SEARCH · Engineering Papers
Results for “PALS”
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.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Ultrafast, asymmetric charge transfer and slow charge recombination in porphyrin/CNT composites demonstrated by time-domain atomistic simulation
Defect-free porphyrin/CNT hybrids can maintain long-lived charge separation; porphyrins and CNTs can be used to harvest light at different wavelengths.
Error reduction of phasor measurement unit data considering practical constraints
Not provided.
Development of a fast scintillator based beam phase measurement system for compact superconducting cyclotrons
In an isochronous cyclotron, measurements of central phase of the ion beam with respect to rf and the phase width provide a way to tune the cyclotron for maximum energy gain per turn and efficient extraction. We report here the development of a phase measurement system and the measurements carried out at the Variable Energy Cyclotron Centre's (VECC's) K= 500 superconducting cyclotron. The technique comprises detecting prompt {gamma}-rays resulting from the interaction of cyclotron ion beam with an aluminium target mounted on a radial probe in coincidence with cyclotron rf. An assembly comprising a fast scintillator and a liquid light-guide inserted inside the cyclotron was used to detect the {gamma}-rays and to transfer the light signal outside the cyclotron where a matching photo-multiplier tube was used for light to electrical signal conversion. The typical beam intensity for this measurement was a few times 10{sup 11} pps.
Experimental investigation of a 1 kA/cm{sup 2} sheet beam plasma cathode electron gun
In this paper, a cold cathode based sheet-beam plasma cathode electron gun is reported with achieved sheet-beam current density ∼1 kA/cm{sup 2} from pseudospark based argon plasma for pulse length of ∼200 ns in a single shot experiment. For the qualitative assessment of the sheet-beam, an arrangement of three isolated metallic-sheets is proposed. The actual shape and size of the sheet-electron-beam are obtained through a non-conventional method by proposing a dielectric charging technique and scanning electron microscope based imaging. As distinct from the earlier developed sheet beam sources, the generated sheet-beam has been propagated more than 190 mm distance in a drift space region maintaining sheet structure without assistance of any external magnetic field.
A multiple gap plasma cathode electron gun and its electron beam analysis in self and trigger breakdown modes
In the present paper, a pseudospark discharge based multiple gap plasma cathode electron gun is reported which has been operated separately in self and trigger breakdown modes using two different gases, namely, argon and hydrogen. The beam current and beam energy have been analyzed using a concentric ring diagnostic arrangement. Two distinct electron beams are clearly seen with hollow cathode and conductive phases. The hollow cathode phase has been observed for ∼50 ns where the obtained electron beam is having low beam current density and high energy. While in conductive phase it is high current density and low energy electron beam. It is inferred that in the hollow cathode phase the beam energy is more for the self breakdown case whereas the current density is more for the trigger breakdown case. The tailor made operation of the hollow cathode phase electron beam can play an important role in microwave generation. Up to 30% variation in the electron beam energy has been achieved keeping the same gas and by varying the breakdown mode operations. Also, up to 32% variation in the beam current density has been achieved for the trigger breakdown mode at optimized trigger position by varying the gas type.
Stoichiometric control of DNA-grafted colloid self-assembly
Significance Recently, there has been an increased interest in understanding the self-assembly of DNA-grafted colloids into different morphologies. Conventional approaches assume that the critical design parameters are the size and number of DNA grafts on each particle. Stoichiometry is viewed as a secondary variable and its exact role in this context is unresolved. In contrast with these expectations, our experiments show that the equilibrium lattice structure can be tuned through variations in the imposed stoichiometry. These findings are captured through simple extensions of the complementary contact model. Stoichiometry is thus shown to be a powerful handle to control these self-assembled structures.
BROADBAND STUDY OF GRB 091127: A SUB-ENERGETIC BURST AT HIGHER REDSHIFT?
GRB 091127 is a bright gamma-ray burst (GRB) detected by Swift at a redshift z = 0.49 and associated with SN 2009nz. We present the broadband analysis of the GRB prompt and afterglow emission and study its high-energy properties in the context of the GRB/SN association. While the high luminosity of the prompt emission and standard afterglow behavior are typical of cosmological long GRBs, its low-energy release (E{sub {gamma}} < 3 Multiplication-Sign 10{sup 49} erg), soft spectrum, and unusual spectral lag connect this GRB to the class of sub-energetic bursts. We discuss the suppression of high-energy emission in this burst, and investigate whether this behavior could be connected with the sub-energetic nature of the explosion.
Confronting quasi-exponential inflation with WMAP seven
We confront quasi-exponential models of inflation with WMAP seven years dataset using Hamilton Jacobi formalism. With a phenomenological Hubble parameter, representing quasi exponential inflation, we develop the formalism and subject the analysis to confrontation with WMAP seven using the publicly available code CAMB. The observable parameters are found to fair extremely well with WMAP seven. We also obtain a ratio of tensor to scalar amplitudes which may be detectable in PLANCK.
Effect of anti-site disorder on magnetism in La 2 NiMnO 6
La 2 NiMnO 6 has been reported to exhibit a paramagnetic to ferromagnetic transition with a transition temperature of ~ 260 K. However, most of its magnetic properties, such as the saturation magnetization and even the transition temperature, appear to vary considerably among different reports. This is possibly because the crystallographic structure as well as the extent of the anti-site disorder (ASD) at the Ni/Mn sites are strongly influenced by the choice of synthesis routes. There are diverse reports connecting the extent of ASD to the valencies of Ni and Mn ions, such as Ni 2+ -Mn 4+ and Ni 3+ -Mn 3+ , including suggestions of thermally induced valence transitions. Consequently, these reports arrive at very different conclusions on the mechanism behind the magnetic properties of La 2 NiMnO 6 . To address the correlation between ASD and valency, we have carried out a comparative study of two monoclinic La 2 NiMnO 6 polycrystals with different degrees of ASD. Using a combination of x-ray absorption spectroscopy, x-raymagnetic circular dichroism, andmagnetometry, we conclude that the valency of the transition metal ions, and the transition temperature, are insensitive to the extent of ASD. Furthermore, we find the magnetic moment decreases strongly with an increasing ASD. We attribute this effect to the introduction of antiferromagnetic interactions in the anti-site disordered regions.
Evidence for the decay B 0 → η π 0
In this work, we report a search for the charmless hadronic decay B 0 → η π 0 with a data sample corresponding to an integrated luminosity of 694 fb - 1 containing 753 × 1 0 6 B B ¯ pairs. The data were collected by the Belle experiment running on the Υ ( 4 S ) resonance at the KEKB e + e - collider. We measure a branching fraction B ( B 0 → η π 0 ) = ( 4. 1 - 1.5 - 0.7 + 1.7 + 0.5 ) × 1 0 - 7 , where the first uncertainty is statistical and the second is systematic. Our measurement gives an upper limit of B ( B 0 → η π 0 ) < 6.5 × 1 0 - 7 at 90% confidence level. Finally, the signal has a significance of 3.0 standard deviations and constitutes the first evidence for this decay mode.
Measurement of e + e – → γ χ c J via initial state radiation at Belle
The process e + e – → γχ cJ (J = 1, 2) is studied via initial state radiation using 980 fb –1 of data at and around the Υ(nS) (n = 1, 2, 3, 4, 5) resonances collected with the Belle detector at the KEKB asymmetric-energy e + e – collider. Here, no significant signal is observed except from ψ(2S) decays. Upper limits on the cross sections between √s = 3.80 and 5.56 GeV are determined at the 90% credibility level, which range from a few pb to a few tens of pb. We also set upper limits on the decay rate of the vector charmonium [ψ(4040), ψ(4160), and ψ(4415)] and charmoniumlike [Y(4260), Y(4360), and Y(4660)] states to γχ cJ .
Search for X Y Z states in Υ ( 1 S ) inclusive decays
The branching fractions of the Υ ( 1 S ) inclusive decays into final states with a J / ψ or a ψ ( 2 S ) are measured with higher precision to be B ( Υ ( 1 S ) → J / ψ + anything ) = ( 5.25 ± 0.13 ( stat ) ± 0.25 ( syst ) ) × 10 - 4 and B ( Υ ( 1 S ) → ψ ( 2 S ) + anything ) = ( 1.23 ± 0.17 ( stat ) ± 0.11 ( syst ) ) × 10 - 4 . The first search for Υ ( 1 S ) decays into X Y Z states that decay into a J / ψ or a ψ ( 2 S ) plus one or two charged tracks yields no significant signals for X Y Z states in any of the examined decay modes, and upper limits on their production rates in Υ ( 1 S ) inclusive decays are determined.
Quantized Brans-Dicke theory: Phase transition, strong coupling limit, and general relativity
Not Available