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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 397 records · Page 22
All sourcesNASA NTRSDOE OSTI
DOE OSTI2010

Hyperfine-mediated static polarizabilities of monovalent atoms and ions

We apply relativistic many-body methods to compute static differential polarizabilities for transitions inside the ground-state hyperfine manifolds of monovalent atoms and ions. Knowledge of this transition polarizability is required in a number of high-precision experiments, such as microwave atomic clocks and searches for CP-violating permanent electric dipole moments. While the traditional polarizability arises in the second order of interaction with the externally applied electric field, the differential polarizability involves an additional contribution from the hyperfine interaction of atomic electrons with nuclear moments. We derive formulas for the scalar and tensor polarizabilities including contributions from magnetic dipole and electric quadrupole hyperfine interactions. Numerical results are presented for Al, Rb, Cs, Yb{sup +}, Hg{sup +}, and Fr.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2011

Effects of tensor correlations on low-lying collective states in finite nuclei

We present a systematic analysis of the effects induced by tensor correlations on low-lying collective states of magic nuclei, by using the fully self-consistent random phase approximation (RPA) model with Skyrme interactions. The role of the tensor correlations is analyzed in detail in the case of quadrupole (2{sup +}) and octupole (3{sup -}) low-lying collective states in {sup 208}Pb. The example of {sup 40}Ca is also discussed, as well as the case of magnetic dipole states (1{sup +}).

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2017

VARIABLE AND POLARIZED RADIO EMISSION FROM THE T6 BROWN DWARF WISEP J112254.73+255021.5

Route and Wolszczan recently detected five radio bursts from the T6 dwarf WISEP J112254.73+255021.5 and used the timing of these events to propose that this object rotates with an ultra-short period of ∼17.3 minutes. We conducted follow-up observations with the Very Large Array and Gemini-North but found no evidence for this periodicity. We do, however, observe variable, highly circularly polarized radio emission. Assuming that the radio emission of this T dwarf is periodically variable on ∼hour timescales, like other radio-active ultracool dwarfs, we infer a likely period of 116 minutes. However, our observation lasted only 162 minutes and so more data are needed to test this hypothesis. The handedness of the circular polarization switches twice and there is no evidence for any unpolarized emission component, the first time such a phenomenology has been observed in radio studies of very low-mass stars and brown dwarfs. We suggest that the object’s magnetic dipole axis may be highly misaligned relative to its rotation axis.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2011

ON THE SPIN-DOWN AND MAGNETIC FIELD OF THE X-RAY PULSAR 1E 1207.4-5209

We analyze all of the archival X-ray timing data from the years 2000-2008 on the weakly magnetized central compact object (CCO) pulsar 1E 1207.4-5209 in an attempt to measure its dipole magnetic field strength via spin-down. because most of these observations were not planned for the purpose of phase-coherent timing, the resulting ephemeris is not unique, but is restricted to two comparably good timing solutions that correspond to B{sub s} = 9.9 x 10{sup 10} G or 2.4 x 10{sup 11} G, respectively, assuming dipole spin-down. One of these should be the correct value and the other one an alias. There are no spinning-up solutions. The smaller value of B{sub s} is close to the surface field of 8 x 10{sup 10} G that is measured independently from the unique absorption lines in the X-ray spectrum of 1E 1207.4-5209, assuming that the lowest-energy line at 0.7 keV is the electron-cyclotron fundamental. We suggest that 1E 1207.4-5209 has the strongest magnetic field among CCOs, which would account for the unique presence of its cyclotron absorption spectrum, while other CCOs likely have even weaker fields for which the cyclotron fundamental falls below the observable soft X-ray band.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

Gravitational waves from pulsars and their braking indices: the role of a time dependent magnetic ellipticity

We study the role of time dependent magnetic ellipticities (ϵ{sub B}) on the calculation of the braking index of pulsars. Moreover, we study the consequences of such a ϵ{sub B} on the amplitude of gravitational waves (GWs) generated by pulsars with measured braking indices. We show that, since the ellipticity generated by the magnetic dipole is extremely small, the corresponding amplitude of GWs is much smaller than the amplitude obtained via the spindown limit.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2011

Warped penguin diagrams

We present an analysis of the loop-induced magnetic dipole operator in the Randall-Sundrum model of a warped extra dimension with anarchic bulk fermions and an IR brane-localized Higgs. These operators are finite at one-loop order and we explicitly calculate the branching ratio for {mu}{yields}e{gamma} using the mixed position/momentum space formalism. The particular bound on the anarchic Yukawa and Kaluza-Klein (KK) scales can depend on the flavor structure of the anarchic matrices. It is possible for a generic model to either be ruled out or unaffected by these bounds without any fine-tuning. We quantify how these models realize this surprising behavior. We also review tree-level lepton flavor bounds in these models and show that these are on the verge of tension with the {mu}{yields}e{gamma} bounds from typical models with a 3 TeV Kaluza-Klein scale. Further, we illuminate the nature of the one-loop finiteness of these diagrams and show how to accurately determine the degree of divergence of a five-dimensional loop diagram using both the five-dimensional and KK formalism. This power counting can be obfuscated in the four-dimensional Kaluza-Klein formalism and we explicitly point out subtleties that ensure that the two formalisms agree. Finally, we remark on the existence of a perturbative regime in which these one-loop results give the dominant contribution.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Tight Constraint on Photon Mass from Pulsar Spindown

Pulsars are magnetized rotating compact objects. They spin down due to magnetic dipole radiation and wind emission. If a photon has nonzero mass, the spin-down rate will be lower than in the zero-mass case. We show that an upper limit of the photon mass, i.e., m{sub γ}≲h/Pc{sup 2}, may be placed if a pulsar with period P is observed to spin down. Recently, a white dwarf (WD)–M dwarf binary, AR Scorpii, was discovered to emit pulsed broadband emission. The spin-down luminosity of the WD can comfortably power non-thermal radiation from the system. Applying our results to the WD pulsar with P = 117 s, we obtain a stringent upper limit of the photon mass between m{sub γ}<6.3×10{sup −50} g, assuming a vacuum dipole spindown, and m{sub γ}<9.6×10{sup −50} g, assuming spindown due to a fully developed pulsar wind.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

Frequency stabilization of spin-torque-driven oscillations by coupling with a magnetic nonlinear resonator

The fundamental function of any oscillator is to produce a waveform with a stable frequency. Here, we show a method of frequency stabilization for spin-torque nano-oscillators (STNOs) that relies on coupling with an adjacent nanomagnet through the magnetic dipole–dipole interaction. It is numerically demonstrated that highly stable oscillations occur as a result of mutual feedback between an STNO and a nanomagnet. The nanomagnet acts as a nonlinear resonator for the STNO. This method is based on the nonlinear behavior of the resonator and can be considered as a magnetic analogue of an optimization scheme in nanoelectromechanical systems. The oscillation frequency is most stabilized when the nanomagnet is driven at a special feedback point at which the feedback noise between the STNO and resonator is completely eliminated.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2026

A Dedicated Muon EDM Experiment in the `g-2 Storage Ring

Spin precession experiments offer exciting motivations to search for new physics. We propose here an idea of using a modified version of the Muon g-2 storage ring for a potential new scientific program to search for a non-zero muon electric dipole moment (EDM). Using both electric and magnetic dipole fields to produce a "frozen spin" condition for the MDM (all the while enhancing the EDM spin precession), the storage ring would operate at a lower central muon momentum than for the present Muon g-2 measurement. The incident proton beam on target for the muon production can be obtained from the PIP-II high intensity proton beam. Preliminary calculations and simulation results of muon production at 800 MeV PoT, along with the determination of the closed orbit inside the hybrid 'g-2' storage ring configuration, shall be presented. Possibilities of using the 'g-2' storage ring as a test bench to demonstrate the freezing of the MDM spin precession shall be discussed. The operational range of the muon's momentum and energy, and their respective window of electric and magnetic field values to establish the frozen spin condition, shall be presented. We shall also briefly discuss the physics prospects and improvements in muon EDM bounds upon using Fermilab's PIP-II beam.

Narayanan, Aakaash [Fermilab] (ORCID:0000000157944↗
DOE OSTI2026

A Dedicated Muon EDM Experiment in the `g-2 Storage Ring

Spin precession experiments offer exciting motivations to search for new physics. We propose here an idea of using a modified version of the Muon g-2 storage ring for a potential new scientific program to search for a non-zero muon electric dipole moment (EDM). Using both electric and magnetic dipole fields to produce a "frozen spin" condition for the MDM (all the while enhancing the EDM spin precession), the storage ring would operate at a lower central muon momentum than for the present Muon g-2 measurement. The incident proton beam on target for the muon production can be obtained from the PIP-II high intensity proton beam. Preliminary calculations and simulation results of muon production at 800 MeV PoT, along with the determination of the closed orbit inside the hybrid 'g-2' storage ring configuration, shall be presented. Possibilities of using the 'g-2' storage ring as a test bench to demonstrate the freezing of the MDM spin precession shall be discussed. The operational range of the muon's momentum and energy, and their respective window of electric and magnetic field values to establish the frozen spin condition, shall be presented. We shall also briefly discuss the physics prospects and improvements in muon EDM bounds upon using Fermilab's PIP-II beam.

Narayanan, Aakaash [Fermilab] (ORCID:0000000157944↗
DOE OSTI2011

Measurement of Linear Stark Interference in {sup 199}Hg

We present measurements of Stark interference in the 6{sup 1}S{sub 0}{yields}6{sup 3}P{sub 1} transition in {sup 199}Hg, a process whereby a static electric field E mixes magnetic dipole and electric quadrupole couplings into an electric dipole transition, leading to E-linear energy shifts similar to those produced by a permanent atomic electric dipole moment (EDM). The measured interference amplitude, a{sub SI}=(a{sub M1}+a{sub E2})=(5.8{+-}1.5)x10{sup -9} (kV/cm){sup -1}, agrees with relativistic, many-body predictions and confirms that earlier central-field estimates are a factor of 10 too large. More importantly, this study validates the capability of the {sup 199}Hg EDM search apparatus to resolve nontrivial, controlled, and sub-nHz Larmor frequency shifts with EDM-like characteristics.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2017

Reply to “Comment on ‘Axion induced oscillating electric dipole moments’”

Here, we respond to a paper of Flambaum et al., claiming there is no effective induced oscillating electric dipole moment, e.g., for the electron, arising from interaction with an oscillating cosmic axion background via the anomaly. The relevant Feynman amplitude, Fig. 1, as computed by Flambaum et al., becomes a total divergence, and vanishes. Contrary to this result, we obtained a nonvanishing amplitude that yields physical electric dipole radiation for an electron (or any magnetic dipole moment) immersed in a cosmic axion field. We argue that Flambaum et al.’s counterclaim is incorrect, and is based upon a misunderstanding of a physics choice vs gauge choice, and an assumption that electric dipoles be defined only by coupling to static (constant in time) electric fields.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

Effects of CSR Generated from Upstream Bends in a Laser Plasma Storage Ring

The recent proposal of a Laser Plasma Storage Ring (LPSR) envisions the use of a laser-plasma (LP) acceleration module to inject an electron beam into a compact 500 MeV storage ring. Electron bunches generated by LP methods are naturally very short (tens of femtoseconds), presenting peak currents on the order of 10 kA or higher. Of obvious concern is the impact of collective effects and in particular Coherent Synchrotron Radiation (CSR) on the beam dynamics in the storage ring. Available simulation codes (e.g. Elegant) usually include transient CSR effects but neglect the contribution of radiation emitted from trailing magnets. In a compact storage ring, with dipole magnets close to each other, cross talking between different magnets could in principle be important.In this note we investigate this effect for the proposed LPSR and show that, in fact, this effect is relatively small. However our analysis also indicates that CSR effects in general would be quite strong and deserve a careful study.

43 PARTICLE ACCELERATORS↗
DOE OSTI2024

Laboratory Study of Magnetic Reconnection in Lunar-relevant Mini-magnetospheres

Abstract Mini-magnetospheres are small ion-scale structures that are well suited to studying kinetic-scale physics of collisionless space plasmas. Such ion-scale magnetospheres can be found on local regions of the Moon, associated with the lunar crustal magnetic field. In this paper, we report on the laboratory experimental study of magnetic reconnection in laser-driven, lunar-like ion-scale magnetospheres on the Large Plasma Device at the University of California, Los Angeles. In the experiment, a high-repetition rate (1 Hz), nanosecond laser is used to drive a fast-moving, collisionless plasma that expands into the field generated by a pulsed magnetic dipole embedded into a background plasma and magnetic field. The high-repetition rate enables the acquisition of time-resolved volumetric data of the magnetic and electric fields to characterize magnetic reconnection and calculate the reconnection rate. We notably observe the formation of Hall fields associated with reconnection. Particle-in-cell simulations reproducing the experimental results were performed to study the microphysics of the interaction. By analyzing the generalized Ohm’s law terms, we find that the electron-only reconnection is driven by kinetic effects through the electron pressure anisotropy. These results are compared to recent satellite measurements that found evidence of magnetic reconnection near the lunar surface.

Astronomy & Astrophysics↗
DOE OSTI2011

Oscillator strengths and transition probabilities for allowed and forbidden transitions in Fe XIX

An extensive set of oscillator strengths, line strengths, and radiative decay rates for the allowed and forbidden transitions in Fe XIX is presented. They correspond to 1626 fine structure levels of total angular momenta 0{<=}J{<=}8 of even and odd parities with 2{<=}n{<=}10, 0{<=}l{<=}9, 0{<=}L{<=}10, and (2S+1)=1, 3, 5. In contrast, the compiled table of the National Institute for Standards and Technology (NIST) lists only 63 observed levels. A total of 289,291 electric dipole allowed transitions are presented. They were obtained in the close coupling approximation using the relativistic Breit-Pauli R-matrix method. The wavefunction expansion included 15 levels of the configurations 2s{sup 2}2p{sup 3}, 2s2p{sup 4}, and 2p{sup 5} of the Fe XX core. The calculated fine structure levels are assigned with spectroscopic identifications using quantum defect analysis. Comparison with the observed energies shows very good agreement, the largest difference being less than 4%. The transitions also compare well with the compiled data by NIST and recent calculations. The forbidden transitions of the electric quadrupole and octupole, and magnetic dipole and quadrupole, type are presented for the 379 levels of the configurations 2s{sup 2}2p{sup 4}, 2s2p{sup 5}, 2p{sup 6}, 2s{sup 2}2p{sup 3}3s, 2s{sup 2}2p{sup 3}3p, 2s{sup 2}2p{sup 3}3d, 2s{sup 2}2p{sup 3}4s, 2s{sup 2}2p{sup 3}4p, 2s{sup 2}2p{sup 3}4d, 2s{sup 2}2p{sup 3}4f, 2s2p{sup 4}3s, 2s2p{sup 4}3p, 2s2p{sup 4}3d, 2s2p{sup 4}4s, 2s2p{sup 4}4p, and 2s{sup 2}2p{sup 2}3s{sup 2} of Fe XIX. They correspond to a total of 66,619 transitions. These results have been obtained from relativistic Breit-Pauli atomic structure calculations using the program SUPERSTRUCTURE. The forbidden transition probabilities show very good agreement with those compiled by NIST. - Highlights: {yields} Presents the most complete (n up to 10) set of transitions for Fe XIX. {yields} Considers both allowed and forbidden transitions. {yields} Large number of new energy levels are found. {yields} Benchmarks existing accurate energies and transitions. {yields} Completeness and accuracy are crucial to solve its abundance in the Sun.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2010

Electromagnetic moments of quasistable particle

We deal with the problem of assigning electromagnetic moments to a quasistable particle (i.e., a particle with mass located at the particle's decay threshold). In this case, an application of a small external electromagnetic field changes the energy in a nonanalytic way, which makes it difficult to assign definitive moments. On the example of a spin-1/2 field with mass M{sub *} interacting with two fields of masses M and m, we show how a conventionally defined magnetic dipole moment diverges at M{sub *}=M+m. We then show that the conventional definition makes sense only when the values of the applied magnetic field B satisfy |eB|/2M{sub *}<<|M{sub *}-M-m|. We discuss implications of these results to existing studies in electroweak theory, chiral effective-field theory, and lattice QCD.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

THE NEAREST MILLISECOND PULSAR REVISITED WITH XMM-NEWTON: IMPROVED MASS-RADIUS CONSTRAINTS FOR PSR J0437-4715

I present an analysis of the deepest X-ray exposure of a radio millisecond pulsar (MSP) to date, an X-ray Multi Mirror-Newton European Photon Imaging Camera spectroscopic and timing observation of the nearest known MSP, PSR J0437-4715. The timing data clearly reveal a secondary broad X-ray pulse offset from the main pulse by {approx}0.55 in rotational phase. In the context of a model of surface thermal emission from the hot polar caps of the neutron star, this can be plausibly explained by a magnetic dipole field that is significantly displaced from the stellar center. Such an offset, if commonplace in MSPs, has important implications for studies of the pulsar population, high energy pulsed emission, and the pulsar contribution to cosmic-ray positrons. The continuum emission shows evidence for at least three thermal components, with the hottest radiation most likely originating from the hot magnetic polar caps and the cooler emission from the bulk of the surface. I present pulse phase-resolved X-ray spectroscopy of PSR J0437-4715, which for the first time properly accounts for the system geometry of a radio pulsar. Such an approach is essential for unbiased measurements of the temperatures and emission areas of polar cap radiation from pulsars. Detailed modeling of the thermal pulses, including relativistic and atmospheric effects, provides a constraint on the redshift-corrected neutron star radius of R > 11.1 km (at 3{sigma} conf.) for the current radio timing mass measurement of 1.76 M {sub Sun }. This limit favors 'stiff' equations of state.

79 ASTRONOMY AND ASTROPHYSICS↗