GEM-based imaging system for X-ray radiation recording with temporal, spatial and energetic resolution
System’s basic features:
- Effective visualization and parameterization of X-rays;
- The GEM detector chamber (see diagram above) is a separate, closed volume selected in such a way as to optimize the quantum detection efficiency for the target photon energy range;
- For the proper operation of the detector, it is necessary to create inside an electric field oriented in such a way that free electrons generated in the process of ionization of the working gas near the entrance window are accelerated towards the multiplication structure and further towards the readout electrode;
- The multiplication structure of the GEM detector typically consists of a Kapton layer approximately 50 microns thick, covered on both sides with a 5-micron copper foil. The multiplication structure is densely perforated, most often in a hexagonal packing. Applying even a relatively small potential difference to both copper foils (e.g. 400 V) will result in the creation of a very strong electric field inside the holes;
- An extremely important element of the GEM detector is the patterned readout electrode (see photos above). Each individual element of the anode surface structure is connected to electrical buses – carrying electrical signals from the anode, which means its full addressability;
- The process of generating the signal in the GEM detector begins when the X-ray quantum ionizes the atom (molecule) of the working gas. The enhanced electron cloud reaches the patterned readout electrode, where it creates a negative charge in the area of a few to several dozen pixels, producing the so-called single event cluster;
- Information about the creation of the cluster serves for: i) determining the moment of an event; ii) reconstruction of the coordinates of the cluster position in relation to the readout electrode surface; iii) estimation of quantum energy.
- The ability to effectively X-rays detection with the GEM-IS can be characterized by three parameters, namely: i) the limiting temporal resolution, which after using dedicated signal processing algorithms does not exceed 50 ns; ii) the limiting spatial resolution of the mapping of the primary ionization site, which for the Micropattern Gas Detectors (MPGD) is not higher than 100 microns; iii) energy resolution, which is usually no worse than 20%.
- In each newly designed GEM-IS, its functional subsystems and their way of cooperation are carefully optimized in such a way that it is possible to achieve the assumed research goals of application.
- Study of the time-space-energy characteristics of X-rays in a wide energy range (1-100 keV);
- Two-dimensional visualization of X-ray sources carried out with high spatial resolution;
- Recording of X-ray images of spatially extensive objects (medical and biological scanners);
- Performing research in the field of inventory and protection of cultural heritage.
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