scholarly journals Monoenergetic Neutrons for Stellar Applications

2009 ◽  
Vol 26 (3) ◽  
pp. 232-236
Author(s):  
M. Mosconi ◽  
M. Heil ◽  
F. Käppeler ◽  
R. Plag ◽  
A. Mengoni ◽  
...  
Keyword(s):  
Inelastic Scattering ◽  
Cross Section ◽  
Cross Sections ◽  
Theoretical Calculations ◽  
Excited Level ◽  
Scattering Cross Section ◽  
Elastic Channel ◽  
Monoenergetic Neutron ◽  
Scattering Cross ◽  
Neutron Beams

AbstractWith modern techniques, neutron-capture cross sections can be determined with uncertainties of a few percent. However, Maxwellian averaged cross sections calculated from such data require a correction (because low-lying excited states are thermally populated in the hot stellar photon bath) which has to be determined by theoretical calculations. These calculations can be improved with information from indirect measurements, in particular by the inelastic scattering cross section. For low-lying levels, the inelastically scattered neutrons are difficult to separate from the dominant elastic channel. This problem is best solved by means of pulsed, monoenergetic neutron beams. For this reason, a pulsed beam of 30 keV neutrons with an energy spread of 7 to 9 keV FWHM and a width from 10 to 15 ns has been produced at Forschungszentrum Karlsruhe using the 7Li(p, n)7Be reaction directly at the reaction threshold. With this neutron beam the inelastic scattering cross section of the first excited level at 9.75 keV in 187Os was determined with a relative uncertainty of 6%. The use of monoenergetic neutron beams has been further pursued at the Physikalisch-Technische Bundesanstalt in Braunschweig, including the 3H(p, n)3He reaction for producing neutrons with an energy of 64 keV.

scholarly journals New equipment for neutron scattering cross-section measurements at GELINA

2020 ◽  
Vol 239 ◽  
pp. 17003
Author(s):  
Markus Nyman ◽  
Thomas Adam ◽  
Catalin Borcea ◽  
Marian Boromiza ◽  
Philippe Dessagne ◽  
...  
Keyword(s):  
Inelastic Scattering ◽  
Neutron Scattering ◽  
Cross Section ◽  
Inelastic Neutron Scattering ◽  
Scattering Cross Section ◽  
Current Status ◽  
Research Centre ◽  
Joint Research ◽  
Elastic Channel ◽  
Scattering Cross

Two new experimental setups are being developed at European Commission’s Joint Research Centre in Geel, Belgium. The scintillator array ELISA (ELastic and Inelastic Scattering Array) is for high-quality neutron scattering cross section and angular distribution measurements. It has the capability to separate neutron-and photon-induced events via pulse-shape analysis. Inelastic scattering can also be resolved from the elastic channel. The ELISA setup and data analysis procedure were validated by performing measurements using carbon and iron samples. The DELCO spectrometer (Detection of ELectrons from COnversion) is intended for inelastic neutron scattering cross-section measurements in cases where the detection of γ rays is not feasible. The current status of DELCO, results from the first tests, and future prospects will be discussed.

Differential cross-section measurements in positron–argon collisions

1996 ◽  
Vol 74 (7-8) ◽  
pp. 505-508 ◽  
Author(s):  
R. M. Finch ◽  
Á. Kövér ◽  
M. Charlton ◽  
G. Laricchia
Keyword(s):  
Elastic Scattering ◽  
Differential Cross Section ◽  
Inelastic Scattering ◽  
Energy Range ◽  
Cross Section ◽  
Cross Sections ◽  
Differential Cross ◽  
Coupling Effect ◽  
Channel Coupling ◽  
Scattering Cross

Differential cross sections for elastic scattering and ionization in positron–argon collisions as a function of energy (40–150 eV) are reported at 60°. Of particular interest is the energy range 55–60 eV, where earlier measurements by the Detroit group found a drop in the elastic-scattering cross section of a factor of 2. This structure has been tentatively attributed to a cross channel-coupling effect with an open inelastic-scattering channel, most likely ionization. Our results indicate that ionization remains an important channel over the same energy range and only begins to decrease at an energy above 60 eV.

Acoustic Scattering Cross Sections of Smart Obstacles: A Case Study

2011 ◽  
Vol 10 (3) ◽  
pp. 672-694
Author(s):  
Lorella Fatone ◽  
Maria Cristina Recchioni ◽  
Francesco Zirilli
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Space Shuttle ◽  
Scattering Problem ◽  
Plane Waves ◽  
Acoustic Scattering ◽  
Scattering Cross Section ◽  
Scattering Cross ◽  
Scattering Cross Sections

AbstractAcoustic scattering cross sections of smart furtive obstacles are studied and discussed. A smart furtive obstacle is an obstacle that, when hit by an incoming field, avoids detection through the use of a pressure current acting on its boundary. A highly parallelizable algorithm for computing the acoustic scattering cross section of smart obstacles is developed. As a case study, this algorithm is applied to the (acoustic) scattering cross section of a “smart” (furtive) simplified version of the NASA space shuttle when hit by incoming time-harmonic plane waves, the wavelengths of which are small compared to the characteristic dimensions of the shuttle. The solution to this numerically challenging scattering problem requires the solution of systems of linear equations with many unknowns and equations. Due to the sparsity of these systems of equations, they can be stored and solved using affordable computing resources. A cross section analysis of the simplified NASA space shuttle highlights three findings: i) the smart furtive obstacle reduces the magnitude of its cross section compared to the cross section of a corresponding “passive” obstacle; ii) several wave propagation directions fail to satisfactorily respond to the smart strategy of the obstacle; iii) satisfactory furtive effects along all directions may only be obtained by using a pressure current of considerable magnitude. Numerical experiments and virtual reality applications can be found at the website: http://www.ceri.uniromal.it/ceri/zirilli/w7.

Inelastic scattering cross section of 172,174 Yb using tof technique

1986 ◽  
Vol 93 (1-4) ◽  
pp. 273-276 ◽  
Author(s):  
T. J. Al-Janabi ◽  
J. D. Jafar ◽  
S. J. Hasan ◽  
A. B. Kadhim ◽  
K. M. Mahmood ◽  
...  
Keyword(s):  
Inelastic Scattering ◽  
Cross Section ◽  
Scattering Cross Section ◽  
Scattering Cross
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