Graduate theses

The universal meter with a very large dynamic range created at the institute is to be used for current measurement using the dual-slope method. The total current is to be divided into many current paths and these are to be measured individually using the dual-slope method. Currents from milliamperes down to picoamperes are to be measured. Of particular interest here is the measurement uncertainty that can be achieved for the total current in this way. A local atomic clock can be used to improve the time measurement for current integration.

Prior knowledge: DMM lecture

Keywords: electronics, frequency measurement

We want to investigate how electrical voltages with very large dynamics can be measured in measurement technology. In other words, how to separate very small voltages from simultaneously measured very large voltages, e.g. 10V amplitude of a sinusoidal signal from 1 nV amplitude of a sinusoidal signal of a different frequency. To do this, we want to use a universal counter with a very large dynamic range using the dual-slope method and test signal processing with 64-bit numbers.

Prior knowledge: DMM lecture

Keywords: electronics, frequency measurement

The Institute of Electrical Measurement Technology and Fundamentals of Electrical Engineering and Ostfalia University of Applied Sciences are collaborating on research into a brain-computer interface (BCI). Textile electrodes are used to measure signals from the brain. The BCI is used to measure visual stimuli that are to be used to control an assistance robot in care. Up to now, the system has used an ATmega microcontroller to record data. This is to be replaced with a Teensy. To this end, the software is to be adapted for use with the Teensy as part of this project.

Previous knowledge: Microcontroller programming and C programming desirable

Keywords: microcontroller, C programming

In order to measure components such as integrated circuits (ICs) on wafers without prior bonding, contacting using fine wafer probers is necessary. At the emg, a rudimentary technology has been developed based on conventional PCB technology, which has already been used to produce the first functioning prototypes. The aim of this bachelor's thesis is to develop a process for laminating copper foil onto a RO4003C board substrate and also for the final gold-plating of the copper surface, which is expected to significantly improve the quality, reproducibility and electrical properties of the probers.

Keywords: wafer prober, board technology, lamination, gold plating

The emg has developed a THz microscope with which it is possible to measure THz and GHz fields with spatial and frequency resolution. The sensor used is a so-called Josephson contact, which makes it possible to draw conclusions about radiated frequencies and their amplitudes simply by measuring its low-frequency current-voltage characteristic. New measurement electronics were developed to extend the measurement setup. In order to further reduce its noise, an analogue preamplifier is to be designed and tested as part of this thesis which, in contrast to the rest of the electronics, is operated at 40 K to minimise thermal noise.

Keywords: measurement electronics, preamplifier, cryogenic, analogue, low noise

The THz microscope at LENA can be used to measure electromagnetic radiation in the THz frequency range. A so-called Josephson cantilever is used to record three-dimensional images of intensity distributions. This system is to be expanded in future to include phase measurement. Additional microwave circuits on the cantilever are required for this phase measurement.

Previous knowledge: High frequency technology, superconductivity

Keywords: THz microscope, microwave simulation

Components made from the superconductor YBCO are manufactured and analysed at the institute. A very relevant step in the production of our superconducting samples is the etching of the samples. An ion beam etching system automated with LabVIEW software is used for controlled etching. Various materials such as gold, silver and the superconductor YBCO are etched in several steps. The times required for this are very different for identical parameters. The etching rates for the different materials are to be analysed and determined as part of this work. In addition, the parameters for etching are to be optimised.

Prior knowledge: Enthusiasm for scientific work, careful and independent work

Keywords: Ion beam etching system, etching rates, YBCO

Components made from the superconductor YBCO are manufactured and analysed at the institute. These include Josephson junction (JJ) arrays, i.e. the series connection of several JJs, which are to be used for the Volt standard. Antenna structures are to be provided on the chip in order to improve field coupling. As part of this thesis, the existing antenna structures are to be evaluated and optimised. Subsequently, samples with these antenna structures will be produced and measured under high-frequency irradiation.

Prior knowledge: Enthusiasm for scientific work, careful and independent work

Keywords: simulation, antennas, CST Studio, YBCO

In the THz microscope at the EMG, three-dimensional field distributions are measured with a sensor up to around 5 THz. The sensor is a so-called Josephson cantilever, which consists of a high-temperature superconductor on a substrate. In order to achieve a high sensitivity of the sensor, antennas are used to improve the field coupling. As part of this final thesis, our new manufacturing process will be used to improve proven antennas and design new antennas. Together with customised filter circuits, the components will then be measured under a THz microscope.

Previous knowledge: Basic understanding of electromagnetic fields

Keywords: simulation, CST Microwave Studio, high-temperature superconductors, antennas

Established methods for the diagnosis of diseases such as real-time PCR require many sophisticated sample preparation steps. The DNA assays developed at emg are based on the resizing of a system of magnetic nanoparticles (MNPs) when a specific target sequence is present in the sample. DNA nanotechnologies are used to initially separate connected MNPs (clusters) from each other, which can be detected by magnetic sensors. Since biological elements do not contribute to the magnetic measurement signal, the magnetic assays are promising for "mix and measure" detection, which significantly simplifies the performance of the tests.

Current research questions:

•     Realising viral detection without complex extraction steps
•     Ensuring the specificity of the magnetic assays
•     Adaptation to alternative RNA targets

Keywords: DNA/RNA detection, magnetism

Quantum computers differ from conventional computers in many ways. While conventional systems perform calculations based on the logic levels ‘0’ and ‘1’, quantum computers use quantum bits (qubits). Qubits can be generated from different quantum states. In the Quantum Valley Lower Saxony (QVLS) project, the spins of electrons of several trapped ions are used as quantum states. Due to their scalability, quantum computers based on ion traps are a promising approach for surpassing the performance of conventional computers (quantum superiority).

Electric fields generated by a resonator are used to trap the ions, which float at a height of 90 µm above the trap surface shown in the figure. The optimisation of the generation of the electric fields and the dynamic impedance matching is urgently required due to the close proximity to the information carriers. Promising components of a final thesis can be tested on a test setup of the quantum computer in Hanover.
Tasks range from design and simulation of different coil geometries, circuit/board design and 3D printing.

Prior knowledge: Depending on the task

Keywords: quantum computer, ion traps, RF resonator

Our interdisziplinary research group focuses on detecting specific targets, such as nucleic acids and proteins, using our custom magnetic nanoparticles. For this purpose, we have employed various measurement technologies, wherein magnetic particle spectroscopy (MPS) emerges as the most frequently used method due to ist fast signal delivery and ease of use. In this thesis, we aim to better understand and differentiate the factors affecting signal changes in MPS, such as separating the influence of molecular weights from that of hydrodynamic sizes. Additionally, how the absolute change in particle size correlates to the signal chang observed in MPS should be thoroughly investigated.

Keywords: Magnetic nanoparticles, DNA nanotechnology, Magnetic measurement methods