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Bertsch, D. L.

Publications and source records attributed to Bertsch, D. L..

At least 73 records · Page 4
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NASA NTRS1992

Performance of the EGRET astronomical gamma ray telescope

On April 5, 1991, the Space Shuttle Atlantis carried the Compton Gamma Ray Observatory (CGRO) into orbit, deploying the satellite on April 7. The EGRET instrument was activated on April 15, and the first month of operations was devoted to verification of the instrument performance. Measurements made during that month and in the subsequent sky survey phase have verified that the instrument time resolution, angular resolution, and gamma ray detection efficiency are all within nominal limits.

Nolan, P. L.↗
NASA NTRS1992

Pulsed high-energy gamma-radiation from Geminga (1E0630 + 178)

The detection of pulsed gamma rays with energy above 50 MeV from the soft X-ray source 1E0630 + 178 is reported, confirming the identification of Geminga with this X-ray source. The period derivative (11.4 +/- 1.7) x 10 exp -15 s/s suggests that Geminga is a nearby isolated rotating neutron star with a magnetic field of 1.6 x 10 exp 12 gauss, a characteristic age of 300,000 yr, and a spin-down energy loss rate of 3.5 x 10 exp 34 erg/s.

Bertsch, D. L.↗
NASA NTRS1992

The EGRET high energy gamma ray telescope

The Energetic Gamma Ray Experiment Telescope (EGRET) on the Compton Gamma Ray Observatory (GRO) is sensitive in the energy range from about 20 MeV to about 30,000 MeV. Electron-positron pair production by incident gamma photons is utilized as the detection mechanism. The pair production occurs in tantalum foils interleaved with the layers of a digital spark chamber system; the spark chamber records the tracks of the electron and positron, allowing the reconstruction of the arrival direction of the gamma ray. If there is no signal from the charged particle anticoincidence detector which surrounds the upper part of the detector, the spark chamber array is triggered by two hodoscopes of plastic scintillators. A time of flight requirement is included to reject events moving backward through the telescope. The energy of the gamma ray is primarily determined by absorption of the energies of the electron and positron in a 20 cm deep NaI(Tl) scintillator.

Hartman, R. C.↗
NASA NTRS1992

The EGRET data products

We describe the Energetic Gamma Ray Experiment Telescope (EGRET) data products which we anticipate will suffice for virtually all guest and archival investigations. The production process, content, availability, format, and the associated software of each product is described. Supplied here is sufficient detail for each researcher to do analysis which is not supported by extant software.

Mattox, J. R.↗
NASA NTRS1992

EGRET detection of high energy gamma rays from the gamma-ray burst of 3 May 1991

On May 3, 1991, the Energetic Gamma Ray Experiment Telescope on the Compton Gamma Ray Observatory detected a gamma-ray burst both in the energy measurement subsystem and independently in the spark chamber assembly. Six individual photons were detected in the spark chamber, allowing a determination of the burst arrival direction which was l(II) = 171.9 deg +/- 1.3 deg, b(II) = 5.3 deg +/- 1.1 deg. Three energy spectra were measured from 1 to 200 MeV; they were measured during the first second after the Burst and Transient Sources Experiment trigger, the next two seconds, and the subsequent four seconds. The first two spectra exhibit a similar differential spectra index of about -2.2 with no apparent high-energy cut-off. By the time of the third spectrum, an additional soft component is evident.

Schneid, E. J.↗
NASA NTRS1992

Detection of high-energy gamma radiation from quasar 3C 279 by the EGRET telescope on the Compton Gamma Ray Observatory

Intense gamma radiation has been observed from the direction of the quasar 3C 279 throughout the energy range from 30 MeV to over 5 GeV by the Energetic Gamma Ray Experiment Telescope (EGRET) during the period June 15-28, 1991. Its spectrum is well represented by a photon differential power-law exponent of 2.0 +/- 0.1, with a photon intensity above 100 MeV of (2.8 +/- 0.4) x 10 exp -6/sq cm s. For E is greater than 100 MeV, the 2-sigma upper limits were 1.0 x 10 exp -6/sq cm s in 1973 from the SAS 2 observations and 0.3 x 10 exp -6/sq cm s for the combined 1976, 1978, and 1980 COS B observations. Hence, there has been a large increase in high-energy gamma-ray intensity relative to the earlier times, as there has been in the radio, infrared, optical, and X-ray ranges. This source is the most distant and by far the most luminous gamma-ray source yet detected.

Hartman, R. C.↗
NASA NTRS1992

Observation of gamma ray bursts and flares by the EGRET telescope on the Compton Gamma Ray Observatory

The Energetic Gamma Ray Experiment Telescope (EGRET) on the Compton Gamma Ray Observatory has observed energetic gamma ray bursts and flares. On May 3, 1991, EGRET detected a gamma ray burst both in the energy measuring NaI (Tl) scintillator and independently in the spark chamber imaging assembly. The NaI spectra were accumulated by a special BURST mode of EGRET. The spectra were measured over a range from 1 to 200 MeV, in three sequential spectra of 1,2, and 4 seconds. During the peak of the burst, six individual gamma rays were detected in the spark chamber, allowing a determination of the burst arrival direction. The intense flares of June were also detected. A solar flare on June 4 was observed to last for several minutes and for a brief time, less than a minute, had significant emission of gamma rays exceeding 150 MeV.

Schneid, E. J.↗
NASA NTRS1991

The estimation of background production by cosmic rays in high-energy gamma ray telescopes

A calculational method of estimating instrumental background in high-energy gamma-ray telescopes, using the hadronic Monte Carlo code FLUKA87, is presented. The method is applied to the SAS-2 and EGRET telescope designs and is also used to explore the level of background to be expected for alternative configurations of the proposed GRITS telescope, which adapts the external fuel tank of a Space Shuttle as a gamma-ray telescope with a very large collecting area. The background produced in proton-beam tests of EGRET is much less than the predicted level. This discrepancy appears to be due to the FLUKA87 inability to transport evaporation nucleons. It is predicted that the background in EGRET will be no more than 4-10 percent of the extragalactic diffuse gamma radiation.

Edwards, H. L.↗
NASA NTRS1988

The project EGRET (Energetic Gamma-Ray Experiment Telescope) on NASA's Gamma-Ray Observatory (GRO)

The design, predicted performance, and scientific objectives of the 20-30,000-MeV gamma-ray telescope EGRET for the NASA GRO spacecraft (scheduled for Space Shuttle launch to a 450-km 28.5-deg orbit in 1990) are reviewed. The other GRO instruments are briefly characterized, including the burst and transient-source experiment, the oriented scintillation spectrometer, and the imaging Compton telescope. EGRET comprises an anticoincidence system, a spark chamber, a triggering telescope, an NaI total-absorption spectrometer, a gas supply capable of refilling the chamber four times, and support electronics. EGRET will operate with energy resolution about 15 percent, effective area about 2000 sq cm, sensitivity about 5 x 10 to the -8th/sq cm sec, angular resolution 0.1-0.4 deg, and FOV about 40 deg FWHM. Observations of Galactic point sources, Galactic and extragalactic diffuse emission, gamma-ray bursts, and solar flares are planned.

Kanbach, G.↗
NASA NTRS1987

Calibration of the EGRET high-energy gamma-ray telescope in the range 20-10,000 MeV with a tunable beam of quasi-monoenergetic gamma rays at SLAC

The EGRET telescope, one of the instruments to be carried on NASA's Gamma Ray Observatory, is designed to explore the high-energy portion (20-24,000 MeV) of the electromagnetic spectrum. A calibration source of gamma-rays over this wide energy range has been used together with an appropriate set of intensity-monitoring instruments, to conduct a calibration of the EGRET telescope over this energy range for the full telescope aperture. The calibration method and an overview of the results are described.

Thompson, D. J.↗
NASA NTRS1985

High energy gamma ray balloon instrument

The High Energy Gamma Ray Balloon Instrument was built in part to verify certain subsystems' performance for the Energetic Gamma Ray Experiment Telescope (EGRET) instrument, the high energy telescope to be carried on the Gamma Ray Observatory. This paper describes the instrument, the performance of some subsystems, and some relevant results.

Thompson, D. J.↗
NASA NTRS1984

The Gamma-Ray Observatory mission objectives and its significance for gamma-ray astronomy

The Gamma Ray Observatory (GRO) is an approved NASA mission, programmed for launch in 1988. Its complement of four detectors has established goals: (1) to study the nature of compact gamma-ray sources such as neutron stars and black holes, or objects whose nature is yet to be understood; (2) to search for evidence of nucleosynthesis especially in the regions of supernovae; (3) to study structural features and dynamical properties of the Galaxy; (4) to explore other galaxies, especially the extraordinary types such as radio, Seyferts, and quasars; and (5) to study cosmological effects by examining the diffuse radiation in detail. This paper discusses the design, objectives, and expected scientific results of each of the GRO instruments in view of the GRO mission goals.

Bertsch, D. L.↗
NASA NTRS1983

Searches for gamma ray emission from radio pulsars

Searches were made for pulsed high energy (E greater than 35 MeV) gamma radiation from 43 pulsars using the SAS-2 data base and radio parameters. No positive results were found, and the upper limits are consistent with the concept that gamma ray production efficiency increases with increasing apparent age. Two limits suggest that efficiency cannot be a simple function of apparent age beyond 1,000,000 years. Previously announced in STAR as N83-24463

Thompson, D. J.↗
NASA NTRS1983

Measurements of galactic plane gamma-ray emission in the energy range 10-80 MeV

A spark chamber gamma ray telescope was developed and flown to observe diffuse gamma ray emission from the central region of the galaxy. The extension of observations down to 10 MeV provides important new data indicating that the galactic diffuse gamma ray spectrum continues as a power law down to about 10 MeV, an observation in good agreement with recent theoretical predictions. Data from other experiments in the range from 100 keV to 10 MeV show a significant departure from the extension of the power-law fit to the medium energy observations reported here, possibly indicating that a different mechanism may be responsible for the emissions below and above a few MeV. The intensity of the spectrum above 10 MeV implies a galactic electron spectrum which is also very intense down to about 10 MeV. Electrons in this energy range cannot be observed in the solar cavity because of solar modulation effects. The galactic gamma ray data are compared with recent theoretical predictions. Previously announced in STAR as N83-17444

Bertsch, D. L.↗
NASA NTRS1983

Searches for gamma ray emission from radio pulsars

Searches were made for pulsed high energy (E 35 MeV) gamma radiation from 43 pulsars using the SAS-2 data base and radio parameters. No positive results were found, and the upper limits are consistent with the concept that gamma ray production efficiency increases with increasing apparent age. Two limits suggest that efficiency cannot be a simple function of apparent age beyond 10,000,000 years.

Thompson, D. J.↗
NASA NTRS1983

EGRET - The high energy gamma ray telescope for NASA's Gamma Ray Observatory

The EGRET high energy gamma-ray telescope under development for NASA's Gamma Ray Observatory will have an energy range of approximately 12 to 30,000 MeV, energy resolution of about 15 percent FWHM over most of that range, an effective area of about 2000 sq cm at high energies, and single photon angular accuracy of approximately 2 deg at 100 MeV, less than 0.1 deg above 5 GeV. This instrument can locate strong sources to an accuracy of about 5 arc min. The instrument utilizes a set of digital spark chambers interleaved with tantalum foils for detection and identification of gamma-ray events, and a large NaI(Tl) scintillator for energy determination. The system is triggered by a coincidence matrix using two arrays of plastic scintillation counters and a large plastic scintillator anticoincidence dome that rejects incident charged particles.

Fichtel, C. E.↗
NASA NTRS1982

Measurements of galactic plane gamma ray emission in the energy range from 10 - 80 MeV

A spark chamber gamma ray telescope was developed and flown to observe diffuse gamma ray emission from the central region of the galaxy. The extension of observations down to 10 MeV provides important new data indicating that the galactic diffuse gamma ray spectrum continues as a power law down to about 10 MeV, an observation in good agreement with recent theoretical predictions. Data from other experiments in the range from 100 keV to 10 MeV show a significant departure from the extension of the power-law fit to the medium energy observations reported here, possibly indicating that a different mechanism may be responsible for the emissions below and above a few MeV. The intensity of the spectrum above 10 MeV implies a galactic electron spectrum which is also very intense down to about 10 MeV. Electrons in this energy range cannot be observed in the solar cavity because of solar modulation effects. The galactic gamma ray data are compared with recent theoretical predictions.

Bertsch, D. L.↗
NASA NTRS1981

Calibration of a gamma-ray telescope using tagged position annihilation photons

Measurements of detection efficiency, angular resolution, and energy resolution properties of a gamma ray telescope used to study celestial gamma rays from balloon flight altitudes are described. Nearly monochromatic photons produced at the National Bureau of Standards tagged photon facility were used for the calibration. Details of the photon beam configuration and properties and results of the measurements made at photon energies of 15.1 and 31.1 MeV are presented. Finally, the data are compared with a Monte Carlo analysis of the instrument properties.

Bertsch, D. L.↗