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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

First Direct Measurements of Superheavy-Element Mass Numbers

An experiment was performed at Lawrence Berkeley National Laboratory’s 88-in. Cyclotron to determine the mass number of a superheavy element. The measurement resulted in the observation of two α-decay chains, produced via the 243 Am( 48 Ca,xn) 291–x Mc reaction, that were separated by mass-to-charge ratio (A/q) and identified by the combined BGS+FIONA apparatus. One event occurred at A/q = 284 and was assigned to 284 Nh (Z=113), the α-decay daughter of 288 Mc (Z=115), while the second occurred at A/q = 288 and was assigned to 288 Mc. In conclusion, this experiment represents the first direct measurements of the mass numbers of superheavy elements, confirming previous (indirect) mass-number assignments.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2014

Externally driven global Alfvén eigenmodes applied for effective mass number measurement on TCABR

The excitation and detection of Global Alfvén Eigenmodes on TCABR for diagnostic purposes are presented. The modes can be excited with one or two in-vessel antennae, with up to 15 A of current in each, in the frequency range from 2 to 4 MHz. This scheme allows the estimation of the effective mass number at the plasma center, which value is affected by impurity concentration in the core. An amplifier based on MOSFETs is used to excite the waves driven by low power, in order to not change the basic plasma parameters. The variation of the GAE with density is verified and the location of the mode resonance at the plasma center is confirmed by the sawtooth beating, so that the correspondingly beating phase inversion improves the precision on the resonant condition determination. The toroidal parity of the modes N = 1,2 is determined by use of two opposite located antennae with different phase of the RF current. Knowledge of toroidal mode number is important as it identifies GAE location and defines the estimated effective mass value. The estimated value for A{sub eff} is ∼1.4–1.5, corresponding to 5–7% of carbon impurity concentration. The measured value of A{sub eff} is used to estimate Z{sub eff}, which is compared to older TCA experiments and the value obtained by the Spitzer conductivity.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2022

Evidence for Nonlinear Gluon Effects in QCD and Their Mass Number Dependence at STAR

The STAR Collaboration reports measurements of back-to-back azimuthal correlations of di-π 0 s produced at forward pseudorapidities (2.6<η<4.0) in p+p, p+Al, and p+Au collisions at a center-of-mass energy of 200 GeV. We observe a clear suppression of the correlated yields of back-to-back π 0 pairs in p+Al and p+Au collisions compared to the p+p data. The observed suppression of back-to-back pairs as a function of transverse momentum suggests nonlinear gluon dynamics arising at high parton densities. Furthermore, the larger suppression found in p+Au relative to p+Al collisions exhibits a dependence of the saturation scale $Q^{2}_{s}$ on the mass number A . A linear scaling of the suppression with A 1/3 is observed with a slope of -0.09±0.01.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

Studies of heavy and super heavy elements with FIONA: the broad impact of mass-number identifications

There have been multiple recent experimental upgrades at the Lawrence Berkeley National Laboratory 88-Inch Cyclotron facility aimed to further what is possible in Heavy and Super Heavy Element research. The addition of FIONA to the focal plane of the Berkeley Gas-Filled Separator now allows for ions of these heavy and superheavy elements, produced in nuclear reactions, to be identified directly by their mass-to-charge ratio. Mass-number measurements can have a broad impact in understanding the fundamental nuclear and chemical properties of the heaviest elements. A detailed review of the Berkeley Gas-filled Separator, FIONA, their capabilities, and an overview of the first science results are presented.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Energy dependence and systematics of level-density parameters in nuclei of mass number in the range of A = 20–60

Existing direct and indirect experimental data on level densities in excited nuclei of mass and charge number in the ranges of A = 20–60 and Z = 11–27, respectively, were compiled and analyzed. Contradictions between values extracted from the results of measurements performed by different methods were revealed. Consistent input data were selected, and a systematics of level-density parameters was created on this basis within the generalized model of superfluid nuclei. The effect of the first discrete vibrational levels on extracted parameters was studied.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2014

Half-life Measurements of Excited Levels in Fission Products around Mass Number 150

A spectrometer to measure nuclear level half-lives has been installed at the on-line isotope separator of the Kyoto University Reactor. This spectrometer consists of a LaBr3 scintillator, a thin plastic scintillator and an HPGe detector. Half-lives are deduced using the β-γ-γ delayed coincidence method. The prompt-time distribution curves measured with the spectrometer give a time resolution (FWHM) of 600 ps for 100-keV γ rays. This resolution means that half-lives down to the subnanosecond range or shorter can be measured. We reported recent measurements of the half-life of {sup 149}Pr and {sup 149}Nd. Some of the more interesting results include the first determination of the half-lives of {sup 149}Pr levels at 86.5 and 125.6 keV, which are 4.2(5) ns and 1.0(2) ns, respectively. In addition, the data indicate that the half-life of the 270.8-keV level in {sup 149}Nd is not 5.1(3) ns as reported previously, but 0.42(3) ns.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2016

Mass-number and excitation-energy dependence of the spin cutoff parameter

Here, the spin cutoff parameter determining the nuclear level density spin distribution ρ(J) is defined through the spin projection as < J 2 z > 1/2 or equivalently for spherical nuclei, (< J(J+1) >/3) 1/2 . It is needed to divide the total level density into levels as a function of J. To obtain the total level density at the neutron binding energy from the s-wave resonance count, the spin cutoff parameter is also needed. The spin cutoff parameter has been calculated as a function of excitation energy and mass with a super-conducting Hamiltonian. Calculations have been compared with two commonly used semiempirical formulas. A need for further measurements is also observed. Some complications for deformed nuclei are discussed. The quality of spin cut off parameter data derived from isomeric ratio measurement is examined.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2024

Development of alpha cluster structure in nuclei of the same mass number

The resonant 14 N+α particle scattering was studied in the 18 F excitation region from 6.5 to 9 MeV at Astana cyclotron using the TTIK approach. The excitation functions for the elastic 14 N+α scattering were analyzed in the framework of R-matrix approach. The observed strong alpha cluster structure in 18 F is compared with that in 18 O.

Nurmukhanbetova, Aliya↗
DOE OSTI2016

A Method to Estimate the Atomic Number and Mass Thickness of Intervening Materials in Uranium and Plutonium Gamma-Ray Spectroscopy Measurements

To accurately characterize shielded special nuclear materials (SNM) using passive gamma-ray spectroscopy measurement techniques, the effective atomic number and the thickness of shielding materials must be measured. Intervening materials between the source and detector may affect the estimated source isotopics (uranium enrichment and plutonium grade) for techniques which rely on raw count rates or photopeak ratios of gamma-ray lines separated in energy. Furthermore, knowledge of the surrounding materials can provide insight regarding the configuration of a device containing SNM. The described method was developed using spectra recorded using high energy resolution CdZnTe detectors, but can be expanded to any gamma-ray spectrometers with energy resolution of better than 1% FWHM at 662 keV. The effective atomic number, Z, and mass thickness of the intervening shielding material are identified by comparing the relative attenuation of different gamma-ray lines and estimating the proportion of Compton scattering interactions to photoelectric absorptions within the shield. While characteristic Kα x-rays can be used to identify shielding materials made of high Z elements, this method can be applied to all shielding materials. This algorithm has adequately estimated the effective atomic number for shields made of iron, aluminum, and polyethylene surrounding uranium samples using experimental data. The mass thicknesses of shielding materials have been estimated with a standard error of less than 1.3 g/cm2 for iron shields up to 2.5 cm thick. The effective atomic number was accurately estimated to 26 ± 5 for all iron thicknesses.

CdZnTe detectors, gamma-ray imaging, gamma-ray spe↗
DOE OSTI2022

Isotope effects under the influence of global radial electric fields in a helical configuration

Isotope effects under the influence of a radial electric field are examined in a helical magnetic field configuration. We perform global gyrokinetic simulations with additional poloidal rotations to estimate quasi-linear heat flux due to ion temperature gradient mode under the mixing length model. In single-ion-species plasmas, the mass number dependency of heat flux agrees with gyro-Bohm scaling in the absence of a radial electric field. Favorable mass number dependencies violating gyro-Bohm scaling are observed in the presence of a global radial electric field or a heavy hydrogen component in multi-ion-species plasmas. The radial electric field and the heavy hydrogen component affect the heat flux through an increase of wavelength as well as mode stabilization. Poloidal Mach number characterizes the transition from unfavorable to favorable mass number dependency under radial electric fields. While the heat flux is independent of mass number for a given poloidal Mach number, the heat flux decreases for higher mass numbers in a given radial electric field. The heat flux is also independent of average mass number in multi-ion-species plasmas because the heavy hydrogen component effectively enhances the light hydrogen heat flux. The present results are potentially relevant to the violation of gyro-Bohm scaling observed in the recent deuterium experiments in the Large Helical Device.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2014

Nuclear Data Sheets for A = 239

Spectroscopic data and level schemes from radioactive decay and nuclear reaction studies are presented here for all nuclei with mass number A=239. In general, a relatively small amount of new data on this mass chain has been reported since the previous evaluation in 2003. However, special evaluations, such as ''Database of prompt gamma rays from slow neutron–capture from elemental analysis'' (2007ChZX), have provided additional precise data for levels in 29 U. Also, new Coulomb excitation measurements in 239 Pu have extended the knowledge of the 1/2[631] rotational band up to Jπ=(55/2+)Jπ=(55/2+), and that of the octupole vibrational band up to Jπ=(53/2-)Jπ=(53/2-). For historical knowledge it is worth mentioning the report on the “Discovery of isotopes of the transuranium elements with 93 <= Z <= 98'' (2013Fr02), where the information for elements Np, Pu, Am, and Cf with mass number A=239 is presented. The alpha hindrance factors (HF) presented in this evaluation were calculated using values of the radius parameter (r 0 ) interpolated from those for even–even adjacent nuclei given by 1998Ak04.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2018

Solid Particle Number and Mass Emissions from Lean and Stoichiometric Gasoline Direct Injection Engine Operation

In this work, engine-out particle mass (PM) and particle number (PN) emissions were experimentally examined from a gasoline direct injection (GDI) engine operating in two lean combustion modes and one stoichiometric mode with a fuel of known properties. Ten steady state operating points, two constant speed load steps, and an engine cold start were examined. Results showed that solid particles emitted from the engine under steady state stoichiometric conditions had a uniquely broad size distribution that was relatively flat between the diameters of 10 and 100 nm. In most operating conditions, lean homogenous modes can achieve lower particle emissions than stoichiometric modes while improving engine thermal efficiency. Alternatively, lean stratified operating modes resulted in significantly higher PN and PM emissions than both lean homogeneous and stoichiometric modes with increased efficiency only at low engine load. Stoichiometric load steps showed minimal soot emissions while ash-mode emissions spike dramatically due to oil consumption caused by piston ring adjustment. Correlation of PN to PM for steady state stoichiometric cases was in good agreement with that reported from multiple prior studies for both diesel and stoichiometric GDI engines. However, the lean cases resulted in higher PN to PM ratios indicating more small particles per unit mass. High ash particle concentration, especially in lean operation illustrates that oil control is important for mitigating impacts on downstream gasoline particulate filters (GPF) from which ash particles are cannot be removed during filter regeneration. Further research is necessary to elucidate the origin and composition of sub-23 nm particles from GDI engines and their effect on aftertreatment technology if lean homogeneous modes are to be employed.

Bock, Noah↗
DOE OSTI2016

100 TeV pp collisions, Exotics type, PYTHIA8 generator: tev100pp_qstar_pythia8_mbins_slim

Excited Fermions in mass range pT=5-40 TeV. 10000 events per file, 100 files per mass. Compositeness scale (Lambda) is set to the mass of the fermion, so the width is expected to be small (see the log files for details) Cross sections are included in the log files (mass dependent) Note that data are slimmed (see the log file). How to decode name: Name: tev100_pythia8_qstar_m[MASS]_[NUMBER] where [MASS] is generator-level mass as given below: Mass bins (in GeV) m[1]=5000 m[2]=10000 ......... How to use: To get a sample with a given mass, use "glob" regular expressions. Slimmed as: Particle records are slimmed (all stable with pT>0.3 GeV) and (PID=5 || PID=6) or PID>22 && PID<38) or PID>10 && PID<17).

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

13 TeV pp collisions, Exotics type, PYTHIA8 generator: tev13pp_qstar_pythia8_mbins

Excited Fermions in mass range pT=6-40 TeV. 5000 events per file, 100 files per mass. Compositeness scale (Lambda) is set to the mass of the fermion, so the width is expected to be small (see the log files for details) Cross sections are included in the log files (mass dependent). How to decode name: Name: tev100_pythia8_qstar_m[MASS]_[NUMBER] where [MASS] is generator-level mass as given below: Mass bins (in GeV) m[1]=2000 m[2]=4000 m[3]=6000 m[4]=8000 m[5]=10000 m[6]=12000 m[7]=14000. How to use: To get a sample with a given mass, use "glob" regular expressions. Slimmed as: Particle records are slimmed (all stable with pT>0.3 GeV) and (PID=5 || PID=6) or PID>22 && PID<38) or PID>10 && PID<17).

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Measurements of production cross sections of 10Be and 26Al by 120GeV and 392MeV proton bombardment of 89Y, 159Tb, and natCu targets

The production cross sections of 10 Be and 26 Al were measured by accelerator mass spectrometry using 89 Y, 159 Tb, and nat Cu targets bombarded by protons with energies Ep of 120GeV and 392MeV. The production cross sections obtained for 10 Be and 26 Al were compared with those previously reported using Ep=50MeV–24GeV and various targets. It was found that the production cross sections of 10 Be monotonically increased with increasing target mass number when the proton energy was greater than a few GeV. On the other hand, it was also found that the production cross sections of 10 Be decreased as the target mass number increased from that of carbon to those near the mass numbers of nickel and zinc when the proton energy was below approximately 1GeV. They also increased as the target mass number increased from near those of nickel and zinc to that of bismuth, in the same proton energy range. Similar results were observed in the production cross sections of 26 Al, though the absolute values were quite different between 10 Be and 26 Al. The difference between these production cross sections may depend on the impact parameter (nuclear radius) and/or the target nucleus stiffness.

120 GeV proton↗