Optimum filter-based analysis for the characterization of a high-resolution magnetic microcalorimeter towards the DELight experiment

Ultra-sensitive cryogenic calorimeters have become a favored technology with widespread application where eV-scale energy resolutions are needed. In this article, we characterize the performance of an X-ray magnetic microcalorimeter (MMC) using a Fe-55 source. Employing an optimum filter-based amplitude estimation and energy reconstruction, we demonstrate that an unprecedented FWHM resolution of $ΔE_{FWHM}=(1.25±0.17(stat)^{+0.05}_{−0.07}(syst))eV$ can be achieved. We also derive the best possible resolution and discuss limiting factors affecting the measurement. The analysis pipeline for the MMC data developed in this paper is furthermore an important step for the realization of the proposed superfluid helium-based experiment DELight, which will search for direct interaction of dark matter with masses below 100 MeV/c$^2$

Activation Energy of Hydrogen–Methane Mixtures

In this work, the overall activation energy of the combustion of lean hydrogen–methane–air mixtures (equivalence ratio = 0.7−1.0 and hydrogen fraction in methane =0, 2, 4) is experimentally determined using thin-filament pyrometry of flames stabilised on a flat porous burner under normal conditions (=1 bar, T = 20 °C). The experimental data are compared with numerical calculations within the detailed reaction mechanism GRI3.0 and both approaches confirm the linear correlation between mass flow rate and inverse flame temperature predicted in the theory. An analysis of the numerical and experimental data shows that, in the limit of lean hydrogen–methane–air mixtures, the activation energy approaches a constant value, which is not sensitive to the addition of hydrogen to methane. The mass flow rate for a freely propagating flame and, thus, the laminar burning velocity, are measured for mixtures with different hydrogen contents. This mass flow rate, scaled over the characteristic temperature dependence of the laminar burning velocity for a one-step reaction mechanism, is found and it can also be used in order to estimate the parameters of the overall reaction mechanisms. Such reaction mechanisms will find implementation in the numerical simulation of practical combustion devices with complex flows and geometries

Some remarks on load modeling in nonlinear structural analysis–Statics with large deformations–Consistent treatment of follower load effects and load control

Load modeling in nonlinear statics, particularly incorporating large deformations differs significantly from the treatment in linear analysis. As in structural dynamics masses in a gravity field generate the loading, their location, and their modifications within the deformation process must be considered in a nonlinear simulation. A specific view besides loading by masses is on gas and fluid interaction with structures. In addition, load control using specifically designed algorithms is evaluated with respect to realistic applications. Within the load modeling an unavoidable, however side aspect, is the general discussion about the so-called follower forces and non-conservative loading. As an example of real-world applications, the specifics of inflated rubber dams are presented

A fresh look at the nested soft-collinear subtraction scheme: NNLO QCD corrections to N-gluon final states in qq‾q\overline{q} annihilation

We describe how the nested soft-collinear subtraction scheme [1] can be used to compute the next-to-next-to-leading order (NNLO) QCD corrections to the production of an arbitrary number of gluonic jets in hadron collisions. We show that the infrared subtraction terms can be combined into recurring structures that in many cases are simple iterations of those terms known from next-to-leading order. The way that these recurring structures are identified and computed is fairly general, and can be applied to any partonic process. As an example, we explicitly demonstrate the cancellation of all singularities in the fully-differential cross section for the $q\overline{q}$ → X + Ng process at NNLO in QCD. The finite remainder of the NNLO QCD contribution, which arises upon cancellation of all ϵ-poles, is expressed via relatively simple formulas, which can be implemented in a numerical code in a straightforward way. Our approach can be extended to describe arbitrary processes at NNLO in QCD; the largest remaining challenge at this point is the combinatorics of quark and gluon collinear limits

Magnetic Microcalorimeters for Primary Activity Standardization Within the EMPIR Project PrimA-LTD

The precision of existing decay data of radionuclides for activity determination is often a limitation for actual applications in science, society and industry. For this reason, the EMPIR project PrimA-LTD aims to introduce an advanced primary activity standardization technique that is based on magnetic microcalorimeters (MMCs) and that will offer very low energy threshold of few eV and a decay scheme-independent detection efficiency close to 100 %. As a proof of concept, we developed two MMC-based detector types in order to standardize an -decaying, a -decaying and an electron capture decaying isotope. One detector type aims to introduce a reusable detector setup, while the other aims to provide highly accurate decay spectra by high-resolution measurements with high statistics. We present the designs, fabrication status and first characterization measurements of both detectors types and outline next steps

Vision through Obstacles—3D Geometric Reconstruction and Evaluation of Neural Radiance Fields (NeRFs)

In this contribution we evaluate the 3D geometry reconstructed by Neural Radiance Fields (NeRFs) of an object’s occluded parts behind obstacles through a point cloud comparison in 3D space against traditional Multi-View Stereo (MVS), addressing the accuracy and completeness. The key challenge lies in recovering the underlying geometry, completing the occluded parts of the object and investigating if NeRFs can compete against traditional MVS for scenarios where the latter falls short. In addition, we introduce a new “obSTaclE, occLusion and visibiLity constrAints” dataset named STELLA concerning transparent and non-transparent obstacles in real-world scenarios since there is no existing dataset dedicated to this problem setting to date. Considering that the density field represents the 3D geometry of NeRFs and is solely position-dependent, we propose an effective approach for extracting the geometry in the form of a point cloud. We voxelize the whole density field and apply a 3D density-gradient based Canny edge detection filter to better represent the object’s geometric features. The qualitative and quantitative results demonstrate NeRFs’ ability to capture geometric details of the occluded parts in all scenarios, thus outperforming in completeness, as our voxel-based point cloud extraction approach achieves point coverage up to 93%. However, MVS remains a more accurate image-based 3D reconstruction method, deviating from the ground truth 2.26 mm and 3.36 mm for each obstacle scenario respectively

Validation of the dynamic simulation capabilities of Serpent2/Subchanflow using experimental data from the research reactor SPERT IV D-12/25

Research nuclear reactors are critical to the development of nuclear technology, but because of the complex configuration of the fuel assemblies and the different initial operating conditions, neutronic and thermal–hydraulic analyzes are performed with dedicated or adapted codes. These simulation tools might not be as accurate, since they use simple resolution methods and assumptions that do not always capture all aspects of the behavior of a nuclear research reactor. On the other hand, as time goes by, the evolution of numerical tools for the core analysis of power reactors have experienced a considerable progress. Nowadays, pin/subchannel level analysis of the core with coupled codes based on transport (SP3, MOC, SN, etc.) or Monte Carlo methods are applied in addition to the nodal diffusion codes. Hence, the research community is adapting and validating selected high-fidelity tools developed for power reactors to perform detail core analysis of e.g. Material Testing Reactors (MTR) cores at plate and subchannel level. This work deals with the validation of the high-fidelity coupled Serpent2/Subchanflow, which was modified and extended for the plate/subchannel analysis of MTR-cores, using the data of rod ejection tests performed in the SPERT IV D-12/25 reactor, especially the tests B-34 and B-35 were selected to validate the dynamic capability of Serpent2/Subchanflow. In these unique tests, experimental data e.g. thermal neutron flux, core power evolution during the rod ejection tests, and the plate cladding temperature was measured. It is noted that, due to the lack of detailed information on the initial conditions, the extraction and introduction scenarios of the transient rod for the reactivity insertion required calibrations and assumptions regarding velocity and position. The comparison of selected parameters predicted by the coupled simulations at plate/subchannel level of the SPERT IV reactor with the measured data at static and transient conditions shows excellent agreement confirming the high accuracy appropriateness of the used code for the analysis of research reactors. The calculated values of thermal neutron flux and core power evolution have a statistical error of 2 sigma. It was also found that the maximum temperature difference between calculated and experimental values is 7 °C and ∼ 10 °C for tests B-34 and B-35, respectively. In addition, the coupled code predicts for the first time the temperature of each plate and subchannel considering the local feedbacks between neutronics and thermal-hydraulics allowing the identification of the hottest/coldest plate in the core. The high-fidelity validation tool can provide comparison solutions for current research reactor core analysis methods, such as core analysis with point kinetics or 3D nodal diffusion codes coupled with fuel assembly-level thermal-hydraulics

Seltene Erden : Rohstoffsicherung und Potenziale der Gewinnung in Europa

Seltene Erden sind ein fundamentaler Rohstoff für technologische Entwicklungen. Ihre Verfügbarkeit ist daher für die Erhaltung der Wettbewerbsfähigkeit in allen Bereichen der Wirtschaft unverzichtbar. Sie sind essenzieller Bestandteil für Technologien der Energie- und Mobilitätswende und der Digitalisierung, sodass der Bedarf an Seltenen Erden perspektivisch massiv steigen wird. Vorkommen und Förderung von Seltenen Erden konzentrieren sich weltweit auf nur sehr wenige Länder außerhalb Europas. Deutschland und die EU sind somit nahezu vollständig von Importen abhängig. Die große Marktmacht einzelner Rohstoffproduzenten und insbesondere die Quasimonopolstellung Chinas als Hauptlieferant bergen dementsprechend große Versorgungsrisiken. Die Erschließung neuer Lagerstätten in Europa, das Recycling und der Aufbau einer Kreislaufwirtschaft sind Ansätze, um diese Importabhängigkeit zu reduzieren. Der Aufbau einer europäischen Bergbau- und Minenindustrie für Seltene Erden hat für Europa und Deutschland fundamentale geopolitische Bedeutung. Mit dem Kommissionsvorschlag für eine Europäische Verordnung zu kritischen Rohstoffen wurden für den Bergbau und die Weiterverarbeitung Seltener Erden erste Weichen in Richtung vereinfachte und verkürzte Genehmigungsverfahren für Minenprojekte gestellt. Lagerstätten innerhalb Europas befinden sich in Schweden, Grönland und Finnland. Auch in Deutschland gibt es in der Nähe von Leipzig ein Vorkommen. Ein Recycling Seltener Erden wird in Europa bisher noch wenig betrieben. Gründe hierfür liegen neben der bislang mangelnden Kosteneffizienz primär in technischen Schwierigkeiten, die sich bei der Gewinnung Seltener Erden aus Altprodukten ergeben. Überdies lassen sich aufgrund des hohen Verteilungsgrades und der niedrigen Materialanteile nur geringe Mengen rückgewinnen. Grundsätzlich finden nur wenige potenzielle Recyclingmaterialien den Weg zur Rückgewinnung. Der Ansatz eines kreislauforientierten Wirtschaftens geht über ein bloßes Recycling hinaus. Er zielt darauf ab, den Wert der Materialien effektiver und länger im System von Gewinnung, Produktion und Verwendung zu führen. Berechnungen zufolge ließe sich ein großer Teil der erwarteten Nachfrage an Seltenen Erden in einer Kreislaufwirtschaft decken, in der technische Innovationen, Recycling und Verhaltensänderungen ineinandergreifen