原子光谱学-X射线ppt课件教学教程电子教案.ppt

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1、 16-3 The basis feature of X-ray1.Features of X-ray1.Ionization action e-1 2.Fluorescence action(use for detection and display of x ray)3.Photochemical action(act as normal electromagnetic way )4.Biological effect(the basis of medical radiation treatment)5.Penetrating ability(wavelength,and the atom

2、ic number Z)2.diffraction of x ray Lattice constant d X ray wavelength Aberration:2dsin So the condition of diffraction is 2dsin=k k=1,2.3.(16-4)That is Braggs Law16-4 material attenuation law for x ray 1.monochromatic x ray The experiments showed that the x ray density attenuation rate in the mater

3、ial is proportional to the density of the point.That is,we obtain:linear attenuation constant with unit:cm-1 I I0 0 I(x)I(x)x x x=0,I=I x=0,I=I0 0 I m m=/m m:mass attenuation constant with unit:cm2/g X Xhalf-thickness:X1/2 or Xm1/2 We get:after penetrated n half-thickness,the density of x-ray:2 mass

4、 attenuation constants formulaK=const 3 4 at medical profession =3.5 for water;air and human tissue.(1)Z m m more efficient to resist x ray.(2)m m easier to be absorbed.16-5 x rays applications at medical professionx ray are mainly used in diagnose and treatment at medical profession.1.Treatment(1)x ray radiation treatment(2)X-ray bistoury(surgical knife)for operation2.Diagnose(1)photography and fluoroscopy(2)X-CT(x ray computer aid transverse tomography 横断层成像横断层成像)Photo rebuild theory.X ray tube,x ray detector Assignment:p327 13-9;13-10;13-11,13-12;01-12-24;02-12-9;05-5-23