arXiv subjects

Lukas Mandok

Publications and source records attributed to Lukas Mandok.

4 recordsLinked to original sources

arXiv2025

New Frontiers in Muon-Spin Spectroscopy Using Si-Pixel Detectors

The study of novel quantum materials relies on muon-spin rotation, relaxation, or resonance (\mSR) measurements. Yet, a fundamental limitation persists: many of these materials can only be synthesized in extremely small quantities, often at sub-millimeter scales. While \mSR ~offers unique insights into electronic and magnetic properties, existing spectrometers lack a sub-millimeter spatial resolution and the possibility of triggerless pump-probe data acquisition, which would enable more advanced measurements. The General Purpose Surface-muon instrument (GPS) at the Paul Scherrer Institute (PSI) is currently limited to a muon stopping rate of \SI{40}{\kilo\hertz} to \SI{120}{\kilo\hertz}, a constraint that will become more pressing with the upcoming High-Intensity Muon Beam (HIMB) project. To overcome these challenges, we demonstrate the feasibility of employing ultra-thin monolithic Si-pixel detectors to reconstruct the stopping position of muons within the sample, thereby significantly enhancing the capability of measuring at higher muon rate. Additionally, we explore the first steps toward a triggerless pump-probe \mSR ~measurement scheme. Unlike conventional pump-probe techniques that require external triggers, a triggerless readout system can continuously integrate stimuli pulses into the data stream, allowing real-time tracking of ultra-fast dynamics in quantum materials. This approach will enable the study of transient states, spin dynamics, and quantum coherence under external stimuli.

physics.ins-det↗

arXiv2025

Advanced muon-spin spectroscopy with high lateral resolution using Si-pixel detectors

Muon-spin spectroscopy at continuous sources has stagnated at a stopped muons rate of ~40 kHz for the last few decades. The major limiting factor is the requirement of a single muon in the sample during the typical 10 {\mu}s data gate window. To overcome this limit and to be able to perform muon-spin relaxation ({\mu}SR) measurements on millimeter-sized samples, one can use vertex reconstruction methods to construct {\mu}SR spectra. This is now possible thanks to the availability of very thin monolithic Si-pixel chips, which offer minimal particle scattering and high count rate. Here we present results from a Si-pixel based spectrometer that utilizes vertex reconstruction schemes for the incoming muons and emitted positrons. With this spectrometer we were able to obtain a first vertex reconstructed {\mu}SR (VR-{\mu}SR) spectrum. The unique capabilities and benefits of such a spectrometer are discussed.

physics.ins-det↗

arXiv2023

An ultra-light helium cooled pixel detector for the Mu3e experiment

The Mu3e experiment searches for the lepton flavour violating decay $μ^+ \rightarrow e^+ e^- e^+$ with an ultimate aimed sensitivity of $1$ event in $10^{16}$ decays. To achieve this goal, the experiment must minimize the material budget per tracking layer to $X/X_0\approx 0.1\,\%$ and use gaseous helium as coolant. The pixel detector uses High-Voltage Monolithic Active Pixel Sensors (HV-MAPS) which are thinned down to $50\, μm$. Both helium cooling and HV-MAPS are a novelty for particle detectors. Here, the work on successfully cooling a pixel tracker using gaseous helium is presented. The thermal studies focus on the two inner tracking layers, the Mu3e vertex detector, and the first operation of a functional thin pixel detector cooled with gaseous helium. The approach, which circulates gaseous helium under ambient pressure conditions with a gas temperature around $0\,°C$ using a miniature turbo compressor with a mass flow of $2\,g/s$ allows the vertex detector to operate below $70\,°C$ at heat densities of up to $350\,mW/cm^2$. Finally, performance data of the final HV-MAPS used by Mu3e, the MuPix11, is presented. These results demonstrate the feasibility of using HV-MAPS combined with gaseous helium as a coolant for an ultra-thin pixel detector exploring new frontiers in lepton flavor.

physics.ins-det↗

arXiv2020

MuPix10: First Results from the Final Design

Many years of research and development of High Voltage Monolithic Active Pixel Sensors (HVMAPS) have culminated in the final design for the Mu3e pixel sensor. MuPix10 is a fully monolithic sensor with an active pixel matrix size of $20\times20\,\mathrm{mm}^2$ produced in the $180\,\mathrm{nm}$ HV-CMOS process at TSI Semiconductors. The pixel size is $80\times80\,\mathrm{μm}^2$. Hits are read out using a column-drain architecture and sent over up to four serial links with up to $1.6\,\left.\mathrm{Gbit}\middle/\mathrm{s}\right.$ each. By means of DC/DC converters and exclusive usage of on-chip biasing, MuPix10 is fully operable with a minimal set of electrical connections. This is an integral requirement by the Mu3e experiment since it enables the construction of ultra-thin pixel modules with $0.1\,$% of a radiation length per layer. First results from lab characterisation and testbeam campaigns are presented.

physics.ins-det↗