The operation frequency of superconducting integrated THz receivers can be enhanced by replacing the commonly used elementary niobium with niobium nitride. This work presents the technology development of high-quality niobium nitride thin films and superconductor-insulator-superconductor multilayers along with the simulation and realization of high-frequency circuits for a superconducting integrated THz receiver using niobium nitride electrodes.

SNSPD sind aufgrund ihrer Einzelphotonenempfindlichkeit und hohen zeitlichen Auflösung interessant für den Einsatz in der Spektroskopie. Bei der Raman-Spektroskopie tritt häufig Fluoreszenz auf. Durch hohe zeitliche Auflösung ist es möglich die Streuung weitestgehend von Fluoreszenz zu separieren. In dieser Arbeit wurden in Form von zwei Schwerpunktthemen sowohl die Parameter untersucht, welche die Zeitauflösung der SNSPD beeinflussen, als auch deren Einsatz in der Spektroskopie adressiert. SNSPDs are interesting for use in spectroscopy due to their single-photon sensitivity and high temporal resolution. Unfortunately, Fluorescence often occurs in Raman-spectroscopy and superimposes the Raman-signal. High temporal resolution allows for almost perfect separation of scattering and fluorescence. In this work, parameters influencing the temporal resolution of SNSPD as well as their application in spectroscopy were investigated in two main topics.

Nuclear fusion is a key technology to satisfy the basic demand for electric energy sustainably. The official EUROfusion schedule foresees a first industrial DEMOnstration Fusion Power Plant for 2050. In this work several high temperature superconductor sub-size cables are investigated for their applicability in large scale DEMO toroidal field coils. Main focus lies on the electromechanical stability under the influence of high Lorentz forces at peak magnetic fields of up to 12 T.

High temperature superconducting (HTS) bulks and stacks of coated conductors can be magnetized to become trapped-field magnets that provide much stronger magnetic fields than those reachable with conventional permanent magnets. This work investigates the flux dynamics during the magnetization of HTS trapped-field magnets and proposes possible strategies to improve the trapped field produced by the pulsed field magnetization method that is promising for practical applications.

This work presents a comprehensive investigation of the influence of geometry-dependent factors on performance metrics of superconducting single-photon detectors. With fundamental knowledge, main investigations are focused to extend the spectral bandwidth and to enhance the detection efficiency, especially in infrared range. The developed technology of single-spiral detectors and unconventional electron-beam lithography allows to improve the performance of superconducting detectors.

Superconducting nanowire single-photon detectors (SNSPDs) are very promising as integrated detectors for future quantum photonic integrated circuits. In this work, main technological challenges for the integration of NbN based SNSPDs onto GaAs based phonic circuits are addressed. A new approach to improve the performance of meander style SNSPDs based on a variable thickness is introduced and the first full integration of a quantum photonic chip on a scalable monolithic platform is demonstrated.

Die Arbeit demonstriert die erfolgreiche Auslese von supraleitenden Einzelphotonen-Detektoren im Frequenzbereich mit zwei neu entwickelten Ausleseverfahren. This work presents two novel ways how to readout large superconducting single-photon detector arrays based on frequency division multiplexing.

Diese Studie führt eine Auslegung von supraleitenden Kabeln für die Anwendung im 380-kV-Drehstromnetz durch und erläutert allgemeine Aspekte des Einsatzes solcher Kabel im Höchstspannungsnetz. Dabei vergleicht sie die Supraleitungstechnologie unter vielen verschiedenen Kriterien mit anderen Leitungstechnologien. This study describes the design of superconducting cables for use in the 380 kV three-phase network and explains general aspects of the use of such cables in the extra-high voltage grid. It compares the superconducting technology with other line technologies under many different criteria.

This work investigates the capability of the high-temperature superconductor YBCO to sense the evolution of the electrical field of THz pulses. A deposition process for ten unit-cell thin films and a sub-µm patterning process were developed to enable high sensitivities. The detector response to THz exctiations and its electrical-field sensitivity were studied. This unique characteristic allows for the investigation of instabilities of the THz radiation emitted from synchrotron storage rings.

This work concerns the characterization of high-temperature superconducting REBCO Roebel cables for use in accelerator magnets. The effects of bending, torsion and compressive stress on the cable are investigated. The second part concerns the effect of inter-strand resistance on the cable properties. A two-parameter model is proposed to describe inter-strand connections and predict the effect on AC loss and stability. Additionally, the AC loss and stability are experimentally investigated.