MEASUREMENT OF NUCLEAR GAMMA-RAY ABSORPTION IN CARBON

1953 ◽  
Vol 31 (4) ◽  
pp. 636-656 ◽  
Author(s):  
R. N. H. Haslam ◽  
R. J. Horsley ◽  
H. E. Johns ◽  
L. B. Robinson
Keyword(s):  
Cross Section ◽  
Gamma Ray ◽  
Nuclear Scattering ◽  
Absorption Mechanism ◽  
Nuclear Absorption ◽  
Resonance Behavior ◽  
Continuous Absorption ◽  
Γ Rays ◽  
Integrated Cross Section ◽  
Nuclear Detectors

The cross section for the absorption of γ rays by carbon has been determined as a function of photon energy by means of "nuclear detectors". The electronic absorption coefficients in the energy range 12 to 20 Mev. are found to be about 1% lower than the theoretical values. The nuclear absorption is shown to exhibit a resonance behavior. The integrated cross section in carbon is considerably lower than predicted. The contribution of nuclear scattering is found to be negligible. Differences in results as determined by three different detecting reactions, C12(γ, n)C11, O16(γ, d)P15, and S32(γ, d)P30, are discussed on the basis of detector sensitivity. It is suggested that the absorption mechanism can be represented by a continuous absorption on which is superimposed absorption peaks.

scholarly journals Radiocarbon Production by the Gamma-Ray Component of Supernova Explosions

Radiocarbon ◽  
1995 ◽  
Vol 37 (2) ◽  
pp. 599-604 ◽  
Author(s):  
Paul E. Damon ◽  
Dai Kaimei ◽  
Grant E. Kocharov ◽  
Irina B. Mikheeva ◽  
Alexei N. Peristykh
Keyword(s):  
Cross Section ◽  
Tree Rings ◽  
Confidence Level ◽  
Gamma Ray ◽  
Visual Observation ◽  
Total Production ◽  
Average Increase ◽  
Supernova Explosions ◽  
Γ Rays ◽  
Γ Ray

We selected SN1006, the brightest and closest to Earth of all supernovas historically observed, for a study of 14C production by e−,e+-bremsstrahlung cascades initiated by hard γ rays (>10 MeV) from that event. During the cascade, bremsstrahlung energies eventually fall within a giant (n,γ), (n,2γ) cross-section, peaking at 23 MeV and approaching effectively zero below 10 MeV and above 40 MeV. The neutrons are absorbed primarily in the reaction 14N(n,p)14C. Cellulose from single-year tree rings from ad 1003 to ad 1020 was measured to determine ∆14C. Three years after the first visual observation of SN1006, ∆14C rose and remained above pre-ad 1009 values until ad 1018. Comparison of the 7 years before ad 1009 with the 9 years following show an average increase of 6.1 ± 1.6 (s.d.)‰ (significant at the 99.6% confidence level). Such a pulse of 14C requires a total production of neutrons of 17.1 × 107n cm−2e, implying an input of 11.3 × 104 ergs cm−2e γ-ray energy. This requires the total supernova γ-ray energy (>10 MeV) to have been 1 × 1050 ergs.

PHOTONEUTRON CROSS SECTIONS IN SILICON AND CALCIUM

1953 ◽  
Vol 31 (1) ◽  
pp. 70-77 ◽  
Author(s):  
R. G. Summers-Gill ◽  
R. N. H. Haslam ◽  
L. Katz
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Neutron Yield ◽  
Threshold Energy ◽  
Threshold Effect ◽  
Monitoring Method ◽  
Dose Monitoring ◽  
Γ Rays ◽  
Integrated Cross Section ◽  
Peak Value

Using the dropping apparatus and dose monitoring method previously reported, the cross sections for the reactions Si28(γ, n)Si27 and Ca40(γ, n)Ca39 have been measured by detecting positron activities in the residual nuclei. The Si28(γ, n)Si27 cross section has a peak value of 21 mbarns at 20.9 Mev. and an integrated cross section to 24 Mev. of 0.070 Mev-barns. The threshold energy is 16.9 ± 0.1 Mev. The Ca40(γ, n)Ca39 cross section has a peak value of 15 mbarns at 19.3 Mev. and an integrated cross section to 24 Mev. of 0.065 Mev-barns. The threshold is 15.8 ± 0.1 Mev.A comparison of our results with the neutron yield measurement of Price and Kerst at 18 and 22 Mev. gives good agreement. A further comparison with the neutron yield work of Baldwin and Elder is made.The sharp discontinuity in (γ, n) yields using lithium γ rays observed by Wäffler and Hirzel is explained as a threshold effect. Integrated cross sections increase more or less smoothly with Z.In addition, improved values for the half-lives of the residual nuclei Si27 and Ca39 have been measured. These are 4.45 ± 0.05 and 1.00 ± 0.03 sec. respectively.

D(3He, γ)5Li reaction from 2 to 11 MeV

1968 ◽  
Vol 46 (14) ◽  
pp. 1585-1587 ◽  
Author(s):  
W. Del Bianco ◽  
F. Lemire ◽  
R. J. A. Lévesque ◽  
J. M. Poutissou
Keyword(s):  
Energy Range ◽  
Cross Section ◽  
Gamma Ray ◽  
Upper Limits ◽  
Integrated Cross Section

The 90° yield of the D(3He, γ)5Li reaction has been measured from 2.3 to 11.2 MeV 3He energy. No clear evidence of a level in 5Li has been found over this energy range. The upper limits for the resonance integrated cross section and gamma-ray width were estimated to be σint ~ 15 μb MeV and Γγ ~ 100eV, respectively.

scholarly journals Installation of NEOPTOLEMOS, the new sum spectrometer for cross section measurements of capture reactions at the ΤANDEM Accelerator Laboratory of NCSR “Demokritos”

2019 ◽  
Vol 24 ◽  
pp. 134
Author(s):  
V. Lagaki ◽  
V. Michalopoulou-Petropoulou ◽  
M. Axiotis ◽  
V. Foteinou ◽  
A. Lagoyannis ◽  
...  
Keyword(s):  
Cross Section ◽  
Large Volume ◽  
Solid Angle ◽  
Nuclear Astrophysics ◽  
Nuclear Level ◽  
Level Densities ◽  
Γ Rays ◽  
Integrated Cross Section ◽  
The University

Cross-section measurements of capture reactions are of key importance in understanding the contribution of the uncertainties of nuclear properties, such as the nucleon-nucleus potential and the nuclear level densities, entering in astrophysics abundance calculations. During the recent years, the Nuclear Astrophysics group of NCSR “Demokritos” has been conducting angle-integrated cross-section measurements using a large-volume NaI(Tl) detector installed at the Dynamitron Tandem Laboratory of the University of Bochum in Germany. Thanks to LIBRA funds a brand new cylindrically shaped NaI(Tl) detector, coined NEOPTOLEMOS, was acquired that is axially segmented in two, covering a solid angle of almost 4π for γ rays emitted at its center.

scholarly journals Spin-one dark matter and gamma ray signals from the galactic center

2020 ◽  
Vol 2020 (8) ◽  
Author(s):  
H. Hernández-Arellano ◽  
M. Napsuciale ◽  
S. Rodríguez
Keyword(s):  
Dark Matter ◽  
Cross Section ◽  
Gamma Ray ◽  
Galactic Center ◽  
Photon Emission ◽  
Scalar Coupling ◽  
Initial State ◽  
Internal Bremsstrahlung ◽  
Resonance Effects ◽  
State Radiation

Abstract In this work we study the possibility that the gamma ray excess (GRE) at the Milky Way galactic center come from the annihilation of dark matter with a (1, 0) ⊕ (0, 1) space-time structure (spin-one dark matter, SODM). We calculate the production of prompt photons from initial state radiation, internal bremsstrahlung, final state radiation including the emission from the decay products of the μ, τ or hadronization of quarks. Next we study the delayed photon emission from the inverse Compton scattering (ICS) of electrons (produced directly or in the prompt decay of μ, τ leptons or in the hadronization of quarks produced in the annihilation of SODM) with the cosmic microwave background or starlight. All these mechanisms yield significant contributions only for Higgs resonant exchange, i.e. for M ≈ MH /2, and the results depend on the Higgs scalar coupling to SODM, gs. The dominant mechanism at the GRE bump is the prompt photon production in the hadronization of b quarks produced in $$ \overline{D}D\to \overline{b}b $$ D ¯ D → b ¯ b , whereas the delayed photon emission from the ICS of electrons coming from the hadronization of b quarks produced in the same reaction dominates at low energies (ω < 0.3 GeV ) and prompt photons from c and τ , as well as from internal bremsstrahlung, yield competitive contributions at the end point of the spectrum (ω ≥ 30 GeV ). Taking into account all these contributions, our results for photons produced in the annihilation of SODM are in good agreement with the GRE data for gs ∈ [0.98, 1.01] × 10−3 and M ∈ [62.470, 62.505] GeV . We study the consistency of the corresponding results for the dark matter relic density, the spin-independent dark matter-nucleon cross-section σp and the cross section for the annihilation of dark matter into $$ \overline{b}b $$ b ¯ b , τ+τ−, μ+μ− and γγ, taking into account the Higgs resonance effects, finding consistent results in all cases.

An investigation of effects of level density models and gamma ray strength functions on cross-section calculations for the production of 90Y, 153Sm, 169Er, 177Lu and 186Re therapeutic radioisotopes via (n,γ) reactions

2019 ◽  
Vol 108 (1) ◽  
pp. 11-17
Author(s):  
Mert Şekerci ◽  
Hasan Özdoğan ◽  
Abdullah Kaplan
Keyword(s):  
Experimental Data ◽  
Cross Section ◽  
Production Cross Section ◽  
Gamma Ray ◽  
Production Cross ◽  
Level Density ◽  
Experimental Studies ◽  
Level Density Models ◽  
Strength Functions ◽  
Cancer Diseases

Abstract One of the methods used to treat different cancer diseases is the employment of therapeutic radioisotopes. Therefore, many clinical, theoretical and experimental studies are being carried out on those radioisotopes. In this study, the effects of level density models and gamma ray strength functions on the theoretical production cross-section calculations for the therapeutic radioisotopes 90Y, 153Sm, 169Er, 177Lu and 186Re in the (n,γ) route have been investigated. TALYS 1.9 code has been used by employing different level density models and gamma ray strength functions. The theoretically obtained data were compared with the experimental data taken from the literature. The results are presented graphically for better interpretation.

Revisiting the238U Thermal Capture Cross Section and Gamma-Ray Emission Probabilities from239Np Decay

2005 ◽  
Vol 150 (3) ◽  
pp. 336-348 ◽  
Author(s):  
A. Trkov ◽  
G. L. Molnár ◽  
Zs. Révay ◽  
S. F. Mughabghab ◽  
R. B. Firestone ◽  
...  
Keyword(s):  
Cross Section ◽  
Capture Cross Section ◽  
Gamma Ray ◽  
Capture Cross ◽  
Gamma Ray Emission
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