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Spectrometry of the multiplicity of gamma quanta on a stationary research reactor
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In this paper we describe the 236U(n,γ) reaction cross section measurement at the GELINA white pulsed neutron source of the Institute for Reference Materials and Measurements (IRMM) in Geel. The sample was placed in the neutron beam at a flight station located at a nominal distance of 30 m from the neutron source. Neutron capture gamma rays were detected by two C 6D6́-based liquid scintillator gamma-ray detectors as a function of the neutron time-of-flight using the pulse height weighting technique. The pulse height weighting function has been derived from Monte Carlo simulations of the detector response to mono-energetic gamma rays. The shape of the neutron flux was measured with a 10B chamber, placed about 60 cm upstream in the neutron beam. The capture yield in the resolved resonance region up to 3 keV has been derived and will be presented here. The analysis of the capture yield in terms of R-matrix resonance parameters is planned for the near future.
The neutron absorption and fission cross sections for ²³⁹Pu and ²³⁵U have been measured over the neutron energy range from 0.02 eV to 200 keV. In addition, the neutron capture cross section for ¹⁹⁷Au was measured from 10 to 50 keV and the fission cross section of ²³³U was measured from 0.1 to 100 keV. Normalization of the ²³⁹Pu and ²³⁵U data was made over the energy region from 0.02 to 0.4 eV to the ENDF/B-III neutron cross sections for these isotopes, Mat 1159 and 1157, respectively. The capture cross section for ¹⁹⁷Au was normalized using the saturated resonance method for the 4.9-eV resonance. For ²³³U fission, the normalization was made using the results of Weston et al. The neutron flux was measured using the ¹⁰B(n,α) reaction; the energy variation used for this reaction was that given in ENDF/B-III.
The pulsed-neutron beam for these measurements was generated using the Oak Ridge Electron Linear Accelerator. A large liquid scintillator about 40 m from the neutron source was used to detect the prompt gamma-ray cascades resulting from neutron absorption in the sample. The time interval between the burst of neutrons and the detection of the absorption event was used to establish the neutron energy scale. The sample of the fissile isotopes was contained in multiplate (pulse) ionization chambers and those neutron absorption events detected in coincidence with a pulse from the ionization chamber were defined as fission events.
In general for ²³⁹Pu and ²³⁵U, these experiments indicated lower neutron fission cross sections than contained in ENDF/B-III for energies above 10 keV. The measured values of the ratio α, neutron capture-to-neutron fission, for ²³⁹Pu agree within errors with those derived from ENDF/B-III, Mat 1159. For the present measurements, the uncertainty on α for ²³⁹Pu is ∼11% at 10 keV and increases to ∼30% at 100 keV.
The experimental results for the neutron capture cross section for ¹⁹⁷Au are ∼15% lower than the ENDF/B-III values. The measurements of the ratio of the neutron fission cross section for ²³³U to that for ²³⁵U are generally higher than the ENDF/B-III values by ∼5%.
In order to measure the neutron-physical constants with high accuracy and to investigate ways of formation and decay of excited nuclei a method has been developed at the I.V. Kurchatov AEI, based on the gamma-quanta and neutrons multiplicity spectrometry. During 1974-1978 there have been constructed a number of multisectional 4..pi..-detectors which have demonstrated great possibilities for this method. A detector permitting the required accuracy of measurements of neutron cross sections and their ratios has been chosen and designed on the basis of these works. The detector with 4..pi..-geometry has 46 sections and was based on naI(Tl) crystals with the total volume of the scintillator of approx. 100 1. The detector was used at the 26-m station. The results of U-235 absolute alpha value measurements are presented. The measurements are carried out over the energy range from 0.1 to 30 keV with the high accuracy - better than 5%. The equipment parameters and measurement conditions are listed. (WHK)
Measurement of the fission and capture cross sections and the value of alpha of235U
- G V Muradyan
- Yu G Shchepkin
- Yu V Adamchuk
G.V. Muradyan, Yu. G. Shchepkin, Yu. V. Adamchuk, et al., "Measurement of the fission and capture cross sections and the value of alpha of =35U," in: Neutron Physics.
Measurement of the fission and capture cross sections and the value of alpha of235U,” in: Neutron Physics
- Yu G V G Muradyan
- Yu V Shchepkin
- Adamchuk
Study of neutron cross sections and quantum characteristics of nuclear levels based on spectrometry of the multiplicity of emissions of nuclei
- G V Muradyan
- Yu G Shchepkin
- Yu V Adamchuk
- G I Ustroev
Setup for coding the multiplicity of coincidences in the CAMAC standard for work with a multisectioned detector
- A A Bogzdel
- Ts
- Ts
- N S Panteleev
- V G Stancheva
- Fo Tishin
- Dik Toan
Measurement of the neutron capture and fission cross sections of Pu-239 and U-235, 0.02 eV to 200 keV, the neutron capture cross sections of Au-197, 10 to 50 keV, and neutron fission cross sections of U-235, 5 to 200 keV
- E R Gwin
- R Silver
- H Ingle
- Weaver
Mechanical system for collimation and monochromatization of a neutron beam in the horizontal channel No. 4 of the reactor IRT-2000
- S T Bak
- G P Rdzhiev
- Georgiev
Collimation of a neutron beam in experiments on the measurement of partial cross sections with a small amount of material
- G V Muradyan
- G I Ustroev
- Yu G Shchepkin
Tishin, and Fo Dik Toan, ?Setup for coding the multiplicity of coincidences in the CAMAC standard for work with a multisectioned detector
- Ts A A Bogzdel
- Ts
- N S Panteleev
- V G Stancheva
A measurement of U-235 absolute alpha value in the neutron energy range from 0.1 to 30 keV
- G Muradyan
- Yu Schchepkin
- Yu Adamchuk
- M Voskanyan