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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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NASA NTRS1989

Role of dust to gas production rate ratio in cometary physics

According to results of Earth based observations and in situ measurements cometary nuclei are intensive sources of both the gaseous and the dusty matter. Investigations of the interaction between gas-dust cometary atmospheres and dust grains of the Zodiacal dust cloud reveals the presence of two principally possible mechanisms: meteor-like and explosive-type ones. The meteor-like mechanism is connected with bombardment of zodiacal dust particles by cometary molecules when the temperatures T = 2000 to 3000 K are developed. This mechanism can create over-saturated vapors of refractory elements (Fe, Si, C etc.) in cometary heads. The explosion-type mechanism is connected with high-velocity impacts between cometary and zodiacal dust particles resulting in the generation of high-temperature plasma (T = 10(exp 5) to 10(exp 7) K) and, hence, of x ray radiation and multicharged ions, i.e., with the processes not yet realized in the laboratory conditions.

Ibadov, S.↗

DOE OSTI2022

Performance of a hardened x-ray streak camera at Lawrence Livermore National Laboratory’s National Ignition Facility

Electron tubes continue to provide the highest speeds possible for recording dynamics of hot high-energy density plasmas. Standard streak camera drive electronics and CCD readout are not compatible with the radiation environment associated with high DT fusion yield inertial confinement fusion experiments >10 13 14 MeV DT neutrons or >10 9 n cm -2 ns -1 . Here, we describe a hardened x-ray streak camera developed for the National Ignition Facility and present preliminary results from the first experiment on which it has participated, recording the time-resolved bremsstrahlung spectrum from the core of an inertial confinement fusion implosion at more than 40× the operational neutron yield limit of the previous National Ignition Facility x-ray streak cameras.

47 OTHER INSTRUMENTATION↗

NASA NTRS2003

The Organic Component of Interstellar Dust

The distribution, chemical structure, and formation of organic matter in the interstellar medium are important to our understanding of the overall evolution of dust. The exchange of dust between the dense and diffuse interstellar medium, and the effects of processing on dust within dense clouds will affect the inventory of material available for incorporation into newly forming star and planetary systems. Observational ground-based studies have confirmed the widespread distribution of the 3.4 pm absorption band attributed to aliphatic hydrocarbons in the diffuse interstellar medium of our own galaxy, and in the dusty spectra of a few nearby galaxies, while space based observations from IS0 probed the signatures of corresponding mid-infrared features. Laboratory experiments which utilize both thermal processes and energetic processing by high energy photons and cosmic rays, produce candidate materials which offer close matches to the observed diffuse interstellar medium and extragalactic hydrocarbon absorption features. Through an analysis of the 4000 to 1000 cm (2.5 to 10 micrometers) region of the spectrum of diffuse interstellar medium (DISM) dust compared with the spectra of thirteen chemical entities produced in the laboratory which serve as analogs to the interstellar material, significant constraints have been placed on the applicability of proposed candidate materials to explain the interstellar features. The results indicate that the organic refractory material in the diffuse interstellar medium is predominantly hydrocarbon in nature, possessing little nitrogen or oxygen, with the carbon distributed between the aromatic and aliphatic forms. Long alkane chains H3C-(CH2),- with n much greater than 4 or 5 are not major constituents of this material. Comparisons to laboratory analogs indicate the DISM organic material resembles plasma processed pure hydrocarbon residues much more so than energetically processed ice residues. This result is consistent with a birthsite for the carrier of the 3.4 micrometers band in the outflow region of evolved carbon stars. Comparisons of dust from our own galaxy with that of distant galaxies suggests that the organic component of interstellar dust is widespread and may be an important universal reservoir of prebiotic organic carbon.

Pendleton, Yvonne↗