Topics for Theses and Lab Works

This page lists (internally) some topics that are possible for lab works (3 or 4 credits), bachelor theses (6 credits) or larger projects. The larger projects could be written up to longer descriptions (1 page) to be able to advertise more easily these topics.

Smaller projects

• Determine the modulation transfer function of the imaging setup

  review different methods

  perform measurements with a chosen method (e.g. slanted knife edge)

  analyze the results to produce the MTF curve

  apply deconvolution to sharpen the images (optional)

• Quantify the absolute efficiency of the imaging detector (i.e. convert the counts to photons for a given incoming spectrum)

  measure absolute counts with the Germanium detector

  compare the pixel value ("gray level") to the incoming total energy per pixel

  check if this relationship holds well for different incoming spectra (also make prediction of this based on the known scintillator properties)

• Quantitative shape analysis from X-ray microCT

  reproducibility of key parameters (angles, linear dimensions, volume)

  relative contribution of different effects: artefacts (esp. beam hardening and cone beam), actual imaging resolution, surface determination by threshold selection, etc.

  relative and absolute reproducibility

• Combining multiple CT scans to increase signal-to-noise ratio

  Take several fast CT scans with low SNR. The assumption is that each scan is so fast that the sample stays basically still

  Then in 3D combine the reconstruction results. This requires registering the sample in case of movements or doing deformations in case the sample has deformed.

  The result should be a high SNR image that cannot be achieved with a single scan because of sample movements / deformations during the scan.

• Nanotom Source size and position stability

  Use a knife edge close to the source to measure the source size

  Use a long duration measurement to measure the positional stability of the source

  Measurements could be done for a few different source operation parameters (voltage, current, modus)

• Literature reviews in X-ray imaging

  • X-ray CT: Beam hardening correction methods
  • Grating-Based Imaging: Methods for analyzing phase stepping images
  • Summary of available synchrotron nano-imaging beamlines: where are the beamlines, what are the techniques used, what are the technologies behind, what are the key parameters.
  • Formation of dark-field contrast
  • Ptychography and iterative phase retrieval methods
  • Cellular imaging with X-rays
  • Review of X-ray optics for hard and/or soft X-rays

Larger projects

• SAXS and Line-Edge Roughness (LER)

  Line edge roughness is a key problem in semiconductor production, being currently the main fundamental limitation in achieving smaller linewidths in semiconductor processing

  • LER stems from variations in light exposure, and molecular level inhomogeneities in the chemicals used in the processing

  routinely LER is measured using SEM on a line pattern: however only information of statistical nature is presented for the final analysis

  Small-angle X-ray scattering produces very similar statistical information as in the critical dimension-SEM for LER (fractal dimension, correlation length).

  It might be possible to exploit SAXS to replace SEM in LER characterization, perhaps allowing in situ measurements of LER during processing

  This thesis topic would need funding and perhaps industrial collaboration to produce suitable samples

  Calculations of the feasibility, development of the technique

  measurements of real samples (either in lab or with paid beamtime at a SR facility)

• Contrast Agent Quantification with Polychromatic Micro-CT

  Baseline CT + images with added contrast agent of known composition

  Determine methods to quantify the absolute amount of contrast agent from the microCT images

  Probably suitably large for a Master's thesis

  Applications in biology where currently typically only qualitative differences are used

• Generic Quantitative Imaging of Density with Polychromatic Micro-CT

  If we have a good a priori knowledge of composition then estimation of actual density becomes possible

  Applications for example in absolute quantification and comparison of dental enamel density

  • Calibration standards in the scan can be used to guide the quantification process

  The main challenge is that the composition change (for example subtance X and Y relative proportion) affects the quantification

  It would already be useful to have a work that describes when quantification is possible and to what accuracy, and also shows how quantification can fail in case of false assumptions

  The use of multi-spectrum measurements (for example with and without a filter) to help in getting a more reliable quantification

• Prediction of Material Mechanical Properties from µCT using Finite Element Modelling

  Samples with good structure, e.g. wood, 3D printed parts, etc.

  µCT → mesh generation → FEM modeling of mechanical properties (strength)

  Comparison with measured mechanical properties

  Requires quite independent student as local support for FEM is limited (but we do have a contact in France, Daniel Pino Munoz,  who is a specialist, and willing to host a student for a learning visit)

  Projects with goal of fluid flow characterization through the structure, etc. would be also possible