Bulletin of the American Physical Society
2016 Annual Meeting of the Far West Section
Volume 61, Number 17
Friday–Saturday, October 28–29, 2016; Davis, California
Session F5: Plasma, Fluids and Atmospheric Physics |
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Chair: Alla Safronova, University of Nevada, Reno Room: Conference Room B |
Friday, October 28, 2016 2:00PM - 2:12PM |
F5.00001: Analysis of K-shell Fe Spectra Created by Irradiation of a Thin Foil by a High Intensity, Ultrafast Laser and from X-pinches A. Stafford, A.S. Safronova, A.Ya. Faenov, T.A. Pikuz, R. Kodama, V.L. Kantsyrev, I. Shrestha, V.V. Shlyaptseva Irradiation of a target with an intense ultrafast laser creates multiple regions with different plasma conditions due to the quick interaction of the target with the laser which occurs faster than the radiative decay of the plasma. Three regions are identified with different plasma parameters in experiments with the J-KAREN laser (\textasciitilde 7 J pulse energy, 35 fs pulse duration, 10$^{\mathrm{10}}$ main pulse to prepulse ratio) at the Kansai Photon Science Institute of QST. The laser was used to irradiate 2 micron stainless steel targets. K-shell Fe radiation in the wavelength range of 1.7-1.97 {\AA} was recorded and analyzed. X-ray Spectra from the same spectral region were collected from X-pinches to compare and contrast the radiative differences. The influence of hot electrons and soft X-ray emission on the Fe spectra will be discussed. [Preview Abstract] |
Friday, October 28, 2016 2:12PM - 2:24PM |
F5.00002: X-ray Characteristics of Mixed Noble Gas Puff Irradiated with the Titan Laser at LLNL K.A. Schultz, V.L Kantsyrev, V.V Shlyaptseva, I.K. Shrestha, E.E. Petkov, A.S. Safronova, J.J. Moschella, M.C. Cooper, G.E. Kemp, K.B. Fournier Typical x-ray sources created by the interaction of a laser pulse with solid targets produce debris that can damage sensitive equipment. Therefore, we investigated a debris-free source of x-ray radiation. A pulsed gas puff containing a mixture of monomers and clusters was irradiated with the frequency doubled (527nm) short pulse (\textless 700fs) Titan laser housed in the Jupiter Laser Facility at LLNL. Two different gas mixtures were used as a target for the laser radiation: a double mixture of Kr and Ar gases and a triple mixture of Xe, Kr, and Ar. X-ray yields measured using filtered Si-diodes and absolutely calibrated PCDs are presented as a function of gas puff composition as well as delay time between the puff initiation and incidence of the laser pulse. Additionally, laser energy transmitted through the gas puff is measured to determine coupling efficiency. X-ray pinhole images of the plasma were captured in different spectral regions to estimate the size of the x-ray radiation source. [Preview Abstract] |
Friday, October 28, 2016 2:24PM - 2:36PM |
F5.00003: X-ray spectrometer and spectropolarimeter for the study of high temperature and density laboratory plasmas M.C. Cooper, V.L. Kantsyrev, A.S. Safronova, I.K. Shrestha, V.V. Shlyaptseva, K.A. Schultz, E.E. Petkov, W. Cline, C. Davidson Facilities like UNR's Zebra pulsed-power generator, femtosecond Leopard Laser, and Sparky Facility provide platforms to search for efficient plasma sources of x-ray and extreme ultraviolet (EUV) radiation. Two new instruments developed to measure radiation from plasmas are a high spectral resolution x-ray focusing spectrometer and a spatially resolved x-ray spectropolarimeter. The Johann-type focusing x-ray spectrometer uses a concave Si crystal as the selectively reflecting element. It recorded experimental laser plasma spectra from K-shell Ar (3.91-4.58 {\AA}) and L-shell Kr (5.26-5.73 {\AA}) ions with resolutions greater than $\lambda $/$\Delta \lambda =$1200. A spectropolarimeter is being developed that uses two convex $\alpha $-quartz crystals as the selectively reflecting elements and will observe radiation from L-shell Mo (4.6-4.85 {\AA}) ions in two orthogonal polarization directions with 1D spatial resolution. The x-ray spectropolarimeter is intended to look for anisotropy of processes in z-pinch or laser plasmas. Application of these two new devices will add to the diversity of measurements of high temperature and density plasma parameters. [Preview Abstract] |
Friday, October 28, 2016 2:36PM - 2:48PM |
F5.00004: K- and L-shell spectra of stainless steel X-pinches with notable effect of interwire angle R.R. Childers, A.S. Safronova, V.L. Kantsyrev, A. Stafford, I.K. Shrestha, V.V. Shlyaptseva, E.E. Petkov Due to \textit{Chandra}'s x-ray data capabilities, laboratory-produced plasma spectroscopy can be benchmarked against astronomical radiation and used as a diagnostic in astrophysical research. X-ray Fe and Ni spectra of astrophysical interest are studied using four-wire, 830 $\mu $g stainless steel (Fe: 69{\%}, Ni: 9{\%}, Cr: 20{\%}) X-pinches on the 1 MA Zebra Generator, where the interwire angle is varied between 31 and 62.5 degrees. Harder x-ray (1.6-2.3 {\AA}) K-shell Fe, Ni and Cr spectra included both ``hot'', ionic (T$_{e} \quad \ge $ 1.5 keV) and ``cold'', characteristic (T$_{e}$: 10-30 eV) lines, indicating a much colder plasma and the existence of an electron beam. For the smaller interwire angle, K-shell emission intensifies, producing both stronger ionic and characteristic lines. Softer x-ray spectra between 8-13 {\AA} include L-shell spectra dominated by 3-2 Ni and higher Rydberg (n$\to $2; n $\ge $ 4) Fe lines. Plasma conditions are estimated using Fe, Ni, and Cr non-LTE spectral models. In addition, shadowgraphy exhibits the formation of jets in the middle of the cross-point region and orthogonal to the wires in the load with an almost column-like plasma resembling a single wire for the 31 degree load. Work was supported by NNSA under DOE grant DE-NA0003047 [Preview Abstract] |
Friday, October 28, 2016 2:48PM - 3:00PM |
F5.00005: Vortex Knots in Non-Ideal Fluids Dustin Kleckner, William T. M. Irvine, Martin Scheeler In ideal fluid flows, vortex lines tied into knots may never untie, resulting in a conserved quantity known as helicity. Although the conservation of helicity in `perfect' fluids has a long history, far less is known about the behavior of knotted structures in non-ideal fluids, e.g. those with viscosity. I will discuss the first experiments to generate vortex knot in viscous fluids, as well as our more recent efforts to study knots in simulated superfluids. [Preview Abstract] |
Friday, October 28, 2016 3:00PM - 3:12PM |
F5.00006: Understanding atmospheric turbulence results from numerical weather prediction models Heather Holmes, Marcus Trail, Xia Sun With the growing increase in computational power the grid resolution of numerical weather prediction (NWP) models has continued to decrease. This decrease enables large regions to be modelled with fine-scale horizontal grid spacing (i.e., less than 4km). With this finer grid resolution small scale atmospheric processes can be simulated, however the results still rely on model parameterizations that were developed for idealized atmospheric conditions and/or intended for use with larger grid resolutions. While atmospheric models are able to capture the synoptic scale atmospheric processes, the models do not adequately simulate the micro-scale processes near the earth's surface.~ Therefore impacting predictions of surface-atmosphere exchange, including the turbulent mixing and accumulation of pollutants in the atmospheric boundary layer. This presentation will present NWP results from the Weather Research and Forecasting (WRF) model where a sensitivity analysis for two case studies was designed to compare simulated surface fluxes to turbulence measurements.~ Hourly momentum, latent heat, and sensible heat fluxes from WRF are evaluated using surface observations.~ Different land surface models (land-atmosphere interactions) and planetary boundary layer (vertical mixing) parameterizations significantly impact the WRF surface flux results but have less of a difference on estimates of surface wind speed, temperature, and water vapor mixing ratio. [Preview Abstract] |
Friday, October 28, 2016 3:12PM - 3:24PM |
F5.00007: Evaluation of Surface Fluxes in the WRF Model: Case Study for Irrigated Farmland in Rolling Terrain Xia Sun, Heather Holmes Surface fluxes, serving as sinks or sources of atmospheric pollutants, are crucial parameters in numerical weather prediction models.The Weather Research and Forecasting Model (WRF), version 3.7.1, is used to simulate surface fluxes near Echo, Oregon, in September2014. Flux tower observations, from 22 to 28 September , provide the evaluation dataset for the model assessment.Atmospheric turbulence data were measured at 10 Hz using a 3D sonic anemometer and surface fluxes were calculated by eddy-covariance technique. The PBL schemes in WRF differ in assumptions of the transport of energy, mass, and moisture.To get the optimal model options with satisfactory evaluation performance, a series of simulations are conducted based on different combinations of PBL schemes, land surface models, and large- scale datasets for boundary conditions.To evaluate the WRF performance on surface flux simulations under varying sets of schemes, the bias, correlation coefficient, and root-mean-square error between the observation and simulation data is compared among these cases. This study assesses the ability of WRF to simulate surface fluxes and determine the sensitivity to different PBL and land surface schemes. [Preview Abstract] |
Friday, October 28, 2016 3:24PM - 3:36PM |
F5.00008: Investigating PM2.5 Sources in Salt Lake City during Persistent Cold Air Pool Events Cesunica Ivey, Heather Holmes, Sivaraman Balachandran, Yongtao Hu, Armistead Russell During wintertime, valley and basin towns often experience temperature inversions, where atmospheric conditions become very stable and the valley floor is colder than the air aloft. This meteorological condition is known as a cold air pool (CAP) event. Salt Lake City has particularly special CAP events due to the large number of air pollutant sources in the valley, leading to tremendous build-up of pollution during the CAP event. The CAP events are identified for January 2007 in Salt Lake City, and the dominant pollution sources are identified and aerosol formation pathways are discussed. A data assimilation model is also be applied to the modeled air pollutant concentrations, and the discrepancies between the model and ground observations are reduced. [Preview Abstract] |
Friday, October 28, 2016 3:36PM - 3:48PM |
F5.00009: Spatial Surface PM2.5 Concentration Estimates for Wildfire Smoke Plumes in the Western U.S. Using Satellite Retrievals and Data Assimilation Techniques . Sandra-Marcela Loria-Salazar, Heather A Holmes Health effects studies of aerosol pollution have been extended spatially using data assimilation techniques that combine surface PM2.5 concentrations and Aerosol Optical Depth (AOD) from satellite retrievals. While most of these models were developed for the dark-vegetated eastern U.S. they are being used in the semi-arid western U.S. to remotely sense atmospheric aerosol concentrations. However, the models developed for the eastern U.S. are not robust in the western U.S. due to different aerosol formation mechanisms, transport phenomena, and optical properties. This region is a challenge because of complex terrain, anthropogenic and biogenic emissions, secondary organic aerosol formation, smoke from wildfires, and low background aerosol concentrations. This research uses and evaluates of satellite remote sensing to estimate surface PM2.5 concentrations from AOD satellite retrievals over California and Nevada during the summer months of 2012 and 2013. The aim of this investigation is to incorporate a spatial statistical model that uses AOD from AERONET as well as MODIS, surface PM2.5 concentrations, and land-use regression to characterize spatial surface PM2.5 concentrations. The results will be used in a spatially resolved health study to determine the association between wildfire smoke exposure and cardiorespiratory health enpoints. This relationship can be used with future projections of wildfire emissions related to climate change and droughts to quantify the expected health impact. [Preview Abstract] |
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