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Science at CSNS

Neutrons and Neutron Scattering

Date: 2017-03-14 Author:

>> What is a neutron?

A neutron is one of the basic constituents of matter. This uncharged particle exists in the nucleus of a typical atom, along with its positively charged counterpart, the proton. Neutrons are abundant in the universe, making up more than half of all visible matter. Because of their unique sensitivity to hydrogen, beams of neutrons can be used to precisely locate hydrogen atoms, enabling a more accurate determination of molecular structure. Neutrons, like x-rays, are a powerful means to probe the structure of the microscopic world.

>> What is neutron scattering?

Neutron scattering provides information about the positions, motions, and magnetic properties of solids. When a beam of neutrons is aimed at a sample, many neutrons will pass through the material. But some will interact directly with atomic nuclei and "bounce" away at an angle, like colliding balls in a game of pool. This behavior is called neutron diffraction, or neutron scattering.

Using detectors, scientists can count scattered neutrons, measure their energies and the angles at which they scatter, and map their final position (shown as a diffraction pattern of dots with varying intensities). In this way, scientists can glean details about the nature of materials ranging from liquid crystals to superconducting ceramics, from proteins to plastics, and from metals to micelles to metallic glass magnets.

>> Neutron spallation science

Neutrons, like x-rays, are a powerful means to probe the structure of the microscopic world. Moreover, neutrons have some special properties that x-rays do not possess:

1) Neutrons bear no charge, but have a magnetic vector;

2) Neutrons have the ability to penetrate through matter;

3) Neutrons are much more sensitive to light elements and isotopes;

4) Neutrons can detect both the structure and dynamics behavior of matter.

For the above reasons, neutron scattering has become a complementary means to x-rays in advanced research in physics, chemistry, biology, life science, material science, alternative energy, as well as in commercial applications.


>> The spallation neutron source in China

Three high performance x-ray sources based on synchrotron radiation facility are operated for users at Beijing (BSRF at IHEP), Hefei (NSRF at USTC), and Shanghai (Shanghai Light Source). However there is no high performance pulsed neutron source in China. To meet the increasing demand from the user community, China has decided to build a world-class spallation neutron source, called the China Spallation Neutron Source (CSNS).

The CSNS facility is designed to provide multidisciplinary platforms for scientific research. The site of the CSNS has been selected at Dongguan, Guangdong Province. It can provide users a neutron scattering platform with high flux, wide wavelength range and high efficiency. The pulsed-beam feature allows studies not only of the static structure but also of the dynamic mechanisms of the microscopic world. The high-flux pulsed neutrons, muons, and protons from the CSNS will also complement continuous-wave neutrons from the China Advanced Research Reactor (CARR).

The China Spallation Neutron Source will be available to researchers from all over the world with varying degrees of experience. Submitted research proposals will be reviewed by independent scientists from within the neutron scattering community, and the most promising ones will be chosen.