THE CROSS SECTION FOR THE REACTION Cs135(n, γ)Cs136

1958 ◽  
Vol 36 (7) ◽  
pp. 863-870 ◽  
Author(s):  
A. P. Baerg ◽  
F. Brown ◽  
M. Lounsbury
Keyword(s):  
Cross Section ◽  
Reaction Rate ◽  
Effective Cross Section ◽  
Reaction Rates ◽  
Resonance Integral ◽  
A Value ◽  
The Cross ◽  
Thermal Cross Section

The effective cross section for the reaction Cs135 (n, γ) Cs136 with reactor neutrons is 10.4 ± 0.5 barns. The measured reaction rate under cadmium yields a value of 61.7 ± 2.3 barns for the resonance integral of Cs135. The thermal cross section is 8.7 ± 0.5 barns as obtained by combining the reaction rates for uncovered and cadmium-covered samples.

MEASUREMENT OF RADIATIVE CAPTURE RESONANCE INTEGRALS IN A THERMAL REACTOR SPECTRUM, AND THE THERMAL CROSS SECTION OF Pu-240

1960 ◽  
Vol 38 (1) ◽  
pp. 57-77 ◽  
Author(s):  
W. H. Walker ◽  
C. H. Westcott ◽  
T. K. Alexander
Keyword(s):  
Cross Section ◽  
Neutron Beam ◽  
Cross Sections ◽  
Radiative Capture ◽  
Effective Cross Section ◽  
Mean Value ◽  
Resonance Integral ◽  
Thermal Reactor ◽  
Thermal Cross Section ◽  
Radiative Neutron Capture

An apparatus is described which detects γ-rays emitted by a thin target placed in a well-denned neutron beam. It has been used to determine the Cd ratios of Au and Pu-240, from which the ratio of the resonance integral to the 2200 m/s cross section for radiative neutron capture in Pu-240 has been deduced, using Au as a reference standard. Using this ratio and previously measured values of the resonance integral of Pu-240 and its effective cross section in two positions in the NRX reactor, three separate estimates of the 2200 m/s cross section of Pu-240 have been made. The mean value is 270 ± 17 barns.In an auxiliary experiment to indicate the shape of the epithermal spectrum of the neutron beam, the activation Cd ratios of Mn and In were compared with that of Au. These results, combined with the known 2200 m/s capture cross sections of these nuclides, yield new values of the radiative capture resonance integrals for both Mn and In.

Hg(63P1)-sensitized decomposition of HNCO vapor and HNCO–H2 mixtures; the reaction of hydrogen atoms with HNCO

1968 ◽  
Vol 46 (4) ◽  
pp. 527-530 ◽  
Author(s):  
N. J. Friswell ◽  
R. A. Back
Keyword(s):  
Quantum Yield ◽  
Cross Section ◽  
Initial Step ◽  
Primary Process ◽  
Hydrogen Atoms ◽  
Direct Photolysis ◽  
A Value ◽  
The Cross

The Hg(63P1)-sensitized decomposition of HNCO vapor has been briefly studied at 26 °C with HNCO pressures from about 3 to 30 Torr. The products detected were the same as in the direct photolysis, CO, N2, and H2. The quantum yield of CO was appreciably less than unity, compared with a value of 1.5 in the direct photolysis under similar conditions. From this and other observations it is tentatively concluded that a single primary process occurs:[Formula: see text]From a study of the mercury-photosensitized reactions in mixtures of HNCO with H2, it was concluded that hydrogen atoms react with HNCO to form CO but not N2. The initial step is probably addition to form NH2CO. From the competition between reaction [1] and the corresponding quenching by H2, the cross section for reaction [1] was estimated to be 2.3 times that of hydrogen.

scholarly journals Improved accuracy in the determination of the thermal cross section of ${}^{14}{\rm N}({\rm n},{\rm p}){}^{14}{\rm C}$ for neutron lifetime measurement

2019 ◽  
Vol 2019 (9) ◽  
Author(s):  
R Kitahara ◽  
K Hirota ◽  
S Ieki ◽  
T Ino ◽  
Y Iwashita ◽  
...  
Keyword(s):  
Cross Section ◽  
Lifetime Measurement ◽  
Reaction Cross ◽  
Proton Accelerator ◽  
Incident Neutron ◽  
Neutron Lifetime ◽  
The Cross ◽  
Thermal Cross Section ◽  
Improved Accuracy

Abstract In a neutron lifetime measurement at the Japan Proton Accelerator Complex, the neutron lifetime is calculated from the neutron decay rate and the incident neutron flux. The flux is obtained by counting the protons emitted from the neutron absorption reaction of ${}^{3}{\rm He}$ gas, which is diluted in a mixture of working gas in a detector. Hence, it is crucial to determine the amount of ${}^{3}{\rm He}$ in the mixture. In order to improve the accuracy of the number density of the ${}^{3}{\rm He}$ nuclei, we have suggested using the ${}^{14}{\rm N}({\rm n},{\rm p}){}^{14}{\rm C}$ reaction as a reference because this reaction involves similar kinetic energy to the $^3$He(n,p)$^3$H reaction and a smaller reaction cross section to introduce reasonable large partial pressure. The uncertainty of the recommended value of the cross section, however, is not satisfied with our requirement. In this paper we report the most accurate experimental value of the cross section of the $^{14}$N(n,p)$^{14}$C reaction at a neutron velocity of 2200 m s$^{-1}$, measured relative to the $^3$He(n,p)$^3$H reaction. The result was 1.868 $\pm$ 0.003 (stat.) $\pm$ 0.006 (sys.) b. Additionally, the cross section of the $^{17}$O(n,$\alpha$)$^{14}$C reaction at the neutron velocity is also redetermined as 249 $\pm$ 6 mb.

THE RATIO OF THE RESONANCE INTEGRAL TO THE THERMAL NEUTRON CROSS SECTION FOR Sm152

1961 ◽  
Vol 39 (8) ◽  
pp. 1184-1192 ◽  
Author(s):  
W. H. Walker ◽  
R. E. Green
Keyword(s):  
Total Cross Section ◽  
Cross Section ◽  
Neutron Cross Section ◽  
Resonance Integral ◽  
Half Maximum ◽  
Thin Foils ◽  
Flight Measurement ◽  
Thermal Neutron Cross Section ◽  
Thermal Cross Section ◽  
Made In

Cadmium ratio measurements have been made in similar lattice positions in ZEEP with thin foils of Sm152 and gold. From a comparison of these cadmium ratios we find[Formula: see text]If gσ0 is assumed to be 212 ± 12 barns, then I′ = 3100 ± 200 barns. On the assumption that only one resonance in Sm152, at 8 ev, contributes appreciably to both the resonance integral and the thermal cross section, it follows that g = 1 and that Γ, the width at half-maximum of the total cross section resonance, is 193 ± 5 milli-ev. Because of the appreciable disagreement between this value and one reported earlier, a new time-of-flight measurement of the resonance parameters has been made, and it is reported in the next paper (Chrien 1961).

An isotope effect on 62P1/2–62P3/2 mixing in cesium, induced in collisions with CH4 and CD4

1969 ◽  
Vol 47 (4) ◽  
pp. 473-474 ◽  
Author(s):  
D. A. McGillis ◽  
L. Krause
Keyword(s):  
Isotope Effect ◽  
Cross Section ◽  
Reaction Rates ◽  
Gas Mixtures ◽  
Excitation Transfer ◽  
Cross Section Ratio ◽  
Section Ratio ◽  
The Cross ◽  
Absolute Reaction

62P1/2 ↔ 62P3/2 excitation transfer in cesium, induced in collisions with CH4 and CD4 molecules, has been studied in relation to the temperature of the vapour–gas mixtures. The variation with temperature of the cross section ratio Q(CH4)/Q(CD4) is ascribed to an isotope effect which is interpreted on the basis of the theory of absolute reaction rates.

scholarly journals Total Monte Carlo acceleration for the PETALE experimental programme in the CROCUS reactor

2019 ◽  
Vol 211 ◽  
pp. 03002 ◽  
Author(s):  
Axel Laureau ◽  
Vincent Lamirand ◽  
Dimitri Rochman ◽  
Andreas Pautz
Keyword(s):  
Monte Carlo ◽  
Cross Section ◽  
Reaction Rate ◽  
Brute Force ◽  
Experimental Programme ◽  
Bayesian Monte Carlo ◽  
Correlated Sampling ◽  
The Cross

The Bayesian Monte Carlo technics requires individual evaluations of random cross section files based on a Total Monte Carlo propagation. This article discusses the use of a Correlated Sampling acceleration applied to TMC calculations for experiments where a brute force technics is too expensive. An e_cient estimation of the reaction rate uncertainties in small dosimeters is obtained, together with the inter-dosimeter correlation associated to the cross section uncertainties.

scholarly journals Correlated energy uncertainties in reaction rate calculations

2020 ◽  
Vol 642 ◽  
pp. A41
Author(s):  
Richard Longland ◽  
Nicolas de Séréville
Keyword(s):  
Monte Carlo ◽  
Cross Section ◽  
Reaction Cross Section ◽  
Reaction Rate ◽  
Resonance Energy ◽  
Reaction Rates ◽  
Reaction Cross ◽  
Current Interest ◽  
Resonance Energies ◽  
The Impact

Context. Monte Carlo methods can be used to evaluate the uncertainty of a reaction rate that arises from many uncertain nuclear inputs. However, until now no attempt has been made to find the effect of correlated energy uncertainties in input resonance parameters. Aims. Our goal is to investigate the impact of correlated resonance energy uncertainties on reaction rates. Methods. Using a combination of numerical and Monte Carlo variation of resonance energies, the effect of correlations are investigated. Five reactions are considered: two fictional, illustrative cases and three reactions whose rates are of current interest. Results. The effect of correlations in resonance energies depends on the specific reaction cross section and temperatures considered. When several resonances contribute equally to a reaction rate, and when they are located on either side of the Gamow peak, correlations between their energies dilute their effect on reaction rate uncertainties. If they are both located above or below the maximum of the Gamow peak, however, correlations between their resonance energies can increase the reaction rate uncertainties. This effect can be hard to predict for complex reactions with wide and narrow resonances contributing to the reaction rate.

scholarly journals New parametrization for the 3He(d, p) 4He fusion reaction rate and refinement of the Lawson criterion for d-3He thermonuclear reactors

2021 ◽  
Vol 2103 (1) ◽  
pp. 012197
Author(s):  
I B Alper ◽  
A I Godes ◽  
V L Shablov
Keyword(s):  
Experimental Data ◽  
Energy Range ◽  
Cross Section ◽  
Reaction Rate ◽  
Nuclear Reactions ◽  
Fusion Reaction ◽  
Theoretical Method ◽  
Reaction Rates ◽  
Lawson Criterion ◽  
Astrophysical Factor

Abstract We present a new parametrization of the d + 3He → p + 4He fusion reaction astrophysical factor based on the effective range approximation, which is an effective theoretical method for describing near-threshold, including resonance, nuclear reactions. In the framework of this approximation we describe experimental data on the energy dependence of the cross section and the astrophysical factor within the experimental uncertainties in the energy range of 0-800 keV. On this basis we calculate the temperature dependence of the Maxwellian-averaged reaction rate in the range of 0-400 keV. In conclusion, we discuss the effect of the calculated reaction rates on the Lawson criterion for thermonuclear reactors based on d-3He fuel.

scholarly journals PENENTUAN DENSITAS PLASMA HIDROGEN NONTERMAL PADA TEKANAN RENDAH

2019 ◽  
Vol 16 (1) ◽  
pp. 29
Author(s):  
Nelda Ipkawati ◽  
Saktioto Saktioto ◽  
Saktioto Saktioto
Keyword(s):  
Reaction Rate ◽  
Impact Ionization ◽  
Hydrogen Plasma ◽  
Low Pressure ◽  
Reaction Rates ◽  
Equilibrium Conditions ◽  
Runge Kutta Method ◽  
A Value ◽  
Equilibrium Process ◽  
The Impact

Before producing hydrogen plasma low pressure in experiment, it is necessary to know the density equilibrium process through a simulation. Hydrogen species densities of non-thermal plasma at low pressure is simulated using chemical kinetik model by Runge Kutta method. This simulation carried out to determine the equilibrium process of densities and reaction rates of hydrogen species in achieving equilibrium conditions. The equation used time-dependent continuity equation and Arrhenius form. The hydrogen species consist of electrons, H, H2, H+ and H2+. The results of show that electron density, H, H2, H+ and H2+ are respectively 1020,23m-3, 1019,69m-3, 1019,91m-3, 1019,39m-3 and 1018,43m-3 during of 23-24 ns. These describe that the density of each species of hydrogen very fast to achieve equilibrium conditions, while the value of the reaction rate obtained can be concluded that the value of the largest reaction rate is the impact ionization process with a value of 9.86x1052m-3 s-1and the smallest one is dissociation process with a value of 1.22x10-5m-3 s-1.

Neutron Field Shaping Using Graphite for Reaction Rate Measurements

2021 ◽  
Vol 7 (2) ◽  
Author(s):  
Mikita Sobaleu ◽  
Michal Košťál ◽  
Jan Šimon ◽  
Evžen Losa
Keyword(s):  
Cross Section ◽  
Reaction Rate ◽  
Nuclear Data ◽  
Data File ◽  
Reaction Rates ◽  
Reaction Cross ◽  
Neutron Field ◽  
Pure Graphite ◽  
24Na Reaction ◽  
Data Libraries

Abstract Neutron field shaping is the suitable method for validation of cross section in various energy regions. By increasing the share of neutrons of a certain energy interval and decreasing the share of other, a reaction becomes more sensitive to selected neutrons. As a result, reaction cross section can be validated in selected energy regions more precisely. The shaping can be carried out by both neutron filters which are materials with high absorption in some energy region, or by diffusion material changing the shape of neutron spectra by means of slowing down process. In the presented experiments, the neutron field of the light reactor 0 (LR-0) research reactor was shaped by both using graphite blocks inserted into the core and Cd cladding for increasing the epithermal reaction rate share in total reaction rates. The calculations were carried out with the Monte Carlo N-Particle Transport Code 6 (MCNP6) code and the most recent nuclear data libraries. The results in the pure graphite neutron field are in good agreement; in case of Cd cladding, significant discrepancies were reported. In case of the 23Na(n,γ)24Na reaction, overestimation by about 14% was reached in International Reactor Dosimetry and Fusion File (IRDFF-II), results in other libraries are comparable. In case of 58Fe(n,γ)59Fe, the overestimation as high as 18% is reported in IRDFF-II. For 64Zn(n,γ)65Zn reasonable agreement was reached in evaluated nuclear data file (ENDF/B-VIII), where discrepancies in pure graphite neutron field or in case of Cd cladding are about 10–15%.

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