Low Energy Gamma Radiation Research Articles

Detection of nuclear gamma rays from Centaurus A

view Abstract Citations (75) References (9) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Detection of nuclear gamma rays from Centaurus A. Hall, R. D. ; Meegan, C. A. ; Walraven, G. D. ; Djuth, F. T. ; Haymes, R. C. Abstract Results are reported for an observation of nuclear gamma rays in the energy range between 0.033 and 12.25 MeV from Centaurus A using a balloon-borne actively collimated NaI(Tl) crystal scintillation counter. The observing procedure is outlined, no systematic errors are found in the data, and power-law fits to the source's energy spectrum are attempted. A power law of approximately 0.86E to the -1.9 power photon/sq cm/sec per keV is shown to give an acceptable fit to the continuum, and the detection of two gamma-ray lines at 1.6 and 4.5 MeV, respectively, is discussed. It is found that the low-energy gamma-ray luminosity of Cen A is 9.4 by 10 to the 43rd power erg/sec for a distance of 5 Mpc and that Cen A is apparently variable in low-energy gamma radiation. It is suggested that the broad feature detected at 1.6 MeV may be due to three blended lines (possibly excited Ne-20, Mg-24, and Si-28), the 4.5-MeV line is most likely due to deexcitation of excited C-12, and the nuclear excitation results from either cosmic-ray bombardment of Cen A's interstellar medium or nucleosynthesis within the source. Publication: The Astrophysical Journal Pub Date: December 1976 DOI: 10.1086/154869 Bibcode: 1976ApJ...210..631H Keywords: Elliptical Galaxies; Galactic Radiation; Gamma Rays; Radio Galaxies; X Ray Sources; X Ray Spectra; Balloon-Borne Instruments; Continuous Spectra; Energy Spectra; Line Spectra; Radiant Flux Density; Scintillation Counters; Space Radiation full text sources ADS | data products SIMBAD (1) NED (1)

Determination of sulphur content in drill core samples by backscattered beta-particles and gamma-ray absorption

A relatively simple method of sulphur determination in drill cores of calcium carbonate matrix is described. The method is based on the combination of measurements of backscattered beta-particles and transmitted low energy gamma-radiation intensities. The transmitted gamma-radiation measurement corrects the errors of sulphur determination caused by the varying strontium sulphate and silicon dioxide content. The method has been tested on 170 samples. It was estimated that the standard deviation of sulphur determination does not exceed 2.5% of sulphur. The apparatus for routine absorption measurement is also described.

Measurements of low-energy gamma radiation from the Crab Nebula and from pulsar NP 0532

view Abstract Citations (40) References (16) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Measurements of low-energy gamma radiation from the Crab nebula and from pulsar NP 0532. Walraven, G. D. ; Hall, R. D. ; Meegan, C. A. ; Coleman, P. L. ; Shelton, D. H. ; Haymes, R. C. Abstract A balloon-altitude measurement of the energy spectra from the Crab Nebula and pulsar NP 0532 was conducted on 1973 May 15. The measurements were conducted in the O. .l 10MeV energy interval with an actively collimated scintillation counter that has a 182 cm2 sensitive area and a 130 beam. A power law with a photon-number spectral index of 2.13 + 0.04 fits the nebular spectrum and a prolongation of the X-ray spectrum observed by others. The pulsar spectrum is also well approximated by a power law, with a number spectral index of 2.2 + 0.2. No statistically significant evidence for departures from these power laws was detected. Subject headtng : Crab Nebula - gamma rays - pulsars - X-ray sources Publication: The Astrophysical Journal Pub Date: December 1975 DOI: 10.1086/153999 Bibcode: 1975ApJ...202..502W Keywords: Crab Nebula; Gamma Rays; Pulsars; Radiation Sources; X Ray Astronomy; Balloon Sounding; Energy Spectra; Nuclear Fusion; Power Series; Scintillation Counters; Stellar Atmospheres; Space Radiation full text sources ADS | data products SIMBAD (2)

Invariant imbedding and radiation dosimetry: IV. finite order scattering of gamma radiation by a target slab

Computation of the transmission and reflection functions of the radiation impinging on a slab with scattering properties which are unisotropic and incoherent are relevant to the problems in radiation dosimetry, where we meet with the passage of low energy gamma radiation through human tissue. Employing the concept of finite order transmission and reflection functions of earlier papers in this series, we obtain recurrence relations for these functions which introduce enormous simplicity in the numerical calculations.

The Spectrum of Low-Energy Gamma Radiation from the Galactic-Center Region.

The Spectrum of Low-Energy Gamma Radiation from the Galactic-Center Region.

Conversion Coefficients of Low-Energy Gamma Radiation Following the Decay ofSe81andSe81m

A Ge(Li) $\ensuremath{\gamma}$-ray spectrometer and a Si(Li) electron spectrometer were standardized for measurements of internal---conversion coefficients using $\ensuremath{\gamma}$ transitions of well-known ${\ensuremath{\alpha}}_{K}$ and ${\ensuremath{\alpha}}_{L}$ values from standard sources. The internal---conversion coefficients of four $\ensuremath{\gamma}$ transitions in $^{81}\mathrm{Br}$ and one in $^{81}\mathrm{Se}$ have been measured. The results for the conversion coefficients are as follows: $^{81}\mathrm{Se}$, 103 keV: ${\ensuremath{\alpha}}_{K}=7.1\ifmmode\pm\else\textpm\fi{}0.3$, ${\ensuremath{\alpha}}_{L}=1.6\ifmmode\pm\else\textpm\fi{}0.3$; $^{81}\mathrm{Br}$, 178 keV: ${\ensuremath{\alpha}}_{K}<0.05$, ${\ensuremath{\alpha}}_{L}<0.003$; 260 keV: ${\ensuremath{\alpha}}_{K}=0.038\ifmmode\pm\else\textpm\fi{}0.001$, ${\ensuremath{\alpha}}_{L}=0.005\ifmmode\pm\else\textpm\fi{}0.002$; 276 keV: ${\ensuremath{\alpha}}_{K}=0.009\ifmmode\pm\else\textpm\fi{}0.001$, ${\ensuremath{\alpha}}_{L}=0.002\ifmmode\pm\else\textpm\fi{}0.001$; 290 keV: ${\ensuremath{\alpha}}_{K}=0.012\ifmmode\pm\else\textpm\fi{}0.001$, ${\ensuremath{\alpha}}_{L}=0.002\ifmmode\pm\else\textpm\fi{}0.001$. The multipolarities are deduced to a fair degree of certainty.

Observation of Low-Energy Gamma Radiation from NP 0532

Observation of Low-Energy Gamma Radiation from NP 0532

Measurement of skin dose from low energy beta and gamma radiation using thermoluminescent discs

A thermoluminescent dosemeter is described, designed to measure the dose to the basal layer in mixed beta - and gamma -radiation fields. Very thin Teflon discs, 8.9 mg cm-2 thick and 1.27 cm diameter, loaded with LiF, provide a convenient measure of the beta -ray dose. When covered by a polyethylene window of 3.7 mg cm-2 their response is equivalent to the dose under 7 mg em-2 of tissue to within 10% for beta -rays with maximum energies of 0.15 to 2.27 MeV. The response to X- and gamma -rays above 80 keV is independent of energy and similar to the beta -ray response, but below 80 keV the sensitivity relative to beta -rays increases to a maximum of 1.5 around 30 keV. The dosemeter can be used in mixed beta - gamma radiation fields and is particularly suited to the measurement of extremity doses.

Low energy gamma radiation in the atmosphere during active and quiet periods on the Sun

Gamma ray pulse height spectra during active and quiet solar periods from midlatitude balloon flights

Low-Energy Gamma Radiation from Cygnus

Low-Energy Gamma Radiation from Cygnus

Reply [to “Discussion of paper by R. C. Haymes, S. W. Glenn, G. J. Fishman, and F. R. Harnden, Jr., ‘Low-energy gamma radiation in the atmosphere at midlatitudes’”

Reply [to “Discussion of paper by R. C. Haymes, S. W. Glenn, G. J. Fishman, and F. R. Harnden, Jr., ‘Low-energy gamma radiation in the atmosphere at midlatitudes’”

Discussion of paper by R. C. Haymes, S. W. Glenn, G. J. Fishman, and F. R. Harnden, Jr., ‘Low-energy gamma radiation in the atmosphere at midlatitudes’

Discussion of paper by R. C. Haymes, S. W. Glenn, G. J. Fishman, and F. R. Harnden, Jr., ‘Low-energy gamma radiation in the atmosphere at midlatitudes’

Low-energy gamma radiation in the atmosphere at midlatitudes

Balloon-borne experiments with directional scintillators that measured the spectrum of gamma radiation with energies between 30 and 570 kev 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−2; the intensity of the continuum depends exponentially on depth for X ≥ 102 g cm−2, 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−1.87 photons cm−2 sec−1 ster−1 kev−1. 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, γ) effects from cosmic-ray neutrons, and an upper limit is established for a line flux at 511 kev. The 95% confidence level upper limit of 0.2 photon cm−2 sec−1 for line radiation at the positron annihilation energy is slightly below the fluxes previously reported by others.

A Comparison of Lithium Fluoride and Film for Personnel Dosimetry

LiF thermoluminescent dosimeters are more accurate than film badges for personnel monitoring in locations where the quality of X-ray or gamma radiation ranges from soft to hard (e.g. plutonium refining areas). Therefore, thermoluminescent dosimeters were added to the film badges of sixty-six employees assigned to a plutonium finishing area at the Savannah River Plant to assist in the interpretation of low-energy gamma radiation exposure. During the first 6 months of 1966, the skin exposure measured by thermoluminescent dosimeters averaged one-half of that measured by the film badges. A second LiF dosimeter with copper and polyethylene filters added to the film badges of the same personnel showed that the low-energy photons also caused a similar error in the measurement of penetrating radiation exposure by the film badge. Observed differences between the LiF and film dosimetry results were reproduced under controlled conditions by giving film badges and thermoluminescent dosimeters known exposures of X-ray and gamma radiation. LiF results were within 20% of the measured exposures; however, at 48 keV the film interpretation of skin dose was high by a factor of 2.0, and at 105 keV the film interpretation was high by a factor of 2.7 for the skin dose and 2.0 for the penetrating dose.

A simplified method for bone mineral measurements in vivo

A method for measurement of the bone mineral content in vivo has been developed by J.R. Cameron and J.A. Sorenson Science 142, 230 (1963). The object of measurement, for example the radius in the forearm, is placed in a water container of even thickness. The transmission rate of low energy gamma-radiation is measured at even-spaced intervals across the bone. This method requires automatic data collection and computer calculations. A simplified method is described in this paper. The transmission rate is measured continuously across the bone, and observed with a ratemeter; the results are registered with a strip-chart recorder. The scale of the chart is based upon the natural logarithm of the ratio of the transmission rate in water to the rate when the radiation in addition crosses the bone. The content of bone mineral can be calculated within a few minutes by taking out from the curve values which correspond to 1 mm intervals across the bone. The results are reproducible to within 4%.

Back scattering of low-energy gamma radiation

Experimental data regarding the spectral and angular distribution of y quanta back-scattered from various scattering substances are presented for the geometry of an isotropic point source; the scattering substances include paraffin, graphite, aluminum, iron, xinc, cadmium, and lead (semiinfinite media). The energy of the primary ~/radiation was 0.145; 0.190; 0.279; 0.320; 0.396; 0.661 and 0. 765 MeV. The numerical and energetic albedos (A and AE) determined experimentally agree closely with the values calculated by the Monte-Carlo method. The results are presented in the form of tables and graphical relationships for A, AE, and A/AE as functions of Z and Eγ.

The multiple compton scattering of low energy gamma radiation

Abstract The emergent angular and spectral distributions of low energy gamma radiation after multiple Compton scattering by a homogeneous plane slab are determined by a method which is based on the theory of Markov processes and the replacement of the set of all possible directions of motion in space by a finite set of directions corresponding to thirty points uniformly spaced on the unit sphere.

Analyses of small samples of monazites with a gamma scintillation spectrometer

AbstractThe possibility of applying gamma ray analysis to approximately 50 mg samples of monazite has been investigated. Three ranges of low energy gamma radiation, under 0.3 MeV, were counted with a Gamma Scintillation Spectrometer.This extremely simple method led to very good results with samples containing only one radioactive component. With monazites containing uranium as well as thorium, the latter component being in excess, results were also good. For uranium contents that were only a few tenths of a per cent, the results did not attain the precision of chemical analysis.In a leached mineral where the simultaneous contents of uranium, radium in excess and thorium had to be determined, the method failed, due to the smallness of the contribution of UX in the emitted radiation with respect to that of the radium family. In this case we were able to calculate an approximate value for the thorium content and make a rough estimate of the total radium content of the mineral.With this spectrometer the use of longer counting times gives only a slight improvement in the precision of the counts. The use of somewhat larger samples will however diminish the important background fraction in the low activity countings and hence it will give a corresponding increase in the reliability of the results.

Remarks on low-energy gamma-radiation at great depths

Remarks on low-energy gamma-radiation at great depths

Low-Energy Gamma Radiation from the Bombardment of Carbon by Protons

Low-Energy Gamma Radiation from the Bombardment of Carbon by Protons