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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

A compact cryogenic pump

A centrifugal cryogenic pump has been designed at Argonne National Laboratory to circulate liquid nitrogen (LN2) in a closed circuit allowing the recovery of excess fluid. The pump can circulate LN2 at rates of 2-10 L/min, into a head of 0.5-3 m. Over four years of laboratory use the pump has proven capable of operating continuously for 50-100 days without maintenance.

Centrifugal pump↗
DOE OSTI2014

Empirical assessment of the detection efficiency of CR-39 at high proton fluence and a compact, proton detector for high-fluence applications

CR-39 solid-state nuclear track detectors are widely used in physics and in many inertial confinement fusion (ICF) experiments, and under ideal conditions these detectors have 100% detection efficiency for ∼0.5–8 MeV protons. When the fluence of incident particles becomes too high, overlap of particle tracks leads to under-counting at typical processing conditions (5 h etch in 6N NaOH at 80 °C). Short etch times required to avoid overlap can cause under-counting as well, as tracks are not fully developed. Experiments have determined the minimum etch times for 100% detection of 1.7–4.3-MeV protons and established that for 2.4-MeV protons, relevant for detection of DD protons, the maximum fluence that can be detected using normal processing techniques is ≲3 × 10{sup 6} cm{sup −2}. A CR-39-based proton detector has been developed to mitigate issues related to high particle fluences on ICF facilities. Using a pinhole and scattering foil several mm in front of the CR-39, proton fluences at the CR-39 are reduced by more than a factor of ∼50, increasing the operating yield upper limit by a comparable amount.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2014

A technique for extending by ∼10{sup 3} the dynamic range of compact proton spectrometers for diagnosing ICF implosions on the National Ignition Facility and OMEGA

Wedge Range Filter (WRF) proton spectrometers are routinely used on OMEGA and the NIF for diagnosing ρR and ρR asymmetries in direct- and indirect-drive implosions of D{sup 3}He-, D{sub 2}-, and DT-gas-filled capsules. By measuring the optical opacity distribution in CR-39 due to proton tracks in high-yield applications, as opposed to counting individual tracks, WRF dynamic range can be extended by 10{sup 2} for obtaining the spectral shape, and by 10{sup 3} for mean energy (ρR) measurement, corresponding to proton fluences of 10{sup 8} and 10{sup 9} cm{sup −2}, respectively. Using this new technique, ρR asymmetries can be measured during both shock and compression burn (proton yield ∼10{sup 8} and ∼10{sup 12}, respectively) in 2-shock National Ignition Facility implosions with the standard WRF accuracy of ±∼10 mg/cm{sup 2}.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2015

Compact tunable Compton x-ray source from laser-plasma accelerator and plasma mirror

We present an in-depth experimental-computational study of the parameters necessary to optimize a tunable, quasi-monoenergetic, efficient, low-background Compton backscattering (CBS) x-ray source that is based on the self-aligned combination of a laser-plasma accelerator (LPA) and a plasma mirror (PM). The main findings are (1) an LPA driven in the blowout regime by 30 TW, 30 fs laser pulses produce not only a high-quality, tunable, quasi-monoenergetic electron beam, but also a high-quality, relativistically intense (a{sub 0} ∼ 1) spent drive pulse that remains stable in profile and intensity over the LPA tuning range. (2) A thin plastic film near the gas jet exit retro-reflects the spent drive pulse efficiently into oncoming electrons to produce CBS x-rays without detectable bremsstrahlung background. Meanwhile, anomalous far-field divergence of the retro-reflected light demonstrates relativistic “denting” of the PM. Exploiting these optimized LPA and PM conditions, we demonstrate quasi-monoenergetic (50% FWHM energy spread), tunable (75–200 KeV) CBS x-rays, characteristics previously achieved only on more powerful laser systems by CBS of a split-off, counter-propagating pulse. Moreover, laser-to-x-ray photon conversion efficiency (∼6 × 10{sup −12}) exceeds that of any previous LPA-based quasi-monoenergetic Compton source. Particle-in-cell simulations agree well with the measurements.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2016

Compact CH 4 sensor system based on a continuous-wave, low power consumption, room temperature interband cascade laser

A tunable diode laser absorption spectroscopy-based methane sensor, employing a dense-pattern multi-pass gas cell and a 3.3 µm, CW, DFB, room temperature interband cascade laser (ICL), is reported. The optical integration based on an advanced folded optical path design and an efficient ICL control system with appropriate electrical power management resulted in a CH 4 sensor with a small footprint (32 x 20 x 17 cm 3 ) and low-power consumption (6 W). Polynomial and least-squares fit algorithms are employed to remove the baseline of the spectral scan and retrieve CH 4 concentrations, respectively. An Allan-Werle deviation analysis shows that the measurement precision can reach 1.4 ppb for a 60 s averaging time. Continuous measurements covering a seven-day period were performed to demonstrate the stability and robustness of the reported CH 4 sensor system.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2020

Feasibility study of a compact heavy ion source for investigation of laboratory magnetospheric plasma

We are developing a laser ion source to provide a high brightness multi-charged heavy ion beam as a part of the heavy ion beam probe system, which will be used to diagnose plasma potential in the Ring Trap 1 device at the University of Tokyo. As a probe beam, Nb2+ was selected, and a detailed laser irradiation condition was explored. It was found that the laser power density of 1.2 × 109 W/cm2 gives the maximum particle number of Nb2+ per laser energy from a niobium foil target. Essential ablation plasma parameters to design the laser ion source were also obtained. The expected beam current was more than 12 mA/cm2, with a pulse width of 3.1 µs at 200 mm away from the target.

Nakamura, K. (ORCID:0000000176882589)↗
DOE OSTI2013

Formation of compact clusters from high resolution hybrid cosmological simulations

The early universe hosted a large population of small dark matter 'minihalos' that were too small to cool and form stars on their own. These existed as static objects around larger galaxies until acted upon by some outside influence. Outflows, which have been observed around a variety of galaxies, can provide this influence in such a way as to collapse, rather than disperse, the minihalo gas. Gray and Scannapieco performed an investigation in which idealized spherically symmetric minihalos were struck by enriched outflows. Here we perform high-resolution cosmological simulations that form realistic minihalos, which we then extract to perform a large suite of simulations of outflow-minihalo interactions including non-equilibrium chemical reactions. In all models, the shocked minihalo forms molecules through non-equilibrium reaction, and then cools to form dense, chemically homogenous clumps of star-forming gas. The formation of these high-redshift clusters may be observable with the next generation of telescopes and the largest of them should survive to the present-day, having properties similar to halo globular clusters.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

THE FATE OF THE COMPACT REMNANT IN NEUTRON STAR MERGERS

Neutron star (binary neutron star and neutron star–black hole) mergers are believed to produce short-duration gamma-ray bursts (GRBs). They are also believed to be the dominant source of gravitational waves to be detected by the advanced LIGO and advanced VIRGO and the dominant source of the heavy r-process elements in the universe. Whether or not these mergers produce short-duration GRBs depends sensitively on the fate of the core of the remnant (whether, and how quickly, it forms a black hole). In this paper, we combine the results of Newtonian merger calculations and equation of state studies to determine the fate of the cores of neutron star mergers. Using population studies, we can determine the distribution of these fates to compare to observations. We find that black hole cores form quickly only for equations of state that predict maximum non-rotating neutron star masses below 2.3–2.4 solar masses. If quick black hole formation is essential in producing GRBs, LIGO/Virgo observed rates compared to GRB rates could be used to constrain the equation of state for dense nuclear matter.

79 ASTRONOMY AND ASTROPHYSICS↗