Project

Development of a diamond X-ray lens by laser ablation

Publisher

Companies / Organizations

Location

Greater Copenhagen area

Recent developments in synchrotron X-ray generation allows for the produced X-ray beam to be virtually coherent. To preserve the coherence of the X-ray beam the current available refractive optics are not ideal due to the inherent grainy structure of Be, Al and Ni that represent the lens materials presently offered. This project focuses on fabricating and characterizing a refractive lens in a single crystal diamond. A lens in single crystal diamond has the potential of being distortion free to the beam coherence while still focusing the beam.

A large part of the project will be to optimize the fabrication process of the lenses. The lens form is ablated into the diamond using a pico second laser and is subsequently treated in various plasma etches. Both the laser ablating and the plasma etching processes have several parameters and due to interdependence and non-linearities it is not a trivial exercise to determine the ideal settings. Once a batch of lenses have been produced, they will be inspected using a confocal optical microscope and there will be iterations to improve on the lens form and the lens roughness. See [1] and [2] for further information on diamond lenses.

To estimate the performance of the made lenses ray tracing simulations is to be conducted. The ray tracing tool will be McXtrace that is partly developed at DTU, see [3] and http://www.mcxtrace.org/. The measured height error and roughness of the diamond lenses will be superimposed onto a lens shape in the software and the detrimental effects of these will be evaluated with respect to coherence preservation and focusing capability.     

Towards the later stage of the project the student will take the best of the lenses to the APS synchrotron in Chicago, USA. At the APS the produced lenses will be characterized using the synchrotron X-ray beam and the coherence degradation of the X-rays can be established, along with characteristics such as focusing and absorption. 

The project is suitable for 1 to 2 students. We suggest the project to be 35 ECTS.

 

The main learning goals of the project are listed below:

•       Learn to structure an extended development process

•       Get familiarized with the physics governing Compound Reflective Lenses, CRLs

•       Optimize the laser ablation of single crystal diamonds to attain a small height error and a small surface roughness

•       Optimize the plasma etch process (the plasma etching is done in the Nanolab cleanroom)

•       Characterize the diamond lenses using a confocal optical microscope (the microscope is in Nanolab cleanroom)

•       Learn to use McXtrace and do ray tracing simulations on the produced lenses incorporating the measured height error and roughens.  

•       Learn to organize large data sets and extract trendlines of any parameter space

•       Go 2-3 week to the APS in Chicago to do X-ray characterization of the lenses, particularly using Talbot interferometry for coherence measurements 

•       Write a concise rapport on a large set of experimental and simulated data

 

Main supervisor:                        Henning Friis Poulsen, DTU PHYSICS

Co-supervisor:                             Jesper Hanberg, DTU NANOLAB

Co-supervisor:                             Erik Bergbäck Knudsen, DTU PHYSICS

Co-supervisor:                             Paw Kristiansen, JJ X-Ray

 

[1] Terentyev, Sergey, et al. "Parabolic single-crystal diamond lenses for coherent x-ray imaging." Applied Physics Letters 107.11 (2015): 111108. https://aip.scitation.org/doi/abs/10.1063/1.4931357

[2] Antipov, S., et al. "Single-crystal diamond refractive lens for focusing X-rays in two dimensions." Journal of synchrotron radiation 23.1 (2016): 163-168. http://scripts.iucr.org/cgi-bin/paper?S1600577515020639

[3] Bergbäck Knudsen, Erik, et al. "McXtrace: a Monte Carlo software package for simulating X-ray optics, beamlines and experiments." Journal of Applied Crystallography 46.3 (2013): 679-696. https://scripts.iucr.org/cgi-bin/paper?he5585

Requirements

Structured approach to experimental work. Some simulation/coding experience will be advantageous.

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Technical University of Denmark

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