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At least 73 records · Page 4

The energy spectrum of Jovian electrons in interplanetary space

The energy spectrum of electrons with energies approximately 10 to approximately 180 MeV measured with the electron telescope on the Voyager 1 and 2 spacecraft in interplanetary space from 1978 to 1983 is reported. The kinetic energy of electrons is determined by double dE/dx measurements from the first two detectors (D1,D2) of a stack of eight solid state detectors and by the range of particle penetration into the remaining six detectors (D3 to D8) which are interleaved with tungsten absorbers.

Christon, S. P.↗

Background suppression techniques in germanium detectors

A new generation of astrophysical gamma ray spectrometers employing germanium solid state detectors for precise energy measurement are currently being planned for spaceflight in the late 1990's and the early 21st century. Because the observations of weak celestial sources are carried out in an intense radiation environment, the key objective of instrument design is to find ways to reduce the background. The current state of the knowledge in this field is reviewed and the new hardware techniques under design and test are discussed. Many of these techniques have already been flight tested on balloon platforms. Recent results from some of these tests are presented. By carefully applying these techniques it should be possible to achieve sensitivities that are factors of 3 to 10 better than would be obtained for a conventional instrument of similar weight.

Gehrels, Neil↗

Field ionization device used for measuring the pulse height defect of He/+/ in silicon

A neutral particle detector using field ionization and liquid-nitrogen-cooled solid state detectors has been developed to investigate the pulse height defect of low energy He(+) ions in silicon. The field ionization tip is fabricated from a short length of tungsten wire; a typical detector is of the surface-barrier Si type with a thin Au window and low capacitance (about 15 pF); the assembly is mounted in a cylindrical vacuum chamber which is pumped to about 10 to the -6th torr. As an example, pulse height distributions for He(+) and H(+) taken at tip bias of 25.7 kV are presented. The detected energy of the H and He ions are studied as a function of the actual energies of accelerated ions, for a detector having a gold front conducting surface layer of 32 micrograms/sq cm.

Curtis, C. C.↗

Low-Power Multi-Aspect Space Radiation Detector System

The advanced space radiation detector development team at NASA Glenn Research Center (GRC) has the goal of developing unique, more compact radiation detectors that provide improved real-time data on space radiation. The team has performed studies of different detector designs using a variety of combinations of solid-state detectors, which allow higher sensitivity to radiation in a smaller package and operate at lower voltage than traditional detectors. Integration of all of these detector technologies will result in an improved detector system in comparison to existing state-of-the-art (SOA) instruments for the detection and monitoring of the deep space radiation field.

Wrbanek, John D.↗

The robot's eyes - Stereo vision system for automated scene analysis

Attention is given to the robot stereo vision system which maintains the image produced by solid-state detector television cameras in a dynamic random access memory called RAPID. The imaging hardware consists of sensors (two solid-state image arrays using a charge injection technique), a video-rate analog-to-digital converter, the RAPID memory, and various types of computer-controlled displays, and preprocessing equipment (for reflexive actions, processing aids, and object detection). The software is aimed at locating objects and transversibility. An object-tracking algorithm is discussed and it is noted that tracking speed is in the 50-75 pixels/s range.

Williams, D. S.↗

Response of AC-coupled low gain avalanche detectors to ionizing and non-ionizing radiation damage

Low gain avalanche diodes with DC- and AC-coupled readout were exposed to ionizing and non-ionizing radiation at levels relevant to future experiments in particle, nuclear, and medical physics and to astrophysics. Damage-related change in their acceptor removal constants and in the resistivity of the region between the guard ring and the active area are reported, as is change in the leakage current and depletion voltages of the active volumes.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

The Energy Spectrum of Jovian Electrons in Interplanetary Space

The energy spectrum of electrons with energies approx 10 to approx 180 MeV measured with the electron telescope on the Voyager 1 and 2 spacecraft in interplanetary space from 1978 to 1983 is studied. The kinetic energy of electrons is determined by double dE/dx measurements from the first two detectors (D sub 1, D sub 2) of a stack of eight solid state detectors and by the range of particle penetration into the remaining six detectors (D sub 3 to D sub 8) which are interleaved with tungsten absorbers. From 1978 to 1983 (radial range approximately 2 to a pproximately 12 AU) electrons of Jovian origin were clearly observable for electrons stopping in D(sub 3(E approximately greater than 4 MeV)) and in D(sub 4 (E approximately greater than 8 MeV)). For electrons stopping in D(sub 5(E approximately greather than 12 MeV)), the jovian flux dominated the galactic electron flux for a period of approximately one year near the encounter with Jupiter. Jovian electrons were also observed in D(sub 6(E approximately greater than 21 MeV)) but not in D(sub 7(E approximately greater than 28 MeV)). A detailed interpretation of the electron variations in all energy channels depends on an accurate subtraction of background induced by energetic protons of a few 100 MeV. This substraction is facilitated by laboratory calibration results at several energies. Further results on the differential energy spectrum of Jovian electrons and limits on the maximum detected energies will be reported.

Christon, S. P.↗

SiC As An Energetic Particle Detector

Several new technologies have been introduced recently in the region of semiconductor material for solid state detectors (SSD). Of particular interest is silicon carbide (SIC) since its band gap is larger than that of pure silicon, reducing its dark current and making SIC capable of operating at high temperatures and more tolerant of radiation damage. But the trade off is that a higher band gap also means fewer electron hole pairs generated, and thus a smaller signal, for detecting incident radiation. To determine what the lower limit of SiC detectors to energetic particles is, we irradiated a SiC diode with particles ranging in energy from 50 keV to 1.6 MeV and masses from 1 to 16 amu. We found that the SiC detectors sensitivity was comparable to that of pure silicon, with the SiC detector being able to measure particles down to 50 keV/amu and possibly lower.

Yan, F.↗

Development and Performance of a Suprathermal Electron Spectrometer to Study Auroral Precipitations

The design, development, and performance of Medium-energy Electron SPectrometer (MESP), dedicated to the in situ observation of suprathermal electrons in the auroral ionosphere, are summarized in this paper. MESP employs a permanent magnet filter with a light tight structure to select electrons with proper energies guided to the detectors. A combination of two avalanche photodiodes and a large area solid-state detector (SSD) provided 46 total energy bins (1 keV resolution for 3-20 keV range for APDs, and 7 keV resolution for greater than 20 keV range for SSDs). Multi-channel ultra-low power application-specific integrated circuits are also verified for the flight operation to read-out and analyze the detector signals. MESP was launched from Poker F1at Research Range on 3 March 2014 as a part of ground-to-rocket electrodynamics-electrons correlative experiment (GREECE) mission. MESP successfully measured the precipitating electrons from 3 to 120 keV in 120-ms time resolution and characterized the features of suprathermal distributions associated with auroral arcs throughout the flight. The measured electrons were showing the inverted-V type spectra, consistent with the past measurements. In addition, investigations of the suprathermal electron population indicated the existence of the energetic non-thermal distribution corresponding to the brightest aurora.

Ogasawara, Keiichi↗

Technology Needs for Gamma Ray Astronomy

Gamma ray astronomy is currently in an exciting period of multiple missions and a wealth of data. Results from INTEGRAL, Fermi, AGILE, Suzaku and Swift are making large contributions to our knowledge of high energy processes in the universe. The advances are due to new detector and imaging technologies. The steps to date have been from scintillators to solid state detectors for sensors and from light buckets to coded aperture masks and pair telescopes for imagers. A key direction for the future is toward focusing telescopes pushing into the hard X-ray regime and Compton telescopes and pair telescopes with fine spatial resolution for medium and high energy gamma rays. These technologies will provide finer imaging of gamma-ray sources. Importantly, they will also enable large steps forward in sensitivity by reducing background.

Gehrels, Neil↗

Technical issues in focal plane development for terrestrial resource observations

Performance goals for solid-state detector arrays operating in the pushbroom scan mode for the high-resolution, high-accuracy remote sensing of earth resources from space are discussed and some of the focal plane and system trades involved are identified. Issues in the development of solid-state pushbroom arrays with radiometric calibration to 0.5% precision detector-to-detector over a dynamic range of 1000:1 are considered, with calibration, temporal stability and spectral response conditions noted. Factors influencing the geometric precision of satellite-borne pushbroom scan mode sensors are then examined, including satellite orbit track and attitude errors, and geometric and radiometric correlation between information in the various spectral bands. Approaches to the alignment of linear arrays of thousands of detectors are then discussed that take into account tradeoffs between fabrication and test complexity and ground processing requirements. Continuing science experiments are indicated as necessary to establish tolerances on performance goals.

Thompson, L. L.↗

Astro-D Prelaunch Mission Operation Report (MOR)

The Prelaunch Mission Operation Report for the Astro-D mission is enclosed for your information. Astro-D is a Japanese-led program involving the United States as a participating partner. The Japanese Institute of Space and Astronautical Science (ISAS) provides overall program management, the launch vehicle, the spacecraft, and two Gas Scintillation Imaging System detectors. NASA is providing four nested, thin-foil, grazing-incidence telescope mirrors and two X-ray charged-coupled device solid-state detectors. NASA also provides telemetry tracking support using Deep Space Network ground stations. In return for its scientific instrument contribution, the U.S. will receive 15 percent of the observing time and will share an additional 25 percent for collaborative U.S./Japan scientific investigations. Launch is scheduled for mid- February 1993 from the ISAS launch center near Kagoshima in southern Japan. This MOR: (a) describes the NASA objectives for the Astro-D mission; (b) provides brief descriptions of the spacecraft and its scientific instruments; (c) provides a chronology of launch and deployment; and (d) describes the ground operation elements that support the mission. .

Source record↗

Signal Conditioning for Satellite Borne Energetic-Charged-Particle Experiments

Many of the spacecraft launched thus far have carried detectors for investigating cosmic rays, solar protons, solar plasmas, and the geomagnetically trapped radiation. These detectors, which will find continued application in the future, include ion chambers; proportional, Geiger-Muller, scintillation, Cerenkov, and solid state detectors; ion collectors; and nuclear emulsions. The instrumentation required to condition the signals from these detectors prior to telemetering is steadily growing more complex in order to permit more meaningful measurements. This report describes a number of instrumentation elements typical of the present state of the art, and a present-generation three-detector system which illustrates the integration of such basic elements into a complex system.

Ludwig, George H.↗

Radiation Design of Ion Mass Spectrometers

In the harsh radiation environment of Jupiter and with the JUpiter ICy moon Explorer (JUICE) mission including two Europa flybys where local intensities are approx. 150 krad/month behind 100 mils of Al shielding, so background from penetrating radiation can be a serious issue for detectors inside an Ion Mass Spectrometer (IMS). This can especially be important for minor ion detection designs. Detectors of choice for time-of-flight (TOF) designs are microchannel plates (MCP) and some designs may include solid state detectors (SSD). The standard approach is to use shielding designs so background event rates are low enough that the detector max rates and lifetimes are first not exceeded and then the more stringent requirement that the desired measurement can successfully be made (i.e., desired signal is sufficiently greater than background noise after background subtraction is made). GEANT codes are typically used along with various electronic techniques, but such designs need to know how the detectors will respond to the simulated primary and secondary radiations produced within the instrument. We will be presenting some preliminary measurements made on the response of MCPs to energetic electrons (20 ke V to 1400 ke V) using a Miniature TOF (MTOF) device and the High Energy Facility at Goddard Space Flight Center which has a Van de Graaff accelerator.

Sittler, Ed↗

Study of energetic solar particle events of 18 November 1968, 25 February 1969, and 30 March 1969

The solar particle events of 18 November 1968, 25 February 1969, and 30 March 1969 were studied using data from the detector system aboard the lunar orbiting satellite Explorer 35. Protons, alpha particles, and Z or = 3 nuclei were registered in the solid state detector of the system. Interplanetary propagation, particle anisotropy, and the intensity ratios of protons to alpha particles and of alpha particles to C, N, and O nuclei above a common specific energy of 0.5 MeV/nucleon were studied. Diffusion coefficients and decay constants for the three events are given, as well as magnitudes and directions of anisotropies.

Venkatarangan, P.↗