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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 361 records · Page 20
All sourcesNASA NTRSDOE OSTI
NASA NTRS1998

Heavy-ion radiobiology: new approaches to delineate mechanisms underlying enhanced biological effectiveness

Shortly after the discovery of polonium and radium by Marie Curie and her husband and colleague, Pierre Curie, it was learned that exposure to these alpha-particle emitters produced deleterious biological effects. The mechanisms underlying the increased biological effectiveness of densely ionizing radiations, including alpha particles, neutrons and highly energetic heavy charged particles, remain an active area of investigation. In this paper, we review recent advances in several areas of the radiobiology of these densely ionizing radiations, also known as heavy ions. Advances are described in the areas of DNA damage and repair, chromosome aberrations, mutagenesis, neoplastic transformation in vitro, genomic instability, normal tissue radiobiology and carcinogenesis in vivo. We focus on technical innovations, including novel applications of pulsed-field gel electrophoresis, fluorescence in situ hybridization (FISH), linkage analysis, and studies of gene expression and protein expression. We also highlight the use of new cellular and animal systems, including those with defined DNA repair deficiencies, as well as epithelial cell model systems to assess neoplastic transformation both in vitro and in vivo. The studies reviewed herein have had a substantial impact on our understanding of the genotoxic effects of heavy ions as well as their distinct effects on tissue homeostasis. The use of these radiations in cancer therapy is also discussed. The use of both heavy-ion and proton therapy is on the upswing in several centers around the world, due to their unique energy deposition characteristics that enhance the therapeutic effect and help reduce damage to normal tissue.

Review, Academic↗
NASA NTRS1971

Differential cross sections at forward angles for hydrogen and helium particles from 62 MeV protons incident on Ni-60

Tabulated differential cross sections are presented for the production, at angles of 15, 20, 25, and 40 deg, of proton, deuteron, triton, helium-3, and alpha particles from Ni-60 bombarded by 62-MeV protons. Continuum cross sections are listed in about 1-MeV bins for energies above lower cutoffs which range from 4 to 15 MeV for the different types of exit particles. Only the integral cross section is known for a considerable energy range within each spectrum. The proton, deuteron, and alpha particle cross sections are the same in the continuum range region above the evaporation peak as those cross sections previously observed for Fe-54 and Fe-56, but the corresponding yield of tritons is higher from Ni-60 and Fe-56 than from Fe-54.

Peelle, R. W.↗
NASA NTRS1973

Solar wind heating beyond 1 AU

The effect of an interplanetary atomic hydrogen gas on solar wind proton, electron and alpha-particle temperatures beyond 1 AU is considered. It is shown that the proton temperature (and probably also the alpha-particle temperature) reaches a minimum between 2 AU and 4 AU, depending on values chosen for solar wind and interstellar gas parameters. Heating of the electron gas depends primarily on the thermal coupling of the protons and electrons. For strong coupling, the electron temperature reaches a minimum between 4 AU and 8 AU, but for weak coupling (Coulomb collisions only), the electron temperature continues to decrease throughout the inner solar system. A spacecraft travelling to Jupiter should be able to observe the heating effect of the solar wind-interplanetary hydrogen interaction, and from such observations it may be possible of infer some properties of the interstellar neutral gas.

Holzer, T. E.↗
NASA NTRS1990

Test results of a prototype dielectric microcalorimeter

The initial development work on a dielectric microcalorimeter is presented. It focuses on the dielectric properties of the ferroelectric material KTa(1-x)Nb(x)O3 (KTN). Measurements of the temperature dependent dielectric constant are given together with the first alpha particle detection results from a prototype composite microcalorimeter operating at 1.3 K. A nonthermal mechanism for detecting 6 MeV alpha particles in a monolithic KTN sample is also reported.

Pfafman, T. E.↗
NASA NTRS1992

Energetic Particles Investigation (EPI)

The EPI instrument operates during the pre-entry phase of the Galileo Probe. The main objective is the study of the energetic particle population in the inner Jovian magnetosphere and in the upper atmosphere. This will be achieved through omnidirectional measurements of electrons, protons, alpha-particles and heavy ions (Z greater than 2) and recording intensity profiles with a spatial resolution of about 0.02 Jupiter radii. Sectored data will also be obtained for electrons, protons, and alpha-particles to determine directional anisotropies and particle pitch angle distributions. The detector assembly is a two-element telescope using totally depleted circular silicon surface-barrier detectors surrounded by cylindrical tungsten shielding. The lower energy threshold of the particle species investigated during the Probe's pre-entry phase is determined by the material thickness of the Probe's rear heat shield which is required for heat protection of the scientific payload during entry into the Jovian atmosphere. The EPI instrument is combined with the Lightning and Radio Emission Detector and both instruments share one interface of the Probe's power, command, and data unit.

Fischer, H. M.↗
NASA NTRS1992

An Alpha-p-x Analytical Instrument for Lunar Resource Investigations

An instrument using alpha backscattering, alpha-proton nuclear reactions, and x-ray production by alpha particles and other auxiliary sources can be used on lunar landers to provide detailed analytical information concerning the lunar surface material. This information is important scientifically and can be the basis for utilizing efficiently lunar resources to build lunar colonies in the future. This alpha particle instrument uses radioactive isotopes, silicon detectors for the alpha and proton modes, and mercuric iodide detectors operating at room temperature for the x-ray mode. The alpha and proton modes of the instrument can provide an analysis for all elements (except hydrogen) present in amounts greater than about 1 percent by atom. These modes have excellent sensitivity and accuracy for the lighter elements, in particular, directly determining the amount of oxygen in the lunar soil. This is an element of paramount significance for the lunar resource mission. The x-ray mode makes possible a determination of Ti, Fe, and other important metals with even greater accuracy. In general, the x-ray mode provides increased sensitivity for heavier elements, in many cases achieving a sensitivity of several hundred ppm.

Economou, T. E.↗
DOE OSTI2023

Collaborative Research Towards a tonne-scale bolometer-based neutrinoless double beta decay experiment (Final Report)

Cryogenic bolometers are an excellent technology for neutrinoless double beta decay searches owing to their very high energy resolution and potential for high radiopurity. The current most advanced large-scale experiment using these detectors is the Cryogenic Underground Observatory for Rare Events (CUORE). The largest source of background in CUORE is degraded alpha particles, emitted from shallow depths of the detector holders, which can deposit a thermal energy signature similar to neutrinoless double beta decay. To mitigate this background, the CUPID concept (CUORE Upgrade with Particle IDentification) proposes to use scintillating cryogenic detectors. Detecting both the scintillation light and the thermal signal allows discrimination between alpha particle events and beta/gamma events. We report on the design and execution of R&D tests to optimize the design of the single detector module, in particular the scintillation light collection efficiency at cryogenic temperatures.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
NASA NTRS1994

Growth rates of new parametric instabilities occurring in a plasma with streaming He(2+)

We consider parametic instabilities of a circularly polarized pump Alfven wave, which propagates parallel to the ambient magnetic field; the daughter waves are also parallel-propagating. We follow Hollweg et al. (1993) and consider several new instabilites that owe their existence to the presence of streaming alpha particles. One of the new instabilites is similar to the famililar decay instability, but the daughter waves are a forward going alpha sound wave and a backward going Alfven wave. The growth rate of this instability is usually small if the alpha abundance is small. The other three new instabilities occur at high frequencies and small wavelengths. We find that the new instability which involves the proton cyclotron wave and alpha sound (i.e., the +f, - alpha) instability, which involves both the proton and alpha cycltron resonances, but if the pump wave must have low frequency and large amplitude. These instabilities may be a means of heating and accelerating alpha particles in the solar wind, but this claim is unproven until a fully kinetic study is carried out.

Jayanti, V.↗
DOE OSTI2017

Elevated Temperature Alpha Spectroscopy with Nickel-Platinum {sup 4}H-SiC Schottky Diodes

In order to protect against the diversion of special nuclear material during pyro-processing of spent nuclear fuel, an online monitoring of the actinide concentrations must be developed. In order to do so, alpha spectroscopy can be employed in order to determine the relative concentrations of various isotopes based on the characteristic alpha spectrum of each isotope of interest. The operating temperatures in the pyro-processing environment are such that high temperature operability of alpha detectors is required. The Idaho National Laboratory (INL) electro-refiner operates at a molten salt temperature of approximately 500 deg. C. The vapor temperature above the molten salt is approximately 100 deg. C. In order to provide reasonably compact online monitoring of the actinide concentrations within the molten salt the detector would be located in this vapor region. The temperature in this location is too high for a commercial silicon detector to operate without serious signal degradation due to thermal noise. As the operating temperature increases, the thermal energy available to the charge carriers within the semiconductor increases. For narrow band-gap semiconductors like silicon, this increase in free charge carriers with increasing temperature leads to unacceptable leakage current at relatively low temperatures when compared with wide band-gap materials. In order to overcome this, a wide band-gap material is employed. An alpha particle sensor utilizing a nickel Schottky barrier {sup 4}HSiC wafer was heated to a temperature of 100 deg. C and an alpha spectrum collected. The performance of the sensor at 100 deg. C was compared to the room temperature performance. Molten salts such as those used in the INL electro-refiner exhibit strong corrosive properties. Any sensor which will be exposed to or submerged in the molten salt must have a ruggedized sensor face capable to withstand the corrosive environment. In the contact design utilized in this paper the Schottky barrier forming metal, nickel, is coated with a thin layer of platinum to serve as a corrosion resistant layer. An additional modification to previous designs was the simplification of the Schottky barrier composition. A Schottky barrier is created when a metal is brought into close physical contact with a semiconductor. To first order, the barrier height of the Schottky barrier is a result of the mismatch between the electron affinity of the semiconductor and the metal work function of the metal. In previous iterations, the high temperature performance of the detectors had been limited by diffusion processes between the various metal layers. In order to reduce the likelihood of such a degradation, the Schottky contact structure was simplified without loss of functionality. By replacing the multiple metal layers with a nickel Schottky forming layer capped with a thin platinum layer, the potential degradation of the Schottky barrier height could be reduced, primarily through the similar Schottky barrier height to nickel formed by platinum with SiC.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2018

Response to Mortazavi et al. on Detecting Bone-seeking Radionuclides in Brain Tissue

WE DISAGREE with most of the issues raised by Mortazavi et al. (2018), both scientifically and inferentially. Cranial deposition of radium (or any other bone seeker) is not relevant to our evaluation of alpha particle exposure to brain tissue (Ellis et al. 2018). Radiochemical analysis of tissues has demonstrated that radium is deposited in the brain and results in alpha particle exposure to brain tissue (Schlenker et al. 1982). Radiochemical analyses also have confirmed brain depositions for other bone seekers including plutonium (James et al. 2003, 2007), americium (McInroy et al. 1985), and uranium (Avtandilashvili et al. 2015 ; Kathren and Tolmachev 2015), as well as for the more nearly uniformly distributed alpha emitter polonium (Nathwani et al. 2016).

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS2001

Radiation dosimetry using three-dimensional optical random access memories

Three-dimensional optical random access memories (3D ORAMs) are a new generation of high-density data storage devices. Binary information is stored and retrieved via a light induced reversible transformation of an ensemble of bistable photochromic molecules embedded in a polymer matrix. This paper describes the application of 3D ORAM materials to radiation dosimetry. It is shown both theoretically and experimentally, that ionizing radiation in the form of heavy charged particles is capable of changing the information originally stored on the ORAM material. The magnitude and spatial distribution of these changes are used as a measure of the absorbed dose, particle type and energy. The effects of exposure on 3D ORAM materials have been investigated for a variety of particle types and energies, including protons, alpha particles and 12C ions. The exposed materials are observed to fluoresce when exposed to laser light. The intensity and the depth of the fluorescence is dependent on the type and energy of the particle to which the materials were exposed. It is shown that these effects can be modeled using Monte Carlo calculations. The model provides a better understanding of the properties of these materials. which should prove useful for developing systems for charged particle and neutron dosimetry/detector applications. c2001 Published by Elsevier Science B.V.

Non-NASA Center↗
NASA NTRS1997

A LiF silicon sandwich counter to measure water content of planetary surfaces

The neutron counter proposed here has a long history and was commercially available in a somewhat different form. This counter would be suitable for a rover or lander since it requires a rather long measuring time for each placement. It consists of two silicon wafer charged-particle counters with a layer of Li-6F deposited on the inner surface of one. The neutron detecting reaction is Li-6(n,H-3)He-4 in which the alpha particle and the triton are emitted from the Li-6 deposit back to back. If one of the detectors sees the alpha particle, the other will see the triton. This allows one to use a coincidence technique that virtually eliminates all background. The signals from each detector can be added together so that the total energy of the reaction, Q=4.6 MeV and the kinetic energy of the neutron, can be recorded.

Drake, D. M.↗
DOE OSTI2019

Collisional alpha transport in a weakly non-quasisymmetric stellarator magnetic field</strong

Alpha particle confinement is a serious concern in stellarators and provides strong motivation for optimizing magnetic field configurations. In addition to the collisionless confinement of trapped alphas in stellarators, excessive collisional transport of the trapped alpha particles must be avoided while they tangentially drift due to the magnetic gradient (the ∇B drift).The combination of pitch angle scatter off the background ions and the ∇B drift gives rise to two narrow boundary layers in the trapped region. The first is at the trapped–passing boundary and enables the finite trapped response to be matched to the vanishing passing response of the alphas. The second layer is a region that encompasses the somewhat more deeply trapped alphas with vanishing tangential ∇B drift. Away from (and between) these boundary layers, collisions are ineffective and the alpha ∇B drift simply balances the small radial drift of the trapped alphas. As this balance does not vanish as the trapped–passing boundary is approached, the first collisional boundary layer is necessary and gives rise to $\sqrt{v}$ transport, with v the collision frequency. The vanishing of the tangential drift results in a separate, somewhat wider boundary layer, and significantly stronger superbanana plateau transport that is independent of collisionality. The constraint imposed by the need to avoid significant energy depletion loss in the slowing down tail distribution function sets the allowed departure of a stellarator from an optimal quasisymmetric configuration.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2019

Collisional alpha transport in a weakly non-quasisymmetric stellarator magnetic field

Alpha particle confinement is a serious concern in stellarators and provides strong motivation for optimizing magnetic field configurations. In addition to the collisionless confinement of trapped alphas in stellarators, excessive collisional transport of the trapped alpha particles must be avoided while they tangentially drift due to the magnetic gradient (the ∇B drift). The combination of pitch angle scatter off the background ions and the ∇B drift gives rise to two narrow boundary layers in the trapped region. The first is at the trapped-passing boundary and enables the finite trapped response to be matched to the vanishing passing response of the alphas. The second layer is a region that encompasses the somewhat more deeply trapped alphas with vanishing tangential ∇B drift. Away from (and between) these boundary layers, collisions are ineffective and the alpha ∇B drift simply balances the small radial drift of the trapped alphas. As this balance does not vanish as the trapped-passing boundary is approached, the first collisional boundary layer is necessary and gives rise to √ν transport, with ν the collision frequency. The vanishing of the tangential drift results in a separate, somewhat wider boundary layer, and significantly stronger superbanana plateau transport that is independent of collisionality. The constraint imposed by the need to avoid significant energy depletion loss in the slowing down tail distribution function sets the allowed departure of a stellarator from an optimal quasisymmetric configuration.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1990

Li-7 and Be-7 de-excitation lines - Probes for accelerated particle transport models in solar flares

The photon energy spectrum of a spectral feature composed of the 429 and 478 keV gamma-ray lines from Be-7 and Li-7 (produced by interactions of flare-accelerated alpha particles with ambient He in the solar atmosphere) depends on the angular distribution of the interacting accelerated particles. This spectrum is calculated for limb and disk-centered flares using a loop model for the transport of the ions. The resulting spectra are compared with data from the April 27, 1981 limb flare obtained with the gamma-ray spectrometer on SMM, providing convincing evidence for the existence of the (Li-7)-(Be-7) feature in this flare. By comparing the fluence of this feature with that of the 511 keV line, it is shown that the accelerated alpha particle abundance or the ambient He abundance, or both, must be enhanced.

Murphy, R. J.↗
DOE OSTI2023

Merging of the superbanana plateau and $\sqrt{v}$ transport regimes in nearly quasisymmetric stellarators

We report alpha particle confinement is one of the most demanding issues for stellarators. It now seems clear that it is possible to design optimized stellarators that confine the background plasma at near tokamak radial transport levels. Moreover, adequate collisionless alpha particle confinement is possible in the core of a highly optimized stellarator. Here, the collisional confinement of barely trapped alphas in an optimized stellarator is considered by accounting for the resonance due to the reversal in direction of the drift within a flux surface and investigating the sensitive role of magnetic shear in keeping this resonance close to the passing boundary in some nearly quasisymmetric stellarator configurations. The treatment relies on a narrow collisional boundary layer formulation that combines the responses of both these resonant pitch angle alphas and the remaining barely trapped alphas. A novel merged regime treatment leads to explicit expressions for the energy diffusivity for both superbanana plateau (or resonant plateau) and $\sqrt{v}$ transport in the large aspect ratio limit for a slowing down tail alpha distribution function, where v is the effective pitch angle scattering collision frequency of the trapped alphas off the background ions. Depending on the details of the optimization scheme and the sign of the magnetic shear, modest magnetic shear can be used to reduce superbanana (or resonant) plateau transport to below the $\sqrt{v}$ transport level. In addition, a quasilinear equation retaining spatial diffusion is derived for a general alpha distribution function that allows the radial alpha transport to modify the distribution so it is no longer isotropic in velocity space.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗