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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 451 records · Page 25
All sourcesNASA NTRSDOE OSTI
DOE OSTI2011

Spectral-domain phase microscopy with improved sensitivity using two-dimensional detector arrays

In this work we demonstrate the use of two-dimensional detectors to improve the signal-to-noise ratio (SNR) and sensitivity in spectral-domain phase microscopy for subnanometer accuracy measurements. We show that an increase in SNR can be obtained, from 82 dB to 105 dB, using 150 pixel lines of a low-cost CCD camera as compared to a single line, to compute an averaged axial scan. In optimal mechanical conditions, phase stability as small as 92 {mu}rad, corresponding to 6 pm displacement accuracy, could be obtained. We also experimentally demonstrate the benefit of spatial-averaging in terms of the reduction of signal fading due to an axially moving sample. The applications of the improved system are illustrated by imaging live cells in culture.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2011

Observation of impurity free monoenergetic proton beams from the interaction of a CO{sub 2} laser with a gaseous target

A monoenergetic proton beam is observed from the interaction of a short-pulse infrared ({lambda} = 10.6 {mu}m) laser at intensity I = 6 x 10{sup 15} W cm{sup -2} with a gas jet target. The proton beam is found to have narrow energy spread ({approx} 4% ), high spectral brightness ({approx} 10{sup 12} protons/MeV/sr), low normalized emittance ({epsilon}{sub n{approx_equal}} 8 nm rad), and high contrast (> 200 x over noise). The narrow energy spread and low levels of impurity makes this method an interesting route for high-repetition rate high quality proton beam production.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2011

A novel high resolution ion wide angle spectrometer

A novel ion wide angle spectrometer (iWASP) has been developed, which is capable of measuring angularly resolved energy distributions of protons and a second ion species, such as carbon C{sup 6+}, simultaneously. The energy resolution for protons and carbon ions is better than 10% at {approx}50 MeV/nucleon and thus suitable for the study of novel laser-ion acceleration schemes aiming for ultrahigh particle energies. A wedged magnet design enables an acceptance angle of 30 deg. ({approx}524 mrad) and high angular accuracy in the {mu}rad range. First, results obtained at the LANL Trident laser facility are presented demonstrating high energy and angular resolution of this novel iWASP.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2011

Very Forward Calorimetry at the LHC--Recent results from ATLAS

We present first results from the ATLAS Zero Degree Calorimeters (ZDC) based on 7 TeV pp collision data recorded in 2010. The ZDC coverage of {+-}{approx}350 {mu}rad about the forward direction makes possible the measurement of neutral particles (primarily {pi}{sup 0}'s and neutrons) over the kinematic region x{sub F} > or approx. 0.1 and out to p{sub T} < or approx. 1.2 GeV/c at large x{sub F}. The ATLAS ZDC is unique in that it provides a complete image of both electromagnetic and hadronic showers. This is illustrated with the reconstruction of {pi}{sup 0}'s with energies of 0.7-3.5 TeV. We also discuss the waveform reconstruction algorithm which has allowed good time-of-flight resolution on leading neutrons emerging from the collisions despite the sparse (40 MHz) sampling of the calorimeter signals used.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2011

Measurement of the temperature of an ultracold ion source using time-dependent electric fields

We report on a measurement of the characteristic temperature of an ultracold rubidium ion source, in which a cloud of laser-cooled atoms is converted to ions by photo-ionization. Extracted ion pulses are focused on a detector with a pulsed-field technique. The resulting experimental spot sizes are compared to particle-tracking simulations, from which an effective source temperature T = (3 {+-} 2) mK and the corresponding transversal reduced emittance {epsilon}{sub r} = 1.4 x 10{sup -8} m rad {radical}(eV) are determined. Space charge effects that may affect the measurement are also discussed.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

Emission Properties of Eu{sup 3+} Doped Different Chlorophosphate Glasses

Absorption and emission spectra of 0.5 mol% of Eu{sup 3+} in different chlorophosphate glasses have been studied. Judd-Ofelt analysis was performed to evaluate the emission properties such as radiative transition probabilities (A{sub rad}), branching ratios ({beta}), radiative lifetimes ({tau}{sub R}) and emission cross-sections ({sigma}{sub P}) for observed emission transitions of emission spectra of these glass matrices.

36 MATERIALS SCIENCE↗
DOE OSTI2011

The MICE Muon Beam Line

In the Muon Ionization Cooling Experiment (MICE) at RAL, muons are produced and transported in a dedicated beam line connecting the production point (target) to the cooling channel. We discuss the main features of the beamline, meant to provide muons with momenta between 140 MeV/c and 240 MeV/c and emittances up to 10 mm rad, which is accomplished by means of a diffuser. Matching procedures to the MICE cooling channel are also described. In summer 2010 we performed an intense data taking campaign to finalize the calibration of the MICE Particle Identification (PID) detectors and the understanding of the beam line, which completes the STEPI phase of MICE. We highlight the main results from these data.

43 PARTICLE ACCELERATORS↗
DOE OSTI2012

Source characterization and modeling development for monoenergetic-proton radiography experiments on OMEGA

A monoenergetic proton source has been characterized and a modeling tool developed for proton radiography experiments at the OMEGA [T. R. Boehly et al., Opt. Comm. 133, 495 (1997)] laser facility. Multiple diagnostics were fielded to measure global isotropy levels in proton fluence and images of the proton source itself provided information on local uniformity relevant to proton radiography experiments. Global fluence uniformity was assessed by multiple yield diagnostics and deviations were calculated to be {approx}16% and {approx}26% of the mean for DD and D{sup 3}He fusion protons, respectively. From individual fluence images, it was found that the angular frequencies of Greater-Than-Or-Equivalent-To 50 rad{sup -1} contributed less than a few percent to local nonuniformity levels. A model was constructed using the Geant4 [S. Agostinelli et al., Nuc. Inst. Meth. A 506, 250 (2003)] framework to simulate proton radiography experiments. The simulation implements realistic source parameters and various target geometries. The model was benchmarked with the radiographs of cold-matter targets to within experimental accuracy. To validate the use of this code, the cold-matter approximation for the scattering of fusion protons in plasma is discussed using a typical laser-foil experiment as an example case. It is shown that an analytic cold-matter approximation is accurate to within Less-Than-Or-Equivalent-To 10% of the analytic plasma model in the example scenario.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2012

Novel energy resolving x-ray pinhole camera on Alcator C-Mod

A new energy resolving x-ray pinhole camera has been recently installed on Alcator C-Mod. This diagnostic is capable of 1D or 2D imaging with a spatial resolution of Almost-Equal-To 1 cm, an energy resolution of Almost-Equal-To 1 keV in the range of 3.5-15 keV and a maximum time resolution of 5 ms. A novel use of a Pilatus 2 hybrid-pixel x-ray detector [P. Kraft et al., J. Synchrotron Rad. 16, 368 (2009)] is employed in which the lower energy threshold of individual pixels is adjusted, allowing regions of a single detector to be sensitive to different x-ray energy ranges. Development of this new detector calibration technique was done as a collaboration between PPPL and Dectris Ltd. The calibration procedure is described, and the energy resolution of the detector is characterized. Initial data from this installation on Alcator C-Mod is presented. This diagnostic provides line-integrated measurements of impurity emission which can be used to determine impurity concentrations as well as the electron energy distribution.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2012

Snowflake divertor configuration studies in National Spherical Torus Experiment

Experimental results from NSTX indicate that the snowflake divertor (D. Ryutov, Phys. Plasmas 14, 064502 (2007)) may be a viable solution for outstanding tokamak plasma-material interface issues. Steady-state handling of divertor heat flux and divertor plate erosion remains to be critical issues for ITER and future concept devices based on conventional and spherical tokamak geometry with high power density divertors. Experiments conducted in 4-6 MW NBI-heated H-mode plasmas in NSTX demonstrated that the snowflake divertor is compatible with high-confinement core plasma operation, while being very effective in steady-state divertor heat flux mitigation and impurity reduction. A steady-state snowflake divertor was obtained in recent NSTX experiments for up to 600 ms using three divertor magnetic coils. The high magnetic flux expansion region of the scrape-off layer (SOL) spanning up to 50% of the SOL width {lambda}{sub q} was partially detached in the snowflake divertor. In the detached zone, the heat flux profile flattened and decreased to 0.5-1 MW/m{sup 2} (from 4-7 MW/m{sup 2} in the standard divertor) indicative of radiative heating. An up to 50% increase in divertor, P{sub rad} in the snowflake divertor was accompanied by broadening of the intrinsic C III and C IV radiation zones, and a nearly order of magnitude increase in divertor high-n Balmer line emission indicative of volumetric recombination onset. Magnetic reconstructions showed that the x-point connection length, divertor plasma-wetted area and divertor volume, all critical parameters for geometric reduction of deposited heat flux, and increased volumetric divertor losses were significantly increased in the snowflake divertor, as expected from theory.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2012

Study and optimization of negative polarity rod pinch diode as flash radiography source at 4.5 MV

The negative polarity rod pinch diode (NPRPD) is a potential millimeter spot size radiography source for high voltage generators (4 to 8 MV) [Cooperstein et al., 'Considerations of rod-pinch diode operation in negative polarity for radiography,' in Proceedings of the 14th IEEE Pulsed Power Conference, 2003, pp. 975-978]. The NPRPD consists of a small diameter (few mm) cylindrical anode extending from the front end of the vacuum cell through a thin annular cathode, held by a central conductor. The polarity has been inverted when compared to the original rod pinch diode [Cooperstein et al., 'Theoretical modeling and experimental characterization of a rod-pinch diode,' Phys. Plasmas 8(10), 4618-4636 (2001)] in order to take advantage from the maximal x-ray emission toward the anode holder at such a voltage [Swanekamp et al., 'Evaluation of self-magnetically pinched diodes up to 10 MV as high resolution flash X-ray sources,' IEEE Trans. Plasma Sci. 32(5), 2004-2016 (2004). We have studied this diode at 4.5 MV, driven by the ASTERIX generator [Raboisson et al., 'ASTERIX, a high intensity X-ray generator,' in Proceedings of the 7th IEEE Pulsed Power Conference, 1989, pp. 567-570.]. This generator, made up of a capacitor bank and a Blumlein line, was initially designed to test the behavior of electronic devices under irradiation. In our experiments, the vacuum diode has been modified in order to set up flash a radiographic diode [Etchessahar et al., 'Negative polarity rod pinch diode experiments on the ASTERIX generator,' in Conference Records-Abstracts, 37th IEEE International Conference on Plasma Science, 2010]. The experiments and numerical simulations presented here allowed the observation and analysis of various physical phenomena associated with the diode operation. Also, the influence of several experimental parameters, such as cathode and anode diameters, materials and surface states, was examined. In order to achieve the most comprehensive characterization of the diode, both optical and x-ray diagnostics were used, including high speed multi-image ICCD (intensified CCD) cameras, streak camera, dosimeters, spot size measurements, and pinhole cameras. A set of new results have been obtained through this study. The plasma emission from the anode and cathode surfaces and its expansion appear to be critical for the diode functioning. Also, for the first time, potential sources of diode instability were identified. Finally, an optimal and stable diode configuration was found with the following parameters: 52 rad at 1 m (in Al) and 2.2 mm spot size.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2012

A digital optical phase-locked loop for diode lasers based on field programmable gate array

We have designed and implemented a highly digital optical phase-locked loop (OPLL) for diode lasers in atom interferometry. The three parts of controlling circuit in this OPLL, including phase and frequency detector (PFD), loop filter and proportional integral derivative (PID) controller, are implemented in a single field programmable gate array chip. A structure type compatible with the model MAX9382/MCH12140 is chosen for PFD and pipeline and parallelism technology have been adapted in PID controller. Especially, high speed clock and twisted ring counter have been integrated in the most crucial part, the loop filter. This OPLL has the narrow beat note line width below 1 Hz, residual mean-square phase error of 0.14 rad{sup 2} and transition time of 100 {mu}s under 10 MHz frequency step. A main innovation of this design is the completely digitalization of the whole controlling circuit in OPLL for diode lasers.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2013

Comb-assisted subkilohertz linewidth quantum cascade laser for high-precision mid-infrared spectroscopy

We report on the linewidth narrowing of a room-temperature mid-infrared quantum cascade laser by phase-locking to a difference-frequency-generated radiation referenced to an optical frequency comb synthesizer. A locking bandwidth of 250 kHz, with a residual rms phase-noise of 0.56 rad, has been achieved. The laser linewidth is narrowed by more than 2 orders of magnitude below 1 kHz, and its frequency is stabilized with an absolute traceability of 2 Multiplication-Sign 10{sup -12}. This source has allowed the measurement of the absolute frequency of a CO{sub 2} molecular transition with an uncertainty of about 1 kHz.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2013

Experimental study of self magnetic pinch diode as flash radiography source at 4 megavolt

The Self Magnetic Pinch (SMP) diode is a potential high-brightness X-ray source for high voltage generators (2–10 MV) that has shown good reliability for flash radiography applications [D. D. Hinchelwood et al., “High power self-pinch diode experiments for radiographic applications” IEEE Trans. Plasma Sci. 35(3), 565–572 (2007)]. We have studied this diode at about 4 MV, driven by the ASTERIX generator operated at the CEA/GRAMAT [G. Raboisson et al., “ASTERIX, a high intensity X-ray generator,” in Proceedings of the 7th IEEE Pulsed Power Conference (1989), pp. 567–570]. This generator, made up of a capacitor bank and a Blumlein line, was initially designed to test the behavior of electronic devices under irradiation. In our experiments, the vacuum diode is modified in order to set up flash radiographic diodes. A previous set of radiographic experiments was carried out on ASTERIX with a Negative Polarity Rod Pinch (NPRP) diode [B. Etchessahar et al., “Study and optimization of negative polarity rod pinch diode as flash radiography source at 4.5 MV,” Phys. Plasmas 19(9), 093104 (2012)]. The SMP diode which is examined in the present study provides an alternative operating point on the same generator and a different radiographic performance: 142 ± 11 rad at 1 m dose (Al) for a 3.46 ± 0.42 mm spot size (1.4× FWHM of the LSF). This performance is obtained in a reproducible and robust nominal configuration. However, several parametric variations were also tested, such as cathode diameter and anode/cathode gap. They showed that an even better performance is accessible after optimization, in particular, a smaller spot size (<3 mm). Numbers of electrical, optical, and X-ray diagnostics have been implemented in order to gain more insight in the diode physics and to optimize it further. For the first time in France, visible and laser imaging of the SMP diode has been realized, from a radial point of view, thus, providing key information on the electrode plasmas evolution, responsible for the gap closure.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2013

Communication: Nuclear quadrupole moment-induced Cotton-Mouton effect in noble gas atoms

New, high-sensitivity and high-resolution spectroscopic and imaging methods may be developed by exploiting nuclear magneto-optic effects. A first-principles electronic structure formulation of nuclear electric quadrupole moment-induced Cotton-Mouton effect (NQCME) is presented for closed-shell atoms. In NQCME, aligned quadrupole moments alter the index of refraction of the medium along with and perpendicular to the direction of nuclear alignment. The roles of basis-set convergence, electron correlation, and relativistic effects are investigated for three quadrupolar noble gas isotopes: {sup 21}Ne, {sup 83}Kr, and {sup 131}Xe. The magnitude of the resulting ellipticities is predicted to be 10{sup −4}–10{sup −6} rad/(M cm) for fully spin-polarized nuclei. These should be detectable in the Voigt setup. Particularly interesting is the case of {sup 131}Xe, in which a high degree of spin polarization can be achieved via spin-exchange optical hyperpolarization.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Nuclear quadrupole moment-induced Cotton-Mouton effect in molecules

Nuclear magneto-optic effects could make important contributions to novel, high-sensitivity, and high-resolution spectroscopic and imaging methods that provide nuclear site-specific structural and dynamic information on molecular and materials systems. Here we present a first-principles electronic structure formulation of nuclear quadrupole moment-induced Cotton-Mouton effect in terms of response theory, as well as ab initio and density-functional theory calculations of this phenomenon for a series of molecular liquids: H{sub 2}O, CH{sub 3}NO{sub 2}, CH{sub 3}CH{sub 2}OH, C{sub 6}H{sub 6}, C{sub 6}H{sub 12} (cyclohexane), HI, XeF{sub 2}, WF{sub 5}Cl, and Pt(C{sub 2}dtp){sub 2}. The roles of basis-set convergence, electron correlation, and relativistic effects are discussed. The estimated order of magnitude of the overall ellipticities induced to linearly polarized light is 10{sup −3}–10{sup −7} rad/(M cm) for fully spin polarized nuclei. The cases with the largest presently obtained ellipticities should be detectable with modern instrumentation in the Voigt magneto-optic setup, particularly for the heavy nuclei.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Feedback control of torsion balance in measurement of gravitational constant G with angular acceleration method

The performance of the feedback control system is of central importance in the measurement of the Newton's gravitational constant G with angular acceleration method. In this paper, a PID (Proportion-Integration-Differentiation) feedback loop is discussed in detail. Experimental results show that, with the feedback control activated, the twist angle of the torsion balance is limited to 7.3×10{sup −7} rad /√( Hz ) at the signal frequency of 2 mHz, which contributes a 0.4 ppm uncertainty to the G value.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2014

A two-dimensional (azimuthal-axial) particle-in-cell model of a Hall thruster

We have developed a two-dimensional Particle-In-Cell model in the azimuthal and axial directions of the Hall thruster. A scaling method that consists to work at a lower plasma density to overcome constraints on time-step and grid-spacing is used. Calculations are able to reproduce the breathing mode due to a periodic depletion of neutral atoms without the introduction of a supplementary anomalous mechanism, as in fluid and hybrid models. Results show that during the increase of the discharge current, an electron-cyclotron drift instability (frequency in the range of MHz and wave number on the order of 3000 rad s{sup −1}) is formed in the region of the negative gradient of magnetic field. During the current decrease, an axial electric wave propagates from the channel toward the exhaust (whose frequency is on the order of 400 kHz) leading to a broadening of the ion energy distribution function. A discussion about the influence of the scaling method on the calculation results is also proposed.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗