic devices with extended diagnostic capabilities and flexible configurations, such as the TORPEX device at SPC.
We are seeking for a Ph.D. candidate to conduct detailed investigations of basic aspects of suprathermal ion-turbulence interaction on TORPEX using a controllable suprathermal ion source and diagnostics, which allow fully time-resolved 3D measurements of the suprathermal ion dynamics. In parallel with the experiments, the Candidate will use state-of-the-art numerical codes to obtain 3D simulations, which will be compared with experimental data and theory predictions. The proposed subject is of fundamental importance for nuclear fusion and crosses the frontier between plasma physics and research in complex systems.

Open positions in experimental physics on the JET tokamak

  • Measurement and interpretation of TAE in JET, including DT experiments.

Contact person: Dr. Duccio Testa

Analysis of the Toroidal Alfven Eigenmode (TAE) measurements obtained in JET using the upgraded TAE system, including real-time control applications, MHD spectroscopy, and in preparation of studies of alpha-driven TAEs during the DT experiment planned at JET for 2017-2018.
Note: the upgraded TAE system should become operational around the end of 2014 or early 2015.
Overall data analysis for JET also to include comparison with all fast ion diagnostics and other turbulence diagnostic.

Plasma Physics Theory

  • Gyrokinetic turbulence simulations with advanced numerical techniques

Contact person: Prof L. Villard

The SPC theory group has been active since many years in the field of numerical simulation of magnetized fusion-relevant plasmas by developing codes that are run on some of the currently most powerful High Performance Computing (HPC) platforms. In particular, the realistic description of low frequency turbulence from first principles using gyrokinetic theory, which remains a great simulation challenge, has been one of the group’s main research focus. The loss of heat and particles associated to this turbulence is a key limiting factor in achieving the conditions required in a fusion reactor. The architecture of the most powerful HPC platforms has been evolving towards more heterogenous systems (CPU+GPU or CPU+MIC) and there is therefore the need to adapt our physics application codes to this new type of machines. We are currently looking for a PhD candidate that is seriously motivated to deal with advanced numerical simulations of gyrokinetic turbulence and actively engage in the current effort to adapt our codes to the new generation platforms. The thesis will thus include both physical studies as well as technical aspects. The successful candidate will interact with our group at SPC and other institutions and laboratories.

  • Simulation of the plasma dynamics at the tokamak edge

Contact person: Prof P. Ricci

The understanding turbulence in the edge of magnetic confinement device is an outstanding open issue in magnetic fusion. The physics of this region determines the boundary conditions of the whole plasma by controlling the plasma refueling, heat losses, and impurity dynamics. Edge dynamics regulates the heat load on the tokamak vessel; this is considered among the most crucial open problems for ITER and future fusion reactors. Since a few years, a project has been initiated at the SPC with the goal of improving the understanding of edge physics. This effort has significantly advanced our grasp of plasma turbulence in the edge of a relatively simple configuration, the circular limited tokamak, and we are now exploring the physics of diverted configurations. Ph.D. theses are proposed with the goal of advancing the simulation and the understanding of edge turbulence in reactor relevant conditions, in particular to consider improved plasma models and advanced exhaust configurations.

Open positions in superconductivity for fusion

  • Investigation of protection limits in Nb3Sn accelerator magnets

Contact person: Dr. P. Bruzzone

  • PhD thesis in Applied Superconductivity on the Investigation of protection limits in Nb3Sn accelerator magnets
  • Development of vacuum impregnated winding samples for the experimental assessment of the maximum allowable hot spot temperature.
  • Experimental evaluation and modeling of the failure mechanism.
  • Development of alternative cable geometries for accelerator magnets.
  • Publication of results in scientific journals and at international conferences

The Superconductivity Group of SPC is located in the premises of the Paul Scherrer Institute (PSI) in Villigen.

Open positions in surface sciences at Uni. Basel

 

Open positions in collaboration with CERN

  • AWAKE

In 2018, the Advanced Wakefield Experiment (AWAKE) reached a milestone demonstrating that plasma wakefields generated by externally injected proton beams can efficiently accelerate charged particles over 10 m distance, thus fulfilling the objective of the AWAKE Run 1 phase. This first ever proof-of-concept boosted the next phase, AWAKE Run 2. The goal of Run 2 is to accelerate an electron bunch with a narrow relative energy spread and an emittance sufficiently low for applications. In parallel to AWAKE Run 2, high-density plasma, generated by a helicon source in a linear geometry, is under development at CERN in collaboration with the Swiss Plasma Center in Lausanne (Switzerland), the Institute for Plasma Physics in Greifswald (Germany), and the University of Madison in Wisconsin (USA). This development poses formidable challenges from the point of view of plasma physics, technology and diagnostics. We are looking for a Ph.D. student who will participate in this joint endeavor, working partly at the Swiss Plasma Center and partly at CERN on the helicon plasma cell and diagnostics development. Should you be interested or know someone who could be, please send an email to [email protected].

Useful links:

http://awake.web.cern.ch/