Simple Low Energy Gamma Ray Spectral Analysis Using Large Nal(Tl) Scintilation Spectrometers

A simple method of conversion of pulse-height distributions measured with a large Nal (Tl) scintillator to energy spectra of gamma rays is described. This method is quite adequate for a low energy region where the peak-to-total ratio is large and for the application of approximate analysis in the outside field of the strict gamma ray spectroscopy. In practical application of this method one needs to know only the peak-to-total ratio and efficiency of the scintillation counter as a function of photon energy. Simulation by a calculation was carried out for the purpose of demonstrating the utility of this method

Response Function of a Three-inch Diameter by Three-inch Long NaI(Tl) Scintillator to Gamma-Rays

The response of a three-inch diameter by three-inch long sodium-iodide scintillator to axially incident gamma-rays has been studied and expressed as a 20 by 20 matrix for the energy ranging from 0 to 1.440 Mev. The matrix was inverted on an automatic computer for the purpose of obtaining response-corrected spectra of scattered gamma-rays

Analysis of Errors in Albedo Monte Carlo Calculation due to Errors in Albedo Data

The error analysis method, which enables one to make an estimation of errors in the streaming neutron flux due to errors in the albedo data in the albedo Monte Carlo calculation, is described. The proposed method is based on a perturbation model which follows the same neutron path as in the unperturbed case, and estimates the flux error as a deviation in the neutron weight each time a neutron has a collision. As an example of the application of the proposed method, neutron duct streaming problems in 2-m long concrete ducts are analyzed. The importance of neutron scattering in each energy group to the streaming neutron flux is quantitatively described by the method

Multi-dimensional Sensitivity Analysis by Monte Carlo Method

A multi-dimensional sensitivity analysis method is proposed for evaluating the neutron flux perturbation due to the variance in the total, total scattering and differential scattering cross sections of the medium. The method is formulated based on the Monte Carlo method. The method uses the perturbation theory where the neutron random paths are not changed, and the variation in the neutron weight is estimated to describe the flux perturbation due to cross section errors. The method is applied to analyze the neutron scattering experiment in the gun-source geometry. It is shown through the analysis that a variety of the flux perturbation is caused at each scattering direction by the cross section errors

Integral Test of Niobium Differential Elastic Scattering Cross-Sections of 60 and 120 Degrees for High-Energy Neutrons

Spectra of scattered neutrons from a niobium disc were measured at the scattering angles of 60° and 120° by an NE-213 scintillator. Comparison of the experimental data with the point-to-point Monte Carlo calculations, using the evaluated data from the ENDF/B-IV file, showed good agreement at 60°, but considerable discrepancy at 120°

Response Function of a 1-inch Diameter by 6-inch Long ³He Proportional Counter to Neutrons

The response of a 1-inch diameter by 6-inch long ³He proportional counter, of which the gas filling is 4 atm ³He and 2 atm krypton, to axially incident neutrons has been studied and expressed as a 50 by 50 matrix for an energy range from zero to 5 MeV. Applications of the matrix were examined for the purpose of obtaining response-corrected spectra of neutrons transmitted through a matter

Backscattering of Gamma Rays from Tin Slabs

The backscattering of gamma rays from tin slabs was investigated as a function of slab thickness. The point isotropic ⁶⁰Co and ¹³⁷Cs sources were placed on the front face of the scatterer. The obtained data was converted to the response-corrected spectra with the aid of an inverse response matrix, and the angular and energy distributions of backscattered photons were obtained and compared with the other experimental and calculated results

Backscattering of Neutrons and Emergence of Secondary Gamma Rays from Iron Slabs Bombarded by 15-MeV Neutrons

Backscattered neutrons and associated gamma rays from iron slabs for 15-MeV incident neutrons were measured by a 2″φ×2″NE-213 scintillator. The associated particle method was used to confine the neutron beam. The time-of-flight method was used auxiliarily to eliminate thermal neutron capture gamma rays, and to estimate the time-independent neutron background. Experimental spectra were compared with the results of the Monte Carlo calculations. Values of the neutron albedo and the secondary gamma ray albedo were shown as functions of slab thickness. These values showed good agreement with the Monte Carlo calculations

Collimation Effect of Water Collimator to D-D and D-T Neutrons

A study of a water collimator is performed for 5-cm and 10-cm diam. cylindrical collimators located in a 100-cm water shield. A point neutron source of D-D or D-T reactions is located at the entrance to the collimator. Results of the Monte Carlo simulation are analyzed as reference data. Two parameters are proposed to measure the collimation effects, i.e. scattered neutron flux on the axis of the collimator and the width of the plateau observed in the scattered flux profile. The flux on the axis is analyzed by a single-albedo-scattering model, while the width of the plateau is represented by a single-scattering model in the shied. The flux on the axis is nearly proportional to the collimator radius. The axial profile of the on-axis flux is closely approximated with an imaginary source assumed at the center of the collimator. The imaginary source reproduces the width of the plateau in the radial profile of the scattered flux

Measurements of Scattered Neutron Spectra at 90゜ Direction for Thin Targets of Ti, Fe, Ni, Cu, Nb, Mo and Pb by ²⁵²Cf Fission Neutrons

The angular spectra of scattered neutrons were measured by using fission neutrons with various thin targets of Ti, Fe, Ni, Cu, Nb, Mo, and Pb to make an integral testing of fast-neutron differential scattering cross sections in the ENDF/B-IV and JENDL-1 files. Parallel beams of the fission neutrons were injected into the targets, and neutrons scattered at 90° in the laboratory system were measured with an NE-213 scintillator. Monte Carlo calculations were done to analyze the experimental spectra. The data in the ENDF/B-IV and JENDL-1 files utilized in the calculations. The following are pointed out in this work : (1) The Fe and Pb spectra were reproduced well by the data in the ENDF/B-IV file. (2) The Mo spectrum was reproduced by the JENDL-1 file better than the ENDF/B-IV file. (3) The Cu spectrum was not reproduced by either the ENDF/B-IV file nor the JENDL-1 file. (4) The calculation by the ENDF/B-IV data gave a harder spectrum for the Nb target than that of the experiment. (5) The calculation by the ENDF/B-IV file gave a slight underestimate to th espectra at low energies for the Ti and Ni targets, compared with the experimental ones