The KM3NeT-neutrino telescope is a large detector under construction in the Mediterranean Sea. Its main objectives are the observation of cosmic high-energy neutrinos and the determination of the...Show moreThe KM3NeT-neutrino telescope is a large detector under construction in the Mediterranean Sea. Its main objectives are the observation of cosmic high-energy neutrinos and the determination of the neutrino mass hierarchy. However, the deep sea is an extraordinary location and environment and entails uncontrolled phenomena like bioluminescence. Bioluminescence is the emission of light by organisms. This light is detected by the KM3NeT-detector when bioluminescent organisms collide with the structure of KM3NeT. It is interesting to study the signal of the bioluminescence, because it tells a lot about life in deep-sea and it can be a nuisance in the quest to observe and research neutrinos. Characteristics of bioluminescence like the amount of detected bioluminescence over a long period of time, the location of the increased bioluminescence in the detector, the number of bioluminescent bursts that happen at the same time, the duration of these bursts and the periodicity of the detected bioluminescence are investigated. Finally in the analysis of the data it has been found that some parts of the detector are showing unexpected behaviour, examples of this behaviour are shown.Show less
The KM3NeT neutrino telescope, currently under construction, aims to detect high energy neutrinos from distant astrophysical sources, as well as studying the properties of neutrinos by exploiting...Show moreThe KM3NeT neutrino telescope, currently under construction, aims to detect high energy neutrinos from distant astrophysical sources, as well as studying the properties of neutrinos by exploiting atmospheric neutrinos. 3-Dimensional arrays of thousands of optical sensors with a total volume of about five cubic kilometres will be distributed over three locations in the Mediterranean Sea. These optical sensor modules will detect the cherenkov light emitted by the charged particles (muons) produced in collisions of neutrinos and the Earth. To be able to reconstruct the path of the muons radiating the detected photons, an accurate time-calibration is vital. For efficient commissioning, already before deployment a pre-timecalibration of the modules is required. Currently, a laser-installation is used to perform this calibration procedure. In this thesis the possibility to use cosmic ray showers to perform this pre-calibration is investigated. Particles (muons, electrons) of secondary radiation reaching the earth in an air shower will hit the detectors at virtually the same moment, which makes the recorded coincident suitable for time-calibration. This study demonstrates that the optical modules can indeed detect these particles from cosmic showers, and that the subsequent data can be exploited for a robust time-calibration with an accuracy of within 0.3 ns.Show less
We investigate the presence of $(trans-10b,10c-dimethyl-10b,10c-dihydropropane)$ (DHP) photochromic molecular switches on 2D gold nanoparticle networks after molecular place exchange. We study the...Show moreWe investigate the presence of $(trans-10b,10c-dimethyl-10b,10c-dihydropropane)$ (DHP) photochromic molecular switches on 2D gold nanoparticle networks after molecular place exchange. We study the networks using spectoscopy, as the presence of the molecular switches on the network changes the surface plasmon resonance absorption frequency. We observed a redshift of $20\ nm$ and an additional peak broadening of $2\ nm$ (FWHM) of the absorption peak of the network compared to before molecular place exchange. From this we conclude that the molecules are present on the network after molecular place exchange.Show less
Recent studies have revealed that gas filaments surrounding the brightest cluster galaxies (BCG) in cool-core clusters often behave unexpectedly: although these structures should fall into the...Show moreRecent studies have revealed that gas filaments surrounding the brightest cluster galaxies (BCG) in cool-core clusters often behave unexpectedly: although these structures should fall into the galaxy centers at velocities above 600 km s−1 , given that they do not participate in regular stellar rotation, they seem to remain relatively stable, displaying infall velocities barely exceeding 100 km s−1 [16, 18, 22]. This discrepancy is purportedly caused by the presence of magnetic fields. However, the existence of these fields has yet to be confirmed by direct observational evidence. We analyze the presumed magnetic fields within the filaments of NGC4696 by means of polarimetric imaging techniques. Of the examined filaments, at least one exhibits non-zero polarization degrees, displaying linear Stokes parameter values given by (Q, U) ≈ (−0.018 ± 0.012, 0.002 ± 0.01). A qualitative examination of the corresponding linear polarization angle suggests that the direction of linear polarization coincides with the spatial orientation of the filament itself, though further analysis is needed to confirm this claim.Show less
In this thesis we present Dijkgraaf-Witten theory. We start by considering a two-dimensional topological quantum field theory that can be used to prove Mednykh's formula along the way. Subsequently...Show moreIn this thesis we present Dijkgraaf-Witten theory. We start by considering a two-dimensional topological quantum field theory that can be used to prove Mednykh's formula along the way. Subsequently, we define the Dijkgraaf-Witten invariant as a partition function where we assign a specified weight to the 3-simplices of a compact, oriented and triangulated 3-manifold with boundary. The partition function depends on how we assign elements of a finite, discrete group G to all the oriented edges of the manifold. We prove that, whenever the triangulation of the boundary is fixed, the invariant does not depend on the triangulation of the manifold. Finally, we define a similar invariant where we model the weight of the 3-simplices to mimic the action of Chern-Simons theory. We demonstrate that by demanding invariance, we obtain the Dijkgraaf-Witten invariant.Show less
Direct imaging of exoplanets is an extremely difficult task limited by distortions caused by both the atmosphere and telescope optics. Current extreme adaptive optics systems (XAO) can correct...Show moreDirect imaging of exoplanets is an extremely difficult task limited by distortions caused by both the atmosphere and telescope optics. Current extreme adaptive optics systems (XAO) can correct these distortions, but require precise wavefront measurements. The Zernike wavefront sensor was developed to do this. The new vector-Zernike wavefront sensor (vZWFS), built using liquid crystal technology, is a promising improvement over the old Zernike wavefront sensor. In this thesis we test a vZWFS prototype and compare its response with the results of a model written in Python. In the experiment we introduce phase aberrations through a spatial light modulator, which are then measured by the vZWFS. We model part of the physical setup and use it to interpret the physical measurements. We create a method to reconstruct the phase and amplitude of the original wavefront, and test the limitations of the vZWFS.Show less
In this bachelor thesis, we investigate cobalt on a Au(111) surface in a sulfiding H2S background by deposition and extended H2S exposure to gain insight in the interactions between Co, H2S and the...Show moreIn this bachelor thesis, we investigate cobalt on a Au(111) surface in a sulfiding H2S background by deposition and extended H2S exposure to gain insight in the interactions between Co, H2S and the Au(111) surface. In particular, we found two CoSx equilibrium structures. A hexagonal structure a which is about 2.1nm in size and is similar to an elsewhere reported Co3S4 structure. Structure g is more rectangular with a size of approximately 1.3nm x 0.8nm. Additionally we observed a structure x decorating the step edge. The experiments done to investigate the mobilization of gold due to H2S in presence of cobalt and the formation of H2S adsorption sites by Co replacing Au atoms, remain inconclusive. Due to the low intensities of the XPS spectra, the elemental compositions of observed CoSx structures could not be calculated and require further research.Show less
This thesis describes the development an easy to use, low cost device which can continuously measure the water transparency throughout different layers in ditches. The development of this device...Show moreThis thesis describes the development an easy to use, low cost device which can continuously measure the water transparency throughout different layers in ditches. The development of this device has started in several forms using several detection methods with LEDs, a laser or a pre-made turbidity sensor. The intended use of the device is in the ditches of the Living Lab in Leiden and might be expanded to ditches across the country. Another part of this thesis describes the development of an automatic air-based monitoring system for the Living Lab using a drone. The first steps towards the automation of this system have been made.Show less
Spectropolarimetry is a versatile technique that allows an observer to measure both the spectrum of an object and the polarization of each point on that spectrum. Spectropolarimeters, like other...Show moreSpectropolarimetry is a versatile technique that allows an observer to measure both the spectrum of an object and the polarization of each point on that spectrum. Spectropolarimeters, like other spectrographs, generally use a slit to restrict their field of view to a line. However, slits have a long history of polarizing the light they transmit. Although multiple theories exist, and the polarizing behavior of slits near wavelength-scale is experimentally well-tested, the polarizing behavior of the generally wider spectrographic slits is less well-known and well-tested. We present a first step towards a new general model of the polarizing effects of slits based on waveguide theory and the eigenmode expansion that already shows the general expected behavior; linear polarization perpendicular to the slit’s long axis, as well as retardation effects with a similar perpendicular fast axis. Additionally, we tried to experimentally test the model’s predictions, but our setup proved insufficient. This was due to systematic errors, which could be removed using a different method, for which we provide suggestions.Show less
We measure the temperature dependent resistance of a niobium nitride (NbN) from room temperature to 4 K. The increasing resistance with decreasing temperature can be explained by tunneling of...Show moreWe measure the temperature dependent resistance of a niobium nitride (NbN) from room temperature to 4 K. The increasing resistance with decreasing temperature can be explained by tunneling of electrons between grain boundaries. Once the detector is in the superconducting regime single photon counts can be registered. We find an optimal setting of the trigger level of 0.2 V to register detection events while minimizing the influence of amplifier noise. From the measured voltage pulses we estimate a kinetic inductance of 200 nH for our devices. We explore the regime of high photon energies by plotting the count rate vs optical power on a double logarithmic scale. For photons with 500 nm wavelength the highest initial slope is equal to 2.6, indicating that detector tomography with 3 photon events realistic. Unfortunately, higher slopes are not observed and makes looking into detection events with more than 10 eV total energy difficult if not impossible.Show less
This thesis paper reports on the development of the Generalised Optical DifferentiationWavefront Sensor (g-ODWFS), a newly introduced wavefront sensor that relies on the polarisation of light to...Show moreThis thesis paper reports on the development of the Generalised Optical DifferentiationWavefront Sensor (g-ODWFS), a newly introduced wavefront sensor that relies on the polarisation of light to measure phase slopes and that may be well suited for applications such as high-contrast imaging. The wavefront sensor has been simulated through a computer model and its (broadband) performance has been analysed on the basis of sensitivity and dynamic range. Furthermore, a g-ODWFS prototype was designed, which has been successfully integrated in a high-speed closed-loop adaptive optics system in the lab.Show less
Chlorophyll-a concentrations are a widely used parameter for analysing and quantifying the quality of surface water. The procedure for determining it is a lengthy chemical process. This report...Show moreChlorophyll-a concentrations are a widely used parameter for analysing and quantifying the quality of surface water. The procedure for determining it is a lengthy chemical process. This report presents an alternative automated process for near-instant chl-a concentration determination through spectral analysis of water samples using quantification of characteristics in transmission signals.Show less
We used modern clean room technologies to produce thin nanopatterned superconductors in an aim to increase their critical temperature. These experiments are based on existing simulations which...Show moreWe used modern clean room technologies to produce thin nanopatterned superconductors in an aim to increase their critical temperature. These experiments are based on existing simulations which indicate that a large change in the electron-phonon coupling parameter lambda is attainable. The simulations were explored in an effort to find an optimal hole geometry and an attempt was made to extend them to a hexagonal lattice of atoms. We obtained ~50nm circular holes spaced 120nm on both MoGe and NbSe2 while also producing contacts to measure these small structures.Show less
In this thesis, the characterisation of the tunnelling current between two has been researched as well as the viability of nucleotide detection in a graphene nanogap. The results of IV- and Iz...Show moreIn this thesis, the characterisation of the tunnelling current between two has been researched as well as the viability of nucleotide detection in a graphene nanogap. The results of IV- and Iz-spectroscopy show reproducible tunnelling currents, confirming the viability of the graphene tunable nanogap. For nucleotide detection there are two promising techniques. The measurement of deviations in the tunnelling current or the investigation of conductance traces. However, no single nucleotide measurements have been performed, due to too long graphene etching, polymer contamination and too long RC time.Show less
The purpose of this research is to improve a quantum dot based single photon source (SPS) by double-pass filtering weak coherent light pulses. This means that a second excitation of the quantum dot...Show moreThe purpose of this research is to improve a quantum dot based single photon source (SPS) by double-pass filtering weak coherent light pulses. This means that a second excitation of the quantum dot is done with light that has previously been scattered off the quantum dot. A double pass through a quantum dot in a cavity has never been done before and this thesis provides the first steps towards this. This could eventually lead to improvements in photonic quantum gates and therefore also in the field of quantum circuits. The polarization configuration of the setup plays an important role because we have to excite the quantum dot efficiently, and we want to filter out all (coherent) background light. The measurements show evidence that this novel scheme is feasible, however we have not yet established a higher single photon purity with respect to the single pass system, which will be subject to future research.Show less
With the help of single-molecule fluorescence detection methods, optical studies have made many breakthroughs in the field of physics. Single-molecule fluorescence resonance energy transfer (FRET)...Show moreWith the help of single-molecule fluorescence detection methods, optical studies have made many breakthroughs in the field of physics. Single-molecule fluorescence resonance energy transfer (FRET) is one of the most generally applied techniques. In this thesis are the details of a setup described, which controls the potential electrochemically. Over 50 single blue copper azurin (CuAz) labeled with ATTO655 (position K122) were analyzed. Its properties, such as the midpoint potential (E0), the distribution of on- and off-times, and the autocorrelation are discussed.Show less
Recent advancements in imaging techniques have enabled the detection of thousands of exoplanets, as well as the characterization of a multitude of protoplanetary disks. These disks are believed to...Show moreRecent advancements in imaging techniques have enabled the detection of thousands of exoplanets, as well as the characterization of a multitude of protoplanetary disks. These disks are believed to form planets, but have mostly been observed around low mass T Tauri stars. No observations of disks around high mass Herbig Be stars exist, raising the question whether planets and especially giant planets can form there. Using archival data from VLT/SPHERE/IRDIS, one of the world’s best direct imagers for exoplanets and protoplanetary disks, we have attempted to image the disk of such a Herbig Be star, MWC147 (alias V700 Mon & HD259431). For this data reduction, a variety of correction techniques are demonstrated and compared against each other. The resulting images reveal the prescence of a second companion, dubbed MWC147 C, and a large bow shaped structure. Furthermore, a model of VLT/SPHERE/ZIMPOL was designed to quantify the effects of instrumental polarization and crosstalk on the polarimetric efficiency of the instrument. Finally, an observing proposal for VLT/SPHERE was written with the goal of obtaining better data of MWC147, such that the bow shaped structure and disk of MWC147 could be better characterized.Show less
A catalogue of a total of 171 galaxies, supplemented with their redshift, is created for three deep, blank fields observed by MUSE. Furthermore, a study of the physical properties of 65 low-mass...Show moreA catalogue of a total of 171 galaxies, supplemented with their redshift, is created for three deep, blank fields observed by MUSE. Furthermore, a study of the physical properties of 65 low-mass galaxies is performed for these fields. A model for the process of star formation in galaxies is discussed, and its parameters are constrained by observed data in the MUSE fields. Here, a relation between star formation rate (SFR) and stellar mass (M_*) of SFR / M_* ~ M_*^a with a = 0.72 +0.11-0.13 is found, with a redshift evolution of SFR / (1 + z) ~ b with b = 5.58 +3.0-2.8. The relation has an intrinsic scatter of s_intr = 0.61 +0.15-0.13. Lastly, the calibration techniques of the MUSE instrument are investigated, showing that the instrument is quite sensible to temperature changes.Show less
Source-free Maxwell equations admit three-dimensional solutions with a knotted optical vortex structure. The theoretical evidence naturally gives rise to the question: Could such peculiar fields...Show moreSource-free Maxwell equations admit three-dimensional solutions with a knotted optical vortex structure. The theoretical evidence naturally gives rise to the question: Could such peculiar fields also exist in nature and in particular, could they be created in a laboratory? Our main objective is to provide an analytic investigation of their characteristic properties, which will provide an insight in how their experimental synthesis could be achieved. A close examination reveals a saddle-shaped local polarization pattern that is transverse everywhere to the vortex line and a broad spectral decomposition. Although the latter feature contradicts the current experimental techniques and therefore complicates their realization; this thesis aims to bring the theory in closer contact with the experiment so to ensure that in the coming years it will be possible to witness an experimentally created knotted optical singularity.Show less
The search for topological insulators has intensified over the last couple of years. One of the candidates theorized to be a topological insulator are bilayers of bismuthene, the bismuth analogue...Show moreThe search for topological insulators has intensified over the last couple of years. One of the candidates theorized to be a topological insulator are bilayers of bismuthene, the bismuth analogue of graphene. During the bachelor project, multiple thin films of Bismuth were grown and their quality under the influence of underlying substrates of NaCl(001) and BaF2(111) has been investigated. Growth was achieved in a high vacuum Thermal Evaporator. The topography of substrates and grown films were analyzed using Atomic Force Microscopy. A large part of the project was focused on restoring a UHV system in which thin films could be grown and analyzed. This system will help improve the quality of the films and therefore improves the chances of producing a sufficiently large sample for electronic measurements. The cleaved barium-fluoride produces ultra-flat plateaus optimal for growth. The grains grown on the barium-fluoride substrates were larger in two-dimensional sizes than the grains grown on sodium-chloride. Further research is required to obtain the crystalline configuration of these grains.Show less
