PhD scholarship in “Nano-scale 3D reconstruction of phase contrast X-ray projections”
DTU Energy seek a ph.d student to improve algorithms for 3D reconstruction of phase contrast X-ray projections. The highly penetrating power of X-rays make them ideal for probing the dynamic structure of realistic, functioning devices for energy conversion and storage, but this is an application that is largely unexplored. With the advances in imaging techniques which by combination of better optics for hard X-ray focusing and new measuring schemes and algorithms taking advantage of coherent X-ray illumination, the potential for sub-nm resolution is within reach.
Because of the hard X-ray penetration, complementary analysis techniques and non-ambient sample environments are relatively easy to integrate with the X-ray experiment for in situ studies, and we have considerable experience with such applications at DTU Energy.
Our expertise in the application of these methods will be applied to real devices for resolving problems relating to up-scaled processing of nano-structured devices, among which fuel cells and 3rd generation solar cells are specific focus areas. The in situ experiments will be applied to advance the fundamental understanding of charge generation and transport in complex 3D nanostructures. Progress in this field constitutes an important part of bridging current advances at the microscale level in the Strategic Research Alliance, CINEMA with the upcoming endeavors into the nano domain.
Responsibilities and tasks
The ph.d will work with improving algorithms for 3D reconstruction of phase contrast X-ray projections, typically from ptychographic tomography. Ptychography is a form of phase contrast imaging, where the sample is illuminated with coherent X-rays in a fine raster pattern with a large degree of overlap between illuminated points. By exploiting the large data redundancy, the iterative phase reconstruction is ensured a fast and robust convergence. In this manner, projections of X-ray phase shift across the sample are retrieved with nanometer resolution. 3D resolution depends on X-ray beam and sample positioning stability, and not least, on the algorithms for aligning projections and reconstructing the phase tomogram. The standard way of reconstructing tomograms from 2D ptychography projections is the well-established filtered back projection, reconstructing the tomogram slice by slice, but much more advanced algorithms for 3D reconstructions have been developed, and research is still in advance in this direction. Under the auspice of CINEMA and in collaboration with DTU Compute, we will explore the possibilities for implementing these methods for reconstruction of ptychographic phase projections. Methods include 3D reconstruction by Total Variation Regularization (TVReg) and other regularized reconstruction algorithms, including methods employing a priori information. We will also explore the possibilities of integrating 3D projection alignment with the reconstruction algorithms and the prospect of reconstructing the phase distribution directly from the 3D array of aligned diffraction data.
Qualifications
Candidates should have a master’s degree in engineering or a similar degree with an academic level equivalent to the master’s degree in engineering.
Approval and Enrolment
The scholarships for the PhD degree are subject to academic approval, and the candidates will be enrolled in one of the general degree programmes of DTU. For information about the general requirements for enrolment and the general planning of the scholarship studies, please see the DTU PhD Guide.
Assessment
- Excellent performance in both bachelor and graduate studies
Further qualifications:
- It is expected that the candidate has a background in mathematics or physics and have skills in programming (matlab, python, C).
- Experience with computational imaging analysis is particularly welcome.
We offer
We offer an interesting and challenging job in an international environment focusing on education, research, public-sector consultancy and innovation, which contribute to enhancing the economy and improving social welfare. We strive for academic excellence, collegial respect and freedom tempered by responsibility. The Technical University of Denmark (DTU) is a leading technical university in northern Europe and benchmarks with the best universities in the world.
Salary and appointment terms
The salary and appointment terms are consistent with the current rules for PhD degree students. The period of employment is 3 years.
The workplace is at DTU Energy, Risø Campus.
Further information
Further information may be obtained from Senior Researcher, Jens Wenzel Andreasen, tel.: +45 21 32 63 01 or from the Head of Section Luise Theil Kuhn, tel.: +45 51 41 93 71.
Additional information about the department can be found on www.energy.dtu.dk
Please do not send applications to this e-mail address, instead apply online as described below.
Application
Please submit your online application no later than 8 June 2015. Apply online at www.career.dtu.dk.
Applications must be submitted as one pdf file containing all materials to be given consideration. To apply, please open the link “Apply online,” fill in the online application form, and attach all your materials in English in one pdf file. The file must include:
- A letter motivating the application (cover letter)
- Curriculum vitae
- Grade transcripts and BSc/MSc diploma (an official translation into English)
- Excel sheet with translation of grades to the Danish grading system (see guidelines and excel spreadsheet here)
Candidates may apply prior to obtaining their master’s degree, but cannot begin before having received it.
All interested candidates irrespective of age, gender, race, disability, religion or ethnic background are encouraged to apply.