Lab results on the refractive index of astrophysically relevant ices are essential for the interpretation of astronomical observations. Previous refractive index measurements have been limited to...Show moreLab results on the refractive index of astrophysically relevant ices are essential for the interpretation of astronomical observations. Previous refractive index measurements have been limited to selective wavelengths (λ) and deposition pressures (Tdep). The Optical Absorption Setup for Ice Spectroscopy (OASIS) combines thin film interferometry with a broadband light source emitting in the UV-vis regime. The addition of a broadband light source into the setup, allows for the simultaneous determination of n(λ) (for 300nm < λ < 800nm). Measurements on the wavelength dependent refractive index of CO2, CO and N2 ices have been performed. Additionally modifications to the setup have been made, allowing for the deposition of mixed ices. This thesis presents the results on CO2 ices deposited between 7.5 K and 80 K, CO ices deposited between 7.5 K and 15 K, and lastly N2 ices deposited at 7.5 K. The refractive indices obtained, are in agreement with the literature data. In the discussion a comparison on the values can be found alongside a discussion of the astrophysical implications. We conclude that the refractive index results obtained using OASIS are reliable and promising for future work regarding mixed ices and the interpretation of astronomical observations.Show less
To study fluctuating two-level spin systems, which limit performance of nanodevices, MRFM (magnetic resonance force microscopy) is a technique with a high potential. MRFM detects spins by measuring...Show moreTo study fluctuating two-level spin systems, which limit performance of nanodevices, MRFM (magnetic resonance force microscopy) is a technique with a high potential. MRFM detects spins by measuring their coupling to a micrometer sized magnet at the tip of a soft cantilever, leading to a shift in resonance frequency and quality factor. In this thesis, we present easyMRFM, a probe-head design for a SQUID-detected MRFM, operating at cryogenic temperatures. We determine a coupling-free resonance frequency of f0 = 393.42134 Hz ± 0.06 mHz and a quality factor of Q = (3.50 ± 0.03) · 104, and determined the temperature dependence thereof. An experiment is proposed and set up to detect the temperature dependent shift in these parameters, induced by spin-magnet coupling to a copper sample, thus realising easyMFM (magnetic force microscopy). A lower and upper limit for the coupling of cantilever deflection to measured signal are experimentally determined at 0.022 mV/μm < dVsignal dx < 0.486 mV/μm.Show less
β−decay is associated with emitting or absorbing an electron (anti)neutrino. By measuring the energies of the other particles involved, the energy of the neutrino can be deduced and with that its...Show moreβ−decay is associated with emitting or absorbing an electron (anti)neutrino. By measuring the energies of the other particles involved, the energy of the neutrino can be deduced and with that its mass. It is proposed to isolate an isotope in a solid-state structure, e.g. graphene or fullerene and to study the detection spectrum from β−decay inside the isotope’s nucleus [E. Baracchini et al., arXiv:1808.01892]. The energy uncertainty due to the zero-point motion of the most popular isotope candidate, Tritium, has been proved to be too great for a feasible experiment [Y. Cheipesh, V. Cheianov, A. Boyarsky, Phys. Rev. D 104, 116004, (2021)]. There is, however, no theoretical objection to heavier isotopes as β−emitters in the experiment. In this thesis, the energy uncertainty (or equivalently the lifetime) of heavier isotopes due to the coupling to graphene is estimated. Also, the influence of the lifetime on the spectrum is studied.Show less
A unique method of measuring compounds in the atmosphere of exoplanets is proposed which uses the polarized light caused by the rainbow effect across the orbit of the planet. This process is...Show moreA unique method of measuring compounds in the atmosphere of exoplanets is proposed which uses the polarized light caused by the rainbow effect across the orbit of the planet. This process is modeled and the feasibility of using this method on exoplanets is examined. We have modeled the light reflected by the lava exoplanet 55 Cnc e for three possible atmospheres, namely for atmospheres consisting of the compounds SiO 2 , SiO or MgO. We found that for each compound, a signal in one wavelength can be measured within measuring 30 hours. A signal in a second wavelength, which can be used to characterize the compounds, can be measured within 70 hours. These measurements could take up to 50 respectively 250 days to complete. These results could be improved greatly when inclined systems are taken into consideration.Show less
This paper considers how the SND neutrino detector at the Large Hadron Collider, CERN, may probe light dark matter. To this end, the leptophobic portal is considered (mostly with a dark matter mass...Show moreThis paper considers how the SND neutrino detector at the Large Hadron Collider, CERN, may probe light dark matter. To this end, the leptophobic portal is considered (mostly with a dark matter mass of 20 MeV). After a review of the sensitivity of the current SND configurations, two alternative configurations are considered: one in the same pseudorapidity range as the current experiment, the other further off-axis. While the former will have a higher sensitivity than the current experiment, for the latter this depends on the mediator mass. For a mediator mass of 7 GeV, the sensitivity of the off-axis configuration is higher than the sensitivity of the current experiment and the other alternative configuration.Show less
In this thesis we look at the frequency dependent properties of a scanning tun- neling Microscope (STM) where both the tip and the sample are superconduc- tors. In that case, the tip-sample system...Show moreIn this thesis we look at the frequency dependent properties of a scanning tun- neling Microscope (STM) where both the tip and the sample are superconduc- tors. In that case, the tip-sample system is considered an ultra-small Josephson junction. The junction has been modelled as an electrical circuit consisting of a capacitive component C, a kinetic inductive component Lk as well as a Josephson inductive component LJ, also called ‘the LC-ciruit model’. Furthermore, the or- der of magnitude of the parameters have been estimated. We found values for C ranging between ∼ 10−13 − 10−17F, Lk between ∼ 10−13 − 10−9H and LJ around ∼ 10−8 − 10−7H. Finally, we simulated the LC-circuit and found that measuring the resonance frequency ωc might be a way to determine the superfluid density n of superconductors.Show less
KM3NeT is a research infrastructure consisting of two neutrino detectors in the Mediterranean Sea. The ARCA detector searches for high-energy cosmic neutrinos, whereas with ORCA the fundamental...Show moreKM3NeT is a research infrastructure consisting of two neutrino detectors in the Mediterranean Sea. The ARCA detector searches for high-energy cosmic neutrinos, whereas with ORCA the fundamental properties of neutrinos are studied. Three possible biases in the detection efficiencies for ORCA and ARCA are investigated. Light from radioactive nearby K-40 decay compared to isotropic light from far away, and anisotropic light emitted by muons compared to simulated muon light are used to examine these biases for wavelength- and angular dependency. Firstly, certain DOMs in ARCA and ORCA show a lower efficiency due to a different gel transparency in the PMTs. Shadowing effects cause a bias in both ORCA (10%) and ARCA (14%). Finally, the sedimentation on top of ARCA DOMs affects the detection efficiencies in a different way than it does on ORCA DOMs.Show less
In hopes of understanding the universe we inhabit, scientists search for signals from the universe that could give as clues about its nature. When these signals are composed of particles, they are...Show moreIn hopes of understanding the universe we inhabit, scientists search for signals from the universe that could give as clues about its nature. When these signals are composed of particles, they are given the name of ”cosmic rays”. Once cosmic rays have reached our atmosphere, they interact with molecules there, creating pions and kaons that decay into muons and neutrinos. Studying these, we can deepen our knowledge and understanding of the universe. It is in the interest of this that this thesis explores the effect of seasonal changes in temperature on the rate of atmospheric muons that reaches the ARCA site of KM3NeT, a neutrino telescope being built in the Mediterranean sea. Exploiting their depth dependence we were able to establish a new method to quantify a muon rate, allowing the investigation of different energy ranges through the filtering of certain coincidences. After fitting these curves to an exponential decay, the fit parameters were extracted and compared to the temperatures in different pressure levels of the atmosphere. This showed a weak negative correlation for the normalization factor and a moderate positive correlation for the slope. For lower energies, the relationship between the slope and temperature was proportional by a factor αT = 0.0029 ± 0.00012. For higher energies, this proportionality was given by αT = 0.0051 ± 0.00034. Due to the weak correlation exhibited, no constant of proportionality was found for the normalization factor.Show less
Mechanical metamaterials are well suited to study pathways, consisting of sequences of discrete snapping events. Here we focus on a biholey metamaterial, which consists of a thick slab of rubber...Show moreMechanical metamaterials are well suited to study pathways, consisting of sequences of discrete snapping events. Here we focus on a biholey metamaterial, which consists of a thick slab of rubber patterned with circular holes. We ‘program’ the behavior of the metamaterial by confining it in the horizontal direction with adjustable clamps, and investigate the mechanical response to vertical compression [2]. First, we explored a single clamp with variable confinement, and find that while we can control the hysteresis loop in this system, as a function of the confinement the material switches between two distinct branches of behavior. We show that this is due to a switch between two flavors of spontaneous left-right symmetry breaking. Second, we introduce a range of clamping methods that explicitly break the left-right symmetry, and achieve better control of the hysteretic behavior of the material under compression.Show less
In this work, magnetic tweezers were used to study the locomotion of active particles in bulk. For this purpose half platinum-coated magnetic spherical Janus particles were suspended in a 5% H2O2...Show moreIn this work, magnetic tweezers were used to study the locomotion of active particles in bulk. For this purpose half platinum-coated magnetic spherical Janus particles were suspended in a 5% H2O2 solution, by which active locomotion was induced. The substrate-particle distance was varied by means of a magnetic field in a magnetic tweezers set-up. By recording the diffraction pattern and the (x,y) positions of these particles during locomotion, the velocity and translational diffusion coefficients were calculated from their Mean-Squared Displacement (MSD) and compared to near-wall locomotion. Although not enough data was gathered to draw conclusions on the influence of the wall on the locomotion of the particles, the applied method appears promising to do so in future research. Namely, it is shown that the magnetic particles can clearly be elevated and be retained in a range of height in bulk. The method is discussed extensively and suggestions for improvements or other approaches are given in the discussion.Show less
KM3NeT is a European research infrastructure hosting the new generation of neutrino telescopes. It is currently under construction and consists of two detectors. This report investigates data from...Show moreKM3NeT is a European research infrastructure hosting the new generation of neutrino telescopes. It is currently under construction and consists of two detectors. This report investigates data from six already deployed units of the ORCA detector to provide a characterisation of the detector efficiencies. The isotropic efficiencies used in the Monte Carlo simulation and estimated from 40K decays are compared to anisotropic efficiency measures based on light created by muons. Shadowing effects are shown to create a bias of approximately 5% in the detected number of photons. The simulation underestimates the amount of direct light and overestimates the amount of indirect light. The latter is likely the result of an overestimation of the muon bundle multiplicity. A comparison between the reference simulation and one that assumes 5% more absorption shows a preference for more absorption for larger distances and time residuals.Show less
