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Silicon semiconductor detectors are widely used for tracking and vertexing in particle physics collider experiments. The "popularization" of this technology came from adapting the planar MOS (Metal Oxide Semiconductor) processes to detector construction. The zoo of shapes and functionalities continued growing, from the first simple diodes, to the latest 3D detectors (with electrodes across the bulk) or High Voltage-CMOS.
When a particle traverses Si it does, in most of the cases, ionize the material and this is the detection signature exploited to have a "signal". However, some of these impinging particles do not lead to signal creation but they damage the Si lattice and their effect is thus detrimental for operation. Within the RD50 collaboration a characterization technique called Transient Current Technique, or TCT, has been tuned and largely used to study the harmful effects of radiation in Si.
In TCT a fast pulsed laser is used to mimic the crossing of a particle. The current induced by this pseudo-track is amplified and time resolved using a wide band oscilloscope. Just by studying the shape of the induced current we can infer information of the doping, electric field and charge collection efficiency of the detector. Developing a radiation-hard Silicon detector implies following the evolution of these parameters as a function of fluence. For that purpose we use TCT.
The CERN-SSD (Solid State Detectors) team counts with years of experience developing and using TCT systems. The talk will present the standard TCT technique, its evolution (Two Photon TCT), an implementation of one of such systems at CERN (TCT+ setup) and will illustrate its reach with several selected examples of detector technologies studied.