X-ray Talbot-Lau interferometry kit / Talint-EDU
What is Talint-EDU?
Talint-EDU is a smartly simplified form of an X-ray Talbot-Lau interferometer consisting of all the necessary hardware to set up and fine-tune the interferometer properly as well as to apply a phase stepping procedure which is required to obtain the three imaging modes: absorption, phase-contrast and dark-field contrast.
The hardware is designed such that, after assembling the (pre-mounted) kit following the instructions, first Moiré fringes will readily be visible on your detector. Further fine-tuning of the Moiré fringe pattern can be done in a straightforward manner by angular rotation of the gratings around the optical axis using the micrometre screws in the G1 and G2 holders.
Talint-EDU kit. From left: G0 (source grating), G1 (phase grating) and G2 (intensity grating)
Talint-EDU specifications
| L x W x H |
600 mm x 150 mm x 200 mm Defined by base plate breadboard with M6 and spacing of 25 mm |
|---|---|
| Mounting | On customer's optical table, breadboard or any posts fitting to 25 mm spacing of Talint-EDU breadboard |
| G0-G1 distance | 290 mm, fixed via precision dowel pins |
| G1-G2 distance | 290 mm, fixed via precision dowel pins |
| Built-in curvature of gratings to prevent shadowing | G0: 75 mm, G1: 365 mm, G2: 655 mm, source to G0 distance of 75 mm for best transmission |
| Open area of gratings |
G0: 15 mm Ø G1: 70 mm Ø G2: 70 mm Ø |
| Interferometer fine-tuning | G1 and G2 gratings can be rotated around the optical axis with precision adjustment micrometre screws |
| Sample placement | Simple rotating table to swing sample in and out of the optical axis, sample to be placed close to G1 |
| Phase stepping | Closed loop piezo stage. 30 nm resolution, controller included |
| Fringe visibility |
> 20% (typ.) Visibility map will be provided upon delivery of the system |
Talint-EDU comparison chart (40 keV and 20.8 keV options)
The gratings are fabricated using the X-ray LIGA technique which ensures high precision and extreme height-to-width ratios (aspect ratios). Further grating characteristics are described in the following table. Detailed description of the grating parameters will be provided for the specific set of gratings delivered with the Talint-EDU kit.
| Talint-EDU | Option 1 | Option 2 |
|---|---|---|
| Design energy | 40 keV | 20.8 keV |
| Talbot order | 1 | 3 |
| FOV | 70 mm round | 70 mm round |
| Phase stepping visibility | > 20% | > 20% |
| Total length | 600 mm | 600 mm |
| G0-G1 distance | 290 mm | 290 mm |
| G1-G2 distance | 290 mm | 290 mm |
| G0, G2 gold thickness | > 120 µm | > 40 µm |
| p0 (G0 period), p2 (G2 period) | 6.0 µm | 4.8 µm |
| p1 (G1 period) | 6.0 µm | 4.8 µm |
| Angular sensitivity (p2/(G1-G2)) | 21 µrad | 17 µrad |
| G0 and G2 substrate | Graphite 400 µm | Graphite 400 µm |
| G1 substrate | Silicon 200 µm | Silicon 200 µm |
Imaging examples
Here are some examples of sample images taken with a Talbot-Lau interferometer using Microworks' X-ray gratings (energy: 40 keV, grating periods: G0: 10.0 µm, G1: 8.9 µm, G2: 8.0 µm).
Metal powder residue in a bellows lattice structure
Bellows lattice structure manufactured from titanium powder. Left: overview photo, centre: absorption image, right: dark-field contrast. The arrows indicate residue positions within the lamellae.
Residual titanium powder is trapped between the lamellae of the sample. Due to the reduced bulk density compared to solid titanium, this residual powder is difficult to detect via standard absorption contrast. However, the powder structure causes a high amount of scattering which can be visualised by dark-field imaging. [1]
Cracks in a honeycomb structure
Scattering caused by crack damage is visible in the dark-field image as indicated with red arrows (right), while they are not visible at all in absorption contrast imaging shown in its left. Sample size: 30 mm x 9 mm x 2 mm
This sample, previously exposed to impact force, is a sandwich specimen with an aluminium honeycomb core and CFRP face sheets, which is often used in the aerospace and automotive fields. Though low-velocity impact damage can be subtle and not visible at the specimen surface, internal micro-cracks can deteriorate structural strength significantly. Early detection of these cracks by dark-field imaging is expected to ensure the safety of critical components. [1]
Reference
[1] Aishwarya Nafre et al., TALINT grating kits for X-ray interferometry in the industrial laboratory, 11th Conference on Industrial Computed Tomography, Wels, Austria (iCT 2022)
Manufacturers and recent results
Manufacturers
Karlsruhe Institute of Technology (KIT)/IMT and its spin-off company Microworks GmbH supply X-ray gratings for Talbot and Talbot-Lau interferometers not only with standard specifications described above but also with ones based on the customers' special requirements. ASICON Tokyo Ltd. serves as their local distributor and as technical partner of customers in Japan, South Korea and Taiwan.
KIT/IMT and Microworks GmbH are two of the world's top authorities in the fabrication of high aspect ratio polymer and metal structures using X-ray lithography and electroplating techniques. With these techniques (LIGA Process), X-ray gratings with both a narrow period and high aspect ratio have been realised.
Imaging examples
■ Internal link (Japanese): X-ray images of some samples taken with X-ray gratings fabricated by Microworks GmbH
[KIT/IMT and Microworks GmbH]