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Results for “PROTON ENERGY”

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 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Development and creation of conditions for the radiation of biological objects with high energy protons

Depth distribution of an absorbed proton radiation dose was studied by both calculation and experimental methods on a cylindrical, homogeneous plexiglass phantom that represented the geometric form of a dog. The basis of the heterogeneous phantom was the natural skeleton of a dog, muscle tissue was simulated by a mixture of paraffin and silica filler, and lung tissue by gelatine capsules.

Popov, V. P.↗
NASA NTRS1974

Observation of low energy protons in the geomagnetic tail at lunar distances

Three suprathermal ion detectors stationed on the moon were used to detect a region of plasma flowing antisunward along the ordered field lines of the geomagnetic tail, exterior to the plasma sheet. The particle flow displays an integral flux, a bulk velocity, temperatures, and number densities uniquely different from the other particle regimes traversed by the moon. No consistent deviation in the field was found to correspond with the occurrence of the events, which have an angular distribution extending between 50 and 100 deg and a spatial distribution over a wide region in both the Y sub sm and Z sub sm directions. The duration of observable particles varies widely between tail passages, with an apparent correlation between the number of hours of observation and the Kp index averages over these times. It is proposed that these particles may have entered through the cusp region.

Hardy, D. A.↗
NASA NTRS1976

Behavior of low-energy protons and alpha particles during a disturbed time period

The paper presents observations of 130- to 1200-keV protons and 40- to 420-keV/nucleon alpha particles made on the earth-orbiting spacecraft Imp 8 and Imp 7 during an active solar period in September 1974, concentrating, in particular, on an energetic storm particle (ESP) event observed in association with an interplanetary shock wave on September 21. It is found that the observed variations in the proton-to-alpha particle ratios and spectral indices can be explained either by 'pileup' or by acceleration models of ESP events. Several instances of local acceleration of particles in the near-earth environment are also discussed.

Ipavich, F. M.↗
NASA NTRS1976

Observations of magnetospheric bursts of high-energy protons and electrons at approximately 35 earth radii with Imp 7

Proton and electron bursts (above 0.29 MeV and above 0.22 MeV, respectively) in the vicinity of the magnetosphere are studied on the basis of a high-sensitivity experiment. Although the bursts are a permanent feature in the upstream solar wind, the range of observed intensities varies by at least 5 orders of magnitude, depending on magnetic activity. The bursts are typically associated with weak fluctuations in the interplanetary magnetic field, which suggests the presence of hydromagnetic waves. Burst are found in and about the magnetosheath, plasma sheet, and magnetotail boundary layer, and also outside the bow shock; however, they rarely appear at distances greater than 10 earth radii north or south of the neutral sheet. Dawn-dusk asymmetries are present in intensity but not necessarily in frequency of occurrence. Proton bursts are highly anisotropic upstream from the bow shock and in the magnetosheath, while electron bursts are anisotropic only in the upstream solar wind.

Sarris, E. T.↗
NASA NTRS1979

High energy proton radiation damage to (AlGa)As-G aAs solar cells

Twelve 2 + 2 sq cm (AlGa)As-GaAs solar cells were fabricated and were subjected to 15.4 and 40 MeV of proton irradiation. The results showed that the GaAs cells degrade considerably less than do conventional and developmental K7 silicon cells. The detailed characteristics of the GaAs and silicon cells, both before and after irradiation, are described. Further optimization of the GaAs cells seems feasible, and areas for future work are suggested.

Loo, R.↗
NASA NTRS1982

Theoretical analysis of low-energy proton and helium anisotropies in the outer heliosphere

Expressions for streaming components are considered along with aspects of azimuthal anisotropy, taking into account a calculation of mean free paths and a comparison with corotation conditions. Questions of polar anisotropy are also taken into account. It is found that the azimuthal anisotropy of 30 - 56 MeV protons near the ecliptic plane at 12 AU in 1977 was consistent with corotation, or slightly faster. This implies that the mean free path is approximately 16 AU. The azimuthal anisotropy of the anomalous 10-21 and 30 - 56 MeV/nucleon helium at the same time and place was an order of magnitude less than the corotation value. This implies a mean free path of approximately 5 AU.

Forman, M. A.↗
NASA NTRS1992

Search for evidence of low energy protons in solar flares

We searched for linear polarization in the H alpha line using the Stokes Polarimeter at Mees Solar Observatory and present observations of a flare from NOAA active region 6659 which began at 01:30 UT on 14 Jun. 1991. Our dataset also includes H alpha spectra from the Mees charge coupled device (MCCD) imaging spectrograph as well as hard x ray observations from the Burst and Transient Source Experiment (BATSE) instrument on board the Gamma Ray Observatory (GRO). The polarimeter scanned a 40 x 40 inch field of view using 16 raster points in a 4 x 4 grid. Each scan took about 30 seconds with 2 seconds at each raster point. The polarimeter stopped 8.5 inches between raster points and each point covered a 6 inch region. This sparse sampling increased the total field of view without reducing the temporal cadence. At each raster point, an H alpha spectrum with 20 mA spectral sampling is obtained covering 2.6 A centered on H alpha line center. The preliminary conclusions from the research are presented.

Metcalf, Thomas R.↗
NASA NTRS1994

Performance, defect behavior and carrier enhancement in low energy, proton irradiated p+nn+ InP solar cells

The highest AMO efficiency (19.1 percent) InP solar cell consisted of an n+pp+ structure epitaxially grown on a p+ InP substrate. However, the high cost and relative fragility of InP served as motivation for research efforts directed at heteroepitaxial growth of InP on more viable substrates. The highest AMO efficiency (13.7 percent) for this type of cell was achieved using a GaAs substrate. Considering only cost and fracture toughness, Si would be the preferred substrate. The fact that Si is a donor in InP introduces complexities which are necessary in order to avoid the formation of an efficiency limiting counterdiode. One method used to overcome this problem lies in employing an n+p+ tunnel junction in contact with the cell's p region. A simpler method consists of using an n+ substrate and processing the cell in the p+ nn+ configuration. This eliminates the need for a tunnel junction. Unfortunately, the p/n configuration has received relatively little attention the best cell with this geometry having achieved an efficiency of 17 percent. Irradiation of these homoepitaxial cells, with 1 Mev electrons, showed that they were slightly more radiation resistant than diffused junction n/p cells. Additional p/n InP cells have been processed by some activity aimed at diffusion. Currently, there has been some activity aimed at producing heteroepitaxial p+nn+ InP cells using n+ Ge substrates. Since, like Si, Ge is an n-dopant in InP, use of this configuration obviates the need for a tunnel junction. Obviously, before attempting to process heteroepitaxial cells, one must produce a reasonably good homoepitaxial cell. In the present case we focus our attention on homoepitaxially on an n+ Ge substrate.

Weinberg, I.↗
NASA NTRS2002

The high-energy proton fluxes in the SAA observed with REM aboard the MIR orbital station

During two years, from November 1994 to 1996, the particle detector REM measured the highly energetic electron and proton environment at the outside of the MIR orbital station. Using mission averaged data we investigate various aspects of the proton fluxes in the SAA. Comparison with the radiation belt model AP8 reveal important differences. c2002 Elsevier Science Ltd. All rights reserved.

long duration↗
NASA NTRS2012

Induction of Cell Death through Alteration of Oxidants and Antioxidants in Epithelial Cells Exposed to High Energy Protons

Radiation affects several cellular and molecular processes including double strand breakage, modifications of sugar moieties and bases. In outer space, protons are the primary radiation source which poses a range of potential health risks to astronauts. On the other hand, the use of proton radiation for tumor radiation therapy is increasing as it largely spares healthy tissues while killing tumor tissues. Although radiation related research has been conducted extensively, the molecular toxicology and cellular mechanisms affected by proton radiation remain poorly understood. Therefore, in the present study, we irradiated rat epithelial cells (LE) with different doses of protons and investigated their effects on cell proliferation and cell death. Our data showed an inhibition of cell proliferation in proton irradiated cells with a significant dose dependent activation and repression of reactive oxygen species (ROS) and antioxidants, glutathione and superoxide dismutase respectively as compared to control cells. In addition, apoptotic related genes such as caspase-3 and -8 activities were induced in a dose dependent manner with corresponding increased levels of DNA fragmentation in proton irradiated cells than control cells. Together, our results show that proton radiation alters oxidant and antioxidant levels in the cells to activate apoptotic pathway for cell death.

Ramesh, Govindarajan↗