Helmholtz Institute Freiberg for Resource Technology
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Studying the impact of electron bunch characteristics on plasma wakefield performance using particle-in-cell simulations
Get PDFThe submitted version of my bachelor thesis + tex files and notebooks used for data evaluation.
Abstract
The accessibility of plasma-based accelerators was greatly expanded by the realization of laser wakefield accelerator (LWFA)-driven plasma wakefield accelerators (PWFA). This development speeds up research on PWFA significantly. In this thesis, 3D particle-in-cell-simulations were used to analyze driver parameters for a PWFA to achieve maximal energy gain for a hypothetical witness beam. Only small increases in witness energy were found when drivers with high kinetic energy were compared. In contrast, great witness energy increases result when the divergence of the driver gets reduced. The transformation of a driver in plasma is analyzed, and the influence of the wakefield on it is discussed. Additionally, evidence for non-constant peak energy is presented, with energy losses in the MeV scale independent from driver characteristics. This could require adjustments to the charge reconstruction of the LWFA bunch after the PWFA stage
Data publication: Influence of fabrication parameters on the magnetic and structural properties of Mn5Ge3
No full textXRD, RBS, el. transport and VSM measurements of fabricated Mn5Ge3 layers on Ge substrates
Data publication: Deconvoluting Cr States in Cr-Doped UO2 Nuclear Fuels via Bulk and Single Crystal Spectroscopic Studies
No full textExperimental and fitted EPR data of Cr-UO2 single crystal grains, EXAFS data Cr-UO2 single crystal grain and powder with Cr redox standards, XANES data Cr-UO2 single crystal grain and powder with Cr redox standard
Hydrodynamics in a bubble column – Part 1: Two-phase flow
No full textMultiphase computational fluid dynamics (CFD) simulation is a useful tool to study the hydrodynamics in a bubble column, if appropriate closure models are known. Systematic assessment of different models is an ongoing venture that benefits from improved validation data. The present study accumulates a database on two-phase flow experiments in a bubble column. This is achieved by using a combination of Particle Image Velocimetry and Shadowgraphy to measure the liquid velocity field and gas dispersion properties simultaneously. This methodology is applied for different needle diameters and gas flow rates.
A detailed description of the experimental setup can be found in Sommer et al. (2023).
The experimental data (Table 1) described in this repository is structured into different folders and files as follows:
Level 1: Folders classified by measurement configuration: TX_Jg_Y_Di_ZZZ as outlined in Table 1
TX = Identifier
Jg_Y = Superficial gas velocity in mm/s
Di_ZZZ = Inner diameter of the needle in µm
Level 2: Folders classified by measurement height: Z_XXX
Z_XXX = Measurement height in mm
Level 3: csv files classified by their analysis parameter:
Gas_Eg_ub_over_x.csv: Each csv file consists of five columns, namely the x-coordinate (in m), the gas holdup, the uncertainty of the gas holdup, the averaged bubble rising velocity (in m/s) and the corresponding uncertainty (in m/s).
Liquid_v_z_over_x.csv: Each csv file consists of three columns, namely the x-coordinate (in m), the averaged liquid velocity (in m/s) and the corresponding uncertainty (in m/s).
Table 1: Overview of the measurement cases in this repository.
| ID | Diameter of needle orifice in µm | Superficial gas velocity in mm/s |
|----|----------------------------------|----------------------------------|
| T1 | 200 | 2 |
| T2 | 200 | 4 |
| T3 | 200 | 6 |
| T4 | 600 | 2 |
| T5 | 600 | 4 |
| T6 | 600 | 6 |This project has received funding from the European Union's Horizon 2020 Marie Skłodowska-Curie Actions (MSCA), Innovative Training Networks (ITN), H2020-MSCA-ITN-2020 under grant agreement No. 955805, and the European Institute of Innovation and Technology (EIT). This body of the European Union receives support from the European Union's Horizon 2020 research and innovation programme
Data publication: Membrane-free alkali metal-iodide battery with a molten salt
No full textRaw data from experiments with membrane-free alkali metal-iodide cells containing XPS results, phase-diagram calculations, neutron radiography images, electrochemical cycling data, and electron microscope images of the carbon felt used.This project has received funding from the European Union's Horizon 2020 research and
innovation programme under grant agreement No 963599 (SOLSTICE - Sodium-Zinc molten salt batteries for low-cost stationary storage
Data publication: Pattern recognition in reciprocal space with a magnon-scattering reservoir
No full textThis data publication contains the data for our publication "Pattern recognition in reciprocal space with a magnon-scattering reservoir" published in Nature Communications. The dataset is structured in folders corresponding to the different figures in the paper. Folder Fig2 and Fig2 contain the experimental data measured with Brillouin-light-scattering microscopy. The files contain the data integrated for the measurement positions described in the methods section in a csv format. Forlder Fig4 contains the evaluated numerical data presented in the corresponding figure. The raw data generated with micromagnetic simulations is too large for this dataset and is available upon request by the authors
Data Publication: Growth and Martensitic Transformation of Ferromagnetic Co-Cr-Ga-Si Epitaxial Films
No full textRaw data of a paper done by Yuru Ge. The paper title is finally signed as: Growth and Martensitic Transformation of Ferromagnetic Co-Cr-Ga-Si Epitaxial Films. The authors are Yuru Ge, Klara Lünser, Fabian Ganss, Peter Gaal, Lukas Fink,and Sebastian Fähler. This is the final version which is accepted by the journal Science and Technology of Advanced Materials on 07.08.202
Data publication: Estimation of the yield strength from small punch testing
No full textFinite element simulations of the small punch test are performed.Generic elastic-plastic material properties are used. A systematic variation of the yield stress, ultimate tensile stress and uniform elongation is performed to investigate the effects of these parameters of the uniaxial stress-strain curve on the characteristics of small punch force-deflection curves. Moreover, the effect of sample thickness is studied. It is shown that the currently used elastic-plastic transition force – obtained by bi-linear fitting – does not only depend on the yield strength but also on the work hardening behavior of the material. An alternative definition of the elastic-plastic transition force is proposed, which significantly less depends on the work hardening of the material. The approach is based on the deviation of the force-deflection curve from the analytical elastic slope derived by Reissner's plate theory. The new definition of the transition force leads to significantly reduced dependence of the correlation factor on the geometry of the small punch set-up
FVV1455: CFD Simulation of Droplet Separators
No full textFor industrial applications, the two-fluid model is preferred due to its efficient modelling of small-scale interfaces. Whereas, a thin film model, based on a long wave approximation, is used for the unresolved interfaces to obtain the film features by solving the 2D Navier-Stokes equations for wall films. Within the project, the target is to develop an experimentally validated 3D-CFD model to investigate the separation efficiency of droplet separators for fuel cell systems. A hybrid model is developed, which couples the two-fluid model with a thin film model via mass transfer terms for droplet deposition, droplet entrainment and film separation. A two-way coupling between droplets and the thin film is established using mass and momentum source terms, derived analytical and from available experiments. The droplet separator is an essential component of an automotive fuel cell system that segregates a significant amount of liquid fractions from the air-water mixture. The flow dynamics inside a droplet separator consist of a dispersed gas and liquid with a wall adhered thin liquid film. The modelling is divided into the following stages due to the complex fluidic phenomenon inside a generic droplet separator:
Droplet deposition model,
Film separation model,
Film transition model, and
Population balance model.
The numerical simulations are validated and fine-tuned with experiments carried out at HZDR.The research project was self-financed (FVV funding no. 1455) by the FVV e.V
µCT data of two drill cores of fractured crystalline rock (Grimsel)
No full textTwo crystalline rock drill cores from the Grimsel site were scanned with a Nikon XT H 225 - scanner. The samples were prepared (formatted and cast in epoxy) by UJV Rez, Czech Republic. The CT-data were acquired and processed at HZDR-FWOT.
Sample 1 (GAM_UJV_1C_1) contains a complex system of interconnected fractures.
Sample 2 (GAM_UJV_1C_2) contains one single end-to-end fracture with larger aperture.
Size of both samples: Diameter 80 mm, length 165 mm.
Two tomograms were acquired for both samples:
1) Complete drill core as one scan, voxel size ca. 75 µm.
2) HR-tomogram merged from three sections with maximum resolution, voxel size ca. 40 µm.
The tomograms were stored as 3D-raw files. Data format, acquisition parameters, and processing workflow, are documented in the tomogram header files (nrrd-format (text): see https://teem.sourceforge.net/nrrd/format.html).
This data format is importable into open-source visualization programs as 3D slicer (https://www.slicer.org) or Paraview (https://www.paraview.org). The data processing has been conducted with Avizo (https://www.thermofisher.com/de/de/home/electron-microscopy/products/software-em-3d-vis/avizo-software.html).
Files:
Sample 1
GAM_UJV_1C_1_complet-2_01_NLM: Graylevel image of complete sample, ring artifact removal, non-local-means filter
GAM_UJV_1C_1_complet-2_01_thresholded: Tentative label image of complete sample, threshold segmentation with manual edit
Merged-GAM_UJV_1C_1_HR.Frac_section: Graylevel image of merged fracture section, unfiltered
Merged-GAM_UJV_1C_1_HR.Frac_section.Threshold: Tentative label image of merged fracture section, adaptive threshold segmentation with manual edit
GAM_UJV_1C_1_complet_2.png: Figure of complete sample
GAM_UJV_1C_1_HR_Frac_Y2.png: Figure of merged high-resolution tomogram
Sample 2
GAM_UJV_1C_2_complet_01.filtered: Graylevel image of complete sample, ring artifact removal, non-local-means filter
GAM_UJV_1C_2_complet_01.filtered.thresholded: Tentative label image of complete sample, threshold segmentation with manual edit
Merged-GAM_UJV_1C_2_A_01.Frac_section.filtered: Graylevel image of merged fracture section, ring artifact removal, non-local-means filter
Merged-GAM_UJV_1C_2_A_01.Frac_section.filtered.segm: Tentative label image of merged fracture section, threshold segmentation with manual edit
GAM_UJV_1C_2_complett_2.png: Figure of complete sample
GAM_UJV_1C_2_HR_Frac_Y2.png: Figure of merged high-resolution tomogram
Original acquistion data are stored on the HZDR bulk data storage system and available for reprocessing on request.
Financial support was granted from the European Union’s Horizon 2020 research and innovation program under grant agreement No. 847593 (EURAD, WP FUTURE, task 2.2)