Publications

Results 26–50 of 112

Search results

Jump to search filters

Robust verification of stochastic simulation codes

Journal of Computational Physics

Radtke, Gregg A.; Martin, Nevin; Moore, Christopher H.; Huang, Andy; Cartwright, Keith

We introduce a robust verification tool for computational codes, which we call Stochastic Robust Extrapolation based Error Quantification (StREEQ). Unlike the prevalent Grid Convergence Index (GCI) [1] method, our approach is suitable for both stochastic and deterministic computational codes and is generalizable to any number of discretization variables. Building on ideas introduced in the Robust Verification [2] approach, we estimate the converged solution and orders of convergence with uncertainty using multiple fits of a discretization error model. In contrast to Robust Verification, we perform these fits to many bootstrap samples yielding a larger set of predictions with smoother statistics. Here, bootstrap resampling is performed on the lack-of-fit errors for deterministic code responses, and directly on the noisy data set for stochastic responses. This approach lends a degree of robustness to the overall results, capable of yielding precise verification results for sufficiently resolved data sets, and appropriately expanding the uncertainty when the data set does not support a precise result. For stochastic responses, a credibility assessment is also performed to give the analyst an indication of the trustworthiness of the results. This approach is suitable for both code and solution verification, and is particularly useful for solution verification of high-consequence simulations.

More Details
TYPE Journal Article YEAR 2022
DOIOSTIScopus

EMPIRE Simulations of the July 2020 photoelectron driven cavity B-Dot experiments at the National Ignition Facility

Christenson, Peggy J.; Flanagan, Timothy M.; Cartwright, Keith

Simulations of several of the end-irradiated cylindrical photoelectron driven cavity experiments (also known as B-Dot cavities) that were fielded during the July 1 through 2, 2020 shot series at the National Ignition Facility are presented in this report with comparisons to experimental measurements. All cavity B-Dots fielded on the second, third, fourth, fifth and seventh shots were simulated using coupled Integrated Tiger Series (ITS) Monte Carlo transport codes and the Electromagnetic Plasmas in Realistic Environments (EMPIRE) electromagnetic particle-in-cell code.

More Details
TYPE SAND Report YEAR 2021
DOIOSTI

Simulation of a relativistic magnetron using a fluid electron model

IEEE International Conference on Plasma Science

Roberds, Nicholas A.; Sandoval, Andrew J.; Cartwright, Keith; Beckwith, Kristian

We present a novel technique for numerically modeling relativistic magnetrons. The electrons are represented with a 5-moment relativistic fluid. Typically, the particle in cell method is used for simulated relativistic high-power microwave sources. This study considers the A6 magnetron presented by Palevsky and Bekefi [1].

More Details
TYPE Conference Presenation YEAR 2021
DOIOSTIScopus

Characterization of the Redesigned Extended MITL for HERMES III

Powell, Troy C.; Cartwright, Keith; Biller, Andrew; Pointon, Timothy

Modeling and simulation of the legacy HERMES III Magnetically Insulated Transmission Line (MITL) has been performed using EMPHASIS, an unstructured time-domain electromagnetic (UTDEM) particle-in-cell (PIC) simulation software. This design when used lost roughly half of its current before the pulse reached the load. The cause of the current loss in the MITL was found to be the vacuum impedance changes along the MITL. The MITL was then redesigned to maintain constant impedance and simulated in EMPHASIS once again. Following predicting simulation results, the new MITL was then built, installed, and tested, showing minimal current loss and good agreement with simulation and theoretical results, all of which are reported here. Additionally, an analysis of experimental voltage calculation techniques using cathode and anode currents is performed and compared to simulation results.

More Details
TYPE SAND Report YEAR 2021
DOIOSTI
Results 26–50 of 112
Results 26–50 of 112