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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 955 records · Page 53
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

Study of the {sup 17}O(n,α){sup 14}C reaction: Extension of the Trojan Horse Method to neutron induced reactions

The experimental study of the {sup 17}O(n,α){sup 14}C reaction has been performed in the energy range 0-350 keV. This reaction could play an important role in explaining heavy elements (s-process) nucleosynthesis in various astrophysical scenario. To overcome the practical problems arising from the neutrons production, a new application of the Trojan Horse Method has been recently suggested. In more details, the {sup 17}O(n,α){sup 14}C reaction has been studied using the quasi-free {sup 2}H({sup 17}O,α{sup 14}C){sup 1}H reaction, induced at an energy of 43.5 MeV. The measurement allows one to investigate the ℓ=3, 75 keV resonance (E*=8.125 MeV, J{sup π}=5{sup −}), absent in the available direct measurements because of centrifugal suppression effects.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2014

Continuous-scanning laser Doppler vibrometry: Extensions to arbitrary areas, multi-frequency and 3D capture

To date, differing implementations of continuous scan laser Doppler vibrometry have been demonstrated by various academic institutions, but since the scan paths were defined using step or sine functions from function generators, the paths were typically limited to 1D line scans or 2D areas such as raster paths or Lissajous trajectories. The excitation was previously often limited to a single frequency due to the specific signal processing performed to convert the scan data into an ODS. In this paper, a configuration of continuous-scan laser Doppler vibrometry is demonstrated which permits scanning of arbitrary areas, with the benefit of allowing multi-frequency/broadband excitation. Various means of generating scan paths to inspect arbitrary areas are discussed and demonstrated. Further, full 3D vibration capture is demonstrated by the addition of a range-finding facility to the described configuration, and iteratively relocating a single scanning laser head. Here, the range-finding facility was provided by a Microsoft Kinect, an inexpensive piece of consumer electronics.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2014

Extension of Chern-Simons forms

We investigate metric independent, gauge invariant, and closed forms in the generalized Yang-Mills (YM) theory. These forms are polynomial on the corresponding fields strength tensors – curvature forms and are analogous to the Pontryagin-Chern densities in the YM gauge theory. The corresponding secondary characteristic classes have been expressed in integral form in analogy with the Chern-Simons form. Because they are not unique, the secondary forms can be dramatically simplified by the addition of properly chosen differentials of one-step-lower-order forms. Their gauge variation can also be found yielding the potential anomalies in the gauge field theory.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2014

Extension of high T{sub e} regime with upgraded electron cyclotron resonance heating system in the Large Helical Device

Enhancement of the output power per gyrotron has been planned in the Large Helical Device (LHD). Three 77-GHz gyrotrons with an output power of more than 1 MW have been operated. In addition, a high power gyrotron with the frequency of 154 GHz (1 MW/5 s, 0.5 MW/CW) was newly installed in 2012, and the total injection power of Electron cyclotron resonance heating (ECRH) reached 4.6 MW. The operational regime of ECRH plasma on the LHD has been extended due to the upgraded ECRH system such as the central electron temperature of 13.5 keV with the line-averaged electron density n{sub e-fir} = 1 × 10{sup 19} m{sup −3}. The electron thermal confinement clearly improved inside the electron internal transport barrier, and the electron thermal diffusivity reached neoclassical level. The global energy confinement time increased with increase of n{sub e-fir}. The plasma stored energy of 530 kJ with n{sub e-fir} = 3.2 × 10{sup 19} m{sup −3}, which is 1.7 times larger than the previous record in the ECRH plasma in the LHD, has been successfully achieved.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2014

Feedback-assisted extension of the tokamak operating space to low safety factor

Recent DIII-D and RFX-mod experiments have demonstrated stable tokamak operation at very low values of the edge safety factor q(a) near and below 2. The onset of n = 1 resistive wall mode (RWM) kink instabilities leads to a disruptive stability limit, encountered at q(a) = 2 (limiter plasmas) and q{sub 95} = 2 (divertor plasmas). However, passively stable operation can be attained for q(a) and q{sub 95} values as low as 2.2. RWM damping in the q(a) = 2 regime was measured using active MHD spectroscopy. Although consistent with theoretical predictions, the amplitude of the damped response does not increase significantly as the q(a) = 2 limit is approached, in contrast with damping measurements made approaching the pressure-driven RWM limit. Applying proportional gain magnetic feedback control of the n = 1 modes has resulted in stabilized operation with q{sub 95} values reaching as low as 1.9 in DIII-D and q(a) reaching 1.55 in RFX-mod. In addition to being consistent with the q(a) = 2 external kink mode stability limit, the unstable modes have growth rates on the order of the characteristic wall eddy-current decay timescale in both devices, and a dominant m = 2 poloidal structure that is consistent with ideal MHD predictions. The experiments contribute to validating MHD stability theory and demonstrate that a key tokamak stability limit can be overcome with feedback.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2014

Extension of spatiotemporal chaos in glow discharge-semiconductor systems

Generation of chaos in response systems is discovered numerically through specially designed unidirectional coupling of two glow discharge-semiconductor systems. By utilizing the auxiliary system approach, [H. D. I. Abarbanel, N. F. Rulkov, and M. M. Sushchik, Phys. Rev. E 53, 4528–4535 (1996)] it is verified that the phenomenon is not a chaos synchronization. Simulations demonstrate various aspects of the chaos appearance in both drive and response systems. Chaotic control is through the external circuit equation and governs the electrical potential on the boundary. The expandability of the theory to collectives of glow discharge systems is discussed, and this increases the potential of applications of the results. Moreover, the research completes the previous discussion of the chaos appearance in a glow discharge-semiconductor system [D. D. Šijačić U. Ebert, and I. Rafatov, Phys. Rev. E 70, 056220 (2004).].

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Extension of anisotropic effective medium theory to account for an arbitrary number of inclusion types

The purpose of this paper is to extend, to multi-components, a previously reported theory for calculating the effective conductivity of a two component mixture. The previously reported theory involved preferentially oriented spheroidal inclusions contained in a continuous matrix, with inclusions oriented relative to a principle axis. This approach was based on Bruggeman's unsymmetrical theory, and is extended to account for an arbitrary number of different inclusion types. The development begins from two well-known starting points; the Maxwell approach and the Maxwell-Garnett approach for dilute mixtures. It is shown that despite these two different starting points, the final Bruggeman type equation is the same. As a means of validating the developed expression, comparisons are made to several existing effective medium theories. It is shown that these existing theories coincide with the developed equations for the appropriate parameter set. Finally, a few example mixtures are considered to demonstrate the effect of multiple inclusions on the calculated effective property. Inclusion types of different conductivities, shapes, and orientations are considered and each of the aforementioned properties is shown to have a potentially significant impact on the calculated mixture property.

36 MATERIALS SCIENCE↗
DOE OSTI2015

The MaxEnt extension of a quantum Gibbs family, convex geometry and geodesics

We discuss methods to analyze a quantum Gibbs family in the ultra-cold regime where the norm closure of the Gibbs family fails due to discontinuities of the maximum-entropy inference. The current discussion of maximum-entropy inference and irreducible correlation in the area of quantum phase transitions is a major motivation for this research. We extend a representation of the irreducible correlation from finite temperatures to absolute zero.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Surface-hopping trajectories for OH(A{sup 2}Σ{sup +}) + Kr: Extension to the 1A″ state

We present a new trajectory surface hopping study of the rotational energy transfer and collisional quenching of electronically excited OH(A) radicals by Kr. The trajectory surface hopping calculations include both electronic coupling between the excited 2{sup 2}A′ and ground 1{sup 2}A′ electronic states, as well as Renner-Teller and Coriolis roto-electronic couplings between the 1{sup 2}A′ and 1{sup 2}A″, and the 2{sup 2}A′ and 1{sup 2}A″ electronic states, respectively. The new calculations are shown to lead to a noticeable improvement in the agreement between theory and experiment in this system, particularly with respect to the OH(X) rotational and Λ-doublet quantum state populations, compared with a simpler two-state treatment, which only included the electronic coupling between the 2{sup 2}A′ and 1{sup 2}A′ states. Discrepancies between the predictions of theory and experiment do however remain, and could arise either due to errors in the potential energy surfaces and couplings employed, or due to the limitations in the classical treatment of non-adiabatic effects.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

BH{sub 2} revisited: New, extensive measurements of laser-induced fluorescence transitions and ab initio calculations of near-spectroscopic accuracy

The spectroscopy of gas phase BH{sub 2} has not been explored experimentally since the pioneering study of Herzberg and Johns in 1967. In the present work, laser-induced fluorescence (LIF) spectra of the A{sup ~} {sup 2}B{sub 1}(Π{sub u})−X{sup ~2}A{sub 1} band system of {sup 11}BH{sub 2}, {sup 10}BH{sub 2}, {sup 11}BD{sub 2}, and {sup 10}BD{sub 2} have been observed for the first time. The free radicals were “synthesized” by an electric discharge through a precursor mixture of 0.5% diborane (B{sub 2}H{sub 6} or B{sub 2}D{sub 6}) in high pressure argon at the exit of a pulsed valve. A total of 67 LIF bands have been measured and rotationally analyzed, 62 of them previously unobserved. These include transitions to a wide variety of excited state bending levels, to several stretch-bend combination levels, and to three ground state levels which gain intensity through Renner-Teller coupling to nearby excited state levels. As an aid to vibronic assignment of the spectra, very high level hybrid ab initio potential energy surfaces were built starting from the coupled cluster singles and doubles with perturbative triples (CCSD(T))/aug-cc-pV5Z level of theory for this seven-electron system. In an effort to obtain the highest possible accuracy, the potentials were corrected for core correlation, extrapolation to the complete basis set limit, electron correlation beyond CCSD(T), and diagonal Born-Oppenheimer effects. The spin-rovibronic states of the various isotopologues of BH{sub 2} were calculated for energies up to 22 000 cm{sup −1} above the X{sup ~} (000) level without any empirical adjustment of the potentials or fitting to experimental data. The agreement with the new LIF data is excellent, approaching near-spectroscopic accuracy (a few cm{sup −1}) and has allowed us to understand the complicated spin-rovibronic energy level structure even in the region of strong Renner-Teller resonances.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2015

Extension of the flow-rate-of-strain tensor formulation of plasma rotation theory to non-axisymmetric tokamaks

A systematic formalism for the calculation of rotation in non-axisymmetric tokamaks with 3D magnetic fields is described. The Braginskii Ωτ-ordered viscous stress tensor formalism, generalized to accommodate non-axisymmetric 3D magnetic fields in general toroidal flux surface geometry, and the resulting fluid moment equations provide a systematic formalism for the calculation of toroidal and poloidal rotation and radial ion flow in tokamaks in the presence of various non-axisymmetric “neoclassical toroidal viscosity” mechanisms. The relation among rotation velocities, radial ion particle flux, ion orbit loss, and radial electric field is discussed, and the possibility of controlling these quantities by producing externally controllable toroidal and/or poloidal currents in the edge plasma for this purpose is suggested for future investigation.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2015

Extension of Nikiforov-Uvarov method for the solution of Heun equation

We report an alternative method to solve second order differential equations which have at most four singular points. This method is developed by changing the degrees of the polynomials in the basic equation of Nikiforov-Uvarov (NU) method. This is called extended NU method for this paper. The eigenvalue solutions of Heun equation and confluent Heun equation are obtained via extended NU method. Some quantum mechanical problems such as Coulomb problem on a 3-sphere, two Coulombically repelling electrons on a sphere, and hyperbolic double-well potential are investigated by this method.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Extension of the BMCSL equation of state for hard spheres to the metastable disordered region: Application to the SAFT approach

A simple modification of the Boublík-Mansoori-Carnahan-Starling-Leland equation of state is proposed for an application to the metastable disordered region. The new model has a positive pole at the jamming limit and can accurately describe the molecular simulation data of pure hard in the stable fluid region and along the metastable branch. The new model has also been applied to binary mixtures hard spheres, and an excellent description of the fluid and metastable branches can be obtained by adjusting the jamming packing fraction. The new model for hard sphere mixtures can be used as the repulsive term of equations of state for real fluids. In this case, the modified equations of state give very similar predictions of thermodynamic properties as the original models, and one can remove the multiple liquid density roots observed for some versions of the Statistical Associating Fluid Theory (SAFT) at low temperature without any modification of the dispersion term.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Re-appraisal and extension of the Gratton-Vargas two-dimensional analytical snowplow model of plasma focus. II. Looking at the singularity

The Gratton-Vargas snowplow model, recently revisited and expanded [S. K. H. Auluck, Phys. Plasmas 20, 112501 (2013)], has given rise to significant new insights into some aspects of the Dense Plasma Focus (DPF), in spite of being a purely kinematic description having no reference to plasma phenomena. It is able to provide a good fit to the experimental current waveforms in at least 4 large facilities. It has been used for construction of a local curvilinear frame of reference, in which conservation laws for mass, momentum, and energy can be reduced to effectively-one-dimensional hyperbolic conservation law equations. Its utility in global parameter optimization of device parameters has been demonstrated. These features suggest that the Gratton-Vargas model deserves a closer look at its supposed limitations near the singular phase of the DPF. This paper presents a discussion of its development near the device axis, based on the original work of Gratton and Vargas, with some differences. It is shown that the Gratton-Vargas partial differential equation has solutions for times after the current singularity, which exhibit an expanding bounded volume (which can serve as model of an expanding plasma column) and decreasing dynamic inductance of the discharge, in spite of having no built-in hydrodynamics. This enables the model to qualitatively reproduce the characteristic shape of the current derivative in DPF experiments without reference to any plasma phenomena, such as instabilities, anomalous resistance, or reflection of hydrodynamic shock wave from the axis. The axial propagation of the solution exhibits a power-law dependence on the dimensionless time starting from the time of singularity, which is similar to the power-law relations predicted by theory of point explosions in ideal gases and which has also been observed experimentally.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2016

Baryon and lepton number violating effective operators in a non-universal extension of the standard model

It is well known that non-abelian Yang-Mills theories present non-trivial minima of the action, the so-called instantons. In the context of electroweak theories these instanton solutions may induce violations of baryon and lepton number of the form ΔB = ΔL = n{sub f}, with n{sub f} being the number of families coupled to the gauge group. An interesting feature of these violations is that the flavor structure of the gauge couplings is inherited by the instanton transitions. This effect is generally neglected in the literature. We will show that the inclusion of flavor interactions in the instanton solutions may be interesting in certain theoretical frameworks and will provide an approach to include these effects. In particular we will perform this implementation in the non-universal SU (2){sub l} ⊗SU (2){sub h} ⊗U (1){sub Y} model that singularizes the third family. Within this framework, we will use the instanton transitions to set a bound on the SU (2){sub h} gauge coupling.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Extension of Alvis compiler front-end

Alvis is a formal modelling language that enables possibility of verification of distributed concurrent systems. An Alvis model semantics finds expression in an LTS graph (labelled transition system). Execution of any language statement is expressed as a transition between formally defined states of such a model. An LTS graph is generated using a middle-stage Haskell representation of an Alvis model. Moreover, Haskell is used as a part of the Alvis language and is used to define parameters’ types and operations on them. Thanks to the compiler’s modular construction many aspects of compilation of an Alvis model may be modified. Providing new plugins for Alvis Compiler that support languages like Java or C makes possible using these languages as a part of Alvis instead of Haskell. The paper presents the compiler internal model and describes how the default specification language can be altered by new plugins.

97 MATHEMATICS AND COMPUTING↗