Pulsed Cold Neutron Research Articles

An accelerator-based cold neutron source

We have developed and installed an efficient and very simple pulsed cold neutron source in a modest capacity electron linear accelerator. Solid methane at 20 K was adopted as the cold moderator. The device has demonstrated satisfactory performance and reliable operation over extended periods. Herein we describe the results obtained in preliminary tests, the design philosophy, the constructional details and our operational experiences using the apparatus.v

A quasielastic spectrometer using a linear accelerator cold neutron source

Herein we describe the design and performance capabilities of a neutron quasielastic scattering spectrometer with conventional resolution. The spectrometer is equipped with an accelerator pulsed cold neutron source (a 20 K methane moderator), and is installed in a 35 MeV electron linear accelerator. Using inverted geometry, the instrument analyses scattered neutrons by focused analyser mirrors. High efficiency is achieved by adopting the large area of the cold moderator and the analyser mirrors. The spectrometer has demonstrated considerable usefulness in experimental spectral profile analysis studies.

中性子準弾性散乱によるセメント硬化過程の研究

Quasi-elastic neutron scattering technique has been used to investigate the time dependence of hardening process in cement pastes. A neutron spectrometer, which has sufficiently high sensitivity and good resolution, enables one to measure accurately the ratio of free water concentration to that of bound water in cement paste during hydration process. It was shown that the interpretation of the scattered neutron spectra by a two-state model, the free and the combined water, is a good approximation. It is concluded that, in the hardened paste, the positions of water molecules in the gel water should not be displaced quickly.The measurements have been performed by using a spectrometer which employs a pulsed cold neutron source, based upon a 35MeV electron linear accelerator with beam power of 1kW, and a crystal analyzer mirror. Performing the special efforts to attain high sensitivity, the advantage of the modest capacity accelerator as a pulsed neutron source for the scattering technique has been demonstrated.

加速器パルス冷中性子源

An accelerator-based pulsed cold neutron source was constructed. The accelerator is a 35MeV electron linear accelerator with 1kW average beam power. The cold neutron beam intensity at a specimen is equivalent to that of a research reactor of 1014 n/cmcm2·s thermal flux in the case of the quasi-elastic neutron scattering measurements. In spite of some limitations to the universal uses, it has been demonstrated by this facility that the modest capacity accelerator-based pulsed cold neutron source is a highly efficient cold neutron source with low capital investment. Design philosophy, construction details, performance and some operational experiences are described.

Time-Dependence of Cold Neutron Pulse Emitted from Methane at 20°K

The time-dependent behavior of monochromatic neutrons from a pulsed cold moderator system provides important information for application of the system as a pulsed cold neutron source. The time distribution of neutron pulses from 20°K methane has been studied using time-of-flight and crystal monochromator techniques. The first time-moments of the neutron pulses and the thermalization time constant have been obtained.

Time-Dependence of Cold Neutron Pulse Emitted from Methane at 20°K

The time-dependent behavior of monochromatic neutrons from a pulsed cold moderator system provides important information for application of the system as a pulsed cold neutron source. The time distribution of neutron pulses from 20°K methane has been studied using time-of-flight and crystal monochromator techniques. The first time-moments of the neutron pulses and the thermalization time constant have been obtained.