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Improved ion source produces beam of ions at any kinetic energy from 1 to 1,000 eV, with little spread in energy or angle. Such ion beams useful in studies of surface properties of materials, surface etching, deposition, and development of plasma-diagnostic instrumentation. Tandemmirror ion source uses electrostatic and magnetic fields to keep electrons in ionization chamber and assure uniform output ion beam having low divergence in energy and angle.
A liquid helium cooled infrared telescope (IRT) was to be flown in July 1985 on Spacelab 2. The instrument is designed to measure both diffuse and discrete infrared astronomical sources, including the zodiacal light, galactic, and extragalactic components, as well as to evaluate the induced Orbiter environment. The focal plane contains ten photoconductive detectors covering six broad bands from 2 to 120 microns. Each detector has a 0.5 by 1.0 deg field of view optimized for detection of extended sources of IR radiation. Except for the 2 micron detector, the system noise is limited by the sky background noise. The measurements planned for the IRT use the 1 meter base of the Plasma Diagnostic Package (PDP), an already existing SL 2 experiment, as the glow generating surface. The measurements are repeated changing the position of the PDP, the attitude of the Orbiter, and the ram direction in an effort to remove both the thermal component of the PDP emission and the cosmic background radiation.
The Pinhole/Occulter Facility is a powerful tool for studying the physics of the extended corona and origins of the solar wind. Spectroscopic data acquired by the P/OF coronal instruments can greatly expand empirical information about temperatures, densities, flow velocities, magnetic fields, and chemical abundances in the corona out to r or approx. 10 solar radii. Such information is needed to provide tight empirical constraints on critical physical processes involved in the transport and dissipation of energy and momentum, the heating and acceleration of plasma, and the acceleration of energetic particles. Because of its high sensitivity, high spatial and temporal resolutions, and powerful capabilities for plasma diagnostics, P/OF can significantly increase our empirical knowledge about coronal streamers and transients and thereby advance the understanding of the physics of these phenomena. P/OF observations can be used to establish the role in solar wind generation, if any, of small-scale dynamical phenomena, such as spicules, macrospicules and coronal bullets, and the role of the fine-scale structures, such as polar plumes. Finally, simultaneous measurements by the P/OF coronal and hard X-ray instruments can provide critical empirical information concerning nonthermal energy releases and acceleration of energetic particles in the corona.
Ion cyclotron waves (ICWs) generated in the magnetosphere by the ion cyclotron instability of 10-100 keV protons are now known to be the origin of short-period (0.1-5 Hz) electromagnetic field oscillations observed by synchronous spacecraft and on the earth's surface. Observations of the various wave characteristics, including spectral and polarization properties, that lead to the identification of generation and propagation mechaniisms, and regions in the magnetosphere are described with reference to ATS-6, GEOS, and ground-based wave data and interpreted using cold plasma propagation theory. The presence of heavy ions (O/+/, He/+/) dramatically modifies ICW magnetospheric propagation characteristics giving rise to spectral slots and polarization reversals. These properties may be used in plasma diagnostics. Finally satellite-ground correlations and techniques for determining the magnetospheric source position of ICWs not seen at synchronous orbit but observed on the ground as structured Pc1 pulsations are considered.
Among the topics discussed are: theory of resonance and autoionization of two-electron atoms and ions; projection and quasi-projection operators for electron impact resonances on many-electron atomic targets; and hole projection methods for calculating Feshbach resonances and inner-shell vacancies. Consideration is also given to: complex stabilization methods; complex coordinate and complex basis function calculations; and the variational principle. The application of autoionization calculations to solar and astrophysical plasma diagnostics is also discussed in detail.
During the Spacelab 2 mission the Plasma Diagnostics Package (PDP) performed a fly-around of the Shuttle at distances of up to 300 meters while an electron beam was being ejected from the Shuttle. A magnetic conjunction of the Shuttle and the PDP while the electron gun was operating in a steady (DC) mode is discussed. During this conjunction, the PDP detected a clear funnel-shaped emission that is believed to be caused by whistler-mode emission from the beam. Ray-path calculations show that the shape of the funnel can be accounted for by whistler-mode waves propagating near the resonance cone. Because the beam and waves are propagating in the same direction, the radiation must be produced by a Landau interaction with the beam. Other types of waves generated by the beam are also described.
Selected problems concerned with the important physical processes that occur in the corona and solar wind acceleration region, particularly time dependent phenomena were studied. Both the physics of the phenomena and the resultant effects on observational signatures, particularly spectroscopic signatures were also studied. Phenomena under study include: wave motions, particularly Alfven and fast mode waves; the formation of standing shocks in the inner heliosphere as a result of momentum and/or heat addition to the wind; and coronal transient phenomena where momentum and/or heat are deposited in the corona to produce transient plasma heating and/or mass ejection. The development of theoretical models for the inner heliosphere, the theoretical investigation of spectroscopic plasma diagnostics for this region, and the analysis of existing skylab and other relevant data are also included.
The goal of MIT's high resolution X-ray spectrometry investigation on the Advanced X-ray Astrophysics Facility is to study the physical conditions in celestial sources by means of detailed measurements of their X-ray spectra. The investigation involves two complimentary dispersive instruments, a Bragg crystal spectrometer (BCS) and a high energy transmission grating spectrometer. Particular attention is given to the BCS which will be used to measure the strengths of individual lines from both point and extended objects in order to apply plasma diagnostic techniques to the study of cosmic X-ray sources.
Observations of secondary, high-inclination ions streams have been reported in the literature. The authors of these previous papers attributed the source of the secondary ions to a disturbed region in the plasma about 10 m from the Space Shuttle Orbiter. A new theory has been developed which shows how v x B induced differential charging on the plasma diagnostics package (PDP) can scatter the ram ion flux. Some of these ions are reflected back to the PDP and may be the sorce of the observed ion distributions. The effect is unique to large spacecraft; it occurs only when the magnitude of the induced v x B potentials are much larger than the electron thermal energy and of the order of the ion ram energy. That the ion streams observed at large angles must have been reflected from the PDP surface is demonstrated with three-dimensional sheath and particle trajectory calculations using the low earth orbit version of the NASA Charging Analyzer Program (NASCAP/LEO).
High spectral and spatial resolution UV and EUV spectroscopy is discussed with emphasis on the spectroscopic observations that are required in order to increase the understanding of the physics of the lower transition region. The properties of the lower transition region are reviewed, and the available lower transition region plasma diagnostics are reviewed for the wavelength range between about 1150 and 2000 A. One important conclusion is that comprehensive spectroscopic coverage over a rather broad temperature range is necessary in order to observe satisfactorily small transition region structures. This is illustrated by two examples from the recent NRL Spacelab 2 HRTS experiment.
During the Spacelab-2 mission a small satellite carrying various plasma diagnostic instruments was released from the Shuttle to coorbit at distances up to 300 m. During a magnetic conjunction of the Shuttle and the satellite an electron beam modulated at 1.22 kHz was emitted from the Shuttle during a 7 min period. The spatial structure of the electromagnetic fields generated by the beam was observed from the satellite out to a distance of 153 m perpendicular to the beam. The magnetic field amplitude of the strongest harmonics were comparable to the amplitude of simultaneously observed whistlers, while the electric field amplitudes were estimated to 1-10 mV/m.
Submillimeter-wave antennas have been fabricated on 1-micron thick silicon-oxynitride membranes. This approach results in better patterns than previous lens-coupled antennas, and eliminates the dielectric loss associated with the substrate lens. Measurements on a wideband log-periodic antenna at 700 GHz, 370 GHz and 167 GHz show no sidelobes and 3-dB beamwidths between 40 and 60 deg. A linear imaging array has similar patterns at 700 GHz. Possible applications for membrane antennas include wideband superconducting tunnel-junction receivers for radio astronomy and imaging arrays for radiometry and plasma diagnostics.
The role of the IUE in the study of planetary nebulae (PN) is discussed as well as extinction, the central star and nebular spectra, plasma diagnostics, the chemical compositions of PN, and nebular models. Some information on the spatial distribution of C(2+) or C(3+) ions may be acquired for extended PN from IUE data, making it possible to probe ionization zones different from those observable in the visual region. For high resolution pertaining to filamentary structure and clumpiness, optical region images and data obtained with the Hubble Space Telescope are needed.
Data obtained with an image-tube scanner at the 3-m Shane telescope are combined with IUE data to obtain plasma diagnostics and chemical compositions for two planetary nebulae of moderately high excitation. Theoretical nebular models were calculated using stellar fluxes given by Husfeld et al. (1984) for T(asterisk) = 85,000 K, log g = 4.72, and elemental abundances were obtained by fitting theoretical to observed line intensities and also by using the model to determine ionization correction factors to be applied to observed ionic concentrations. Although C appears to be about 1.5 times as abundant in NGC 6644 as in NGC 6565, N, O, Ne, S, Cl, and Ar are depleted by factors ranging from 2 to 6 in NGC 6644 as compared to NGC 6565. The high-velocity object, NGC 6644, was evidently made from a less metal-rich mixture than the sun.
Detailed measurements of the electric field strength associated with the Ku-band radar and S-band communication link were made by the Plasma Diagnostics Package (PDP) on STS 51F. These measurements were made while the PDP was attached to the Remote Manipulation System arm and again while the PDP was released as a subsatellite. The results indicate that cargo elements that remain inside of the scan limits of the radar should experience fields less than 2 V/m and that elements that may encounter the main beam can use 300 V/m as a design guideline with adequate safety margin. S-band fields tended to be several dB lower than worst-case predictions. Safe design practice indicates that an electric field E = 100/r (r in meters) should be used as a guideline for deployable systems. S-band electric fields within the cargo bay envelope should be less than 2 V/m even with edge diffraction effects and reflections from other payloads taken into account. The absolute accuracy of these measurements is about 2 dB.
Wall-level CW solid-state sources in the millimeter-wave region are needed for plasma diagnostics. Monolithic metal-grid arrays containing in excess of 1000 Schottky diodes have produced watt-level output at 66 GHz in a doubler configuration, in excellent agreement with the large-signal predictions of the frequency multiplication. Current efforts are concentrated on fabricating and developing arrays of a novel barrier-intrinsic-N+ (BIN) diode which promise increased performance in a tripler configuration. Initial tests will be made for a configuration where a tripling efficiency of 35 percent at an output frequency of 100 GHz is predicted. Eventual goals are monolithic BIN diode grids operating at 1 THz.
Progress made by space experimentation in obtaining solar spectra satisfactory for extensive applications of plasma diagnostic techniques is reviewed. Particular attention is given to solar spectroscopy in the FUV-X-ray wavelength regions in the 1.7-2000 A range. The quality of the available spectra obtained in each region is evaluated, concentrating on spectral resolution, wavelength coverage and accuracy, and line intensity and line-profile information.
During the Spacelab-2 mission of July 1985, electron beams (1 keV, 50-150 mA) pulsed at ELF and VLF frequencies were emitted from the Space Shuttle Orbiter. The wave fields generated by the beam were monitored by a Plasma Diagnostics Package which was released as a free-flying subsatellite during a six hour period. Measurements of the Orbiter potential and the return current during beam emissions were obtained from a Charge and Current Probe mounted in the payload bay.