SEARCH · Search NASA
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.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Beam impinges on palladium-silver tube, which is target, and heats impinged surface causing local hot spot. Contained gas diffuses through hot spot to meet incoming beam and produce desired particles. When beam is turned off, target spot cools and stops dispensing contained gas.
This paper reviews observations of interplanetary particle beams of the kind that frequently accompany a solar flare. It is shown that the most frequently observed beams are beams of electrons which are associated with radio bursts of type III, but occasionally with flares and X-ray bursts. Although the main features of these beams and their associated plasma waves and radio bursts are known, uncertainties remain in terms of the correlation between electron beams and filamentary structures, the relative importance of the quasi-linear and the nonlinear wave emissions as the dominant process, and the mechanism of conversion of some of the Langmuir wave energy into radio emissions. Other particle beams discussed are those composed of protons, neutrons, He ions, or heavy ions. While most of these beams originate from sun flares, the source of some of particle beams may be the earth, Jupiter, or other planets as well as comets.
An apparatus to measure the incident charged particle beam flux while effectively eliminating losses to reflection and/or secondary emission of the charged particle beam being measured is described. It comprises a sense cup through which the charged particle beam enters. A sense cone forms the rear wall of the interior chamber with the cone apex adjacent the entry opening. An outer case surrounds the sense cup and is electrically insulated therefrom. Charged particles entering the interior chamber are trapped and are absorbed by the sense cup and cone and travel through a current measuring device to ground.
A key issue in choosing the appropriate site for a manned lunar base is the availability of resources, particularly oxygen and hydrogen for the production of water, and ores for the production of fuels and building materials. NASA has proposed two Lunar Scout missions that would orbit the Moon and use, among other instruments, a hard X-ray spectrometer, a neutron spectrometer, and a Ge gamma ray spectrometer to map the lunar surface. This passive instrumentation will have low resolution (tens of kilometers) due to the low signal levels produced by natural radioactivity and the interaction of cosmic rays and the solar wind with the lunar surface. This paper presents the results of a concept definition effort for a neutral particle beam lunar mapper probe. The idea of using particle beam probes to survey asteroids was first proposed by Sagdeev et al., and an ion beam device was fielded on the 1988 Soviet probe to the Mars moon Phobos. During the past five years, significant advances in the technology of neutral particle beams (NPB) have led to a suborbital flight of a neutral hydrogen beam device in the SDIO-sponsored BEAR experiment. An orbital experiment, the Neutral Particle Beam Far Field Optics Experiment (NPB-FOX) is presently in the preliminary design phase. The development of NPB accelerators that are space-operable leads one to consider the utility of these devices for probing the surface of the Moon using gamma ray, X-ray, and optical/UV spectroscopy to locate various elements and compounds. We consider the utility of the NPB-FOX satellite containing a 5-MeV particle beam accelerator as a probe in lunar orbit. Irradiation of the lunar surface by the particle beam will induce secondary and back scattered radiation from the lunar surface to be detected by a sensor that may be co-orbital with or on the particle beam satellite platform, or may be in a separate orbit. The secondary radiation is characteristic of the make-up of the lunar surface. The size of the spot irradiated by the beam is less than 1 km wide along the ground track of the satellite, resulting in the potential for high resolution. The fact that the probe could be placed in polar orbit would result in global coverage of the lunar surface. The orbital particle beam probe could provide the basis for selection of sites for more detailed prospecting by surface rovers.
Tissue dosages from alpha particles and heavy nuclei in solar particle beams in space
Two difficulties with the use of laser-propelled lightsails for interstellar propulsion are the extremely low energy efficiency, and the extremely large lenses required. Both the energy efficiency and the required lens size may be greatly improved by use of a particle beam, rather than a light beam. The particle beam is reflected by a magnetic field on the spacecraft, for example, by a magnetic sail or a mini-magnetosphere inflated by a plasma current. This results in a net force on the sail with no expenditure of propellant, allowing extremely high delta-V missions, such as an interstellar probe, to be accomplished.
Radiation exposure in solar particle beams behind very low shielding - radiation protection of space suit
Characteristics of studies on board the Shuttle involving the interaction of particle beams with the atmosphere and the ionosphere, and the effects of the beams on the electrical potential of the platform, are discussed. Noting that the Shuttle allows greater weight and power demands by scientific payloads than previous satellite launches, the OSS-1 Vehicle Charging and Potential experiment and the Spacelab 1 Particle Accelerator and Phenomena Induced by Charged Particle Beams are described. Instrumentation details are provided, including charge and current probes, the Spherical Retarding Potential Analyzer, the Fast Pulse Electron Generator, and digital control and interface units. The SEPAC equipment, which comprises an electron beam accelerator, and MPD plasma jet, and diagnostic units are detailed, and operating procedures and experiment objectives are outlined.
A real-time charged particle beam probe was developed, which can be used both as a beam diagnostic (beam tuning) and to quantitatively determine the three-dimensional density distribution of a beam. The probe consists of a microchannel plate, an aluminized phosphor screen deposited on a fiber-optic faceplate, a flexible fiber-optic bundle, and a charge injection device (CID) in tandem. Digital or analog video output of the CID is fed into a computer or oscilloscope, respectively, for analysis or observation. The probe can be moved continuously along the beams' paths to obtain 'pictures' of the beam at any desired interval, thus giving three-dimensional form factors. The beams, singly or simultaneously, may be observed on the monitor facilitating the task of beam adjustment for optimum overlap. The digital output is used for quantitative computation of the beam overlaps. The device is linear with beam intensity, but the performance degrades with time due to beam damage of the microchannel plate.
A technique has been developed to support the study of the effects of cosmic rays on integrated circuits. The system is designed to determine the particle distribution across the surface of an integrated circuit accurately while the circuit is bombarded by a particle beam. The system uses photomultiplier tubes, an octal discriminator, a computer-controlled NIM quad counter, and an IBM PC. It provides real-time operator feedback for fast beam tuning and monitors momentary fluctuations in the particle beam. The hardware, software, and system performance are described.
One potential use for neutral particle beam (NPB) technology is as an active orbital probe to investigate the composition of selected locations on the lunar surface. Because the beam is narrow and can be precisely directed, the NPB probe offers possibilities for high resolution experiments that cannot be accomplished using passive techniques. Rather, the combination of both passive and active techniques can be used to provide both full-coverage mapping (passively) at low resolution (tens of kilometers) and high-resolution information for discrete locations of special interest. A preliminary study of NPB applicability for this dual-use application was recently conducted. The study was completed in Feb. 1993. A novel feature was the consideration of the use of a Russian launch vehicle (e.g., the Proton). The use of other Russian space hardware and capabilities was also encouraged. This paper describes the lunar prospector system design. Other researchers discuss the issues and opportunities involving lunar scientific experimentation using an NPB. The NPB lunar prospector utilizes a modified design of the Far Field Optics Experiment (FOX). Like the Earth-orbiting FOX, the core capability of the NPB lunar prospector will be a pulsed RF LINAC that produces a 5-MeV proton beam that is projected to the target with a 30-micro-r beam divergence and a 10-micro-r beam-pointing accuracy. Upon striking the lunar surface, the proton beam will excite characteristic radiation (e.g., X-rays) that can be sensed by one or more detectors on the NPB platform or on a separate detector satellite.
Particle beam power density detection and measurement apparatus
An electron beam system was operated over a wide range of beam currents and energies for periods both in sunlight and in eclipse. Complex pitch angle modulations of the electron spectra are separately decomposed for each beam operation. When electrons are emitted perpendicular to the magnetic field with an energy of 3 keV and a current of 0.10 mA they return as a coherent beam only to the parallel detector. Throughout the beam operations the pitch angle distributions show electrons with energy less than beam energy streaming along the field line. Analytic expressions for the satellite electric field are constructed and particle trajectories are determined.
Astronauts with thin shielding in radiation exposure from heavy nuclei in solar particle beams
A computer program for a PDP-15 is presented which calculates, to first order, the characteristics of charged-particle beam as it is transported through a sequence of focusing and bending magnets. The maximum dimensions of the beam envelope normal to the transport system axis are continuously plotted on an oscilloscope as a function of distance along the axis. Provision is made to iterate the calculation by changing the types of magnets, their positions, and their field strengths. The program is especially useful for transport system design studies because of the ease and rapidity of altering parameters from panel switches. A typical calculation for a system with eight elements is completed in less than 10 seconds. An IBM 7094 version containing more-detailed printed output but no oscilloscope display is also presented.
The injection of energetic particles along the Earth's magnetic field lines is a possible remote sensing method for measuring the electric fields parallel to the magnetic field with good time resolution over the entire magnetic field. Neutralization processes, return-current effects, dynamics of the beams, triggered instabilities, and waves must be investigated before the fundamental question about proper experimental conditions, such as energy, intensity and divergence of the beams, pitch-angle injection, ion species, proper probes and detectors and their location, and rendezvous conditions, can be resolved. An experiment designed to provide a better understanding of these special physical processes and to provide some answers to questions concerning beam injection techniques is described.
Cell adhesion molecules (CAMs) are proteins which anchor cells to each other and to the extracellular matrix (ECM), but whose functions also include signal transduction, differentiation, and apoptosis. We are testing a hypothesis that particle radiations modulate CAM expression and this contributes to radiation-induced lens opacification. We observed dose-dependent changes in the expression of beta 1-integrin and ICAM-1 in exponentially-growing and confluent cells of a differentiating human lens epithelial cell model after exposure to particle beams. Human lens epithelial (HLE) cells, less than 10 passages after their initial culture from fetal tissue, were grown on bovine corneal endothelial cell-derived ECM in medium containing 15% fetal bovine serum and supplemented with 5 ng/ml basic fibroblast growth factor (FGF-2). Multiple cell populations at three different stages of differentiation were prepared for experiment: cells in exponential growth, and cells at 5 and 10 days post-confluence. The differentiation status of cells was characterized morphologically by digital image analysis, and biochemically by Western blotting using lens epithelial and fiber cell-specific markers. Cultures were irradiated with single doses (4, 8 or 12 Gy) of 55 MeV protons and, along with unirradiated control samples, were fixed using -20 degrees C methanol at 6 hours after exposure. Replicate experiments and similar experiments with helium ions are in progress. The intracellular localization of beta 1-integrin and ICAM-1 was detected by immunofluorescence using monoclonal antibodies specific for each CAM. Cells known to express each CAM were also processed as positive controls. Both exponentially-growing and confluent, differentiating cells demonstrated a dramatic proton-dose-dependent modulation (upregulation for exponential cells, downregulation for confluent cells) and a change in the intracellular distribution of the beta 1-integrin, compared to unirradiated controls. In contrast, there was a dose-dependent increase in ICAM-1 immunofluorescence in confluent, but not exponentially-growing cells. These results suggest that proton irradiation downregulates beta 1-integrin and upregulates ICAM-1, potentially contributing to cell death or to aberrant differentiation via modulation of anchorage and/or signal transduction functions. Quantification of the expression levels of the CAMs by Western analysis is in progress.
We review some results on longitudinal beam dynamics obtained in the framework of the Thermal Wave Model (TWM). In this model, which has recently shown the capability to describe both longitudinal and transverse dynamics of charged particle beams, the beam dynamics is ruled by Schroedinger-like equations for the beam wave functions, whose squared modulus is proportional to the beam density profile. Remarkably, the role of the Planck constant is played by a diffractive constant epsilon, the emittance, which has a thermal nature.