The KM3NeT neutrino telescope, located presently at two different sites in the Mediterranean Sea, consists of two neutrino detecors As the telescope is still being built, the calibration is fully...Show moreThe KM3NeT neutrino telescope, located presently at two different sites in the Mediterranean Sea, consists of two neutrino detecors As the telescope is still being built, the calibration is fully underway. This research focuses on four potential biases present in the astrophysical focused part of the detector, ARCA. Muon light, both detected and reconstructed from simulations and $^{40}$K decay being used to determine the size of those biases. It is found that the PMTs shadowed by the titanium collar on the DOM show a different bias dependent on what hemisphere they are located. Furthermore it is found that the different gel transperacy in the DOMs causes different efficiencies, and that the new PMTs show lower efficiencies than the old PMTs.Show less
The unification of general relativity and quantum mechanics has been a persistent challenge in the field of physics. This study introduces a design for a milligram-scale gravity source, termed the...Show moreThe unification of general relativity and quantum mechanics has been a persistent challenge in the field of physics. This study introduces a design for a milligram-scale gravity source, termed the Gravity Propeller. When coupled with the Magnetic Zeppelin, a gravity detector of comparable scale, it could potentially enable the measurement of gravitational interactions between two milligram objects. This measurement could provide insights into the unification of general relativity and quantum mechanics. The propeller, composed of two sets of Meissner levitated magnets connected by a stick, is designed to levitate within a type I superconducting trap and rotate to create a variable gravity potential. This research confirms the levitation of the propeller and demonstrates several optimizations, for instance, the minimization of damping. However, the rotation of the propeller is yet to be accomplished.Show less
In this project, the simulation software MRI2D was developed. It is a program that allows students to simulate the motion of spins during the magnetic resonance imaging experiment. Already...Show moreIn this project, the simulation software MRI2D was developed. It is a program that allows students to simulate the motion of spins during the magnetic resonance imaging experiment. Already available tools did not model multiple spins rotating to image tissues. Besides filling this niche, other design requirements were taken from existing educational tools. All requirements have been met. MRI2D is open-source software and can be downloaded for free. It comes with a manual for downloading and installing and three example exercises directly for classroom use. MRI2D is ready to now be implemented in education. Further development suggestions are given.Show less
Transition metal dichalcogenides (TMDs, MX2) are Van der Waals materials with properties such as the band structure depending on chemical structure and the number of layers. Low energy electron...Show moreTransition metal dichalcogenides (TMDs, MX2) are Van der Waals materials with properties such as the band structure depending on chemical structure and the number of layers. Low energy electron microscopy (LEEM) provides a manner of characterizing TMDs, by controlling the landing energies at which electrons reach the desired sample and measuring the reflection of the electrons. Besides real space imaging, our LEEM instrument is able to image reciprocal space, which is especially interesting to the characteristic hexagonal lattice of TMDs. This thesis will discuss a number of energy-resolution limiting factors. One of these factors is the energy distribution of electrons incident on the sample. It will discuss a method to correct for this energy dispersion and use it to decrease noise in electron reflectivity spectra. Also, fluctuations in electron current will be discussed and corrected for. Further, this thesis will examine oxidation of TMDs, as the rate of oxidation and impact on properties differs greatly depending on the specific composition of the TMD. It will discuss methods of exfoliating TMDs in vacuum, i.e. in situ, and show successful exfoliation in vacuum of around 10−6 mbar inside the LEEM. Also, the research will study exfoliation of Si/SiO2 substrates with gold evaporated to produce large flakes of few-layer TMDs. This yielded MoS2 few-layers flakes of up to 100 microns. The findings in this study regarding enhanced energy resolion in LEEM measurements of TMDs and improved techniques for TMD exfoliation will help the progress in understanding and characterization of TMD materials.Show less
Recent developments in the field of quantum optics have observed fine spectra in Fabry-P\'erot microcavities that can be substantiated with theory. This thesis describes the development of a...Show moreRecent developments in the field of quantum optics have observed fine spectra in Fabry-P\'erot microcavities that can be substantiated with theory. This thesis describes the development of a software that calculates the fine spectrum of a microcavity. A rotational-symmetric system is considered, with perfectly-reflecting mirrors. Paraxial theory states that these cavities have resonant modes in the form of scalar Laguerre-Gauss functions. Nonparaxial theory has added 2 scalar and 1 vector correction to the resonance frequencies. We use an object-oriented approach to propagate field profiles through a cavity with the help of Fourier transforms. Some numerical integration and interpolation tricks are used in the computations. Nonparaxial phase delays are compared to theoretical predictions and a first step is made to finding the eigenfunctions of a cavity by modal decomposition. The software only provides scalar corrections and needs improvement in some areas, but shows promising results for the scalar correction. It could potentially lead to more advanced extensions, like a composite cavity which can help experimentalists to understand more complex resonance spectra.Show less
Superconductivity is a macroscopic quantum phenomenon based on a transition from a fermionic electron system to a bosonic condensate of electron pairs. This condensate is characterized by two...Show moreSuperconductivity is a macroscopic quantum phenomenon based on a transition from a fermionic electron system to a bosonic condensate of electron pairs. This condensate is characterized by two length scales, λ and ξ, which separate superconductivity in a 3D limit (physical system size larger than intrinsic length scales) from lower dimensional structures. Although superconductivity is well studied in both the 3D and 2D limits, little is known about ‘fractional dimensional’ systems, exhibiting a non-integer dimensionality induced by the geometry. This thesis explores the behaviour of planar Josephson junctions featuring electrodes structured as Sierpiński carpet fractals (Hausdoff dimension ∼ 1.8). Although the magnetic response of these junctions is dominated by flux-trapping effects, the underlying interference pattern is unconventional and cannot be described by simulations based on the electrode geometry. This warrants further study of the flow of supercurrents in fractional dimensional superconducting systems.Show less
The results from Magnetic Resonance Force Microscopy measurements on electron spins in a diamond sample at milliKelvin temperatures are presented. A spin density on the surface of the diamond...Show moreThe results from Magnetic Resonance Force Microscopy measurements on electron spins in a diamond sample at milliKelvin temperatures are presented. A spin density on the surface of the diamond sample of (3.7 ± 0.2) · 10^6 µm^−2 was found by examining the resonance frequency of the cantilever as a function of the temperature of the sample. Also the energy in the motion of the cantilever was determined at different temperatures to conclude whether the cantilever was purely thermally excited. The results from these measurements are in contradiction with expectations, since the energy in the motion of the cantilever is smaller then expected at greater temperatures. The result could point to a temperature gradient in the setup. Furthermore, RF-pulses with different frequencies, durations and powers were sent, which made it possible to investigate the frequency shift in the resonance frequency of the cantilever as a function of the frequency of the pulse, the power of the pulse and the duration of the pulse. In addition, the relaxation of the spins in the sample, after sending an RF-pulse, was inspected with the result that the relaxation of the spins cannot be described by a single exponential function. This outcome could indicate an interaction between electron spins and nuclear spins.Show less
T-cycle EPR is a novel technique developed for determining reaction rates and trapping reaction intermediates in the sub-second time domain [1]. In T-cycle EPR a sample containing two reactants is...Show moreT-cycle EPR is a novel technique developed for determining reaction rates and trapping reaction intermediates in the sub-second time domain [1]. In T-cycle EPR a sample containing two reactants is placed at low tempera- ture in a cryostat to halt the reaction. While in this cryostat the sample is then briefly heated with a laser. This will make the reaction proceed. After this heating pulse the sample is immediately cooled back to prevent it from reacting any further. In between each heating pulse, an electron paramagnetic resonance (EPR) spectrometer takes a spectrum. From these spectra the reaction can be followed and information about chemical rates and intermediates obtained. For T-cycle EPR to be possible one needs to know the temperature of the sample after heating, how fast the sample heats up to this temperature and possibly what temperature the sample reaches if the heating pulse is shorter than this heating time. This thesis focuses on answering these questions. For this a 275 GHz homebuilt EPR spectrometer was used. Here spectra were taken of a solution containing the nitroxide TEMPOL while heating at different heating laser powers. These spectra were then compared to spectra taken at known tempera- tures to find the sample temperature for each heating power. To find the heating time and the temperature reached for shorter heating pulses, the spectra were analyzed at one specific field position. This calibration has been done before by Panarelli [1] who got different results using the same setup. This shows the importance of repeating this calibration every time an experiment is performed as small changes in the hardware configura- tion may have an impact on the temperature calibration.Show less
This thesis discusses the development of a setup for measuring photocathode quantum efficiency (QE) in the preparation chamber of the Low Energy Electron Microscope setup (LEEM). The photocathodes...Show moreThis thesis discusses the development of a setup for measuring photocathode quantum efficiency (QE) in the preparation chamber of the Low Energy Electron Microscope setup (LEEM). The photocathodes are necessary for a new microscopy technique called Optical Near-field Electron Microscopy (ONEM). At the time of writing, a photocathode sample holder, and an anode have been created, along with the corresponding electrical connections and measurement software. To test whether the setup produced photoemission, two measurements were performed with an uncollimated 450 nm laser beam incident on a chromium photocathode that was cesiated with a Cs evaporator. The results show a current from anode to cesium evaporator, but no photoemission can be confirmed as the observed current fluctuations cannot be attributed to the laser beam with certainty.Show less
Scanning Tunneling Microscopy (STM) is a technique that allows its user to make scans of the surface topography of a sample. Via a capacitive approach, a tip is brought in close proximity to the...Show moreScanning Tunneling Microscopy (STM) is a technique that allows its user to make scans of the surface topography of a sample. Via a capacitive approach, a tip is brought in close proximity to the sample, by which eventually a tunneling current is measured that is used to obtain a scan. It can be interesting to do STM experiments at extremely low temperatures (< 4 K), which can be done by placing an STM into a dilution refrigerator. It is difficult to do so in a dry dilution refrigerator, because of the pulse tube system that brings lots of mechanical vibrations. This research shows the performance of the newly developed `PAN-motor' and `linear cryo-walkers', two new types of motors for STM-approaches at extremely low temperatures. The cryo-walkers in particular have allowed for a full approach at millikelvin temperatures due to its low heat dissipation, whereas this approach normally has to be done above 4 K. By realizing dry dilution refrigerator STM, more research at millikelvin temperatures would be made possible, due to these dry dilution refrigerators being closed systems, allowing for time-unlimited measurements. This advancement could allow for experiments with low T_c superconductors, or shot noise experiments with the new Multi-LC circuit, that has shown to enable the measurement of shot noise with a total measuring time of \tau \approx 98 h.Show less
We study the mathematics and physics involved in the generation of grav- itational waves by stellar mass binary black holes and their subsequent detection by LISA, a space based interferometer...Show moreWe study the mathematics and physics involved in the generation of grav- itational waves by stellar mass binary black holes and their subsequent detection by LISA, a space based interferometer detector. We show that LISA will be capable of detecting nearby binary black holes with a maxi- mal relative distance error of 0.2 and skylocation error of 1 square degree if the total mass of the binary is at least eighty solar masses.Show less
Over the past century, scientists have tried to find the minimum number of photons that is required to evoke a visual response of humans. Us- ing single-photon sources, researchers found that...Show moreOver the past century, scientists have tried to find the minimum number of photons that is required to evoke a visual response of humans. Us- ing single-photon sources, researchers found that humans most likely can indeed detect single photons with an above-chance probability. In this project, an experimental setup is developed towards firstly using quan- tum detector tomography to determine the accuracy of the human eye to observe few-photon number states. The setup contains two optical beams, one to fixate the eye of the subject and one to target the photons at the proper area of the retina. The focus position and beam divergence are determined with three different methods. Additionally, simulations of the eye show that reliable experiments on humans can be conducted using the devised setup. First tests with humans show that the setup fulfils the re- quirements and we can reliably target the desired spots on the retina. It is further shown that both the head and the orientation of the eye are stable enough to perform reliable experiments using human observation.Show less
The current through a Josephson junction is governed by the current-phase relation (CPR) that depends on the phase difference between the electrodes. Notable applications are qubits, Josephson...Show moreThe current through a Josephson junction is governed by the current-phase relation (CPR) that depends on the phase difference between the electrodes. Notable applications are qubits, Josephson diodes and microscopic imaging techniques. This thesis presents a method to measure the CPR based on [1]. The junction under study is incorporated into a superconducting loop that is inductively coupled to a dc-SQUID magnetometer. The measured flux is proportional to the junction’s phase and by controlling the current through the junction’s loop it is possible to directly measure the CPR. This thesis outlines several important considerations and constraints of this method. Furthermore we provide CPR measurements of a superconductor-normal- superconductor (SNS) junction made from Nb and Cu. It shows a clear temperature dependence with a qualitative change in shape as well as a quantitative change in amplitude of the current-phase relation. These results are in agreement with theory. In the future a flux-locked loop can be used to further improve the measurements.Show less
This thesis presents a detailed study into the development of a custom- made cryogenic sample stage which was designed, fabricated, and retrofitted in a Scanning Electron Microscope (SEM) for...Show moreThis thesis presents a detailed study into the development of a custom- made cryogenic sample stage which was designed, fabricated, and retrofitted in a Scanning Electron Microscope (SEM) for performing Cryo-EBID, a cryogenic variation of the microfabrication technique known as ’Electron Beam Induced Deposition’ (EBID). It provides an overview of all relevant aspects of the design process, from the concept design to a fully integrated and functional product. The goal of the project is to implement Cryo-EBID for the fabrication of nanowires using a tungsten hexacarbonyl (W(CO)6) precursor, offering an immense increase in deposition rate compared to traditional EBID. The setup’s efficacy in creating microstructures is eval- uated at various electron doses and a small set of prototype nanowires were fabricated and characterized. This project serves to provide valuable insights into the development process of a cryogenic sample stage and a method for creating nanowires using cryo-EBID while also setting the stage for future cryo-EBID experiments.Show less
The effects of the continuous spontaneous localization (CSL) collapse model can theoretically be observed through an increase of the mean energy of a collapsing system. The force noise of a...Show moreThe effects of the continuous spontaneous localization (CSL) collapse model can theoretically be observed through an increase of the mean energy of a collapsing system. The force noise of a magnetically cooled force sensor is used to measure its kinetic energy and improve upper bounds of certain CSL parameters, but this demands an environment with temperatures in the sub-mK regime. Measurements in this temperature range are performed with a primary flux noise thermometer and a resistance thermometer, which are subsequently compared to each other and examined for their accuracy. The result is that the two thermometers do not line up in temperature, differing in 1-2 mK at all times. Standalone, their accuracy also cannot be sufficiently ascertained. The two different sensors of the resistance thermometer have a mean temperature difference of 0.93 ± 0.07 mK due to being calibrated elsewhere, causing their RC time delay to scale differently over temperature. The noise spectra of the flux noise thermometer contain interference, which is minimized as much as possible. This procedure works better for lower frequencies than for higher frequencies and has a clear effect on the flux noise power. The reliability of this thermometer is affected by a forced best fit estimation that is caused by a limiting calibration process. Besides this, the force noise measurements could not be done because the experiment did not manage to cool down enough. The reasons for this stem from small oversights in the experimental setup. However, given that the setup has undergone improvements since the last time these measurements were performed, one can expect to improve upper bounds in future runs. This is especially the case if the temperature can be further lowered by implementing a second magnetic cooling stage.Show less
