Krypton assay in xenon at the ppq level using a gas chromatographic system and mass spectrometer

We have developed a new method to measure krypton traces in xenon at unprecedented low concentrations. This is a mandatory task for many near-future low-background particle physics detectors. Our system separates krypton from xenon using cryogenic gas chromatography. The amount of krypton is then quantified using a mass spectrometer. We demonstrate that the system has achieved a detection limit of 8 ppq (parts per quadrillion) and present results of distilled xenon with krypton concentrations below 1 ppt.Comment: 7 pages, 4 figure

Intrinsic 85Kr and 222Rn Backgrounds in the XENON Dark Matter Search

The XENON Dark Matter search is aiming for the direct detection of Dark Matter in the form of weakly interacting massive particles (WIMPs) scattering off xenon nuclei. This process is expected to be extremely rare, if at all existing. To be detectable, competing background has to be suppressed to unprecedented level. This defines the framework for this thesis. First, the data analysis is sketched that resulted in todays strongest limit on the spin-independent WIMPnucleon scattering for WIMP masses above 8 GeV/c2 using an exposure of 225 live days x 34 kg collected by the Xenon100 detector. For this analysis we develop a successfully employed consistency condition rejecting non-physical background. In the main part of this thesis, we investigate the intrinsic backgrounds 85Kr and 222Rn. To be sensitive to a potential WIMP signal, ultra-low concentrations have to be achieved in the liquid xenon target. We developed a method to determine krypton traces in xenon above a detection limit of only 6 parts per quadrillion (ppq) - two orders of magnitude below previous achievements. We prove that the cryogenic fractional distillation reaches a krypton level in xenon below 1 parts per tril (ppt). This represents a crucial proof-of-principle for the needs of the upcoming Xenon1T detector. Moreover, we present a 222Rn emanation assay of the Xenon100 detector and apply our results to cast projections on the future background handling in Xenon1T. Finally, we introduce two promising realizations of radon removal systems and argue for the utmost importance of 222Rn emanation assays

Determinants of Bicycle Crashes at Urban Signalised lntersections

Bicycle usage is increasing in urban (as well as rural) areas, which increases demand for better and safer infrastructure. Whilst the total number ofbicycle fatalities in European countries has been stable over the last ten years (:::: 2.000 fatalities per year for all European Union member states), bicycle fatalities and injuries in Germany have been increasing in this time. About two-thirds of all bicycle crashes in Germany occur at intersections, this proportion is highe:r than in Denmark and the N ethe:rlands (three-fi:fths). lntersections are tbus of high relevance for bicyclists' safety andin addition, they require sophisticated research methods because of their complex designs and the high numbers and types of uscr interactions and conflicts compared to street sections. This study analyses determinants of bicycle crashes at 269 signalised intersections in two major eitles in Germany (Dresden, Munich) as the basis for developing evidence-based recomm.endations for improving bicyclists' safety at existing intersections and for ensuring high safety levels at newly planned intersections from the very beginning. This study is part ofthe research project SiRou (nrvp.de/21520). The project is funded by the German Federal Ministry for Digital and Transport within the National Cycling Plan 2020(NRVP)

Detection of 133^{133}Xe from the Fukushima nuclear power plant in the upper troposphere above Germany

After the accident in the Japanese Fukushima Dai-ichi nuclear power plant in March 2011 large amounts of radioactivity were released and distributed in the atmosphere. Among them were also radioactive noble gas isotopes which can be used as tracers to test global atmospheric circulation models. This work presents unique measurements of the radionuclide $^{133}$Xe from Fukushima in the upper troposphere above Germany. The measurements involve air sampling in a research jet aircraft followed by chromatographic xenon extraction and ultra-low background gas counting with miniaturized proportional counters. With this technique a detection limit of the order of 100 $^{133}$Xe atoms in litre-scale air samples (corresponding to about 100 mBq/m$^3$) is achievable. Our results provide proof that the $^{133}$Xe-rich ground level air layer from Fukushima was lifted up to the tropopause and distributed hemispherically. Moreover, comparisons with ground level air measurements indicate that the arrival of the radioactive plume at high altitude over Germany occurred several days before the ground level plume.Comment: 8 pages, 5 figure

Rigidity of plasticizers and their miscibility in silica-filled polybutadiene rubber by broadband dielectric spectroscopy

An efficient use of plasticizers in rubber compounds requires an understanding of their miscibility behavior. Besides the chemical properties of both rubber and plasticizer, the rigidity of the plasticizer plays an important role for their miscibility. The miscibility is investigated here using the glass transition measured by differential scanning calorimetry and broadband dielectric spectroscopy (BDS). Additionally, the interfacial relaxation and phase separation measured by BDS are confirmed by transmission electron microscopy. While the flexible plasticizer, poly-(α-methylstyrene), stays miscible in a silica-filled polybutadiene rubber compound, the more rigid plasticizer, indene-coumarone (IC), shows a phase separation at high concentrations. The phase-separated IC tends to accumulate at the silica surface

DELight: a Direct search Experiment for Light dark matter with superfluid helium

To reach ultra-low detection thresholds necessary to probe unprecedentedly low Dark Matter masses, target material alternatives and novel detector designs are essential. One such target material is superfluid $^4$He which has the potential to probe so far uncharted light Dark Matter parameter space at sub-GeV masses. The new ``Direct search Experiment for Light dark matter'', DELight, will be using superfluid helium as active target, instrumented with magnetic micro-calorimeters. It is being designed to reach sensitivity to masses well below 100\,MeV in Dark Matter-nucleus scattering interactions.Comment: IDM2022 proceedings submitted to SciPos

Graph-based collaboration analysis of an agile medical engineering project with structural metrics

Agile development approaches are gaining popularity in hardware product development and medical engineering. Consequently, techniques of structural complexity management can be applied on agile projects. This paper analyses the collaboration data of a twelve-month project to design a 3D-printed microtiter plate. Exchanged e-mails, created artifacts, and conducted tasks were analyzed to identify typical barriers of inter-disciplinary collaboration. Appropriate improvement measures to overcome these barriers were suggested and evaluated in a four-hour workshop with members of the core team of the project. As a result, out of the collaboration network with 851 nodes and 9001 edges, six main barriers were identified. The most hindering barriers according to the experts' opinion were matched with appropriate improvement measures. After an assessment of the cost/benefit ratio, two measures were chosen for implementation