The 0.5 MeV gamma ray flux and the energy loss spectrum in CsI(Tl) at 4 g/cm2

Balloon-borne experiments with directional scintillators that measured the spectrum of gamma radiation with energies between 30 and 570 key in the atmosphere up to 130,000 feet were conducted during 1967 and 1968. These data are of interest in connection with understanding the origin of atmospheric photons and with estimating planetary and stellar gamma albedos, as well as effecting improvements in gamma-ray astronomy. The measurements, conducted in the United States and in Australia, showed that a continuum and structure are present at depths X greater than 90 g cm-•; the intensity of the continuum depends exponentially on depth for X _• 102 gcm -•, but the shape is relatively depth-independent. The spectrum softens considerably at lesser depths. Structure is observed in the spectrum at 130,000 feet, superimposed on a continuum approximated by the power law 27.8E -•'s7 photons cm-' sec -x ster -• kev-L The latitude, altitude, and energy variations of the spectrum are discussed in terms of the various factors responsible at various depths for the spectrum; it is shown that several factors are responsible for the continuum and that the observed structure is mainly due to (n, y) effects from cosmic-ray neutrons, and an upper limit is established for a line flux at 511 key. The 95% confidence level upper limit of 02 photon cm -• sec -x for line radiation at the positron annihilation energy is slightly below the fluxes previously reported by others. ß ß ß ß ß ß ß ß ß ß ß ß IIi ß Ii ß ß ß ß ß ß ß %, * _ oo ©e• ee ß e.e ß ß ß edge qb _

“…The presence of a 511-key line has been reported by Peterson [1963] and by Chupp et al [1967]. It is possible that they observed a feature similar to the one we have detected.…”

Section: F(p E) = A(e) + B(e) Exp --P/d(e) At 710 Mb •_ P _•supporting

confidence: 88%

“…Inspection of the data presented by Chupp et al [1967] indicated a feature at least 30 key above 51l key.…”

Section: F(p E) = A(e) + B(e) Exp --P/d(e) At 710 Mb •_ P _•mentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Low-energy gamma radiation in the atmosphere at midlatitudes

Haymes¹,

Glenn²,

Fishman³

et al. 1969

“…The presence of this line in atmospheric gamma radiation and the explanation of its origin as annihilation of positive electrons have been known for many years [Peterson, 1963;Rocchia et al, 1966;Chupp et al, 1967]. In diffuse extraterrestrial or point source gamma radiation this line has been predicted, but to date, experimental data, including upper limits, are very limited: Metzget et al [1964], Ling et al [1977], and Trombka et al [1973] for diffuse background; and Hayroes et al [1975c, Johnson andHayroes [1973], Leventhal et al [ 1978], and Albernhe et al [ 1978] for the region of the galactic center.…”

Section: Introductionmentioning

confidence: 99%

The positron annihilation line at 511 keV in the upper atmosphere

Albernhe¹,

Védrenne²,

Martin³

1979

We present the results of a series of balloon flights made at two latitudes over Aire sur l'Adour, France (4.5 GV), and Sao José dos Campos, Brazil (12.5 GV). We used two types of omnidirectionnal detectors: a 4.5 × 5.1 cm NaI crystal and a 23 cm³ Ge‐Li high‐energy resolution detector. The two were surrounded by a 0.8‐cm thick plastic anticoincidence. These measurements allowed us to determine precisely the characteristics of the 0.511‐MeV line versus altitude and latitude. We have also determined from the analysis of the growth curves at the two latitudes an extraterrestrial component value of (4.3±1.5) × 10−2 photons/cm² s and an upper limit of 4 × 10−3 photons/cm² s for the flux from the galactic center region.

“…Although several measurements of atmospheric gamma rays have been performed in the past [Vette. 1962;Chupp et al, 1967;Fichtel et al, 1969;Peterson et al, 1973;Klumpar et al, 1973;Thompson, 1974;Kinzer et al, 1974;Kraushaar et al, 1972;Matteson et aI., 1974;Ling, 1975], our knowledge in this area is still quite limited. The separation of atmospheric gamma rays from the diffuse cosmic compopent has been complicated by the similarities in intensity and spectral shape of the two components.…”

Section: Introductionmentioning

confidence: 99%

High-Resolution Measurements of Atmospheric Gamma Rays from a Satellite

Imhof¹,

Nakano²,

Reagan³

1976

Data are presented on the gamma rays emitted from the atmosphere to satellite altitudes in the absence of bremsstrahlung X rays associated with electron precipitation from the radiation belts. The measurements (40 keV to 2.7 MeV) were performed with a high‐resolution germanium spectrometer on board the polar‐orbiting satellite 1972‐076B. With the collimated spectrometer on the spinning vehicle (5‐s period) it was possible to separate sensor and vehicle backgrounds from the atmospheric and diffuse cosmic contributions. The atmospheric component was obtained by unfolding published values for the diffuse cosmic spectrum. Owing to variances in the measured values of the diffuse cosmic spectrum the uncertainties in the atmospheric gamma ray spectrum are greater near the equator and at lower energies than over the polar caps and/or at higher energies, where the atmospheric gamma rays dominate, and the errors in the atmospheric spectrum associated with the diffuse component are small. The variations of the atmospheric gamma rays with invariant latitude are presented. Over the polar caps the energy spectra are similar to those observed near the magnetic equator, and the intensities are higher by about a factor of 4. The spectral indices for least squares power law fits to the continuum are −1.34 ± 0.03 and −1.39 ± 0.08 for the polar cap and equatorial regions, respectively. A search was made for gamma ray lines emitted from the atmosphere in addition to the 511‐keV annihilation line. Several peaks were observed in the background spectrum, but no other lines were seen to be emitted from the atmosphere with a significant intensity.