Engaging Physics Tutoring: A didactical toolbox for teaching assistants (TAs)

[EN] In this paper we present a project dedicated to the development of a didactical toolbox of material for teaching assistants (TAs) supervising exercise classes for non-physics majors at ETH Zurich. With our materials we were able to support TAs in preparing high-quality exercise sessions for their class which go beyond direct instruction and activate students intellectually and emotionally. The materials are developed for 13 exercise sessions and are presented in the form of an eBook. The materials were immediately used by several TAs in dedicated focus groups. The positive feedback of students and TAs suggests that our material helped to activate and engage the students, enhancing their learning - even in the challenging setting of online teaching.The EPT project was supported by the ETH Zurich Rector’s Impulse Fund.Bondar, V.; Nuber, J.; Zeyen, M.; Schiltz, G.; Dissertori, G. (2021). Engaging Physics Tutoring: A didactical toolbox for teaching assistants (TAs). En 7th International Conference on Higher Education Advances (HEAd'21). Editorial Universitat Politècnica de València. 9-16. https://doi.org/10.4995/HEAd21.2021.12949OCS91

Passive alignment stability and auto-alignment of multipass amplifiers based on Fourier transforms

The stability properties of Fourier-based multipass amplifier to misalignments (tilts) of its optical components has been investigated. For this purpose, a method to quantify the sensitivity to tilts based on the amplifier small signal gain has been elaborated and compared with measurements. To improve on the tilt stability by more than an order of magnitude a simple auto-alignment system has been proposed and tested. This study, combined with other investigations devoted to the stability of the output beam to variations of aperture and thermal lens effects of the active medium, qualifies the Fourier-based amplifier for the high-energy and the high-power sector.Comment: 10 pages, 11 figure

Studies of muonium emission into vacuum and diffusion of muonic hydrogen in the μp hyperfine splitting experiment at PSI

Muonium (M = µ⁺ + e⁻) and muonic hydrogen (µp p⁺ + µ⁻) are exotic versions of the hydrogen atom, in which the proton or electron are replaced with an antimuon or a muon respectively. In muonium, the antimuon serves as a leptonic nucleus without any measurable size or electro-magnetic sub-structure, which makes it an excellent atomic system for precision tests of quantum electrodynamics and indirect searches for new physics. Muonic hydrogen, on the other hand, is eminently suited for precision studies of the proton’s internal structure, to which its atomic states are more sensitive due to the larger mass of the muon compared to the electron. Currently, a number of fundamental physics experiments with M and µp atoms are in preparation at the Paul Scherrer Institute (PSI). Although these experiments may have implications for physics at high energy scales, their measurement principles all involve low-energy processes, such as exotic atoms diffusing through the target after formation or travelling through vacuum at thermal energies. This thesis is mainly concerned with such low-energy processes and presents studies of the emission of M atoms from target samples at room temperature, as well as simulations of the diffusion of µp atoms through hydrogen gas. The LEMING Collaboration is currently preparing an experiment at PSI with the aim of measuring the gravitational interaction of muonium atoms with the Earth. While much effort in recent years has been dedicated to the development of a cryogenic muonium source using superfluid helium, additional measurements of muonium emission into vacuum from conventional target samples were carried out at room temperature during test beams in 2018 and 2020. The room-temperature measurement in 2018 was carried out before the start of this PhD thesis. Detection of M decays in vacuum was performed using small scintillator bars to detect decay positrons in combination with a system to accelerate and detect the atomic electrons in coincidence. In 2020, two different roomtemperature setups were used, which had both been developed within this PhD project. One of these setups featured an optimized arrangement of scintillator bars to detect M decays with increased efficiency and without the need for an atomic electron detection system. The other setup contained two Micromegas tracking detectors used in a telescope configuration to obtain an image of the cloud of M decays in vacuum. In this thesis, the three room-temperature studies are discussed and analyses of the measured data are presented. Comparing measured data with simulations, emission characteristics of the tested laser-ablated aerogel samples and zeolite samples are examined and muon-tovacuum-muonium conversion efficiencies are extracted. With that, this thesis contributes to the research field investigating muonium emission from novel target materials. For the development of a cryogenic muonium source with superfluid helium, elastic scattering of M atoms with ⁴He atoms in the gas phase must be taken into account. A measurement of the scattering strength was pursued during the test beam in 2018 by observing M emission into low-density helium gas. Within this thesis, calculations of the elastic cross sections for M–⁴He scattering are carried out assuming an empirical interaction potential. The cross sections were used for the implementation of M–⁴He scattering simulations in G4BEAMLINE. Within uncertainties, good agreement between the simulations and measured data provide validation of the calculated cross sections and the underlying scattering potential. Another experiment which is currently being prepared at PSI is a measurement of the ground-state hyperfine splitting (HFS) in muonic hydrogen. This is part of a comprehensive effort by the CREMA Collaboration to further the understanding of the proton structure with laser spectroscopy experiments using muonic atoms. In this particular experiment, negative muons are stopped in a cryogenic hydrogen gas target and form µp atoms, which then diffuse through the target. µp atoms reaching one of the gold-coated target walls lead to muonic gold x rays which can be measured outside the target cell. Exciting the diffusing µp atoms with a laser on the resonance frequency of the HFS transition increases their probability of reaching one of the walls. A peak in the x-ray yield consequently occurs at the resonance frequency and thus allows for precise determination of the desired HFS transition frequency. In the scope of this thesis, simulations of the µp diffusion process through the hydrogen gas were implemented and carried out in G4BEAMLINE. These simulations use differential cross sections for the scattering of µp atoms with hydrogen molecules which were calculated by a collaborator. In combination with inputs of theoretical and experimental origin, the diffusion simulations are used to predict the event rates of signal and background to be expected in the measurement. Based on these rates, the measurement time needed to find the resonance and the precision which can be reached in the measurement are estimated. With that, the simulations provide important input for the planning of the measurement campaign and for the further development of the experimental system

Engaging Physics Tutoring: A didactical toolbox for teaching assistants (TAs)

In this paper we present a project dedicated to the development of a didactical toolbox of material for teaching assistants (TAs) supervising exercise classes for non-physics majors at ETH Zurich. With our material we were able to support TAs in preparing high-quality exercise sessions for their class which go beyond direct instruction and activate students intellectually and emotionally. The materials are developed for 13 exercise sessions and are presented in the form of an eBook. The materials were immediately used by several TAs in dedicated focus groups. The positive feedback of students and TAs suggests that our material helped to activate and engage the students, enhancing their learning - even in the challenging setting of online teaching

Radar imaging system for in-service wind turbine blades inspections : initial results from a field installation at a 2 mw wind turbine

This paper presents an imaging radar system for structural health monitoring (SHM) of wind turbine blades. The imaging radar system developed here is based on two frequency modulated continuous wave (FMCW) radar sensors with a high output power of 30 dBm. They have been developed for the frequency bands of 24,05 GHz-24,25 GHz and 33.4 GHz-36.0 GHz, respectively. Following the successful proof of damage detection and localization in laboratory conditions, we present here the installation of the sensor system at the tower of a 2 MW wind energy plant at 95 m above ground. The realization of the SHM-system will be introduced including the sensor system, the data acquisition framework and the signal processing procedures. We have achieved an imaging of the rotor blades using inverse synthetic aperture radar techniques under changing environmental and operational condition. On top of that, it was demonstrated that the front wall and back wall radar echo can be extracted from the measured signals demonstrating the full penetration of wind turbine blades during operation

Room-temperature emission of muonium from aerogel and zeolite targets

Novel emitters of muonium (Mu = μ+ + e−) with high conversion efficiencies can enhance the precision of muonium spectroscopy experiments and enable next-generation searches for new physics. At the Paul Scherrer Institute (PSI), we investigate muonium production at room-temperature as well as in cryogenic environment using a superfluid helium converter. In this paper, we describe the development of compact detection schemes which resulted in the background-suppressed observation of atomic muonium in vacuum, and can be adapted for cryogenic measurements. Using these setups, we compared the emission characteristics of various muonium production targets at room temperature using low momentum (pμ = 11–13 MeV/c) muons, and observed muonium emission from zeolite targets into vacuum. For a specific laser-ablated aerogel target, we determined a muon-to-vacuum-muonium conversion efficiency of 7.23 ± 0.05(stat)+1.06 −0.76(sys) %, assuming thermal emission of muonium. Moreover, we investigated muonium-helium collisions and from it we determined an upper temperature limit of 0.3 K for the superfluid helium converte.ISSN:1094-1622ISSN:0556-2791ISSN:1050-294

Development of next generation muon beams at the Paul Scherrer Institute

The Paul Scherrer Institute (PSI) provides the world's highest intensity muon beam of $\mathcal{O}(10^{8})\,\mu^{+}/$s at 28$\,$MeV/c. The HiMB project aims to improve this rate by two orders of magnitude. Meanwhile, the muCool collaboration is developing a device which converts a standard surface $\mu^{+}$ beam of cm-size and MeV-energy into a beam of 1$\,$mm-size and 1$\,$eV energy spread by achieving a compression of 6-dimensional phase space by 10 orders of magnitude with an efficiency of $10^{-3}$

Muonic atom spectroscopy with microgram target material

Muonic atom spectroscopy–the measurement of the x rays emitted during the formation process of a muonic atom–has a long standing history in probing the shape and size of nuclei. In fact, almost all stable elements have been subject to muonic atom spectroscopy measurements and the absolute charge radii extracted from these measurements typically offer the highest accuracy available. However, so far only targets of at least a few hundred milligram could be used as it required to stop a muon beam directly in the target to form the muonic atom. We have developed a new method relying on repeated transfer reactions taking place inside a 100 bar hydrogen gas cell with an admixture of 0.25% deuterium that allows us to drastically reduce the amount of target material needed while still offering an adequate efficiency. Detailed simulations of the transfer reactions match the measured data, suggesting good understanding of the processes taking place inside the gas mixture. As a proof of principle we demonstrate the method with a measurement of the 2p-1s muonic x rays from a 5 μ g gold target