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At least 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Using the Criticality Accident Alarm System modeling capabilities in SCALE [Slides]

The following is a summary of advice for CAAS modeling in SCALE. Refer to the SCALE Criticality Safety and Radiation Shielding training slides or to the SCALE manual for exact syntax. Use a mesh for the fission source that is the most adequate for the problem to solve (coarse/fine). Don’t spend unnecessary resources; simplify the model if it does not impact the final results of interest. Be careful to deactivate secondary fissions in MAVRIC or the calculation may never end. Check that k eff and $\overline{\upsilon}$ calculated results are logical. Between KENO and MAVRIC, cross section libraries, materials, geometry, and mesh grid can be the same or different. Iterative calculations are usually complex problems that need variance reduction. It will be hard to find the best solving parameters in the first attempt; expert judgement is needed. Check each step separately. Use Fulcrum to visualize fission source, mesh source, and spatial/energy distributions to find potential errors or impactful imprecisions.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

Proceedings of RIKEN BNL Research Center Workshop: Predictions for sPHENIX [Slides]

To complete the RHIC mission, sPHENIX was specifically designed to measure jet and heavy-flavor observables with a level of precision not previously achievable at RHIC. This will enhance our understanding of the quark-gluon plasma (QGP) properties and their temperature dependence beyond what is possible with existing and planned data from the LHC and other RHIC experiments. A major goal of the sPHENIX program is to address the question of the approach to thermalization of the quark-gluon plasma and its transport properties using hard probes such as jets and heavy flavor. The current three-year run plan includes Au+Au, p+Au and p+p collisions at 200 GeV. The Au+Au dataset provides a large QGP system to study the QGP properties. The p+Au dataset will allow for additional studies of the intriguing behavior observed in flow measurements from other RHIC experiments as well as transport properties of cold QCD matter and proton/nuclear structure. The p+p collisions provide a necessary reference for Au+Au and p+Au collisions and also allow for additional studies of proton structure. Anticipated measurements include but are not limited to, jet substructure observables, photon and heavy flavor tagged jets as well as comparisons of the production of the different upsilon states in all three collision systems. To maximize the rich physics sPHENIX is capable of accessing, this workshop will enhance the discussions between the experimentalists making the measurements and the theorists whose models will be tested and constrained by the new data. Since sPHENIX will start taking data in early 2023, this workshop is timely for theorists wishing to make final predictions of anticipated observables before data collection commences. In addition, it will provide an opportunity for theorists and experimentalists to propose and discuss new observables.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2026

Bayesian Optimization of The Relativistic Heavy Ion Collider Luminosity via s * Control

A state-of-the-art jet detector named sPHENIX was proposed, commissioned, and operated at the Rel ativistic Heavy Ion Collider (RHIC) from 2023 to 2025. This detector featured precision tracking and calorime try that enable high-statistics studies of the Quark Gluon Plasma through jet modification, upsilon suppres sion, and open heavy flavor production. The innermost component of the three sPHENIX tracking systems is the Monolithic-Active-Pixel-Sensor-based Vertex Detec tor (MVTX) (Fig. 1), which has an acceptance within | s | < 0.1m of the interaction point (IP).

43 PARTICLE ACCELERATORS↗
NASA NTRS1972

The near ultraviolet spectrum of B and A type main sequence stars

Scans of lambda Lep, eta UMa, xi Dra, epsilon Dor, alpha Leo, phi Dra, upsilon Dra, beta Aur, alpha Pic and alpha Dor have been obtained with scanner OAO-2 over the range 1800-3600 A. These scans have been reduced to tracings of F sub lambda in the 20 A pass band vs. wavelength using a wavelength conversion scale and a relative spectral sensitivity function. The general trend of the relative flux plots compares well with the continua predicted by simple model atmospheres.

Underhill, A. B.↗
NASA NTRS1973

Spectrophotometric results from the Copernicus satellite. III - Ionization and composition of the intercloud medium.

Interstellar lines have been studied in the unreddened stars lambda Sco, upsilon Sco, alpha Leo, and alpha Eri, which are located between 20 and 150 pc from the sun. The lines are on the linear and saturated Doppler portions of the curve of growth. Preliminary analysis shows that processes producing large amounts of highly ionized species are not dominant. Doubly ionized C, N, Si, and S have been detected, but are all quite weak relative to the singly ionized species. Abundances relative to nitrogen are in the cosmic ratios or slightly lower, with some indication of general depletion of the heavier elements. Hydrogen number densities range from a measured value of 0.22 per cu cm for lambda Sco to a derived value of 0.02 per cu cm for alpha Leo assuming nitrogen to have its solar abundance relative to hydrogen.

Rogerson, J. B.↗
NASA NTRS1974

Ionization mechanisms of the intercloud medium

A generalized treatment of the ionization equilibrium of the intercloud medium is developed, which is model-independent in the steady-state approximation, and which is suited to an interpretation of ultraviolet absorption data. It is found that the most satisfactory models require the presence of density inhomogeneities along the line of sight. In all models considered for lambda Sco, 2-MeV cosmic rays and X rays are found to lead to large disagreements with the observations, and data on upsilon Sco, alpha Leo, and other stars seem to support this conclusion. Therefore, it would seem that these cannot be the physical agents responsible for the bulk of the ionization of the gas. An alternative model is developed, in which the ionization below 24.58 eV is provided by ultraviolet photons. This model appears to satisfy theoretical requirements, and leads to good agreement with the data.

Meszaros, P.↗
NASA NTRS1979

Detection of the 12.28 micron rotational line of molecular hydrogen in the Orion molecular cloud

The pure rotational S(2) transition of molecular hydrogen at 12.28 microns has been detected in emission from the region of vibrational-rotational line emission in Orion. The line was resolved both spectrally and spatially, and the line shapes, widths, and velocities are consistent with those observed in the upsilon = 1-0 transitions. The results put new constraints on the structure, temperature, and dynamics of the region of molecular hydrogen emission.

Beck, S. C.↗
NASA NTRS1981

Discovery of phase-locked variable polarization in an RS Canum Venaticorum-like star, HR 5110

Using measurements on 79 nights in 1980 January-August, it is established that the polarization in the ultraviolet (U band) varies synchronously on the known binary period of 2.6132 days, with a peak-to-peak amplitude of 0.03%. The pattern is mainly second harmonic in character, as typical of binary star examples such as Algol and Upsilon Her. Reflection by the cooler star, by a plasma concentration, or both, is suggested. The scale of the polarization seems to be consistent with Rayleigh scattering by neutral hydrogen on the cooler star, and a roughly lambda to the -4th wavelength dependence should be searched for. The QU curve suggests a sizeable inclination for the system, of about 45 deg, but this is preliminary. Separately, a possible weak periodicity might be present on a subsidiary period, conceivably related to a rotating star spot.

Barbour, M. S.↗
NASA NTRS1982

The hot components of hydrogen deficient binaries

Low resolution IUE observations of the hot components of three very similar but peculiar objects: LSS 4300, Upsilon Sgr, and KS Per were compared. The possible evolutionary scenarios from observations and the extremely low hydrogen contents of the visible stars are discussed. It is suggested that the hot secondaries in hydrogen deficient binaries should also be hydrogen deficient.

Drilling, J. S.↗
NASA NTRS1982

The hot component of KS Persei /HD 30353/

The presence of a hot companion for the single-lined spectroscopic binary KS Per (HD 30353) has been detected in a study of low-resolution IUE spectra. The system as a whole is very similar to Upsilon Sgr. The observations are consistent with a model in which the primary is a helium supergiant of about 1 solar mass and the secondary is an overluminous early-type star with a mass of 5-6 solar masses. This model predicts that the system is now undergoing its second mass exchange.

Drilling, J. S.↗
NASA NTRS1985

Correlation between solar neutrino flux and other solar phenomena

A study was made of the solar neutrino data with a tank of CC14 located 4800 mwe underground for the period 1970 to 83. These observations are on the production rates of Ar37 atoms via the reaction upsilon sub e + Cl37 yields Ar37 plus e(-) in the tank caused presumably by a flux of neutrinos from the Sun. The idea of possible time variations in the data shown is discussed and an attempt is made to correlate the variations to two other phenomena of solar origin-the sunspot number and the geomagnetic Ap index.

Lal, S.↗
NASA NTRS1985

Hybrid TLC-pair meter for the Sphinx Project

The chief aims in THE SPHINX PROJECT are research of super lepton physics and new detector experiments. At the second phase of THE SPHINX PROJECT, a hybrid TLC-PAIR METER was designed for measuring high energy neutrino sources (E upsilon * TeV), searching high energy muon sources (E mu TeV) and measuring muon group (E mu 1 TeV). The principle of PAIR METER has been already proposed. In this TLC-PAIR METER, electromagnetic shower induced by cosmic ray muons are detected using TL (Thermoluminescence) sheets with position counters.

Wada, T.↗
NASA NTRS1985

Results of low energy background measurements with the Liquid Scintillation Detector (LSD) of the Mont Blanc Laboratory

The 90 tons liquid scintillation detector (LSD) is fully running since October 1984, at a depth of 5,200 hg/sq cm of standard rock underground. The main goal is to search for neutrino bursts from collapsing stars. The experiment is very sensitive to detect low energy particles and has a very good signature to gamma-rays from (n,p) reaction which follows the upsilon e + p yields n + e sup + neutrino capture. The analysis of data is presented and the preliminary results on low energy measurements are discussed.

Aglietta, M.↗
NASA NTRS1986

Advanced infrared astronomy

The CO2 laser heterodyne spectrometer was used at the 3-m IRTF on Mauna Kea to make measurements of Mars during the 1984 opposition. Analysis of the observations of the mesospheric non-thermal emission demonstrated the existence of a warming of the Mars polar mesosphere, similar to the seasonal effects which are well known to occur at the Earth's mesopause. A search for CO2 and NH3 on Comet Halley was done with the new Kitt Peak system as well as with the IRTF heterodyne system. A Lamb-dip absorption cell was designed and constructed. Its use will allow extreme frequency stabilization of the laser local oscillator, which will greatly facilitate measurements of winds and dynamical phenomena. The Lamb-dip cell was used at Kitt Peak to study zonal and meridional winds in the atmosphere of Venus. Water vapor was detected in Comet Halley using Fourier transform spectrometer. The 2.65 micrometer upsilon sub 3 band was seen in emission, confirming non-thermal-equilibrium excitation models for comets. A study was made of the variability of Jovian ethane emission. The average volume mixing ratio of ethane in the Jovian stratosphere was found to be 3x10 to the -6 power, with the greatest variability seen in the auroral regions.

Mumma, M. J.↗
NASA NTRS1986

Near-infrared observations of IRAS sources in and near dense cores

We report 0.4 to 20 micron photometry of 27 Infrared Astronomy Satellite (IRAS) point sources associated with dense cores in nearby dark clouds. It is found that these objects have a bimodal distribution of spectral slopes. The objects in the group with steep spectral slopes are typically within one half power radius of the core peak and are not visible on the POSS. The remainder of the objects are typically further from their cores, are optically visible and have shallow spectral slopes (s is approximately 0.6). Most of the sources in this group which have been previously identified are T Tauri stars. Both the groups of objects have essentially the same luminosity function with median luminosity of 1 to 2 L(solar), which is similiar to the luminosity function for T Tauri stars. The near-infrared (J,H,K,L) colors of the objects have been used to estimate the visual extinction to the stars. This indicates that the typical steep spectrum source has extinction A(upsilon) of approximately 30 magnitudes, which is larger by a factor of 3 to 4 than a uniform core can provide, thus the density must rise steeply in the vicinity of the star. For those objects where optical estimates of the extinction are available the optical estimates are typically smaller than our IR estimates by a factor of 1.6. For multiple scattering by grains that scatter primarily in the forward direction, this implies a grain albedo of 0.4 at V, consistent with theoretical predictions for bare grains. Using this derived extinction, the FIR emission from a spherical shell with an inverse power law density which contributes the correct amount of extinction has been modelled. It is shown that to be consistent with both the observations of the density of the core at a scale of 1.5 x 10(17) cm and the extinction derived from the near-IR colors there must be a circumstellar hole of radius 10-100 A.U. for all density laws with exponents greater than 1.2. It is also shown that a component in addition to the star and circumstellar shell is necessary to match the observed spectrum of steep spectrum sources.

Fuller, G. A.↗
NASA NTRS1988

The orbit of the Cepheid AW Per

An orbit for the classical Cepheid AW Per was derived. Phase residuals from the light curve are consistent with the light-time effect from the orbit. The companion was studied using IUE spectra. The flux distribution from 1300 to 1700 A is unusual, probably an extreme PbSi star, comparable to a B7V or B8V star. The flux of the composite spectrum from 1200 A through V is well matched by F7Ib and B8V standard stars with Delta M(sub upsilon) = 3(m) multiplied by 1. The mass function from the orbit indicates that the mass of the Cepheid must be greater that 4.7 solar mass if it is the more massive component. A B7V to B8V companion is compatible with the 1 sigma lower limit (3.5 solar mass) from the mass function. This implies that the Cepheid has the same mass, but the large magnitude difference rules this out. It is likely that the companion is itself a binary.

Evans, Nancy Remage↗
NASA NTRS1988

Chaos in a spatially-developing plane mixing layer

A spatially-developing plane mixing layer was analyzed for chaotic behavior. A direct numerical simulation of the Navier-Stokes equations in a 2-D domain infinite in y and having inflow-outflow boundary conditions in x was used for data. Spectra, correlation dimension and the largest Lyapunov exponent were computed as functions of downstream distance x. When forced at a single (fundamental) frequency with maximum amplitude, the flow is periodic at the inflow but becomes aperiodic with increasing x. The aperiodic behavior is caused by the presence of a noisy subharmonic caused by the feedback between the necessarily nonphysical inflow and outflow boundary conditions. In order to overshadow this noise the flow was also studied with the same fundamental forcing and added random forcing of amplitude upsilon prime sub R/delta U = 0.01 at the inlet. Results were qualitatively the same in both cases: for small x, spectral peaks were sharp and dimension was nearly 1, but as x increased a narrowband spectral peak grew, spectra decayed exponentially at high frequencies and dimension increased to greater than 3. Based on these results, the flow appears to exhibit deterministic chaos. However, at no location was the largest Lyapunov exponent found to be significantly greater than zero.

Broze, J. G.↗
NASA NTRS1989

Intrinsic ultraviolet (912-3200 A) energy distribution of OB stars

Low-dispersion 500-3200-A spectra of 20 OB stars are used to derive three individual extinction curves in the wavelength range 912-1200 A. The dependence of the intrinsic UV fluxes of OB stars on both spectral type and luminosity is demonstrated. UV color indices are proposed. The results confirm the previous finding that O star spectra are not significantly bluer than the spectrum of the B0 main-sequence star Upsilon Ori.

Longo, Renata↗