Optical readout of GEM-based detectors: concepts and applications
Modern imaging sensors allow direct readout of scintillation light produced in MPGDs during electron avalanche multiplication. Using gas mixtures with scintillation light spectra compatible with the quantum efficiency of CCD or CMOS cameras, optical readout can be used to record high resolution 2D images without the need for extensive reconstruction and with an inherent stability against electronic noise. The suitability of optically read out detectors in various fields ranging from high energy physics to material characterisation and medical physics has been extensible studied and demonstrated and promises numerous future applications.
The first part of the seminar will cover the concept of optical readout by the example of optically read out GEM-based detectors. Besides different mechanism for light production, readout with fast photon detectors as well as high resolution CCD cameras will be presented.
Applications of optical readout with a focus on recent developments in the GDD lab will be discussed in the second part of the seminar. Combining the high resolution of state-of-the-art cameras with the high gain factors achievable by multi-layer GEM structures, integrated x-ray imaging with remarkable position resolution and signal-to-noise ratios as well as energy resolved imaging enabled by single photon sensitivity for applications such as X-ray fluorescence for material characterisation can be realised. Augmenting 2D images with timing information obtained from fast photon detectors, full 3D reconstruction in an optically read out TPC has been demonstrated. To overcome the issue of parallax-broadening in thick drift regions which are necessary for low-intensity applications such as x-ray crystallography, a planispherical GEM-based detector prototype has been developed which preserves position resolution by employing radially focused drift field lines. The low material budget of gas-based detectors also makes them an attractive candidate for beam monitoring and a prototype of an optically read out proton beam monitoring detector for radiotherapy is presented.
The seminar is organised in such a way that no specific background is required.