Engineering topics

Chupp, E. L.

Publications and source records attributed to Chupp, E. L..

At least 19 records

NASA NTRS1995

The LXeCAT instrument for gamma-ray astrophysics

The Liquid Xenon Coded Aperture Telescope (LXeCAT) and its capability to image astrophysical gamma-ray sources in the MeV region is described. The gamma-ray detector is a Liquid Xenon Time Projection Chamber (LXeTPC) triggered by the primary scintillation light. Effective background rejection is a direct consequence of the intrinsic three-dimensional imaging capability of the LXeTPC. Initial results with a 10 liter prototype confirm an energy resolution of 6% FWHM, a position resolution of 1 mm RMS and a light triggering efficiency higher than 90% for 1 MeV gamma-rays.

Aprile, E.↗

NASA NTRS1992

Gamma-ray and X-ray time profiles expected from a trap-plus-precipitation model for the 7 June 1980 and 27 April 1981 solar flares

Hard X-ray and prompt gamma-ray line emissions are the most direct signatures of, respectively, electron and ion acceleration during solar flares. The peak time of the gamma-ray emission for some events is delayed with respect to the peak time of the hard X-ray flux. These delays are either interpreted as evidence of a two-step acceleration process or as the result of the partial trapping and/or propagation of the particles from the acceleration region to the emission sites. It was shown earlier that hard X-ray and prompt gamma-ray line delays can be qualitatively reproduced in the frame of the latter hypothesis with models describing the time-dependent transport of energetic electrons and ions between these two sites. Here we focus on the close examination of the temporal evolution of X-ray and gamma-ray fluxes for the 7 June 1980 and 27 April 1981 events which exhibit delays between X-ray and gamma-ray maxima. The parameters of the ambient medium and of the accelerated particles are deduced for the two events and it is shown that the relative timing of X-ray and gamma-ray emissions is quantitatively reproduced in the present context.

Hulot, E.↗

NASA NTRS1992

Accelerator measurement of NaI response to medium energy neutrons and application to a satellite-borne spectrometer

We report on the response of a prototype detector to medium energy neutrons. The neutrons were produced by n-p scattering of a neutron beam on a hydrogen target. The measurements provide unique data on the efficiency and response of large NaI scintillators to neutrons in the energy range 36-709 MeV. We apply the results to the high-energy mode of the Gamma-Ray Spectrometer (GRS) on the Solar Maximum Mission satellite by estimating its efficiency for neutron detection. This estimate is compared to earlier Monte Carlo calculations of the GRS efficiency.

Dunphy, P. P.↗

NASA NTRS1992

Gamma-rays and neutrons as a probe of the proton spectrum during the solar flare of 1988 December 16

We have previously reported on high-energy gamma-rays and neutrons from the flare of 1988 December 16 detected by the Gamma-Ray Spectrometer on the SMM satellite. In this paper, we present results on gamma-ray lines seen by the same detector during this flare. Together, these measurements constitute a powerful probe of the proton spectrum that produces the flare neutrals. Analysis of the data suggests a Bessel-function proton spectrum with a shape parameter (alpha T) of 0.054 +/- 0.004 and the number of protons above 30 MeV equal to (9.0 +/- 0.9) x 10 exp 32. The number of neutrons detected from this flare is much smaller than what is predicted from an isotropic distribution of the protons, indicating that the distribution may be nonisotropic.

Dunphy, P. P.↗

NASA NTRS1990

Transient particle acceleration associated with solar flares

Mechanisms that apply to solar flares are discussed, and their applicability to other astrophysical sites, where transient X-ray and gamma-ray bursts occur, is tested. Two different approaches are used to determine the characteristics of the charged particles, accelerated in association with solar flares: (1) measurement of the energy spectra and composition of charged particles observed in space and believed to be associated with a specific solar flare; and (2) recording of electromagnetic emissions in the visible, ultraviolet, soft X-ray, hard X-ray, and gamma-ray spectral regions, and also high-energy neutrons produced in the solar atmosphere by the particles accelerated in association with the solar flare. It is suggested that, at the present level of knowledge, regions where particle acceleration and interactions occur are unlikely to be specified.

Chupp, E. L.↗

NASA NTRS1989

Report from solar physics

A discussion of the nature of solar physics is followed by a brief review of recent advances in the field. These advances include: the first direct experimental confirmation of the central role played by thermonuclear processes in stars; the discovery that the 5-minute oscillations of the Sun are a global seismic phenomenon that can be used as a probe of the structure and dynamical behavior of the solar interior; the discovery that the solar magnetic field is subdivided into individual flux tubes with field strength exceeding 1000 gauss. Also covered was a science strategy for pure solar physics. Brief discussions are given of solar-terrestrial physics, solar/stellar relationships, and suggested space missions.

Walker, A. B. C.↗

NASA NTRS1989

Search for Doppler-shifted gamma-ray emission from SS 433 using the SMM spectrometer

Data accumulated from 1980 to 1983 with the Gamma Ray Spectrometer aboard NASA's Solar Maximum Mission (SMM) satellite were searched for evidence of red and blue Doppler-shifted 1.37 MeV Mg-24 nuclear lines from SS 433. The SMM data base covers 270 days when SS 433 was in the field of view and includes periods of radio flaring and quiescence. No evidence was found for Doppler-shifted line emission in any of the spectra. The range of 3-sigma upper limits for individual 9 day integration periods was 0.0008-0.0023 photons/sq cm per sec for the blue beam, encompassing the reported about 1.5 MeV line, and 0.0008-0.002 photons/sq cm per sec for the red beam, encompassing the reported about 1.2 MeV line; the average 3-sigma upper limit in each beam for shifted about 1.37 MeV lines is 0.0015 photons/sq cm per sec for single 9 day integrations. The 3-sigma upper limit on 1.37 MeV gamma-ray emission over 23 9-day integration intervals for the red beam and 28 intervals for the blue beam is 0.0002 photons/sq cm per sec. These new limits from SMM can be reconciled with the HEAO 3 results only if SS 433 emits gamma radiation at or above the SMM sensitivity limit on rare occasions due to variable physical conditions in the system.

Geldzahler, B. J.↗

NASA NTRS1989

Studies on post-flare loop prominence of 1981 April 27

This paper examines the characteristics of the loop prominence of the April 27, 1981 solar flare event, which occurred on the limb (about 90 deg), using the results of H-alpha observations by the Astrophysical Observatory in Catania (Italy), the Purple Mountain Observatory in Nanking (China), together with hard-X-ray and gamma-ray burst data from the SMM Gamma-Ray Spectrometer. The analysis shows that there existed a second abrupt energy release for this event, almost 20 min after the end of the impulsive phase of the flare, which appears to be associated with the rapidity in upward motion or activation of the loop prominence. It is suggested that a possible mechanism for a second energy release may be the reconnection of new emerging magnetic field with the existing magnetic field lines.

Zhang, He-Qi↗

NASA NTRS1989

Satellite observation of atmospheric nuclear gamma radiation

Satellite observations of the spectrum of gamma radiation from the earth's atmosphere in the energy interval from 300 keV to 8.5 MeV were obtained with a gamma-ray spectrometer during 1980-1983. A total of 20 atmospheric line features are superimposed on a continuum background which is modeled using a power law with an index of -1.16. The line energies and intensities are consistent with production by secondary neutrons interacting with atmospheric N-14 and O-16. The intensity and spectrum of photons at energies below the 511-keV line, in excess of a power law continuum, are explained by Compton scattering of the annihilation line photons in traversing an average of 21 g/sq cm of atmosphere.

Letaw, John R.↗

NASA NTRS1989

Comparison of backgrounds in OSO-7 and SMM spectrometers and short-term activation in SMM

The backgrounds in the OSO-7 Gamma-Ray Monitor and the Solar Maximum Mission Gamma-Ray Spectrometer are compared. After scaling to the same volume, the background spectra agree to within 30 percent. This shows that analyses which successfully describe the background in one detector can be applied to similar detectors of different sizes and on different platforms. The background produced in the SMM spectrometer by a single trapped-radiation belt passage is also studied. This background is found to be dominated by a positron-annihilation line and a continuum spectrum with a high energy cutoff at 5 MeV.

Dunphy, P. P.↗

NASA NTRS1989

Instrumental and atmospheric background lines observed by the SMM gamma-ray spectrometer

Preliminary identifications of instrumental and atmospheric background lines detected by the gamma-ray spectrometer on NASA's Solar Maximum Mission satellite (SMM) are presented. The long-term and stable operation of this experiment has provided data of high quality for use in this analysis. Methods are described for identifying radioactive isotopes which use their different decay times. Temporal evolution of the features are revealed by spectral comparisons, subtractions, and fits. An understanding of these temporal variations has enabled the data to be used for detecting celestial gamma-ray sources.

Share, G. H.↗

NASA NTRS1988

A cosmic and solar X-ray and gamma-ray instrument for a scout launch

An overview is presented for a set of simple and robust X-ray and gamma ray instruments which have both cosmic and solar objectives. The primary solar scientific objective is the study of the beaming of energetic electrons and ions in solar flares. The instrument will measure spectra and polarization of flare emissions up to 10 MeV. At X-ray energies both the directly emitted flux and the reflected albedo flux will be measured with a complement of six X-ray sensors. Each of these detectors will have a different high Z filter selected to optimize both the energy resolution and high rate capabilities in the energy band 10 to 300 keV. At energies greater than 100 keV seven 7.6 x 7.6 cm NaI and a set of 30 concentric plastic scattering detectors will record the spectra and polarization of electron bremsstrahlung and nuclear gamma rays. All of the components of the instrument are in existence and have passed flight tests for earlier space missions. The instrument will use a spinning solar oriented Scout spacecraft. The NaI detectors will act as a self-modulating gamma ray detector for cosmic sources in a broad angular band which lies at 90 degrees to the Sun-Earth vector and hence will scan the entire sky in 6 months.

Forrest, D. J.↗

NASA NTRS1988

A summary of major activities of the UNH and NRL groups

The major activities of the SMM GRS team members at the University of New Hampshire and the Naval Research Laboratory since the last semi-annual report are summarized. An updated list of published papers and invited papers or contributed papers presented at scientific meetings is provided.

Chupp, E. L.↗

NASA NTRS1988

The gamma-ray spectrometer experiment on the solar maximum mission satellite

The major activities (through 15 November l987) of the Solar Maximum Mission Gamma-Ray Spectrometer (SMM GRS) team members at the University of New Hampshire and the Naval Research Laboratory and the work of the Guest Investigators since the last Semi-Annual Report are summarized. In addition, an updated list of published papers and invited papers or papers presented at scientific meetings is provided.

Chupp, E. L.↗

NASA NTRS1988

Gamma-ray line emission from SN1987A

The inferred average line flux at about 847 keV in the background-subtracted spectrum of SN1987A from August 1 to October 31, 1987 is about (1.0 + or - 0.25) x 10 to the -3rd photons/sq cm/s at an energy of 843 + or - 5 keV. This feature cannot be explained by any statistical or systematic fluctuations observed in the seven previous years of gamma-ray spectrometer data. There is also evidence for the 1238-keV line from Co-56 decay, with an average flux of about (6 + or - 2) x 10 to the -4th photons/sq cm/s. This observation confirms that Co-56 is present in the supernova ejecta and that nucleosynthesis occurred during the explosion.

Matz, S. M.↗

NASA NTRS1988

Solar neutron observations and their relation to solar flare acceleration problems

The current observational knowledge on the production of neutrons in association with solar flares is reviewed. From a study of the observations, it is shown that unique information can be obtained on the spectral properties of accelerated ions produced during the flare. Also, the abundance of He-3/H in the photosphere can be directly determined. The current interpretations of all available neutron observations and in particular highlight the uncertainties are also reviewed.

Chupp, E. L.↗

NASA NTRS1987

The directivity of high-energy emission from solar flares - Solar Maximum Mission observations

The data base consisting of flares detected by the gamma-ray spectrometer (GRS) on board the Solar Maximum Mission (SMM) satellite is used to study the directivity of high-energy radiation. A number of observations are presented that, strongly indicate that the high-energy emission from flares is anisotropic. They are the following: (1) the fraction of events detected at energies above 300 keV near the limb is higher than is expected for isotropically emitting flares; (2) there is a statistically significant center-to-limb variation in the 300 keV to 1 MeV spectra of flares detected by the SMM GRS; (3) the 25-200 keV hard X-ray spectra measured during the impulsive phase by the SMM GRS show a center-to-limb variation; and (4) nearly all of the events detected at above 10 MeV are located near the limb.

Vestrand, W. Thomas↗

NASA NTRS1987

Gamma-ray observations of the Crab Region using a coded-aperture telescope

The region of the Galactic anticenter, including the Crab Nebula, was observed during a balloon flight of the University of New Hampshire Directional Gamma-Ray Telescope employing the coded-aperture imaging technique to image celestial gamma-radiation between 160 keV and 9.3 MeV. The background systematics are treated with a simple and relatively straightforward correction procedure. The results demonstrate that the coded-aperture procedure is a viable approach for imaging not only point sources of radiation, but also extended sources of emission. The results for the Crab's photon spectrum are consistent with a power-law spectrum. Upper limits on the flux levels of line emission at 405 keV and 1050 keV and on the flux from the X-ray binary source A0535 + 26 and diffuse Galactic emission from the anticenter region are derived.

Mcconnell, M. L.↗