Producing the Powder
Our high-performing Ultra Fast Ceramic and Solid Screen scintillators are designed, manufactured and assembled to highest standards of quality and performance in our high-tech detector center Forchheim in Southern Germany. Our scientists and engineers continuously work to perfect Siemens UFC technology and production processes – at affordable prices.
Multi-stage manufacture process
Scintillation characteristics and quality depend to a high extent on the scintillator manufacturing method, specifically on grain size, powder concentration and other aspects. While we will not give you the exact recipe, here is a short outline of the process starting from highly pure raw material, to ceramics with a pore-free, homogenous crystal structure, to a fully structured array of finest Ultra Fast Ceramic.
Synthesis of the ceramic material
First the basic ceramic raw materials are dissolved in water. They contain rare earth oxysulfides and other compounds. With the application of heat, a chemical transformation takes place. Tiny rod-like crystallites of microscopic size grow from the supersaturated solution. Following the filtering off of water and subsequent drying, a powdered intermediate product results.
In the oven process which then follows, the powder is reduced in a gaseous atmosphere to the actual fluorescing detector material. This compacted powder now consists of the special UFC chemical formula.
Sintering the Ceramic Material
Scintillator ceramics must be optically translucent to transparent to ensure maximum transmittance of radiation. Only high-density ceramic with extremely low residual porosity, inclusions or grain boundaries (voids) meets this requirement.
Pressure-assisted sintering of the powder to a nearby 100% dense, homogeneous ceramic material allows the UFC properties required for detectors to emerge. Densification is achieved at very high temperatures with the simultaneous application of a compressive force of several tons.
Following cooldown, the compact UFC pieces are cut with a high-precision saw into wafers of different thickness, depending on the final product. The diamond coated saw blades used are extremely thin, measuring only 0.3 mm. The wafers are then ground to their exact final size.
Structuring the Array
From the unstructured ceramic wafers to the UFC array ready for assembly it is still a long way: Each CT product line has its own requirements in regard to pixel size, number and layout of the pixels.
First, the required 2D chessboard-like pattern is transferred fully automatically with an ultrahigh-precision saw to the wafer. Imagine a human hair being cut lengthways several times – this would come close to describing how precise these tools are. We only tolerate deviations of < 10 μm.
The interstitial zones of the pixels and the rear of the array are coated with a special reflecting polymer so as not to lose any of the light produced in the scintillator and to optically separate the pixels. Several tests are carried out to verify conformity with rigorous mechanical and optical tolerances.