Search NASA⌕ Search

Engineering topics

Schwarz, Jens

Publications and source records attributed to Schwarz, Jens.

At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Development of a colinear Second-Harmonic Orthogonal Polarization (SHOP) interferometer for electron areal density measurements in Magnetically Insulated Transmission Lines (MITLs)

Experimental measurements of low density plasmas forming in Magnetically Insulated Transmission Line (MITL) regions are desired to improve our understanding of current loss and power flow. Therefore, a new optical interferometer diagnostic was commissioned via this LDRD project. To measure the expected 10 13 - 10 17 cm -3 electron densities inside the 0.5 - 6 mm Anode-Cathode (A-K) gaps, a colinear SHOP interferometer diagnostic was constructed. The diagnostic was initially fielded on the University of New Mexico (UNM) Helicon-Cathode (HelCat) plasma device which provided a highly repeatable and well understood plasma source for which the colinear SHOP interferometer’s functionality could be verified and measured. Utilizing the highly repeatable plasma source and shot averaging, the interferometer was able to achieve an areal density sensitivity of 1×10 14 cm -2 . This work at UNM lead to a Review of Scientific Instruments (RSI) publication [20], DOI:10.1063/5.0101687. After the diagnostic’s capability was proven at UNM, the colinear SHOP interferometer was commissioned for use on the Sandia National Laboratories (SNL) Mykonos accelerator. Here, it provided the first temporal areal density measurements of plasma formation in a parallel plate MITL. The diagnostic was able to achieve a single shot (no multi-shot averaging like at UNM) areal density sensitivity of 1×10 15 cm -2 along a ~ 2mm probing path length, which provided adequate capability to conduct fundamental physics research of MITL plasma formation. CHICAGO and ALEGRA simulations support the diagnostics experimental findings. More experimental and computational work will continue, likely leading to another publication(s). The smaller scale Mykonos accelerator work has also provided justification that the colinear SHOP interferometer is a capable diagnostic for measuring plasma areal densities in the inner MITL and convolute regions of larger TW-class accelerators like SNL’s Z machine.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2023

Self-assembled Seashell Like Coatings for Large Area Robust Debris Shields for Next Generation Pulsed Power Drivers

During this LDRD project, our team developed a technology which enables the fabrication of novel nanostructures replicating seashell – “nature’s toughest material”. The resulting coatings exhibit high thermal stability up to 1650°C, which exceeds the hardness of Spectra® by ~44%, as well as the compressive strength of aluminum by ~57%. Coatings made with this technology are stronger, environmentally friendly, more sustainable, and more versatile than other comparable materials. Beryllium wafers, the current, most favorable shielding material in terms of thermal and mechanical properties, are very toxic and cost hundreds of times more than the new material developed in this project. The coatings on silicon wafer and stainless steel, respectively, have been tested as ride-along on the Z machine and clearly outperform the bare substrate. Use of this technology will have a profound global impact for pulsed power and fusion energy development, debris mitigation for spacecraft and satellites, durability of drill bits used in deep well drilling and tunnel boring operations, thermal protection of aircraft and manned spacecraft, and various other thermal and mechanical protection applications.

36 MATERIALS SCIENCE↗
DOE OSTI2023

A generalized approach to x-ray data modeling for high-energy-density plasma experiments

Accurate understanding of x-ray diagnostics is crucial for both interpreting high-energy-density experiments and testing simulations through quantitative comparisons. X-ray diagnostic models are complex. Past treatments of individual x-ray diagnostics on a case-by-case basis have hindered universal diagnostic understanding. Here, in this study, we derive a general formula for modeling the absolute response of non-focusing x-ray diagnostics, such as x-ray imagers, one-dimensional space-resolved spectrometers, and x-ray power diagnostics. The present model is useful for both data modeling and data processing. It naturally accounts for the x-ray crystal broadening. The new model verifies that standard approaches for a crystal response can be good approximations, but they can underestimate the total reflectivity and overestimate spectral resolving power by more than a factor of 2 in some cases near reflectivity edge features. We also find that a frequently used, simplified-crystal-response approximation for processing spectral data can introduce an absolute error of more than an order of magnitude and the relative spectral radiance error of a factor of 3. The present model is derived with straightforward geometric arguments. It is more general and is recommended for developing a unified picture and providing consistent treatment over multiple x-ray diagnostics. Such consistency is crucial for reliable multi-objective data analyses.

Nagayama, Taisuke↗