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Introduction

› X-radiation is called Röntgen radiation, after Wilhelm Röntgen, who is usually

credited as its discoverer, and who had named it

› The X-Rays are the waves of electromagnetic spectrum and Wavelength is 0.01

- 10 nm.

› X-rays are produced when the free electrons cause energy to be released as

they interact with the atomic particles in the target.

› They are shorter in wavelength than UV rays and longer than gamma rays.

X-Ray and Gamma ray are overlapping band and distinction between is source of 

generation .

History

› 1895 X-rays discovered by Roentgen

› 1914 First diffraction pattern of a crystal made by Knipping and von Laue

› 1915 Theory to determine crystal structure from diffraction pattern developed

by Bragg.

› 1953 DNA structure solved by Watson and Crick

› Now Diffraction improved by computer technology; methods used to

determine atomic structures and in medical applications

Properties of x-ray

 The properties of X-rays are given below:

›  They are shorter wavelength waves of the electromagnetic spectrum.

›  They have very high frequency hence requires high voltage to produce them.

›  They penetrate most of the material with ease and hence are used mostly to

scan object without touching them.

›  They affect photographic plate and hence are used to capture the human

skeleton defects.

› It is used in treatment of the cancer for cancerous cells management.

›  They travel in straight line and do not carry electric charge with them.

›  They are invisible to eye since they lie in the band between UV and gamma

rays for which we are blind.

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› It cannot be smelt or heard or either felt. The only way to observe them is by

the use of the photographic film.

›  They exhibit the property of interference, diffraction and refraction which are

similar to the visible light.

›  They can capable of traveling in vacuum.

We can observe the attenuation, absorption and scattering phenomenon from the X-

Rays.

X-ray diffraction

› X-ray diffraction is a method of determining the arrangement of atoms within a

crystal.

› Beam of X-rays strikes a crystal and causes the beam of light to spread into

many specific directions.

› A crystallographer can produce a three-dimensional picture of the density of 

electrons within the crystal.

› The mean positions of the atoms in the crystal chemical bonds, disorder is

determined from this electron density.

X-ray diffraction important for Solid-state physics

›  Textile

›

Biophysics

› Medical physics

› Chemistry and Biochemistry

› An interaction of a particular crystalline solid with X-rays helps in investigating

its actual structure.

›  The constituent particles in the crystals are arranged in planes at close

distances in repeating patterns.

›

 The phenomenon of diffraction of X-rays by crystals was studied by W.L.Braggand his father W.H.Bragg in 1913.

 They used crystals of zinc sulphide (ZnS) for this purpose. The experimental setup is

shown in the figure.

Dragg’s law

› Similar principle to multiple slit experiments

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› Constructive and destructive interference patterns depend on lattice spacing

(d) and wavelength of radiation (l)

› By varying wavelength and observing diffraction patterns,

› information about lattice spacing is obtained

›  These specific directions appear as spots on the diffraction pattern.

X-ray generator

Most standard X-ray systems have three main components

› X-ray tube

› a high voltage power supply

› a control unit.

 The following three requirements include a source of 

› Electrons

› a means of acceleration,

› a target for interaction.

› Electrical power

Fiber diffraction

› Fiber diffraction is a subarea of scattering, In fiber diffraction the scattering

pattern does not change, as the sample is rotated about a unique axis

› In crystallography fiber symmetry is an aggravation regarding the

determination of crystal structure

› The ideal fiber pattern exhibits 4-quadrant symmetry.

› In the ideal pattern the fiber axis is called the meridian, the perpendicular

direction is called equator.

Correction of polypropylene

›  The figure on the right shows a typical fiber pattern of polypropylene before

mapping it into reciprocal space.

› The mirror axis in the pattern is rotated by the angle with respect to the

vertical direction. This shortcoming is compensated by simple rotation of the

picture.

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› 4 straight arrows point at 4 reflection images of a chosen reference reflection.

 Their positions are used to determine the fiber tilt angle .β

›  The image has been recorded on a CCD detector.

› It shows the logarithmic intensity in pseudo-color representation.

› Here bright colors represent high intensity.

› After determination of the distance between sample and detector isβ  

computed using known crystallographic data of the reference reflex ion.

› A uniformly gridded map for the representative fiber plane in reciprocal space

is constructed and the diffraction data are fed into this map.

›  The figure below shows the result.

Application of x-ray diffraction

› Find structure to determine function of proteins

› Identification of fiber structure

› Convenient three letter acronym: XRD

› Distinguish between different crystal structures with identical compositions

› Study crystal deformation and stress properties

›

Study of rapid biological and chemical processes

Conclusion

After the invention of X-ray by Wilhelam Rontgen, it has been used in various

Scientific and technological field. Although it was invented a long years ago the

important of x-ray revolutionized the way of determining the physical properties of 

fiber and quality control of textile material.