Nano-CT

The TXM is a research setup with the aim to achieve the highest resolution on the laboratory scale due to the application and evaluation of state-of-the-art X-ray optics. These optics are a relatively new field of research, since X-ray radiation intuitively cannot be manipulated by classical lenses. In a spacious radiation protection hutch with numerous remotely controllable nano positioning systems, the TXM offers a great deal of freedom for the realization of new experimental set-ups. Most people are familiar with the principle of a simple tabletop microscope. The light from a lamp is bundled by a lens and passes a specimen, while a second optical system projects the image highly magnified into the observer's eye. The TXM uses state-of-the-art X-ray optics to replicate this beam path in order to exploit the advantages of X-rays such as the penetration of matter and short wavelengths. Various capillary and mirror optics are used as condensors, as well as diffractive zone plates (Fresnel lenses) and refractive lenses as imaging systems.

A high-performance microfocus tube is used as X-ray source. The special feature is the liquid metal jet system serving as an anode. A liquid gallium alloy is injected at high pressure into the vacuum chamber and is used as a constantly renewing target for the electron beam. The jet system offers a much better heat dissipation than conventional anodes and therefore allows a much higher power to be deposited on a small focal spot.

In a close cooperation between the chair and researchers of the Fraunhofer Group Nano CT Systems it was possible to successfully develop a compact nano CT system with outstanding performance compared to commercial systems available on the market so far. The ntCT is based on state-of-the-art technologies in the field of X-ray tubes and detectors and allows the three-dimensional examination of objects with a resolution down to 150 nm. Due to its fully integrated system design and intuitive user interface, the ntCT is a close-to-market system and therefore also a showcase for the instrument development capabilities

The magnification of the sample is based on geometric magnification, well known from the intersept theorem. For this purpose, the sample must be prepared as small as possible and positioned as close as a few hundred micrometers to the exit window of the X-ray source. A multi-axis sample manipulator with nanometer accuracy is available for this purpose. The X-ray source generates a source spot of only 300 nm on a tungsten transmission target. The radiation image is taken by a direct photon counting X-ray detector with 75 µm pixels. The ntCT is available to the chair for the investigation of various samples from the fields of materials science, microelectronics and biology.

The XRM-II nanoCT is a CT system which is integrated into a scanning electron microscope (SEM). Like the ntCT, it is based on the principle of geometric magnification, so that a smallest possible focal spot is required. This is ensured by the focusing electron optics of the SEM and the specially manufactured tungsten/molybdenum reflection targets. The targets are shaped like a needle with a tip diameter of less than 100nm. With this system, resolutions below 100 nm in 2D and 130 nm in 3D can be achieved.

The XRM-II nanoCT is designed to still provide the full functionality of an electron microscope despite the CT addition. This has the advantage that samples can be examined not only with X-rays but also with electrons.