Nexray: Network of integrated miniaturized X-ray systems operating in complex environments
Project Leader: Alex Dommann of CSEM +41 32 720 50 35
Pierangelo Gröning of EMPA Thun/Schutz, expert in plasma deposition of organic molecules
Hans von Kaenel of ETHZ/D-PHYS/SOLID/Physics of New Materials, expert in low-dimensional magnetism. liquid crystals. semiconductor photoelectro-chemistry. epitaxial interfaces and surfaces. scanning probe techniques. epitaxial growth
This project targets the development of novel pocket X-ray sources and X-ray direct detectors that will be combined in a distributed network to solve important tasks, for example in the field of security, by ensuring reliable and real-time monitoring of failure sensitive parts in large manufacturing plants or in public transportation.
The miniaturized X-ray sources are based on multi-wall carbon nanotube (CNT) cold electron emitters and advanced microsystems technology. The electron field emission properties of CNTs, with their high current densities, make them prime candidates for cold emitter cathodes. Using CNT cold electron emitters will make it possible to miniaturize the whole X-ray source. Additionally, as opposed to classical thermionic emission, field electron emission of the CNT is voltage-controlled which allows for high modulation frequencies up to GHz level. The X-ray direct detectors in turn are based on crystalline germanium absorption layers grown directly on a CMOS sensor chip yielding high resolution and high sensitivity X-ray detectors. Single photon detection will allow for a significant improvement of contrast for applications in security, health care and nondestructive testing.
A first landmark application is for example the extraction of depth information from an X-ray image without the need to do tomography. With X-ray time-of-flight measurements based on Compton backscattering, the depth inside objects where scattering occurs can be precisely measured. This calls for an intensity-modulated X-ray signal in the MHz range which can be achieved with CNT based cold emitters. An obvious application would be the detection of buried landmines: the Compton backscattering signal can indeed indicate the landmine position with much better accuracy than metal detectors.
Another key application is in the area of tomographic imaging, making use of the fact that both the X-ray source and the X-ray detector are pixelated. Since the X-ray source is built as a matrix of micro X-ray sources that can also be addressed and controlled individually, the combination of pixelated X-ray sources and detectors brings up completely new imaging capabilities, in particular the possibility to do static tomographic imaging and therefore reduce costs or increase throughput.
posters from 2011
Miniaturized X-ray source: packaging aspects Sandra Giudice, Alex Dommann
Technology of the absorbent layer for the next generation X-ray detectors Claudiu Falub, Hans von Känel, A. Dommann, P. Niedermann, A. Neels, R. Kaufmann
Notable Publications
Near infrared image sensor with integrated germanium photodiodes R. Kaufmann, G. Isella, A. Sanchez-Amores, S. Neukom, A. Neels, L. Neumann, A. Brenzikofer, A. Dommann, C. Urban, and H. von Känel, J. Appl. Phys. (0, 2011)
This project targets the development of novel pocket X-ray sources and X-ray direct detectors that will be combined in a distributed network to solve important tasks, for example in the field of security, by ensuring reliable and real-time monitoring of failure sensitive parts in large manufacturing plants or in public transportation.