Semiconductors are essential in experimental particle physics because of their excellent spatial and energy resolution, as well as fast timing capabilities. They are found in the innermost parts of particle collider detectors. As experiments at colliders require increasingly precise detectors, techniques for characterising detectors must also be appropriately improved. In the scope of this thesis a system for transient current technique measurements with two-photon absorption (TPA-TCT) for silicon detectors was commissioned.
The theoretical introduction presents the fundamentals of semiconductor particle detectors and the formation of transient current, which constitutes the signal in the detector. It explains the interaction of laser light with silicon, with emphasis on two-photon absorption (TPA). The characteristics of the Gaussian beam are also described.
The main part of the thesis consists of measurements that characterise the TPA-TCT setup. The parameters of the Gaussian beam were measured to be $w_0 = (1.3 \pm 0.1) \mathrm{\mu m}$ and $z_0 = (11.2 \pm 0.2) \mathrm{\mu m}$. The use of the setup was demonstrated with measurements of 3D sensors with a small 35 $\mathrm{\mu m}$ unit cell.
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