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At least 1,207 records · Page 67
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Warm‐Season Afternoon Precipitation Peak in the Central Bay of Bengal: Process‐Oriented Diagnostics

Abstract Past studies have indicated that precipitation over tropical open oceans generally peaks in the early morning. However, an intriguing departure from this pattern is observed in the central Bay of Bengal (CBoB), where rainfall exhibits a distinct afternoon peak during the South Asian summer monsoon season. By using a novel satellite‐based cloud classification and tracking data set, we found that more than 75% of the afternoon rainfall (15–17 LST) over the CBoB comes from mesoscale convective systems (MCSs). Most of the MCSs contributing to the CBoB afternoon rainfall peak originate either locally over the CBoB or near the west and east coasts of the BoB, in contrast to the northern BoB as highlighted in previous studies. Analyses show that MCSs initiated near coastlines are primarily influenced by land‐sea breezes, whereas MCSs initiated over the BoB open ocean during early morning are strongly associated with diurnal radiative forcings. In addition, there are clear diurnal propagating MCS initiation signals from the west and north coastlines of the BoB to the CBoB, which are related to diurnal gravity waves emitted from the coastlines. The thermodynamic conditions conducive to MCS initiation over different sub‐regions of the BoB are also investigated. No systematic differences found in environmental convective available potential energy between days with and without MCS initiation. However, over most sub‐regions, days with MCS initiation generally have higher total column water vapor than days without MCS initiation. This difference suggests that the lower‐free‐tropospheric moisture content plays an important role in MCS initiation over the BoB.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2022

Accurate temperature diagnostics for matter under extreme conditions

The experimental investigation of matter under extreme densities and temperatures, as in astrophysical objects and nuclear fusion applications, constitutes one of the most active frontiers at the interface of material science, plasma physics, and engineering. The central obstacle is given by the rigorous interpretation of the experimental results, as even the diagnosis of basic parameters like the temperature T is rendered difficult at these extreme conditions. Here, we present a simple, approximation-free method to extract the temperature of arbitrarily complex materials in thermal equilibrium from X-ray Thomson scattering experiments, without the need for any simulations or an explicit deconvolution. Our paradigm can be readily implemented at modern facilities and corresponding experiments will have a profound impact on our understanding of warm dense matter and beyond, and open up a variety of appealing possibilities in the context of thermonuclear fusion, laboratory astrophysics, and related disciplines.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2022

Transcript and blood-microbiome analysis towards a blood diagnostic tool for goats affected by Haemonchus contortus

The Alpine goat (Capra aegagrus hircus) is parasitized by the barber pole worm (Haemonchus contortus). Hematological parameters from transcript and metagenome analysis in the host are reflective of infestation. We explored comparisons between blood samples of control, infected, infected zoledronic acid-treated, and infected antibody (anti-γδ T cells) treated wethers under controlled conditions. Seven days post-inoculation (dpi), we identified 7,627 transcripts associated with the different treatment types. Microbiome measurements at 7 dpi revealed fewer raw read counts across all treatments and a less diverse microbial flora than at 21 dpi. This study identifies treatment specific transcripts and an increase in microflora abundance and diversity as wethers age. Further, F/B ratio reflect health, based on depression or elevation above thresholds defined by the baseline of non-infected controls. Forty Alpine wethers were studied where blood samples were collected from five goats in four treatment groups on 7 dpi and 21 dpi. Transcript and microbiome profiles were obtained using the Partek Flow (St. Louis, Missouri, USA) software suites pipelines. Inflammation comparisons were based on the Firmicutes/Bacteriodetes ratios that are calculated as well as the reduction of microbial diversity.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2020

Design of target irradiation and diagnostic chamber to study ps-laser generated plasma as a source of singly charged ions for external injection into an electron beam ion source

High repetition-rate (~10 kHz) ps-lasers are becoming available on the market with reasonable cost and may offer several advantages compared to ns-lasers by generating nearly continuous beams of singly charged ions appropriate for the “slow” injection mode into the Electron Beam Ion Source (EBIS). To evaluate these advantages, we will perform studies of a ps-laser generated plasma using a laser with a pulse duration of 8 ps and energy up to 5 mJ per pulse. A vacuum chamber equipped with a 3D target positioner, a focusing lens, and a Faraday Cup has been designed and built for this study. Lens-to-target distance variations have been measured using a laser tracker over the whole range of horizontal and vertical translation for all five targets we will use. The variations were found to be within ±150 µm. This level of “target flatness” should be acceptable for our experimental conditions. Ion currents and ion pulse durations of various elements (from Al to Ta) will be measured for different target irradiation conditions (focal spot size and laser pulse energy). The results obtained will allow us to specify all parameters and geometry of a laser ion source based on a ps-laser to provide external ion injection into the relativistic heavy ion collider EBIS

43 PARTICLE ACCELERATORS↗
DOE OSTI2021

DANTE as a primary temperature diagnostic for the NIF iron opacity campaign

The Opacity Platform on the National Ignition Facility (NIF) has been developed to measure iron opacities at varying densities and temperatures relevant to the solar interior and to verify recent experimental results obtained at the Sandia Z-machine, that diverge from theory. The first set of NIF experiments collected iron opacity data at ∼150 eV to 160 eV and an electron density of ∼7 × 1021 cm−3, with a goal to study temperatures up to ∼210 eV, with electron densities of up to ∼3 × 1022 cm−3. Among several techniques used to infer the temperature of the heated Fe sample, the absolutely calibrated DANTE-2 filtered diode array routinely provides measurements of the hohlraum conditions near the sample. However, the DANTE-2 temperatures are consistently low compared to pre-shot LASNEX simulations for a range of laser drive energies. We have re-evaluated the estimated uncertainty in the reported DANTE-2 temperatures and also the error generated by varying channel participation in the data analysis. An uncertainty of ±5% or better can be achieved with appropriate spectral coverage, channel participation, and metrology of the viewing slot.

Opachich, Y. P. (ORCID:0000000314323989)↗
DOE OSTI2021

Ray-tracing analysis for cross-polarization scattering diagnostic on MAST-upgrade spherical tokamak

A combined Doppler backscattering/cross-polarization scattering (DBS/CPS) system is being deployed on MAST-U for simultaneous measurements of local density turbulence, turbulence flows, and magnetic turbulence. In this design, CPS shares the probing beam with the DBS and uses a separate parallel-viewing receiver system. In this study, we utilize a modified GENRAY 3D ray-tracing code to simulate the propagation of the probing and scattered beams. The contributions of different scattering locations along the entire beam trajectories are considered, and the corresponding local B̃ wavenumbers are estimated using the wavevector matching criterion. The wavenumber ranges of the local B̃ that are detectable to the CPS system are explored for simulated L- and H-mode plasmas.

Hong, R. (ORCID:0000000347508015)↗
DOE OSTI2022

A Pockels cell enabled heterodyne phase contrast imaging diagnostic for detection of ion cyclotron emission

This work describes a novel optical heterodyne detection scheme that significantly extends the frequency response of the phase contrast imaging method to detect electron density fluctuations in tens of megahertz frequency range. The system employs a variable frequency electro-optic modulator to allow operation at any frequency in the range 10–40 MHz without the need to realign the system. The frequency coverage of the system makes it suitable to measure the radial structure of the electron density component of ion cyclotron emission on devices having confining magnetic field of a few tesla, thus extending the purely temporal measurements provided so far by magnetic probes.

47 OTHER INSTRUMENTATION↗
DOE OSTI2022

Design study of an edge current density diagnostic using new high-performance single-channel beam emission spectrometers at DIII-D

A novel Motional Stark Effect spectroscopy system has been designed for application at the DIII-D tokamak. The system is optimized for studies of the poloidal and toroidal magnetic field in the plasma pedestal region with frame rates of up to 10 kHz. Further, light from an existing high-photon-throughput collection lens is analyzed using four single-channel f/2.8 Czerny–Turner spectrometers that use custom-made lens systems instead of mirrors. Each spectrometer has two separate outgoing legs and is operated in a positive grating order, which allows for simultaneous observations of D-alpha and D-beta spectra. Forward modeling using the code FIDASIM shows a radial resolution of the system close to 0.6 cm and sufficiently good spectral resolution when masking the high throughput light collection lens in the horizontal direction to avoid overly strong Doppler broadening of beam emission lines. Moreover, a detailed sensitivity study considering realistic levels of readout and photon noise shows that the poloidal and toroidal magnetic field strengths can be inferred with an uncertainty of less than 1%, which will allow the inference of changes of the plasma current during transient events.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2022

Observation and diagnostic application of Kr K-shell emission in magnetized liner inertial fusion experiments at Z

In a series of Magnetized Liner Inertial Fusion (MagLIF) experiments performed at the Z pulsed power accelerator of Sandia National Laboratories, beryllium liners filled with deuterium gas pressures in the 4–8 atm range and a tracer amount of krypton were imploded. At the collapse of the cylindrical implosion, temperatures in the 1–3 keV range and atom number densities of ∼1023 cm−3 were expected. The plasma was magnetized with a 10 T axial magnetic field. Krypton was added to the fuel for diagnosing implosion plasma conditions. Krypton K-shell line emission was recorded with the CRITR time-integrated transmission crystal x-ray spectrometer. The observation shows n = 2 to n = 1 line emissions in B-, Be-, Li-, and He-like Kr ions and is characteristic of the highest electron temperatures achieved in the thermonuclear plasma. Detailed modeling of the krypton atomic kinetics and radiation physics permits us to interpret the composite spectral feature, and it demonstrates that the spectrum is temperature sensitive. We discuss temperatures extracted from the krypton data analysis for experiments performed with several filling pressures.

Clapp, J. T. (ORCID:0000000219928146)↗
DOE OSTI2024

Design and commissioning of resistive foil bolometer diagnostics on the ST40 tokamak

Following successful campaigns on the compact high field spherical tokamak ST40, resistive gold foil bolometers have now been installed to measure the radiated power profile. Positioned on the midplane, two bolometer cameras offer perspectives of the horizontal and vertical planes, while the third camera, situated above the midplane, provides a vertical view of the top divertor plates, including the X-point and the strike points. Further, these cameras use a commercial off-the-shelf data acquisition platform with modules specifically designed for bolometers in a Wheatstone bridge configuration, providing both phase sensitive detection and in situ calibration. This paper presents an overview of the design and functionality of all three cameras and the commissioning of the horizontal plane camera. The commissioning of the horizontal camera shows data from a range of plasma pulses, presenting a positive correlation between the relative profiles measured from the bolometer camera and an absolute extreme ultraviolet diode camera viewing along similar lines of sight.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2024

Improvements to the characterization of Agfa x-ray film for use on opacity spectroscopy diagnostics

The National Ignition Facility uses a soft x-ray opacity spectrometer for x-ray spectral imaging in high-energy-density experiments. The increased demand for a better spectral resolution prompted the investigation into the Agfa D4 film. Characterization is already under way for the film. A Manson x-ray source using six different anodes was used to expose film to the linear optical density (OD) region. This is a continuation of the previous work, and the updated analysis process is communicated here. The identified uncertainties have been reduced with the updated steps that improve the results of the characterization process. In conclusion, when the Stanford Synchrotron Radiation Lightsource Beamline 16-2 was operational, the film was characterized at that source. Its beam offered a higher fluency with a lower exposure time needed to reach saturation. Results for both sources are compared in this paper.

47 OTHER INSTRUMENTATION↗
DOE OSTI2024

Characterization of a CMOS camera based film digitization platform for gated x-ray imaging diagnostics at the National Ignition Facility

Hardened gated x-ray detectors use photographic film as the data recording medium due to its low sensitivity to the high-yield neutron environments at the National Ignition Facility (NIF). The photographic film is digitized with a Photometric Data Systems (PDS) microdensitometer, which measures the film’s optical density. The PDS scanner is able to measure a dynamic range of 0–5 OD; however, raster scanning the film is time consuming and maintenance of the instrument is challenging due to legacy technology. Since film usage at NIF is expected to continue in the foreseeable future, a digitization platform that is faster and more maintainable would benefit the NIF’s current and future operations. Here, this work presents the characterization of the digital transitions (DT) atom, a CMOS camera-based digitization platform that records film data in a single image capture very quickly and has widely available user support. The preliminary results suggest that the DT atom is able to reconstruct exposures accurately enough to be a competitive alternative to the PDS Scanner.

47 OTHER INSTRUMENTATION↗