..Interference and Diffraction With Neutron

CHAPTER I

INTRODUCTION

In some of a country with an advanced economy, oxide superconductors such as YBa₂ Cu₃Ox (phase-123) was applicable, among others, the electric energy industry. This is possible because the material that can conduct current super at liquid nitrogen temperatures, non-toxic, easy to make and well reproducible. In general, the crystal structure of the green phase is still interesting to be analyzed further by performing neutron diffraction studies. Crystal structures need to be known with certainty, because the properties of materials can not be properly understood if the structure not yet establish accurately. Neutron diffraction technique has advantages over x-ray diffraction techniques. First, because the neutron beam scattering amplitude does not depend on the number of electrons in the atom, but changed irregularly from element to element and from isotope to another isotope of the same and of order, i.e., between 10-13-10-12 cm.

While the x-ray scattering amplitude depends on the number of electrons in the atom and changes monotonically from one element to and from isotope to another isotope. Second, the amplitude of neutron scattering is isotropic, because the wavelength of thermal neutrons (»10 -8 cm) is much larger of the dimensions of the nucleus as a target scattering (»10 -13 cm). While the x-ray scattering amplitude is isotropic and decreases with increasing scattering angle, this is because the x-ray wavelength is comparable to the dimensions of the electron cloud that serve as targets scattering.

Crystals constructed by a set of atoms A occupy certain points on the lattice crystal. Influence of temperature, the atoms-vibrate around the equilibrium position, called the thermal vibrations. Thermal vibration amplitude increases when the temperature increases. If a beam of x-rays or neutrons were dropped on the crystal, there will be a phenomenon of scattering of radiation by a large number of dots that make up scattering the crystal lattice. This phenomenon is called diffraction. In the case of x-ray diffraction, the point is it scattering electrons, while the neutron diffraction it scattering point atomic nuclei or electrons unpaired (for magnetic material). Because in the crystal, the point is made ​​periodically scattering, then the scattered rays have a specific phase relationship to each other such that in a certain direction interference is mutually beneficial and in the other direction weakens the mutual interference.

CHAPTER II

PREVIEW OF LITERATURE

1.      About Neutron

A neutron is one of the fundamental particles that make up matter. This uncharged particle exists in the nucleus of a typical atom, along with its positively charged counterpart, the proton. Protons and neutrons each have about the same mass, and both can exist as free particles away from the nucleus. In the universe, neutrons are abundant, making up more than half of all visible matter. Beams of neutrons provide an excellent way to observe effects depending on the wave behavior of material particles.

Neutrons produced from a nuclear reactor is usually a low-energy neutrons. In general, low energy neutrons can be classified in three types of cold neutrons (cold neutrons), thermal neutrons (thermal neutrons), and thermal neutrons (hot neutrons). Neutron scattering is a good technique to observe the structure and dynamics of a material. Usefulness of the scattering techniques because of the fundamental properties of neutron-owned as one of the constituent particles of atomic nuclei.

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